Respiratory System

The Nasal cavity’s functions are to warm, filter and moisten the incoming air. The nose is the only external part of the respiratory system. The nose is divided into the external nose and the internal nasal cavity. When you breathe air enters the nasal cavity by passing through the nostrils.   

Pharynx is where the throat divides into the trachea which is the wind pipe and oesophagus which is the food pipe. The pharynx is a small length of tubing which connects the nasal cavity and mouth. There is also a small flap of cartilage called the epiglottis. This prevents food from entering the wind pipe.  

The Larynx is also known as the voice box because it’s where sound is generated. It is made of cartilage and has a section that comes above the surface which is known as Adams apple. The larynx is located between the pharynx and the trachea. The larynx provides an open airway and guides air and food into the correct channels. It also helps out with the vocal cords. It also helps protect the trachea by producing a strong cough reflex if any solid objects pass the through. 

Trachea is also known as the windpipe, it carries air from the throat into the lungs. The inner part of the trachea is covered in tiny hairs which catch dust and then is removed when we cough. The trachea is surrounded by 15-20 C shaped rings of cartilage at the front and side which help protect the trachea and keep it open.

Bronchi are formed by divisions of the Trachea and carry air into the lungs. There are to bronchi one which enters the right lung and one that enters the left lung. The right bronchus is wider, shorter and more vertical than the left. When inhaled air reaches the bronchi it is warm. Inside the lungs each bronchi divide into lobar bronchi three on the right and two on the left. Bronchioles are very narrow tubes less than 1 millimetre in diameter. There is no cartilage within the bronchioles and they lead to alveolar sacs.   

Lungs occupy most of the thoracic cavity and extend down to the diaphragm. The lungs differ in shape and size and the left lung is smaller than the right.

The lungs are divided into lobes. The left lung contains two lobes and the right has three. Each lobe has an artery and vein and receives air from an individual bronchus.  

The Pleural membrane helps keep the lungs apart and air tight. If one lung is punctured the other one can remain functional and work normally due to being held in a separate cavity.

Pleural cavity is found in between the parietal pleura and the visceral pleura. The pleural cavity is filled with pleural fluid.

The parietal pleura covers the thoracic wall and the top of the diaphragm it then continues around the heart and between the lungs. The parietal pleura is the outermost of the two pleura membranes.

Thoracic cavity I the chamber of the human body that is protects by the thoracic wall. It is separated from the abdominal cavity by the diaphragm.

Visceral pleura is the innermost of the two pleural membranes. It covers the surface of the lung and dips into the spaces between the lobes.

The pleural membranes produce Pleura fluid which fills the pleural cavity between them. The pleural fluid allows the lungs to glide easily over the thorax wall. The pleural fluid also provides the surface tension that keeps the lung surface in contact with the chest wall.

Alveoli have very thin walls which allow the exchange of gases oxygen and carbon dioxide. They also are surrounded by a network of capillaries. There are approximately 3 million alveoli within an average adult lung. There are over 300,000,000 alveoli in the lungs providing a large area for gaseous exchange to occur.

The Diaphragm is a broad band of muscle which sits underneath the lungs, attaching to the lower ribs, sternum and lumbar spine and forming the base of the thoracic cavity. Contraction of the diaphragm increases the volume of the chest cavity which draws into the lungs during inspiration. When the diaphragm is relaxed it involves the recoil of the diaphragm and decreases the volume of the chest cavity pumping out air. The Diaphragm and Intercostals are muscles that aid breathing.

Internal and external intercostals lie between the ribs to help inhalation and exhalation the muscles extend and contract. The external intercostals pull the ribs upwards and outwards increasing the volume of the chest cavity and drawing air into the lungs during inspiration. The internal intercostals draw the ribs downward and  inwards decreasing the volume of the chest cavity and forcing air out of the lungs during expiration

Mechanisms of breathing

Inspiration

When the air pressure inside the lungs decreases, more air flows in. Air pressure inside the lungs is decreased by increasing the size of thoracic cavity. Due to surface tension between the two pleural membranes, the lungs follow the chest wall and expand.

The muscles involved in expanding the thoracic cavity include the diaphragm and the external intercostals muscles. As the diaphragm contracts, it flattens out. As a result, the superior-inferior dimension of the thoracic cavity increases. Contraction of the intercostals muscles lifts the rib cage and pulls the sternum upwards. Although these actions expand the thoracic cavity by only a few millimetres this is enough to increase the thoracic volume by almost 500ml the usual volume of air that enters the lung during normal inspiration.

When at rest the external intercostals muscles contract and the internal intercostals muscles relax. During forced inspirations that occur when exercising. The thoracic volume increases further. 

Expiration

Expiration is a passive process that depends more a lung elasticity than on muscle contraction. As the inspiration muscles relax, the rib cage descends and the lungs recoil. Thus, the thoracic volume decreases.     

During expiration at rest the diaphragm and external intercostals muscles relax and return to their original positions.  When exercising the contraction of the internal intercostals forces air out of the lungs.  

Breathing rate is all controlled by chemoreceptors within the main arteries which monitor the levels of oxygen and carbon dioxide within the blood.

Tidal Volume                                                                                                                       

The amount of air which enters the lungs during normal inhalation at rest. The average tidal volume is 500ml. The same amount leaves the lungs during exhalation.

Inspiratory reserve volume

By breathing in deeply it is possible to take in more than usual 350cm3 of fresh air that reaches the alveoli. This is especially important during exercise. In addition to the tidal volume you can also breathe in up to an additional 3,000cm3 of fresh air. This is known as the inspirational reserve volume. It is the amount air inhaled above tidal volume. 

Expiratory reserve volume

The expiratory reserve volume can be up to 1,500cm3 and is the amount of additional air that can be breathed out after normal expiration. At the end of normal breath, the lungs contain the residual volume plus the expiratory reserve volume. This is the amount of air exhaled above tidal volume during a forceful breath.

Vital capacity residual volume

Vital capacity is the amount of air that can be forced out of the lungs after maximal respiration. The volume is around 4,800cm3. It is the most air you can exhale after taking deepest breath you can. It can be up to ten times more than you would normally exhale.  

Taking Residual volume

Residual volume is the amount of air left in the lungs after maximal respiration, which is when you breath out as hard as you can. The volume is around 1,200cm3 for an average male. If you then exhale as much as possible only the residual volume remains. There is also some air left in the lungs to stop the lungs from collapsing.

Total lung capacity

Total lung capacity is the volume of air contained in the lungs after maximal inspiration. The volume is usually between 4,00cm3 and 8,000cm3, with 6000cm3 for an average sized male.

Spirometry means the measure of breath. It is the most common of the pulmonarary function test, measuring lung function and specifically the measurement of the amount of volume and speed or flow of air that can be inhaled and exhaled. Spirometry is an important tool used for generating pneumotachographs. This is an apparatus for recording the rate of air flow to and from the lungs.  This is helpful in assessing conditions such as asthma.  

Transport of gases and gaseous exchange

The main function of the respiratory system is gaseous exchange. This refers to the process of Oxygen and Carbon Dioxide moving between the lungs and blood

Oxygen

The oxygen absorbed into the blood in the capillaries combines with haemoglobin in the red blood cells form oxyhaemoglobin. The concentration of red blood cells and their haemoglobin affects the amount of oxygen taken up by blood. The red blood cells typically make up 45 per cent of blood volume. These concentrations increase during exercise as more fluid moves from the plasma to the tissues and more water is lost from the plasma as sweat. Long term endurance training can result in an increase in red blood cells and therefore haemoglobin. 

Carbon Dioxide

Carbon dioxide is a waste product of aerobic metabolism and collects in tissues. It is carried to the veins by the cardio vascular system. It is cleared from the tissues by the blood in veins. It is carried by the haemoglobin in red blood cells and diffused into the lungs where it is expired when you breathe out. 

Haemoglobin                                                                                                                      

Haemoglobin is a large protein that can combine reversibly with oxygen. Haemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues to the lungs. Haemoglobin also plays a part in maintaining the shape of red blood cells.

Oxyhaemoglobin                                                                                              

Oxyhaemoglobin is when oxygen attaches to haemoglobin. Haemoglobin forms an unstable reversible bond with oxygen. Blood carries oxyhaemoglobin to tissue  where the oxygen is released during a process known as tissue respiration. Oxyhaemoglobin is bright red and in oxygen unloaded form it is called deoxyhemoglobin and is purple-blue.

Control of breathing

Neural control                                                                                                                                                                                Neurones conduct nerve impulses from the medulla and pons which are both part of the brain stem. The medulla is the lower part of the brain stem responsible for controlling several major autonomic functions of the body and pons are located on the brain stem and responsible for providing linkage between the upper and lower levels of the central nervous system.  In the pons there is the pneumotaxic centre and the apneustic centre. The pneumotaxic centre limits the contraction of the inspiratory muscles and prevents the lungs from overinflating. The appneustic centre stimulates the inspiratory center, prolonging the contraction of inspiratory muscles. Neurones from two areas of the medulla are critical in respiration. These are the DRG, the dorsal respiratory group and the VRG, the ventral respiratory group. The VRG is responsible for rhythm generation it is located in the medulla and contains both inspiratory and expiratory neurons. It is almost in active during normal respiration but is active when increased ventilation. The DRG is a cluster of inspiratoty nerve cells found in the medulla. It sends impulses to the diaphragm and inspiratory intercostals muscles. The DRG also receives impulses form chemoreceptors.        

Chemical control                                                                                                                     

Levels of carbon dioxide and oxygen are constantly changing. In order to monitor this, the body has receptors called chemoreceptors in the medulla, aortic arch and carotid arteries. Chemoreceptors are receptors sensitive to various chemicals in solution, aortic arch is the major artery that has three branches to deliver oxygenated blood throughout the body and carotid arteries feed the head and brain with oxygenated blood. Chemoreceptors in the carotid arteries and aorta, detect the levels of carbon dioxide in the blood and causes these receptors to stimulate the respiratory centre to increase the inspiratory rate. It then sends nervous impulses to the external intercostal muscles and the diaphragm via the phrenic nerve to increase breathing rate and the volume of the lungs during inhalation. Stretch receptors in the walls of bronchi and bronchioles are activated when the lungs expand to their limit. These receptors signal the respiratory center to discontinue stimulation of the inspiratory muscles which allow expiration to begin, this response is called the inflation reflex.

Cardiovascular System

The endocardium lines the inner heart chambers and covers heart valves and is continuous with the inner lining of blood vessels. Purkinje fibers are located in the endocardium. They participate in the contraction of the heart muscle. The endocardium also allows the blood to flow freely

Myocardium is the middle layer of the heart wall. It is composed mainly of cardiac muscle and forms the bulk of the heart. The myocardium is the layer that contracts and is surrounded by the endocardium and the epicardium. Myocardium stimulates heart contractions to pump blood from the ventricles and relaxes the heart to allow the atria to receive blood. These contractions produce a heartbeat. The beating of the heart drives the cardiac cycle which pumps blood to cells and tissues of the body.

The epicardium is a superficial layer of the serous pericardium, a double-layered envelope surrounding the heart it is an outer protective layer that prevents over extension during heart beats

Bicuspid valve is situated between the left atrium and the left ventricle. It allows blood to flow one way only, from the left atrium into the left ventricle. The Tricuspid valve is situated between the right atrium and the right ventricle. It allows blood to flow from the right atrium into the right ventricle. The job of the bicuspid and tricuspid valves is to prevent backflow into the atria when the ventricles are contracting and forcing blood into the circulatory system.

Chordae tendineae are chord-like tendons that connect to the bicuspid and tricuspid valves. They prevent the valves from turning inside out.

The pulmonary vein carries oxygen rich blood from the lungs to the left atrium of the heart. There are four pulmonary veins which extend from the left atrium to the lungs. They are the right superior, right inferior, left superior, and left inferior pulmonary veins.

The pulmonary artery carries deoxygenated blood from the heart to the lungs it is the only artery in the body that carries deoxygenated blood.  The main pulmonary artery extends from the right ventricle of the heart and branches into left and right pulmonary arteries. The left and right pulmonary arteries extend to the left lung and right lungs.

Vena cava are the two largest veins in the body. These blood vessels carry de-oxygenated blood from various regions of the body to the right atrium of the heart. As the de-oxygenated blood is returned to the heart and continues to flow through the cardiac cycle, it is transported to the lungs where it becomes oxygenated. The blood then travels back to the heart and is pumped out to the rest of the body by the aorta. Superior vena cava is a large vein that carries deoxygenated blood from the upper half of the body to the right atrium. Inferior vena cava is the large vein that carries deoxygenated blood from the lower half of the body into the heart. It enters the right atrium at a lower right posterior side of the heart.

The aorta is the largest artery in the human body originating from the left ventricle of the heart down to the abdomen where it branches off into smaller arteries. The aorta transports oxygenated blood to all parts of the body.

The heart is divided into four chambers that are connected by heart valves. The upper two heart chambers are called atria. Atria receive blood returning to the heart from the body and ventricles pump blood from the heart to the body. The atria receive and collect the blood coming to the heart. They then deliver blood to the lower left and right ventricles which pump blood away from the heart through powerful, rhythmic contractions. The atria are the receiving chambers for blood returning to the heart from the body. They need to contract only minimally to push blood into ventricles so the atria are relatively small. The right atrium receives blood returning to the heart from the superior and inferior vena cava. The superior vena cava returns de-oxygenated blood the upper part of the body to the right atrium. The inferior vena cava returns de-oxygenated blood from the lower body regions to the right atrium. The left atrium receives blood returning to the heart from the pulmonary veins. The pulmonary veins extend from the left atrium to the lungs and bring oxygen-rich blood back to the heart.

The lower two chambers of the heart are called ventricles. The right ventricle receives blood from the right atrium and pumps blood into the pulmonary artery which routes the blood to the lungs where gas exchange occurs. The left ventricle receives blood from the left atrium and pumps blood into the aorta the largest artery which takes oxygenated blood away from the heart and around the body. This ventricle has a thick wall because it has to pump blood around the body    

The aortic valve is one of the four valves in the heart, this valve is situated at exit of the left ventricle of the heart where the aorta begins. The aortic valve lets blood from the left ventricle be pumped up into the aorta but prevents blood once it is in the aorta from returning to the heart. The pulmonary valve stands at the opening from the right ventricle. It lets blood head in the right direction and keeps it from sloshing back from the pulmonary artery into the heart. The aortic and pulmonary valves guard the bases of the lager arteries attached to the ventricles and prevent backflow into ventricles. The aortic and pulmonary valves are known as semilunar valves. Theses valves are forced open as the blood rushes past them. When the ventricles relax and the blood flows backwards toward the heart the valves close.  

Blood vessels

Arteries

Arteries take oxygenated blood away from the heart to be delivered around the body The arteries deliver the oxygen rich blood to the capillaries where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste  blood to the veins for transport back to the lungs and heart. The large artery that leaves the right ventricle is called the pulmonary artery and the artery that leaved the left ventricle is the aorta. Pulmonary arteries carry blood from the heart to the lungs where the blood picks up oxygen. The oxygenated blood is then returned to the heart via the pulmonary veins. The aorta is the main systemic artery and the largest artery of the body. It originates from the heart and branches out into smaller arteries which supply blood to the head region, the heart itself and the lower regions of the body. The muscular wall of the artery helps the heart pump the blood. When the heart beats the artery expands as it fills with blood. When the heart relaxes the artery contracts which has a force that is strong enough to push the blood along. This rhythm between the heart and the artery results in an efficient circulation system.The blood moves under pressure into smaller arteries, finally reaching the smallest branches known as arterioles. As the arteries devide further they become smaller and smaller, until they are classed as arterioles.

Arterioles

These are smaller versions of arteries and they connect arteries to capillaries. Major arterioles are thick walled with small diameters. Arterioles are responsible for blood flow and blood pressure. They contain muscles that allow the vessel to constrict and stop blood flow to certain areas if it is not required. 

Capillaries

Capillaries are the smallest blood vessels in the body. They are microscopic. They are just one cell thick to allow capillary exchange. A capillary bed is the capillary structure found in a body organ or skeletal muscle. Capillary beds contain thousands and millions of capillaries for each muscle structure or body organ. As blood passes through the muscle or organ capillary system, it gives up oxygen and nutrients and takes in carbon dioxide and other waste products. Each capillary connects to a vein and an arterial end which connects to an artery. Capillaries are also involved in the body's release of excess heat. During exercise, for example, your body and blood temperature rises. To help release this excess heat, the blood delivers the heat to the capillaries which then rapidly release it to the tissue.

Veins

Veins are similar to arteries but they transport blood at a lower pressure so they are not as strong as arteries. Veins also differ in that they are supported by valves. Valves prevent a backflow of blood and ensure that the blood in veins is not under pressure. The vein valves are necessary to keep blood flowing toward the heart, but they are also necessary to allow blood to flow against the force of gravity. For example, blood that is returning to the heart from the foot has to be able to flow up the leg. Veins act as low pressure reservoirs and move stored blood into general circulation during exercise. Pulmonary veins  carry oxygenated blood from the lungs to the left atrium of the heart. Systemic veins return deoxygenated blood from the rest of the body to the right atrium of the heart. Superficial veins are located close to the surface of the skin and are not located near a corresponding artery. Deep veins are located deep within muscle tissue and are typically located near a corresponding artery

Venules

The smallest veins in the body are called venules. They receive blood from the arteries via the arterioles and capillaries. But unlike capillaries venules have some connective tissue in their walls. Venules collect the outflow of blood from the capillary bed at low pressure. The venules branch into larger veins which eventually carry the blood to the largest veins in the body, the vena cava. The blood is then transported from the superior vena cava and inferior vena cava to the right atrium of the heart.

Vasodilatation and Vasoconstriction

Blood flow is controlled by pressure, this is achieved by pressure by the vasoconstriction and vasodilatation

Vasodilatation is the widening of blood vessels due to the relaxation of smooth muscular vessel walls, particularly in the large and small arterioles and large veins. Vasodilatation involves an increase in the diameter of the blood vessels resulting in an increased blood flow to the muscle area supplied by the vessel. Opening the vessels to the skin allows the heat to be carried to the surface of the body where it escapes into the atmosphere. This is why you go red when you exercise.  

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the smooth muscular wall of the vessels, particularly the large arteries, small arterioles and veins. Vasoconstriction involves a decrease in the diameter of a blood vessel walls resulting in the reduction of blood flow. In cold weather blood flow to the skin is decreased through vasoconstriction meaning that less heat is lost to the atmosphere.

How the heart works

Cardiac cycle

The cardiac cycle is the sequence of events that take place during one complete heart beat. There are 4 stages and each stage depends on whether the heart chambers are filling with blood while the heart is relaxing.

The four stages of the cardiac cycle are

1.     Atrial diastole. This is where the atrium is relaxed and receives the blood

2.     Atrial systole. This is where the atrium contracts and pushes blood down into the ventricles

3.     Ventricular diastole. This is where the ventricle is relaxed and where it receives the blood from the atrium

4.     Ventricular systole. This is where the ventricle contracts and pushes blood into the aorta and pulmonary vein

During the diastole phase, the atria and ventricles are relaxed. Blood flows into the right and left atria. The sino atrial node contracts which makes the atria contract. The valves located between the atria and ventricles are open, allowing blood to flow through to the ventricles the semilunar valves close to prevent blood from back flowing back into the atria 

During the systole phase, the ventricles contract pumping blood into the arteries. Atrioventricular valves close and semilunar valves open. The right ventricle sends blood to the lungs via the pulmonary artery. The left ventricle pumps blood to the aorta.

SAN sino atrial node

SA Node is a pacemaker in the atrial wall below the opening of the superior vena cava. When the sinoatrial node contracts it generates nerve impulses that travel throughout the heart wall It sends electrical impulse that triggers each heart beat. The impulse spreads through the atria. This causes both atria to contract. The SA node is located in the upper wall of the right atrium. It is composed of nodal tissue that has characteristics of both muscle and nervous tissue.

AVN atrio ventricular node

The atrio ventricular bundle is a bundle of specialised fibres in the heart that transmit the cardiac impulses form the atria to the ventricles. The atrio ventricular node is found in the right atria. The atrio ventricular node in turn sends an impulse through the nerve network to the ventricles. When the impulses from the sino atrial node reach the atrio ventricular node they are delayed for a sight second. This delay allows the atria to contract and empty their contents first.  

Bundle of his

The impulses are then sent down the atrioventricular bundle. This bundle of fibres branches off into two bundles and the impulses are carried down the centre of the heart to the left and right ventricles.

Purkinje fibres

These are found in the inner ventricular walls of the heart beneath the endocardium. At the base of the heart the atrioventricular bundles start to divide further into Purkinje fibres. When the impulses reach these fibres they trigger the muscle fibres in the ventricles to contract. These fibres are specialised myocardial fibres that conduct an electrical stimulus, which make the heart contract in a rhythmical way.

Autonomic nervous system

Sympathetic

When the sympathetic nervous system is activated by emotional or physical stressors such as exercise or anxiety, sympathetic fibres release chemical called norepinephrine which is a chemical transmitter substance realised at nerve endings to increase the heart rate. The chemoreceptor’s detect carbon dioxide in the blood and sends a signal to the medulla which then sends of a signal to the sympathetic nervous system that controls adrenaline. The sympathetic nervous systems then release adrenaline into the heart which makes it increase its flow in blood and increases in cardiac output/stroke volume which means there’s an increase in heart rate.

Parasympathetic

The parasympathetic system opposes sympathetic effects and effectively reduces heart rate when a stressful situation has passed. Parasympathetic responses are managed by a chemical called acetylcholine, acetylcholine is a chemical transmitter substance released at nerve endings to relax the heart rate.  Barorecpetor’s detect change in blood pressure and sends a signal to the parasympathetic nervous system that controls acetylcholine. The parasympathetic nervous system then releases acetylcholine into the heart which makes the heart rate decrease.   

Muscular System

Muscles of the body

Muscle origins and insertions

The origin of a muscle is the point at which it attaches to a bone (usually) or another muscle. The structure that the origin is attached to is not moved by the contraction of the muscle^. The opposite end of the muscle is called the insertion. This definition means that there is a functional aspect to the definition of a muscle's origin and insertion. Both origin and insertion are important for understanding the physiological function of the muscle.

Muscle Functions

Agonist or prime mover

This is the muscle which is responsible for movement and lengthens during contraction

Antagonist

This is the muscle assisting the movement and lengthens during contraction.

Fixator

These are the muscles supporting the movement and providing a base for the other muscles to pull against. Fiaxtors stabilise the origin. They stabilise the origin so that the agonist can achieve maximum and effective contraction.

Synergists

These are the other muscles which prevent any unwanted movement during the action. They work together to enable the agonists to operate more effectively. Synergists add a little extra force to the same movement to help agonists. 

Origin

This is the part of the body usually a bone where the muscle attaches and does not move when the muscle contracts

Insertion

This is the part of the body where the muscle attaches and moves when the muscles contracts.

Types of muscles

Cardiac

 This type of muscle only occurs in the heart and forms the bulk of the wall of the heart. It is specifically found in the myocardium, which is the middle and the thickest layer of the heart wall. This muscle is responsible for pumping blood through the heart chambers and into the blood vessels the heart beats non stop about 100,000 times each day, it can do this because of the cardiac muscle. Its does this by contracting when it is relaxed it fills your heart with blood. Unlike other muscles the cardiac muscles never gets tired, it works constantly without pausing to rest. It consists of specialised fibres which do not tire. The cardiac muscle is also controlled but it is also an involuntary muscle which can continue to function without the generation of nerve impulses, so it works automatically. The heart muscle has a built in pacemaker known as the sino-atrial node. The sino-atrial node controls the rate of the heartbeat. The rate of which the heart beats is involuntary but it can be influenced by factors such as stress, medication, illness and exercise. These influences change the reaction of the nervous system and the hormones that are released, this results in a change of heart rate. Cardiac muscle cells rely on a blood supply to deliver oxygen and nutrients and to remove waste products like carbon dioxide. The cardiac muscle is adapted to be highly resistant to fatigue, so it has a high number of mitochondria. The cells are y shaped and are shorter and wider than skeletal muscle cells. Some of the cardiac muscle cells are auto-rhythmic. Cardiac muscle is reliant on oxygen to function. It also has its own blood supply.  

Skeletal

 Skeletal muscle tissue are named for there location, they are attached to bones by tendons. Skeletal muscles cover your skeleton which gives your body its shape. When you work out you will gain good muscle tone and shape and it is skeletal muscle you are training.The entire muscle is surrounded by a layer of connective tissue which is called the epimysium. The epimysium is a connective tissue that surrounds and holds muscles in the body. The epimysium provides a smooth surface which allows other muscles to glide on. Within the muscles are large bundles of fibres or fasiculi surrounded by the perimysium. The perimysium is a membrane that protects and supports groups of fibres within the skeletal muscles. Each individual fibre is wrapped by a thin layer of connective tissue layers which are connected to each other so that when the muscle fibres contract they are ultimately linked to the tendons, this creates movement. Skeletal muscles control movement so you control what they do and they are voluntary. Most of your body movements are controlled by skeletal muscles contracting. Skeletal muscle is also important for keeping your bones in the correct position and prevents your joints from dislocating. Skeletal muscles come in many different sizes and shapes to allow them to do many types of jobs. Some of your biggest and most powerful muscles are in your back, near your spine. These muscles help keep you upright and standing tall. They also give your body the power it needs to lift and push things. They also generate heat as a by product from muscle activity, this is heat that keeps your normal body temperature. Skeletal muscles also have the ability to stretch or contract and still return to their original shape. Two main types of striated skeletal muscle can be distinguished on the basis of their speed of contraction. Type1 and type 2.        

Smooth

This is concerned with the movements of internal organs. So it is found in the walls of organs like the stomach, the intestines, blood vessels and urinary bladder. Smooth muscles are used for many functions. Muscles in your bladder wall contract to expel urine from your body. When they're relaxed, they allow you to hold in urine until you can get to the bathroom. Then they contract so that you can push the urine out. Smooth muscles in a woman's womb help to push babies out of the body during childbirth and the muscular walls of your intestines contract to push food through your body. Smooth muscles work in your eyes as well, the muscles help the eye focus.  You can see rows of smooth muscle cells running circularly around blood vessels, especially prominent around muscular arteries Smooth muscles are arranged in layers with the fibres in each layer running in a different direction. This makes the muscle contract in all directions.  Smooth muscles are involuntary muscles and work automatically. I.e. you’re not under conscious control. Your brain and body tell smooth muscles what to do without you even having to think. It is well adapted to producing long slow contractions. Some smooth muscle tissue can undergo hypertrophy. The structure and function is basically the same in smooth muscle cells in different organs. Most smooth muscle is of the single-unit variety, that is, either the whole muscle contracts or the whole muscle relaxes. Smooth muscle containing tissue tends to demonstrate greater elasticity and function within a larger length-tension curve than striated muscle. This ability to stretch and still maintain contractility is important in organs like the intestines and urinary bladder. In the relaxed state, each cell is spindle-shaped, 20-500 micrometers in length. Smooth muscle fibres contain no striations and sarcomeres.      

The smooth muscle works like the sliding filament to contract the muscle cells.  Intermediate filamets (desmin and vimentin) help with the contraction by pulling the cell ends in (shortening the cell).

Differences and similarities of the type of muscles  

A similarity of cardiac muscle and skeletal muscles is that they are multinucleate and striated. This means they have one or more nucleus in one cell and have fibres that have combined into parallel fibres. This is different to smooth muscles because they are not striated or multinucleate. A similarity of cardiac and smooth muscle is that they both have nuclease centrally located. Cardiac muscle differs from both skeletal muscle and smooth muscle because it has cells that are branched and are joined to one another by an intercalated disk. Intercalated disks allow communication between the cells. Cardiac muscle also differs from the other two muscle types in that contraction can occur even without an initial nervous input, these cells are called pacemaker cells. Another similarity between cardiac and smooth muscles are that they both are involuntary and work automatically and a skeletal muscles is voluntary e.g. when you kick a ball you have to think about it and this will allow your skeletal muscles contract to allow movement. A difference of all the muscles types are that they are all found in different places. The skeletal muscles are found on the skeleton, the cardiac muscle is found in the heart and the smooth muscles are found in internal organs. Another difference is that they all do different jobs. The skeletal muscle makes you move and protects your skeleton, the cardiac muscle pumps blood around the body and fills your heart with blood and the smooth muscles help push out babies and push food through your body. The cardiac muscle never gets tired, it works constantly without pausing to rest.    

Muscle fibre types

Type 1 (slow twitch or slow oxidative fibres)

Type 1 fibres are also known as slow twitch or slow oxidative fibres. They contain large amounts of myoglobin which make them red in colour, they also have many mitochondria and many blood capillaries. This type of fibre split ATP at a slow rate and has a slow contraction velocity. These fibres are very resistant to fatigue and have a high capacity to generate ATP. The slow muscles are more efficient at using oxygen to generate more fuel (known as ATP) for continuous, extended muscle contractions over a long time. Slow twitch muscle fibres use oxygen for power. Type 1 fibres suit activates that need endurance. Athletes such as marathon runners have a high number of this type of fibre. Marathon runners have a high rate of type 1 fibres because they run for a long time at a steady speed without getting fatigue. Paula Radcliffe would have a high number of type 1 fibres because she is a marathon runner and has to run for a long time without getting fatigue. You can tell she has a high rate of type 1 fibres because she can run for a long time at the same speed without getting fatigue. Also slow twitch fibres are great at helping athletes bicycle for hours and long distance swimmers because they can go for a long time without getting fatigue. Type 1 fibres are generally employed at the beginning of exercise, regardless of the intensity of exercise.

Type 2 A fibres (fast twitch or fast oxidative)

These fibres are called type 2 A or fast twitch or fast oxidative fibres. They contain very large amounts of myoglobin, mitochondria and blood capillaries like type 1 fibres. They also are red in colour like type 1 fibres. These fibres split ATP at a very high rate and also have a very high capacity for generating ATP. They have a fast contraction velocity and are resistant to fatigue. They can use both aerobic and anaerobic metabolism almost equally to create energy. In this way, they are a combination of Type I and Type II muscle fibers.  400m runners would have a high number of type 2A fibres because the race is not completely aerobic or anaerobic it’s in between, so they have to run at a fast pace for a while. Michael Johnson would have a lot of type 2A fibres because he was a 400m runner and had to run intensely for 400meters.   


Type 2 B fibres (Fast twitch or fast glycolytic fibres)

These fibres are also called fast twitch or fast glycolytic fibres they contain a low content of myoglobin so they are white in colour. They also contain low mitochondria and low blood capillaries content but have large amounts of glycogen. Type 2 B fibres generate ATP anaerobically and are not able to supply skeletal fibres continuously with ATP so fatigue easily. The purpose of this type of muscle is to provide rapid movement for short periods of time. Fast twitch muscles do not use oxygen - they use glycogen. Reactions using glycogen require anaerobic enzymes to produce power. They split ATP at a fast rate and have a fast contraction velocity. 100m sprinters have a high rate of type 2B fibres because they sprint for a short time but intense. Usain Bolt will have a high rate of type 2B fibres because he is a 100m sprinter and has to sprint intensely for 100m, you can tell he has a high rate of type 2B fibre because he looks fatigue after a race.      

Differences and similarities of muscle fibre types

A similarity between Type 1 fibres and Type 2A fibres are that they both contain a large amount of myoglobin. This makes both fibres red in colour. Type 2B is different to these two fibres because it is white in colour because it has a low content of myoglobin. It is also different to type 1 and type 2A because it has a low mitochondira and blood capillaries content and the other two have a high content of mitochondria and blood capillaries. A similarity between type 2A and type 2B are that they both split ATP at a very fast rate and have a fast contraction velocity. Type 1 is different to both other fibres because it splits ATP at a slow rate and has a slow contraction velocity. Another similarity between type 1 and type 2A fibres are that they both are resistant to fatigue. This is different to Type 2B because they fatigue easily. Another similarity between type 1 and type 2A fibres are that they generate ATP at a very high capacity but type 2B is different because they generate ATP anaerobically. A difference between all muscle fibre types is that type 1 fibres are found in large numbers in the neck, type 2A fibres are infrequently found in humans and type 2B fibres are found in large numbers in the muscles of the arms. Type 2 fibres adapt to high intensity anaerobic exercise involving explosive or powerful movements, but they are also increasingly employed during low intensity endurance workout as performer fatigue increases.    

Muscle Contraction

Isotonic contraction

Isotonic contractions are those which cause the muscle to change length as it contracts and causes movement of a body part

Concentric

This is the main type of muscle contraction. In this type of muscles contraction the muscles gets shorter in length and the two ends of the muscle move closer together. This happens when the muscle contracts. This type of contraction is most common type of muscle contraction and occurs frequently in daily and sporting activities.

 An example of an isotonic contraction is when we flex the bicep muscle. The bicep muscle shortens as it contracts, the two ends of the muscle gets closer. Another example is a squat and a pull up.  Concentric contractions are common to many sports in which you need to generate a lot of power or explosive force.

Eccentric

Eccentric contractions are the opposite of concentric. So in this type of muscle contraction the muscle increases in length as it contracts. The two ends of the muscle move further apart. This type of contraction is normally evident in a

Downwards phase in a movement. An example is lowering phase of a bicep curl. Another example is when when kicking a football the Hamstrings contracts eccentrically to decelerate the motion of the lower leg. Another example is walking .

Isometric

In this type of muscle contraction the muscle stays the same length and doesn’t change shape. There is no movement of the muscle or body part that is attached. Balancing or pushing against something is an example of an isometric contraction so a ski squat is a good example. Another example is when you grip something e.g. a tennis racket. There is no movement in the joints of the hand, but the muscles are contracting to provide a force sufficient enough to keep a steady hold on the racket. Another example is during the crucifix position on the rings in gymnastics. Tension occurs in the muscle but the distance between the ends stay the same. Other examples are a wall sit, holding free weights at a static position and the plank.     

Differences and similarities of muscle contractions

A difference between the muscle contractions is the concentric contraction gets shorter in length when they contract, eccentric contractions get longer when they contract and isometric contractions stay the same when they contract. 

Muscle Structure

Each fibre itself is made up of smaller fibres called myoribrils. It is in here that the contractile process takes place in very small units called sarcomeres

Sarcolemma is the cell membrane.

Sarcoplasmic reticulum is a network of internal membranes that run throughout the sarcoplasm and are responsible for the transportation of materials within the cell.

T vesicle is a sac containing chemicals needed to start muscle contraction.

Sliding filament theory

At first the muscle is relaxed. To get the muscle to contract the actin has to be brought close together. To get the actin together the myosin has cross bridges which pull them near each other but the actin has proteins tropmyosin and troponin which stop the cross bridges from pulling them together. Actin is a blue filament and myosin is a green filament, they work together to produce these contractions, as they are arranged in filaments that slide past each other, giving sliding filament theory its name Troponin and tropomyosin are proteins that form part of the thin or actin filament. The tropomyosin is rod shaped and stiffens the actin core. Tropoin binds to the tropomyosin and helps it bind to the actin. To get rid of the troponin and tropmyosin, calcium (Ca++) which is an Ion comes along and breaks them off which allows the cross bridges to pull the actin together which makes the muscle contract. The skeleton acts as a major mineral storage site for the element and releases calcium ions into the bloodstream under controlled conditions. The ions are stored in the sarcoplasmic reticulum of muscle cells.    

Joints And Their Function

Types of joints

Any point in the body where two or more bones meet is classed as a joint.

Fixed joints

Fixed or fibrous joints allow no movement at all. Fixed joints are held together by a tough fibre that permits no movement and these joints also have no joint cavity. An example of a fixed joint is the skull because it can’t be moved which allows it to protect the brain. An example of fixed joint used in sport is football because you header the ball with your head.

Slightly movable joints

Slightly movable or cartilaginous joints allow very limited movement. Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Ligaments or cartilage stops them from moving the joints too far. The joints have a cushion of cartilage in between the bones with bones vesting on these beds of cartilage. The cushion of cartilage stops the bones from rubbing together. An example of slightly movable joints is the joint between two vertebrae only a small amount of movement is permitted, and indeed necessary between the bones, but excessive movement would cause damage to the spinal cord. An example of when you use slightly movable joints in sport is in gymnastics. When you do stretch and do flips. 

Synovial joints

Synovial joints are freely movable and the most common type of joint. The Synovial joint has existence of capsules surrounding the articulating surfaces of a Synovial joint and the presence of lubricating Synovial fluid within that capsule. Examples of Synovial joints are hinge, ball and socket, pivot, condyloid, saddle and gliding.

Differences and similarities of the types of joints

The similarities of synovial joints and slightly movable joints are that they both can move in different directions, but fixed joints cannot move at all because they are fused together and have no joint cavity. Differences between synovial and slightly movable joints are that synovial joints are freely movable and slightly movable joints allow very limited movement, synovial joints are also more common in the body than slightly movable joints and fixed joints. Ligaments or cartilage stops slightly movable joints from moving too far, this is different to fixed joints because they are held together by tough fibre and different to synovial joints because they have capsules surrounding the articulating surfaces. Slightly movable joints also have a cushion of cartilage in between the bones, which stops them from rubbing. Fixed joints are fused together so they cannot rub together and synovial joints have a lubricating synovial fluid. A similarity of these joints is that they achieve movement at the point of contact of the articulating bones.

Hinge

The hinge joint allows movement similar to a hinge. It has a convex and concave surface and allows movement in one plane about a single axis. It allows flexion and extension movements. Examples of a hinge joint are the elbow, knee and wrist joints. An example of when the hinge joint is used in sport is football. When a player kicks a ball they use their knee joint, which flexes and then extends.   

Ball and socket

The ball and socket joint allow the greatest range of movement. It moves three planes and three axis. It allows flexion, extension, rotation, abduction, adduction and circumduction. Examples of ball and socket joints are the hip and shoulder. An example of when the ball and socket joint is used in sport is cricket. When a player is bowling they use their shoulder which goes all they way round.

Pivot

The pivot joint allows rotation of one bone around another. Pivot joints are found in humans in the neck, forearms, knees, and other parts of the skeletal system that are able to rotate. The pivot joint in the neck allows the head to move side to side. Example of a pivot joint in sport is when you are stretching and you turn your head side to side.

Condyloid

The condyloid joint allows movement in two planes and can produce flexion, extension, abduction and adduction movements. Examples of a condyloid joint are your wrists. Example of a condyloid joint used in sport could be basketball. When the players are dribbling with the ball they are using their wrist.

Saddle

This joint allows movement in one plane and one axis. The bones in a saddle joint can rock back and forth and from side to side, but they have limited rotation. The thumb is an example is a saddle joint. Example of a saddle joint used in sport is in a thumb war. The thumb is moving side to side an back and forth in a thumb war.

Gliding

The gliding joint allows one bone to slide over another. These occur between the surfaces of two flat bones that are held together by ligaments. Some of the bones in your wrists and ankles move by gliding against each other. Examples are the vertebrae and joints between the carpals and tarsals.

Differences and similarities of synovial joints

Hinge, pivot, ball and socket, saddle, conyloid and gliding joint all have similarities and differences. A similarity of all these synovial joints are that they all can move and a difference between all these joints are that they have a different range of movement and move in different directions.

Hinge – Flexion and Extension

Pivot - Rotation of one bone around another

Ball and socket – Flexion, Extension, Adduction, Abduction, Internal and External Rotation

Saddle – Flexion, Extension, Adduction, Abduction and Circumduction

Conyloid – Flexion, Extension, Adduction, Abduction and Circumduction

Gliding - Gliding movements

Another similarity is that all the joints are in the human body. A difference is that they are all in different places.

Movement at joints

Flexion

Flexion is the bending movement that decreases the angle between two parts. The angle is 180 degrees and gets decreased in size. Bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed.

Extension

Extension is the opposite of flexion and is where a straightening movement that increases the angle between body parts. In a conventional handshake, the fingers are fully extended.

Hyper-Extension

Hyper-extension is the movement or extension of joints, tendons, or muscles beyond the normal limit or range of motion which is 180 degrees.  

Plantar flexion

Plantar flexion is flexion of the entire foot and pointing your toes. This occurs from the ankle. Pressing a car pedal down is an example of plantar flexion.

Dorsiflexion

Dorsiflexion is extension of the entire foot and brining your toes up. Taking your foot off a car pedal is an example of dorsiflexion.  

Pronation

Pronation is when you rotate your palms to a face down position and when your arms rotate inwards. This can only be done if your arms are half flexed.  

Supination

Supination is the opposite of pronation. It’s when your palms are facing upwards and when your arms bones rotate outwards.

Abduction

Abduction is when a limb in your body is taken away from midline of your body. Raising the arms laterally, to the sides, is an example of abduction.

Adduction

Adduction is when you bring a limb towards the centre line in of your body. Dropping the arms to the sides, or bringing the knees together, are examples of adduction. The fingers or toes, adduction is closing the digits together.

Sporting examples

Bicep curls

When doing bicep curls your hinge joint in your elbow allows your arms to flex and extend. Your hinge joint is attached to the humerus, radius and ulna. When you are bringing the weights up towards you, your hinge joint is allowing your elbow to flex, decreasing a 180 degrees angle and making your forearm come up towards you. When you bring the weights down, your hinge joint is allowing your elbow to extend, bringing back the arm to 180 degrees

Squat

When doing a squat your hinge joint in your knee allows your legs to flex and extend. Your hinge joint is attached to the tibia and femur. When doing a squat you go down like you’re sitting in a chair, your hinge joint is allowing your knees to flex, decreasing a 180 degrees angle.  When you are going back up your hinge joint is allowing your knees to extend, bringing back your legs to 180 degrees.

Heading

When you header a ball in football you are using your pivot joint in the top of your neck, this allows your head to move side to side. This means you can get a better movement of the head to header the ball where you want it.  

Bowling in cricket

When you bowl in cricket you’re using your ball and socket joint in your shoulder. The ball and socket joint in your shoulder allows you to rotate your arm all the way round, so it extends, hyper-extends and flexes all in one. This allows the bowler to bowl faster. Bowlers also can put spin on the ball, they can do this by twisting their wrist which has a conydloid joint. 

 Arm raises

When performing an arm raise laterally you are using your ball and socket joint in your shoulder. When performing lateral arm raises you are bringing your arms away from the midline of your body which is abduction. Doing lateral arm raises also makes you do adduction because you’re bringing your arms back to the centre line of your body.   

Calf raises

When doing calf raises you are using a hinge joint in your ankle. When doing calf raises you are doing flexion and extension with your foot. When you do a calf raise you push the weight up by using plantar flexion and when you go down its dorsiflexion.

Baseball Catch  

When catching in baseball you are using your saddle joint and you condlyoid joint in your hand. You are using these joints when you catch the ball. You do all types of movement to catch the ball, but when it’s in your hand and you clench your fist you are doing flexion