- Created by: zoe harris
- Created on: 15-03-11 17:06
Joints and movement
- muscles bring about movement at a joint
- muscles can only pull they cannot push so two muscles are needed to move a bone back and forth.
- a pair of muscles like these are called antagonistic.
- a muscle that contracts to cause extension of a joint is called an extensor
- a flexor contracts to reverse the movement
- the hip, knee and ankle joints are examples of synovial joints
- the bones that move in the joint are separated by a cavity filled with synovial fluid.
- the bones are held in position by ligaments that control and restrict movement.
-tendons attach muscles to the bones
- cartilage protects bones within joints.
Joints and movement continued
At a joint there is:
- tendon: joins muscle to bone
- cartilage: absorbs synovial fluid and acts as shock absorber
- pad of cartilage: gives additional protection
- fibrous capsule: encloses joints
- ligament: joins bone to bone and is strong and flexible
- synovial membrane: secretes synovial fluid
- synovial fluid: acts as lubricant
How do muscles work?
- muscle is made up of bundles of muscle fibres, each fibre is a single muscle cell
- each muscle cell is multinucleate (has more than one nucleus) this is because a single nucleus could not effectively control the metabolism of such a long cell.
- Tendons connect muscle to bone
- the muscle is made up of bundles of muscle fibres. these are bound together by connective tissue.
- each muscle fibre is a single muscle cell surrounded by a cell surface membrane.
- Inside the muscle fibre is the cytoplasm containing mitochondria and the other organelles found in a cell.
- Within each muscle fibre there are also numerous myofibrils, each is composed of repeated contractile units called sarcomeres.
Inside a muscle fibre
- each muscle fibre is made up of myofibrils
- these are made up of contractile units called sarcomeres
- the sarcomere is made up of two types of protein, mainly actin, and thicker ones made from the protein myosin.
- contractions are made by the sliding of these protein filaments within the muscle sarcomeres.
- where actin filaments appear on their own there is a light band on the sarcomere.
- where both actin and myosin filaments occur there is a dark band.
- there only myosin filaments occur there is a intermediate-coloured band.
- when the muscle contracts the dark band overlaps the intermediate band shortening the length of the muscle and the sarcomere.
How the sarcomere shortens
When a nerve impulse arrives at a neuromuscular junction calcium ions are released from the sarcoplasmic reticulum. This moves the protein filaments in these steps:
- Ca2+ attaches to the troponin molecule, causing it to move.
- because of this the tropomyosin on the actin filament moves its position, exposing myosin binding sites on the actin filaments.
- Myosin heads bind with myosin binding sites on the actin filament, forming cross-bridges.
- When the myosin head binds to the actin, ADP and Pi on the myosin head are released.
- the myosin changes shape, causing the myosin head to nod forward. This moves the filaments and the actin moves over the myosin.
- An ATP molecule binds to the myosin head. this causes the myosin head to detach.
How the sarcomere shortens continued
- An ATPase molecule on the myosin head hydrolyses the ATP, forming ATP and Pi.
- This hydrolysis causes a change in the shape of the myosin head. It returns to its upright position.The cycle starts again.
The minimum energy requirement of the body at rest to fuel basic metabolic processes is called your BMI.
- a series of enzyme-controlled reactions, known as respiration is linked to ATP synthesis.
- cells use the molecule ATP as an energy carrier molecule.
- ATP is created from ADP and inorganic phosphate (Pi)
- when one phosphate group is removed from the ATP by hydrolysis, ADP forms.
when removed the phosphate group becomes hydrated, a lot of energy is released as bonds form between the water and phosphate.
ATP in water -> ADP in water + hydrated Pi + energy transferred
In low intensity exercise enough oxygen is supplied to cells to enable ATP to be regenerated through aerobic respiration of fuels.
C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy released
- in aerobic respiration the hydrogen stored in glucose is brought together with oxygen to form water again.
- there is a release of energy that can be used to generate ATP.
- glucose and oxygen are not brought together directly because this would release large amounts of energy too quickly and could damage the cell.
- glucose is split apart in a series of small steps. Carbon dioxide is released as a waste product.
- hydrogen from the glucose is reacted with oxygen to release large amounts of energy as water s formed.
The initial stages of carbohydrate breakdown occur in the cytoplasm, including the sarcoplasm of muscle cells.
- two phosphate groups are added to glucose from two ATP molecules, this increases its reactivity. It can now split into two molecules of 3-carbon (3C) compounds.
- each intermediate 3C sugar is oxidised producing a 3-carbon compound, pyruvate.
- two hydrogen atoms atoms are removed during the reaction and taken up by the coenzyme NAD, a non-protein organic molecule.
- phosphate from the intermediate compounds is transferred to ADP, creating ATP.
- this is called substrate level phosphorylation, because energy for the formation of ATP comes from the substrates ( the intermediate compounds.)
- two ATP's are made, two pairs of hydrogen atoms and two molecules of 3-carbon pyruvate.
The link reaction
If oxygen is available the 3C pyruvate created at the end of glycolysis passes into the mitochondria. There it is completely oxidised, forming carbon dioxide and water.
-decarboxylated (carbon dioxide is released as a waste product)
- dehydrogenated (two hydrogens are removed and taken up by the coenzyme NAD)
The 2 carbon molecule made combines with coenzyme A to form acetyl coenzyme A (or acetyl CoA) the two hydrogens released are involved in ATP formation. The coenzyme A carries the 2C acetyl groups to the Krebs cycle.
- each glucose provides two pyruvates so the cycle turns twice per glucose.
- the hydrogens are taken up by hydrogen acceptors (FAD and NAD which then become reduced FAD and reduced NAD)
The Krebs cycle
The Krebs cycle continued
The Krebs cycle takes place in the mitochondrial matrix, where the enzymes that catalyse the reactions are located.
- each 2-carbon acetyl CoA combines with a 4-carbon compound to create one with 6 carbons.
- in a circular pathway of reactions the original 4-carbon compound is recreated.
Each 2-carbon molecule entering the Krebs cycle results in the production of:
- two carbon dioxide molecules.
- one molecule of ATP by substrate-level phosphorylation.
- and four pairs of hydrogen atoms, which are taken up by hydrogen acceptors.
- fatty acids can also be respired to release energy.
- fatty acids are broken down generating the same 2-carbon compound which can be put into the Krebs cycle for oxidation.
The electron transport chain
- reduced coenzyme carries H+ and electron to electron transport chain on inner mitochondrial membrane.
- Electrons pass from one electron carrier to the next in a series of redox reactions; the carrier is reduced when it receives the electrons and oxidised when it passes them on.
- protons (H+) move across the inner mitochondrial membrane creating high H+ concentrations in the intermembrane space.
- H+ diffuse back into the mitochondrial matrix down the electrochemical gradient.
- H+ diffusion allows ATPase to catalyse ATP synthesis.
-Electrons and H+ ions recombine to form hydrogen atoms which then combine with oxygen to create water.
- if the supply of oxygen stops the electron transport chain and ATP synthesis stops.
ATP synthesis by chemiosmosis
how the electron transport chain leads to ATP synthesis:
- energy is released as electrons pass along the electron transport chain
- this energy is used to move hydrogen ions from the matrix, across the inner mitochondrial membrane, and into the intermembrane space.
- this creates a steep electrochemical gradient across the inner membrane
- making the intermembrane space more positive than the matrix
- the hydrogen ions diffuse down the electrochemical gradient through hollow protein channels in stalked particles on the membrane
- as the hydrogen ions pass through the channel ATP synthesis is catalysed by ATPase in each stalked particle
ATP synthesis by chemiosmosis continued
- the hydrogen ions cause a change in shape in the enzymes active site so the ADP can bind
- within the matrix the H+ and electrons re combine to form hydrogen atoms
- these combine with oxygen to form water
- the oxygen acts as the final carrier in the electron transport chain and is therefore reduced
- this method of synthesising ATP is known as oxidative phosphorylation
How much ATP is produced?
The maximum number of ATP's that can be made per glucose is 38
This is based on the assumption that:
- each reduced NAD that is reoxidised forms 3 ATP molecules
- each reduced FAD results in the production of two ATP molecules
How much ATP is produced? continued
Rate of respiration
n small organisms the rate of respiration can be determined by measuring the uptake of oxygen using a respirometer.
- respiration is a series of enzyme-controlled reactions
- it is affected by enzyme concentration, substrate concentration, temperature and pH.
- the concentration also has a role in the control of respiration.
- ATP inhibits the enzyme in the first step of glycolysis.
The enzyme responsible for glucose phosphorylation can exist in two forms:
- in the presence of ATP the enzyme has a shape that makes it inactive so it cannot catalyse the reaction.
- as ATP is broken down the enzyme becomes an active form and catalyses the phosphorylation of glucose.
- this is end point inhibition: the end product inhibits an early step in the metabolic pathway which controls the whole precess.
In exercise oxygen demand in the cells exceeds supply:
- without oxygen to accept the hydrogen ions and electrons the electron transport chain does not work:
- The reduced NAD created during glycolysis, the link reaction and the krebs cycle is not oxidised.
- most respiration reactions cannot continue.
- it is possible to oxidise the reduced NAD without oxygen.
- the pyruvate created during glycolysis is reduced to lactate and the oxidised form of NAD is regenerated.
- anaerobic respiration partially breaks down glucose to make a small amount of ATP.
- the net yield is just 2 ATP molecules per glucose molecule.
The effect of lactate bulid-up
The end product of anaerobic respiration is lactate:
- it builds up in the muscles and must be disposed of
- lactate forms lactic acid in solution so as lactate accumulates the pH of the cell falls inhibiting the enzymes that catalyse the glycolysis reactions.
- enzymes function best over a narrow pH range.
- as hydrogen ions from the lactic acid accumulate in the cytoplasm they neutralise the negatively charged groups in the active site of the enzyme.
- the attraction between charged groups on the substrate and in the active site will be affected.
- the substrate may no longer bind to the enzymes active site.
Getting rid of lactate
- most lactate is converted back into pyruvate.
- it is oxidised directly to carbon dioxide and water via the Krebs cycle and releases energy to synthesis ATP.
- so oxygen uptake is greater than normal in the recovery period after exercise.
- this oxygen requirement is called the oxygen debt or post-exercise oxygen consumption.
- it is needed to fuel the oxidation of lactate.
- some lactate may also be converted into glycogen and stored in the muscle or liver.
Yeast cells cope differently with anaerobic conditions:
- they reduce pyruvate to ethanol and carbon dioxide using the hydrogen from reduced NAD.
- this recreates oxidised NAD and allows glycolysis to continue.
- this is called alcoholic fermentation.
Supplying instant energy
- at the start of exercise immediate regeneration of ATP is achieved using creatine phosphate (PC)
- this is a substance stored in muscles that can be hydrolysed to release energy.
- This energy can be used to regenerate ATP from ADP and phosphate, the phosphate is given by the creatine phosphate.
- creatine phosphate breakdown starts as soon as exercise starts.
creatine phosphate -> creatine + Pi
ADP + Pi -> ATP
- the reactions do not require oxygen and provide energy for 6-10 seconds of intense exercise.
- this is known as the ATP/PC system its is used for regeneration of ATP.
Three energy systems
- At the start of exercise aerobic respiration cannot meet the demands for energy because the supply of oxygen to the muscles is insufficient.
- the lungs and circulation are not delivering oxygen quickly enough and ATP will be regenerated without using oxygen.
- first the ATP/PC system and then the anaerobic respiration system allow ATP regeneration.
- in endurance type exercise an increased blood supply to the muscles ensures higher oxygen supply to the muscle cells.
- aerobic respiration can regenerate ATP as quickly as it is broken down.
- this allows the exercise to be sustained for long periods.
- being able to go for long periods of strenuous exercise depends on maintaining a constant supply of ATP, and this depends on aerobic capacity: ability to take in/transport/use oxygen.
- VO2 is the volume of oxygen we consume per minute.
- VO2(max) is the maximum amount of oxygen we can consume per minute.
- cardiac output is the volume of blood pumped by the heart in a minute.
When running oxygen supply is maintained by:
- increasing cardiac output
- faster rate of breathing
- deeper breathing
Cardiac output and stroke volume
the volume of blood pumped by the heart in one minute.
Cardiac output depends on the volume of blood ejected from the left ventricle (the stroke volume) and the heart rate: Cardiac output (CO) = stroke volume (SV) x heart rate (HR)
Is the volume of blood pumped out of the left ventricle each time the ventricle contracts.
- how much blood the heart pumps out with each contraction is determined by how much blood is filling the heart, this is the volume of blood returning to the heart from the body.
- during exercise there is greater muscle contraction so more blood returns to the heart this is called venous return.
- in diastole during exercise the heart fills with a larger volume of blood.
- the heart muscle is stretched to a greater extent, this increases stroke volume and cardiac output.
differences in resting heart rate are caused by:
- different size
- body size
- genetic factors
- A larger heart usually has a lower resting hear rate.
- It will expel more blood with one beat and so does not have to beat as frequently to keep the circulation of blood constant.
- Endurance training produces a lower resting heart rate
- this is because increase in size of the heart
- resulting from thickening of the muscle cell walls.
How does the heart beat?
- the heart is myogenic; it can contract without external nervous stimulation.
- contraction of cardiac muscle is initiated by small changes in the electrical charge of cardiac muscle cells.
- when these cells have a slight positive charge on the outside they are polarised. when this charge is reversed they are depolarised.
- this polarity spreads amongst the cells and causes them to contract.
- depolarisation starts and the sinoatrial node (SAN).
- the SAN is a small area of specialised muscle fibres located in the wall of the right atrium beneath the opening to the superior vena cava.
- the sinoatrial node is also known as the pacemaker.
How does the heart beat? continued
- the SAN generates an electrical impulse this spreads across the left and right atria causing them to contract at the same time.
- the impulse then travels to some specialised cells called the atrioventricular node (AVN)
- the impulse is then sent to the ventricles after a delay of 0.13 seconds. this delay makes sure the atria have fully contracted.
- the signal then reaches the purkyne fibres. these are large specialised muscle fibres that conduct impulses to the apex of the ventricles.
- there are right and left bundles of fibres and these together are called the bundle of His.
- the purkyne fibres continue around each ventricle so the impulse makes the ventricles contract from the apex upwards.
- this is so the blood is pushed upwards into the aorta and pulmonary artery.
Measuring electrical activity
- the electrical activity can be detected and displayed on an electrocardiogram (ECG).
- it is the most common test to check for problems with the heart.
- electrodes are attached to the person's chest and limbs to record the electrical currents produced during the cardiac cycle.
- when there is a change in polarisation of the cardiac muscle.
- there is a small electrical current that can be detected on the skins surface.
- an ECG is usually performed when the patient is at rest.
- but it is also used to detect heart problems only when the heart is working hard.
What does an ECG trace show us?
- P wave: depolarisation of the atria leading to atrial contraction (atrial systole)
- PR interval: the time taken for impulses to be conducted from the SAN across the atria to the ventricles, through the AVN.
- QRS complex: the wave of depolarisation resulting in contraction of the ventricles (ventricular systole).
- T wave: repolarisation (recovery) of the ventricles during the hearts relaxation phase (diastole).
- the ECG does not show atrial repolarisation because the signals generated are small and are hidden by the QRS complex.
- you can work out the time for one complete cardiac cycle by: multiplying the the number of squares between QRS complexes by 0.2 and then doing 60 divided by the answer.
- a heart rate of less than 60bpm is known as bradycardia.
- a heart rate of more than 100bpm is known as tachycardia.
- during a period of ischaemia the heart muscle does not receive blood due to atherosclerosis causing blockage of the coronary arteries.
- this causes the normal electrical activity and rhythm of the heart to be disrupted.
- and arrhythmias is caused which is irregular beatings of the heart caused by electrical disturbances. an ECG can provide information about:
- abnormal heartbeats
- areas of damage
- inadequate blood flow
-hypertrophic cardiomyopathy: is an inherited condition in which gene mutations cause abnormally thick walls in the left ventricle.
Nervous control of heart rate
- heart rate is under the control of the cardiovascular control centre located in the medulla of the brain.
- nerves forming the part of the autonomic nervous system lead from the cardiovascular control centre to the heart.
- there are two nerves going from the cardiovascular control centre to the heart
- sympathetic nerve (accelerator)
- vagus nerve which is a parasympathetic nerve (decelerator)
- stimulation of the SAN by the sympathetic nerve increases the heart rate whereas impulses from the vagus nerve slow down the heart rate.
- the cardiovascular control centre detects accumulation of carbon dioxide and lactate in the blood, reduction of oxygen, and increased temperature.
- mechanical activity in the muscles and joins is detected by sensory receptors in muscles, and impulses are sent to the cardiovascular control centre.
Hormonal effects on heart rate
- fear, excitement and shock cause a release of the hormone adrenaline into the blood from the adrenal glands located above the kidneys.
- adrenaline has an effect on the hear rate similar to stimulation by the sympathetic nerve.
- it has direct on the SAN increasing the heart rate to prepare the body for physical demands.
- adrenaline also causes dilation of the arterioles supplying skeletal muscles
- it also causes constriction of arterioles going to the digestive system and other non-essential organs.
- this maximises blood low to the active muscles.
- adrenaline causes an anticipatory increase in hear rate before the start of a race.
- the volume of air we breathe in and out at each breath is our tidal volume (at rest around 0.5 dm3).
- the maximum volume of air we can inhale and exhale is out vital capacity (most people 3-4 dm3).
- lung volumes can be measured using a spirometer.
- the volume of air taken into the lungs in one minute is the minute ventilation. This is calculated by:
minute ventilation = tidal volume x breathing rate
The control of breathing
- The ventilation centre in the medulla oblongata of the brain controls breathing.
- the ventilation centre sends nerve impulses every 2-3 seconds to the external intercostal muscles and diaphragm muscles. both sets of muscles contract using inhalation.
- when inhaling the external intercostals and diaphragm muscles are also used.
- as the lungs inflate stretch receptors in the bronchioles are stimulated.
- the stretch receptors send inhibitory impulses back to the ventilation centre.
- impulses to the muscles stop and the muscles relax stopping inhalation and allowing exhalation.
- exhalation is caused by the elastic recoil of the lungs and gravity helping to lower the ribs.
- the internal intercostal muscles only contract during deep exhalation.
Controlling breathing rate and depth
an important stimulus controlling the breathing rate and depth is the concentration of dissolved CO2 in the arterial blood. a small increase in CO2 concentration causes a large increase in ventilation:
- carbon dioxide dissolves in the blood plasma, making carbonic acid.
- carbonic acid dissociates into hydrogen ions and hydrogencarbonate ions, this lowers the pH of the blood
CO2 + H2O <=> H2CO3 <=> H+ + HCO3-
- chemoreceptors sensitive to hydrogen ions are located in the ventilation centre of the medulla oblongata. they detect a rise in H+ concentration.
- impulses are sent to other parts of the ventilation centre
- impulses are sent from the ventilation centre to stimulate the muscles involved in breathing.
Controlling breathing during exercise
what controls breathing?:
- impulses from the motor cortex have a direct effect on the ventilation centre in the medulla increasing ventilation sharply.
- ventilation is also increased in response to impulses reaching the ventilation centre from stretch receptors in tendons and muscles involved in movement.
- the various chemoreceptors sensitive to CO2 levels and to changes in blood temperature increase the depth and rate of breathing via the ventilation centre.
Slow twitch fibres
- slow twitch fibres are specialised for slower sustained contraction
- they can cope with long periods of exercise to do this they carry out a lot of aerobic respiration
- they have many mitochondria and high concentrations of respiratory enzymes to carry out the aerobic reactions.
- they also have a little sarcoplasmic reticulum and a low glycogen content.
- they also contain large amounts of the dark red pigment myoglobin.
- it has a high affinity for oxygen, and only releases it when the concentration of oxygen in the cells falls very low.
- it acts as an oxygen carrier within muscle cells
- slow twitch fibres are associated with numerous capillaries to ensure a good oxygen supply.
Fast twitch fibres
- they are specialised to produce fast contractions
- the ATP used in these contractions is produced almost entirely from anaerobic glycolysis.
- the fast twitch fibres have few mitochondria, high glycogen content, and extensive sarcoplasmic reticulum.
- they also have very little myoglobin so they have few reserves of oxygen and few associated capillaries.
- they rely on anaerobic respiration which means there is a rapid build up of lactate, so the fast twitch muscle fibres fatigue easily
- with aerobic training fast twitch fibres can take on some of the characteristics of slow twitch fibres
- for example they could have more mitochondria allowing them to use aerobic respiration reactions when contracting.
- homeostasis is the maintenance of a stable internal environment.
- this is partly achieved by maintaining stable conditions within the blood.
- in the blood the concentration of glucose, ions, carbon dioxide, water potential, pH and temperature of the blood also needs to be kept within narrow limits.
- each condition that is controlled has a norm value or a set point that the homeostatic mechanisms are trying to maintain.
- receptors are used to detect changes from the norm.
- these receptors are connected to a control mechanism which turns on or off effectors to bring conditions back to the norm.
- thermoregulation is the control of body temperature.
- our body stays at around 37 degrees, this allows enzyme-controlled reactions to occur at a reasonable rate.
- At lower temperatures the reactions would occur too slowly for the body to remain active, and at higher temps the enzymes could denature.
- in humans temperature is maintained by a negative feedback system.
- the system involves receptors that detect changes in the blood temperature. these receptors are located in the hypothalamus.
- they hypothalamus detects changes and turns on effectors when needed to return to norm temp.
Temperature control continued
Heat loss centre: stimulates - sweat glands to produce sweat.
inhibits - contraction of arterioles in skin (dilates capillaries in the skin)
- hair erector muscles (relax - hairs lie flat)
- liver (reduces metabolic rate)
- skeletal muscles (relax - no shivering)
Heat gain centre: Inhibits - sweat glands
stimulates - arterioles in the skin to constrict
- hair erector muscles to contract
- liver to raise metabolic rate
- skeletal muscles to contract in shivering
Temperature control: Sweat and hairs
- sweat released via the sweat ducts evaporates taking energy from the skin
- sweat glands are stimulated by nerves from the hypothalamus
- they are raised in cold weather by contractions of the erector muscles.
- this is a reflex we have no control over.
- the aim is to trap a layer of air that insulates the body.
- although due to our shortage in hair this is better in other mammals and birds compared with humans.
- most of us wear clothes for further insulation.
Temperature control: Skin
- energy is lost from the blood flowing through the surface capillaries by radiation.
- in cold condition the muscles in the arteriole walls contract causing the arterioles to constrict
- this reduces the blood supply to the surface capillaries.
- blood is diverted through the shunt vessel which dilates as more blood goes through it.
- blood flows further from the skin surface so less energy is lost.
- this is known as vasoconstriction.
Temperature control: Skin
- constriction of the arterioles and shunts is controlled by the hypothalamus.
- in warm conditions the shut vessel constricts and muscles in the walls of the arterioles relax.
- blood flows through the arterioles making them dilate.
- blood flows closer to the surface so more energy is lost.
- this is known as vasodilation.
How energy is transferred to and from the body
- sweat evaporation increases energy loss.
- evaporation from moist surfaces of lungs increases energy loss.
- arteriole vasoconstriction decreases blood flow to skin reducing energy loss by conduction, convection and radiation.
- arteriole vasodilation increases blood flow to skin increasing energy loss by conduction, convection and radiation.
- Hairs raised by contraction of erector muscles reduces energy loss by conduction, convection and radiation.
- voluntary muscle contraction and involuntary shivering release energy, raising body temperature.
Methods of energy transfer
- energy can be radiated from one object to another through air, or through a vacuum, as electromagnetic radiation.
- our bodies are usually warmer than the surrounding environment so we radiate energy.
- energy loss by conduction involves direct contact between objects, and energy transfer from one to the other.
Methods of energy continued
- air lying next to the skin will be warmed by the body
- as the air expands and rises it will be replaced by cooler air which is then warmed by the body.
- the energy loss by bulk movement of air is called convection.
- energy is needed to convert water from liquid to vapour.
- the energy required to evaporate sweat is drawn from the body cooling it.
- in conditions with high humidity it is much harder to evaporate sweat.
- some animals pant to keep cool, by evaporation of water from gas exchange surfaces.
Excessive exercise and immune suppression
- athletes engaged in heavy training programmes seem more prone to infection than normal.
- upper respiratory tract infections (sore throat and flu-like symptoms) are most common.
- two main factors that can contribute to higher infection rates:
- increased exposure to pathogens
- and suppressed immunity with hard exericise
- some scientists believe there is a U-shaped relationship between risk of infection and amount of exercise.
Effects of exerice on immunity
- components of the non-specific and specific immune systems are effected by both moderate and excessive exercise.
- increases the number of a lymphocyte called natural killer cells.
- they are found in the blood and lymph
- they are not like B and T cells because they do not use specific antigen recognition.
- they provide non-specific immunity against cells invaded by viruses and cancerous cells.
- they are sctivated by cytokines and interferons and they target cells that are non self
- they release the protein perforin which makes pores in the targeted cell membrane.
Effects of exerice on immunity continued
- after vigorous exercise the number of some cells in the immune system falls:
- natural killer cells
- B cells
- T helper cells
- the decrease in T helper cells reduces the amount of cytokines available to activate lymphocytes.
- this then reduces the amount of antibody being produced.
- physical exercise and psychological stress cause secretion of hormones such as adrenaline and cortisol.
- both of these hormones are known to suppress the immune system.
How are joints damaged by exercise
- professional athletes risk developing joint injuries bue to high forces the sport generates on their joints.
- repeated forces on such joints of the knee can lead to wear or tear in the joint.
- knees are particularly susceptable to wear and tear injuries:
- the articular cartilage covering the surfaces of the bones wears away and they grind on eachother causing damage.
- Patellar tendonitis occurs when the kneecap (patella) does not glide smoothly across the femur due to damage of the articular cartilage on the femur.
- the fluid sacs swell up with extra fluid, as a result they may push against other tissues in the joint causing inflamtion.
- sudden twisting or abrupt movement of the knee often result in damage to the ligaments.
How can medical technology help?
- using fibre optics or minute video cameras
- it is possible to repair damaged joints or to remove diseased organs through small holes.
- keyhole surgery on joints is known as arthroscopy.
- damage to the cruciate ligaments in the knee can be tackled particulary well with keyhole surgery.
- is an artificial body part used by someone with a disability to enable him or her to regain near to normal function.
Taking enough exercise
Advantages of doing exercise:
- increasing arterial vasodilartion lowers blood pressure (reduces the risk of CVD)
- increases the lovel of blood HDLs which transport cholesterol to the liver where it is broken down.
- reduces LDLs which are associated with the development of atherosclerosis.
- helps maintain a healthy weight.
- increased sensitivity of muscle cells to insulin improves blood glucose regulation, and reduces the likelihood of getting type II diabetes.
- increases bone density and reduces its loss during old age.
- reduces the risk of getting some cancers
- improves mental well-being.
- hormones are chemical messengers that are released directly into the blood from endocrine glands.
- most are produced either in an inactive form or packaged within secretory vesicles by the golgi apparatus.
- the vesicles fuse with the cell surface membrane releasing their content by exocytosis.
glands and hormones:-
pituitary gland: hormone - growth hormone
- follicle-stimulating hormone
- antidiuretic hormone
Function - stimulates growth
- controles testes and ovaries
- causes reabsoption of water in kidneys
glands and hormones:-
Thyroid gland: hormone - thyroxine
function - raises basal metabolic rate
Adrenal gland: hormone - arenaline
function - raises basal metaboic rate
- dilates blood vessels
- prepares the body for action
Pancreas: hormone - insulin
function - lowers blood glucose concentration
glands and hormones:
Ovary: hormone - oestrogen
function - promotes development of ovaries
- promotes female secondary sexual characteristics
testis: hormone - testosterone
function - promotes development of male secondary sexual characteristics
- each hormone affects only specific target cells modifying their activity
- hormones are carried around by the blood stream
- they either entr the target cells or they bind to complimentary receptor molecules on the outside of the cell membranes.
How hormones affect cells
- peptide hormones are protein chains
- even though they are relatively small molecules they can not pass through cell membranes easily because they are charged
- they bind to a receptor on the cell membrane
- this receptor activates another molecule in the cytoplasm called a second messenger
- the second messenger brings about chemical changes in the cell by affecting gene transcription
- steroid hormones are formed from lipids and have complex ring structures.
- the hormone- receptor complex functions as a transcription factor, switching enzyme synthesis on or off.
How transcription factors work
In transcription only occurs when the transcription initiation complex is formed.
- protein repressor molecules can attach to the transcription factors
- this prevents them from forming the transcripton initiation complex.
- so the gene is switched off and is not transcribed within the cell.
- activator molecules stimulate the binding of the transcription initiaton complex.
- genes are switched on by successful formation and attachment of the transcription initiation complex to the promoter region
- the transcription factors attach the RNA polymerase to the promoter region.
Hormones used to enhance performance
- is a peptide hormone produced naturally by the kidneys
- it stimulates the formation of new red blood cells in bone marrow
- it can be made using DNA technology and is used to treat anaemia
- if you have too much it can make the body produce too many red blood cells and can cause heart attack and stroke.
- is a steroid hormone
- produced in the testes by males and in the adrenal glands in males and females
- testosterone is in a group of male hormones called androgens
- it causes the development of the male sexual organs
- testosterone binds to androgen receptors
Hormones used to enhance performance continued
- is not banned
- it is considered to be a nutrition supplement
- it is amino acid derived
- it is naturally found in meat and fish
- once ingested it is absorbed and unchanged and carried in the blood to tissues
- it is also synthesised in the body from the amino acids glycine and arginine
- some side effects include diarrhoea, nausea, vomiting, high blood pressure, kidney damage and muscle cramps.