Topic 7 Flashcards
what parts of the body does movement involve
skeletal muscles, tendons, ligaments and joints
what do tendons do
attach skeletal muscles to bones
what do ligaments do
ligaments attach bones to other bones to hold them together
what do skeletal muscles do
skeletal muscles contract and relax to move bones at a joint
what is a flexor muscle
a muscle that bends a joint when it contracts is called a flexor
what is an extensor muscle
a muscle that straightens a joint when it contracts is called an extensor
what is an antagonistic pair
muscles that work together to move a bone
why do muscles work in pairs
muscles work in pairs as they can only pull (cant push) so two muscles are needed to create opposite forces to move a bone
as one contracts the other relaxes
so must have extensors and flexors
what happens when your bicep contracts
when your biceps contracts your triceps relaxes → this pulls the bone so that your arm bends (flexes) at the elbow
what happens when your triceps contract
- when your triceps contracts, your biceps relaxes
- this pulls the bone so your arm straightens (extends) at the elbow
recall the components which make up skeletal muscles
skeletal muscle is made up of large bundles of long cells which are called muscle fibres
sarcomella
sarcoplasm
transverse (T) tubules
sarcoplasmic reticulum
mitochondria
myofibrils
are multinucleate → contain many nuclei
what is the sarcomella
the cell membrane of muscle fibre cells is called the sarcolemma
what are T tubules
- bits of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm (which is a muscle cells cytoplasm)
- these folds are called transverse (T) tubules
what is the sarcoplasm
a muscle cells cytoplasm
what do T tubules do
they help to spread electrical impulses throughout the sarcoplasm so that they reach all parts of the muscle fibre
what is the sarcoplasmic reticulum and what does it do
a network of internal membrane that runs through the sarcoplasm
it stores and releases calcium ions → needed for muscle contraction
why do muscle fibres have lots of mitochondria
to provide ATP for muscle contraction
what are myofibrils
- long, cylindrical organelles called myofibrils
- they are made up of proteins and are highly specialised for contraction
draw a labelled diagram of a muscle fibre
what are myofibrils made up of
myofibrils contain bundles of thick and thin myofilaments that move past each other to make muscles contract
- thick myofilaments are made of the protein myosin
- thin myofilaments are made of the protein actin
what are A bands on a myofibril
dark bands→ contain the thick myosin filaments and some overlapping thin actin filaments which are called A bands
what will you see if you look at a myofibril under an electron microscope
will see a pattern of alternating dark and light bands
what are I bands on myosin
light bands contain thin actin filaments only → called I-bands
what are sarcomeres
a myofibril is made up of many short units→ called sarcomeres
describe the structure of a sarcomere
- end of each sarcomere is marked with a Z-line
- sarcomeres are joined lengthways at their Z-line
in the middle of each sarcomere is an M-line - M-line is in the middle of the myosin filaments
- around the M-line is the H-zone
- H-zone only contains myosin filaments
draw a labelled diagram of a sarcomere
describe the sliding filament theory
- myosin and actin filaments slide over one another to make the sarcomeres contract
- the myofilaments don’t contract
- the myosin and actin molecules stay the same length
- the simultaneous contraction of lots of sarcomeres means that the myofibrils and muscle fibres contract
- sarcomeres return to their original length as the muscle relaxes
what happens when a sarcomere is contracted
- I-band gets shorter
- H-zones get shorter
- A band stays the same
- therefore the sarcomere gets shorter
describe the structure of myosin filaments
- myosin filaments have globular heads that are hinged so they can move back and forth
- each myosin head has a binding site for actin and a binding sire for ATP
describe the structure of actin filaments
- actin filaments have a binding site for myosin heads → called actin-myosin binding sites
- tropomyosin and troponin are found between actin filaments
what is the role of troponin and tropomyosin
- these proteins are attached to each other
- they help myofilaments move past each other
what blocks the actin-myosin binding site and why?
- in a resting muscle, the actin-myosin binding site is blocked by tropomyosin which is held in place by troponin
- this is so that myofilaments cant slide past each other as myofilaments cant bind to the actin-myosin binding site on the actin filaments
what does an action potential do
an action potential triggers muscle contraction
what happens in the first step of muscle contraction
- action potential triggers an influx of calcium ions
- when an action potential from a motor neurone stimulates a muscle cell → depolarising the sarcolemma- depolarising is when the difference in charge across the sarcolemma is reduced
- depolarisation spreads down the T-tubules to the sarcoplasmic reticulum
- this causes the sarcoplasmic reticulum to released stored Ca2+ ions into the sarcoplasm
- Ca2+ ions bind to troponin which causes it to change shape - this pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament
- this exposes the binding site → allows myosin head to bind
- the bond formed when a myosin head binds to an actin filament is called an actin-myosin cross bridge
- depolarising is when the difference in charge across the sarcolemma is reduced
what is the second step of muscle contraction
- ATP provides the energy needed to move past the myosin head
- Ca2+ ions also activate ATPase → which breaks down ATP into ADP and P1 (inorganic phosphate)- provides the energy needed for muscle contraction
- energy released from ATP moves the myosin head which pulls the filament along in a rowing motion
- provides the energy needed for muscle contraction
what is the third step for muscle contraction
- breaking the cross bridge
- ATP also provides the energy to break the actin-myosin cross-bridge → so the myosin head detached from the actin filament after its moved
- myosin then reattached to a different binding site further along the actin filament
- a new actin-myosin cross-bridge is formed → this cycle is repeated (attach, move, detach, reattach to new binding site)
- many cross-bridges form and break rapidly which pulls the actin filament along- this shortens the sarcomere → causes the muscle to contract
- the cycle will continue as long as Ca2+ ions are present and bound to troponin
- this shortens the sarcomere → causes the muscle to contract
what fibres are skeletal muscles made up of
- skeletal muscles are made up of two types of muscle fibres→ slow and fast twitch
- different muscles have different proportions of slow and fast twitch fibres
what are the properties of slow twitch fibres
- contract slowly
- muscles used for posture have a higher proportion of slow twitch muscle fibres e.g those in the back
- good for endurance activities e.g maintaining posture, long-distance running
- can work for a long time without getting tired→ fatigue resistant
- energy released slowly through aerobic respiration
- lots of mitochondria and blood vessels supply the muscles with oxygen
- reddish in colour as they are rich in myoglobin → a red-coloured protein which stored oxygen
what are the properties of fast twitch fibres
- contact very quickly
- muscles used for fast movement have a high proportion of them e.g those in the legs and eyes
- good for short bursts of speed and power e.g sprinting, eye movement
- gets tired quickly
- energy released through anaerobic respiration using glycogen (stored glucose)
- very few mitochondria or blood vessels
- whiteish in colour as they don’t have much myoglobin (so cant store much oxygen)
what does aerobic respiration do
releases a large amount of energy by splitting glucose into CO2 → waste product, and H2
- H2 combines with atmospheric O2 to produce H2O
- is an example of a metabolic pathway → made up of a series of chemical reactions
- energy released is used to phosphorylate ADP to ATP
- ATP is used to provide energy for all biological processes in a cell
what is the equation for aerobic respiration
what are the 4 stages in aerobic respiration
glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation
two stages in glycolysis → phosphorylation + oxidation
- products from first 3 stages are used in the final stage to produce ATP
- first stage happens in the cytoplasm of cells and the other 3 stages take place in the mitochondria
which enzyme determines the overall rate of respiration
- each reaction is catalysed and controlled by a specific intracellular enzyme
- enzyme with the slowest activity is rate limiting → determines the overall rate of respiration
what coenzymes are used in aerobic respiration and what does it do
- NAD and FAD transfer hydrogen from one molecule to another → can reduce (give hydrogen to) or oxidise (take hydrogen from) a molecule
- coenzyme A transfers acetate between molecules
what happens in the phosphorylation stage in glycolysis in aerobic respiration
- glucose is phosphorylated by adding 2 phosphates from 2 molecules from ATP
- this creates 2 molecules of triose phosphate and 2 molecules of ADP
what happens in the oxidation stage in glycolysis in aerobic respiration
- triose phosphate is oxidised (lses hydrogen)→ forms two molecules of pyruvate
- partial oxidation
- NAD collects hydrogen ions → forms 2 reduced NAD
- 4 ATP produced but 2 were used up in stage 2 → net gain of 2 ATP
- the two molecules of reduced NAD are used in oxidative phosphorylation
- the 2 pyruvate molecules goes into the matrix of the mitochondria for the link reaction
describe what happens in the link reaction
- enzymes and coenzyme needed for the link reaction are located in the mitochondrial matrix
- so link reaction occurs in the matrix
- pyruvate is decarboxylated → one carbon atom removed from pyruvate in the form of CO2
- NAD is reduced → it collects hydrogen from pyruvate, changing pyruvate into acetate
- acetate combined with coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA)
- no ATP produced in this reaction
- link reaction and krebs cycle occurs twice for every glucose molecule because 2 molecules of pyruvate are made for every glucose molecule
what are the products of the link reaction
- 2 molecules of acetyl coenzyme A go into krebs cycle
- 2 molecules of CO2 are released as a waste product
- 2 molecules of reduced NAD are formed and used in oxidative photophosphorylation
describe the first stage in the krebs cycle
- Acetyl CoA combines with oxaloacetate → forms citrate
- coenzyme A goes back to the link reaction to be used again
describe the second stage in the krebs cycle
- the 6C citrate molecule is converted to a 5C molecule
- decarboxylation occurs → CO2 removed
- dehydrogenation also occurs→ hydrogen is removed
- hydrogen is used to produce reduced NAD from NAD
describe the third stage in the krebs cycle
- the 5C molecule is then converted to a 4C molecule
- decarboxylation and dehydrogenation occur→ producing one molecule of reduced FAD and 2 molecules of reduced NAD
- ATP is produced by the direct transfer of a phosphate group from an intermediate compound to ADP
- when phosphate group is directly transferred from one molecule to another→ called substrate-level phosphorylation
- citrate has now been converted to oxaloacetate
where the products of the krebs cycle go
1 coenzyme A → reused in next link reaction
1 oxaloacetate→ regenerated for use in the next krebs cycle
2 CO2→ released as a waste product
1 ATP→ used for energy
3 reduced NAD→ used for oxidative phosphorylation
1 reduced FAD → used for oxidative phosphorylation
describe the process of oxidative phosphorylation in aerobic respiration
- hydrogen atoms are released from reduced NAD and reduced FAD → so they’re oxidised back to NAD and FAD
- the hydrogen atoms split into H+ and electrons
- the e- move down the electron transport chain which is made up of electron carriers (and they lose energy at each carrier)
- the energy is used by the electric carrier to pump H+ (protons) from the mitochondrial matrix into the intermembrane space
- intermembrane space is the space between the inner and outer mitochondrial membranes
- conc. of protons now higher in the intermembrane space than in the matrix → forms an electrochemical gradient back into the matrix via the enzyme ATP synthase
- this movement of protons back into the matrix drives the synthesis of ATP from ADP and P1
- movement of H+ ions across a membrane which generates ATP is called chemiosmosis
- in the matrix, at the end of the electron transport chain → protons, electrons and O2 from the blood form water
- oxygen is the last electron acceptor
what do metabolic poisons do
- some metabolic poisons target e- carriers in oxidative phosphorylation
- prevents them from passing on e-
- stops e- moving down e- transport chain and therefore stops chemiosmosis
- reduced NAD and FAD no longer oxidised
- therefore NAD and FAD arent regenerated for the Krebs cycle
- therefore reduces ATP synthesis
- not enough ATP produced to fuel ATP- requiring processes
- could be fatal
how much ATP can be made form one glucose, and each NAD and FAD molecule in aerobic respiration
- 38 ATP can be made from one glucose molecule
- 3 ATP made from each reduced NAD
- 2 ATP made from each reduced FAD
what piece of equipment can be used to measure the rate of respiration and how
respirometer
- volume of oxygen taken up/ volume of CO2 produced in a given time indicates rate of respiration
- respirometer measures the volume of oxygen taken up in a given time
- the more oxygen taken up→ faster rate of respiration
draw the setup of a respirometer
describe the set up of a respirometer
- each tube contains potassium hydroxide solution → absorbs carbon dioxide
- control tube→ contains beads that have the same mass as the invertebrate organism
- syringe is used to set the fluid manometer to a known level
how does a respirometer work
- apparatus is left for a set period of time
- during this time there will be a decrease in the volume of air due to oxygen consumption by the organism
- all the CO2 produced is absorbed by potassium hydroxide
- decrease in volume of air will reduce the pressure in the test tube → will cause the coloured liquid in the manometer to move towards the test tube
- the distance moved by the liquid in a given time is measured
- this value can then be used to calculate the volume of oxygen taken in by the woodlice per minute
- control temperature, vol of KOH in each test tube
- repeat to obtain more precise results
- mean vol of O2 is calculated
how does anaerobic respiration work
- glucose converted to pyruvate via glycolysis
- reduced NAD from glycolysis transfers hydrogen to pyruvate → form lactate and NAD
- NAD can then be reused in glycolysis
- this means that glycolysis can continue even if there isn’t much oxygen
- small amount of ATP produced
after a while lactic acid builds up
what are the two ways animals can break down lactic acid
- cells can convert lactic acid to pyruvate → then re-enters aerobic respiration at the krebs cycle
- liver cells can convert lactic acid back to glucose → can then be respired or stored
what does it mean when it says the cardiac muscle is myogenic
- can contract and relax without receiving signals from neurones
- stimulation generated within the muscle which results in depolarisation
- this electrical activity in the heart creates the pattern of contractions → coordinates regular heartbeat
what is the SAN
- it sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
- causes right and left atria to contract at the same time
like a pacemaker
- causes right and left atria to contract at the same time
what is the bundle of His
is a group of muscle fibres responsible for conducting the waves of electrical activity to the finer muscle fibres in the left and right ventricle walls
these finer muscle fibres in the ventricle walls are called the purkyne fibres
what do the purkyne fibres do
the purkyne fibres carry the waves of electrical activity into the muscular walls of the left and right ventricles → causes them to contract simultaneously from the bottom up
what is the process of the heart beating
starts in the sino-atrial node (SAN) → in the wall of the right atrium which causes right and left atria to contract at the same time
- a band of non-conducting collagen tissue prevents the waves of electrical activity from being passed directly from the atria to the ventricles
- these waves of electrical activity are transferred from the SAN to the AVN (atrioventricular node)
- AVN is responsible for passing on waves of electrical activity onto the bundle of His
- however, there’s a slight delay before the AVN reacts → to make sure the ventricles contract after the atria have emptied
the bundle of His conducts waves of electrical activity to the purkyne fibres which causes the left and right ventricles to contract simultaneously from the bottom up
what is an electrocardiograph
- a machine that records the electrical activity of the heart
- can check someones heart function using this
how does an electrocardiograph work
- the heart muscle depolarises (loses electrical charge) when it contracts and repolarises (regains charge) when it relaxes
- electrocardiograph records these changes in electrical charge using electrodes which are placed on the chest
- the trace produced by an electrocardiograph is called an electrocardiogram (ECG)
describe what each part of this diagram means
- P wave is caused by contraction (depolarisation) of the atria → P on diagram
- the main peak of the heartbeat together with the dips at either side is called the QRS complex
- its caused by contraction of the ventricles
- the T wave is due to relaxation (repolarisation) of the ventricles → T on diagram
- height of wave indicates how much electrical charge is passing through the heart
what does a bigger wave mean on an electrocardiogram
- bigger wave= more electrical charge
- so for the P and R waves, a bigger wave = stronger contraction
how can ECGs be used to diagnose heart problems
- doctors compare their patients ECGs with a normal trace
- helps them diagnose any problems with the hearts rhythm → may indicate cardiovascular disease or other heart conditions
what does a heartbeat of around 120bpm mean
- heartbeat too fast (Around 120 bpm) is called tachycardia
- this is okay when exercising
- however it may show that the heart isn’t pumping blood efficiently
what does a heartbeat below 60bpm mean
heartbeat can also be too slow (below 60bpm) → called bradycardia
what is an ectopic heartbeat
- can be caused by earlier contraction of the atria or of the ventricles
- occasional ectopic heartbeats in a healthy person don’t cause a problem
what is fibrillation
- fibrillation→ a really irregular heartbeat
- atria and ventricles completely lose their rhythm and stop contracting properly
- can result in anything from chest pain, fainting to lack of pulse and death
how does the body replace the energy used during excerise
- when you exercise your muscles contract more frequently → they use more energy
- to replace this energy more aerobic respiration needs to occur
- therefore needs to take in more oxygen and breathe out more CO2
how does the body increase the rate of aerobic respiration
- increasing breathing rate and depth to obtain more O2 and get rid of more CO2
- increase heart rate to deliver more O2 (and glucose) to the muscles faster and remove extra CO2 produced by the increased rate of respiration in muscle cells
where at the ventilation centres found
medulla oblongata
what are the name of the 2 ventilation centres and what do they do
- the inspiratory centre and the expiratory centre
- they control the rate of breathing
how do the ventillation centres control the rate of breathing
- the inspiratory centre in the medulla oblongata sends nerve impulses to the intercostal and diaphragm muscles to make them contract
- this increases the volume of the lungs which lowers the pressure in the lungs
- the inspiratory centre also sends nerve impulses to the expiratory centre
- these impulses inhibit the action of the expiratory centre
- air enters the lungs due to the pressure different between the lungs and the air outside
- as the lungs inflate→ stretch receptors in the lungs are stimulated and they send nerve impulses back to the medulla oblongata
- these impulses inhibit the action of the inspiratory centre
- the expiratory centre which is no longer inhibited, sends nerve impulses to the diaphragm and intercostal muscles to relax → causes lungs to deflate, expelling air
- as the lungs deflate the stretch receptors become inactive. the inspiratory centre is no longer inhibited and the cycle starts again
how does exercise trigger an increase in breathing rate
- during exercise the level of CO2 in the blood increases which decreases the pH of the blood
- chemoreceptors in the medulla oblongata, aortic bodies and carotid bodies → sensitive to changes in blood pH
- if chemoreceptors detect a decrease in blood pH → they send nerve impulses to the medulla oblongata which sends more frequent nerve impulses to the intercostal muscles and diaphragm
- this increases the rate of breathing
- this causes gaseous exchange to speed up → CO2 level drops and extra CO2 is supplied for the muscles which causes pH to return back to normal and breathing rate decreases
what do chemoreceptors do
receptors that sense chemicals
what are aortic bodies
clusters of cells in the aorta
what are the carotid bodies
clusters of cells in the carotid arteries
what is the ventilation rate
- ventilation rate→ the volume of air breathed in or out in a period of time
- it increases during exercises because breathing rate and depth increases
what is the heart rate controlled by
heart rate is controlled unconsciously by the cardiovascular control centre in the medulla oblongata
what does the cardiovascular control centre control
the cardiovascular control centre controls the rate at which the SAN fires → the SAN generates electrical impulses that cause the atria to contract which sets the rhythm of the heartbeat
what are baroreceptors
- chemical receptors and pressure receptors detect stimuli in the blood
- pressure receptors called baroreceptors in the aortic and carotid bodies
- stimulated by high and low blood pressure
what do the chemoreceptors do in the medulla oblongata
- chemoreceptors in the aortic and carotid bodies and in the medulla oblongata
- monitor oxygen level in the blood
- also monitor CO2 and pH → indicators of O2 levels
electrical impulses from the chemo and baroreceptors are sent to the medulla oblongata along sensory neurones
what does the cardiovascular control centre do with the impulses it receives from the chemo and baroreceptors
- the cardiovascular control centre processes the info and sends impulses to the SAN along sympathetic or parasympathetic neurones
- these release neurotransmitters onto the SAN which determines whether it speeds up or slows down the heart rate
what does the sympathetic nervous system do
- sympathetic nervous system → gets body ready for action
- fight or flight system
- helps to increase heart rate during exercise
what does the parasympathetic nervous system do
- parasympathetic nervous system → calms the body down
- rest and digest system
- helps to decrease heart rate after exercise
how does the heart respond to high blood pressure as a stimulus
- baroreceptors detect high BP
- impulses sent to cardiovascular control centre → sends impulses along the parasympathetic neurones. the neurone secretes acetylcholine (a neurotransmitter) which binds to receptors on the SAN
- the SAN fires impulses less frequently to slow heart rate and reduce BP back to normal
how does the heart respond to low blood pressure as a stimulus
- baroreceptors detect low BP
- impulses sent to cardiovascular control centre → sends impulses along sympathetic neurones which secrete noradrenaline (a neurotransmitter - nt) which binds to receptors on the SAN
- the SAN fires impulses more frequently to increase heart rate and inc. BP back to normal
how does the heart respond to high blood O2 , low CO2/high pH levels
- chemoreceptors detect chemical changes in the blood
- impulses are sent to the cardiovascular control centre → sends impulses along the parasympathetic neurones → secrete acetylcholine → nt binds to receptors on the SAN
- SAN fires impulses less frequently to decrease heart rate and return O2, CO2 and pH levels back to normal
how does the heart respond to low blood O2, high CO2 or low pH levels
- chemoreceptors detect chemical changes in the blood
- impulses sent to cardiovascular control centre → sends impulses along sympathetic neurones → secrete noradrenaline → nt binds to receptors on the SAN
- SAN fires impulses more frequently to increase heart rate and return O2, CO2 and pH levels back to normal
- explains why heart rate increases during exercise
what is the name of the neurotransmitter that sympathetic neurones secrete
noradrenaline
what is the name of the neurotransmitter that parasympathetic neurones secrete
acetylcholine
what is cardiac output and its units
cardiac output is the total volume of blood pumped by a ventricle every minute cm3 min -1
how do you calculate cardiac output
heart rate (bmp) x stroke volume (cm3) = cardiac output (cm3 min -1)
what is meant by stroke volume
volume of blood pumped by one ventricle each time it contracts
when does cardiac output increase
increases during exercise because heart rate and stroke volume increase
what is meant by tidal volume
the volume of air in each breath, usually o.4 dm3
what is meant by breathing rate
how many breaths are taken, usually in a minute
what is meant by oxygen consumtpion
the volume of oxygen used by the body, expressed as a rate
what is respiratory minute ventilation
- the volume of gas breathed in or out in a minute
- can also be called ventilation rate (per minute)
how do you calculate respiratory minute ventilation
tidal volume x breathing rate (breaths per minute)
What is a spirometer
a spirometer is a machine that can give reading of tidal volume and allow measurement of a person’s breathing rate, O2 consumption and respiratory minute ventilation
how does a spirometer work
- a spirometer has an oxygen-filled chamber with a moveable lid
- a person breathes through a tube connected to the oxygen chamber
- as the person breathes in, the lid of the chamber moves down and when they breathe out it moves up
- these movements are recorded by a pen attached to the lid of the chamber → this writes on a rotating drum, creating a spirometer trace
why does the total volume of gas in the chamber of the spirometer decrease
- decreases over time because the air that’s breathed out is a mixture of O2 and CO2 but the CO2 is absorbed by the soda lime in the tube
- this means that there’s only oxygen in the chamber that the person inhales from
- since this oxygen gets used up by respiration → total volume decreases
draw the set up of a spirometer and label
what does exercise cause
exercise causes an increase in breathing rate and tidal volume, O2 consumption and respiratory minute ventilation
how can you investigate the effect of exercise on breathing rate and tidal volume, O2 consumption and respiratory minute ventilation
spirometer can be used to investigate the effect that exercise has on these things
- a person breathes into the spirometer for one min at rest and recordings are taken
- then the person exercises for two mins
- while the person is exercising the spirometer chamber is refilled with oxygen
- immediately after the person stops exercising they breathe into the spirometer again and recordings are taken for another minute
- the recordings taken before and after exercise are then compared
how can you analyse data from a spirometer trace
- breathing rate per minute- count the number of peaks in the trace in a minute
- tidal volume- find the average difference in the volume of gas between each peak and trough on the trace
- oxygen consumption- find the change in volume of gas in the spirometer (read values from the troughs)
what can the students T-test be used for
used to test whether exercise has a significant effect on tidal volume at rest
what is the equation for the T test
what is the equation for standard devation
how do you use the T test
- null hypothesis- no significant difference
- calculate the mean and standard deviation for each set
- substitute values into the formula
- calculate the degree of freedom by doing (n1 + n2) - 2
- look up values for t in critical values table
what does it mean if the value obtained from the t-test is greater than the critical value at 5%
- (value obtained greater than critical value) then you can be 95% confident that the difference is significant and not due to chance
- can reject null hypothesis
what happens if the t-value is smaller than the critical value
suggests there’s no significant difference between the two sets of data so would accept the null hypothesis
what does homeostasis involve
- homeostasis involves control systems that keep your internal environment within narrow limits/ in a state of dynamic equilibrium
- i.e fluctuating around a normal level
- e.g during exercise
why is homeostasis necessary
keeping your internal environment constant is vital for cells to function normally and stop them from being damaged
- e.g if body temp too high enzymes may become denatured → enzyme molecules may vibrate too much breaking the H bonds that’s holding them in their 3D shape
- shape of enzymes active site changed so can no longer work as a catalyst meaning that metabolic reactions are less efficient
how is the supply of energy controlled
- cells need constant supply of energy so glucose conc. must be carefully controlled → monitored by cells in the pancreas
- blood glucose conc. falls after exercise as more glucose is used in respiration to release energy
how is the amount of water in the blood controlled
- amount of water in the blood needs to be kept constant
- water lost in sweat and urine
- kidneys regulate the water content of the blood and urine
what is the definition of homeostasis
the maintenance of a stable internal environment
what is the homeostatic systems involve
involve receptors, nervous or hormonal system and effectors
what do effectors do
- effectors respond to counteract the change and bring the level back to normal
- usually turned on or off by nerve signals or impulses from the control centre
what do receptors do
detect deviations from the norm
what is meant by negative feedback
- negative feedback→ mechanism that restores the level to normal
- however it only works within certain limits. if the change is too big then the effector may not be able to counteract it
what happens in positive feedback
- positive feedback mechanisms amplify a change from the normal level
- effectors respond to further increase the level away from the normal level
its useful to rapidly activate something - positive feedback can also happen when the homeostatic system breaks down
- isn’t involved in homeostasis as it doesn’t keep your internal environment stable
how does positive feedback act to form a blood clot after injury
- platelets become activated and release a chemical which triggers more platelets to be activated
- platelets very quickly form a blood clot at the injury site
- the process ends with negative feedback when the body detects the clot has been formed
recall the mechanisms used to reduce body temp
sweating
hairs lie flat
vasodilation
how does sweating reduce body temp
- more sweat secreted from sweat glands when body is hot
- water in sweat evaporates from the surface of the skin and evaporates which takes heat energy from the body
- the skin is cooled
how does hairs lying flat reduce body temperature
- when its hot erector pili muscles relax so hairs lie flat
- less air is trapped so the skin is less insulated and heat can be lost more easily
how does vasodilation reduce body temperature
- arterioles neat the surface of the skin dilate
- more blood flows through the capillaries in the surface layers of the dermis
- more heat is lost from the skin by radiation and the temperature is lowered
recall the mechanisms used to increase body temperature
shivering
less sweat
hairs stand up
vasoconstriction
hormones
how does shivering increase body temperature
- muscles contract in spasms
- makes the body shiver
- more heat produced from increased respiration
how does less sweat increase body temperature
- less sweat is secreted
- less heat loss
how does hairs standing up increase body temperature
- erector pili muscles contract
- makes hairs stand up
- this traps more air which acts as insulation
- prevents heat loss
how does vasoconstriction increase body temperature
- arterioles near the surface of the skin constrict
- less blood flows through the capillaries in the surface layers of the dermis
- reduces heat loss
how does hormones increase body temperature
- body releases adrenaline and thyroxine
- this increases metabolism so more heat is produced
what is the hypothalamus
- hypothalamus is the part of the brain that maintains body temperature at a constant level in mammals
- hypothalamus receives information about temperature from thermoreceptors
how does thermoregulation work
- thermoreceptors send impulses along sensory neurones to the hypothalamus
- hypothalamus then sends impulses along motor neurones to effectors (muscles and glands)
- the effectors respond to restore body temperature back to normal
- this is called thermoregulation
what are the ways energy can be transferred to and from the body
radiation
conduction
convection
evaporation
what is radiation
energy can be radiated from one object to another through air or through a vacuum as EM radiation
what is conduction
involves direct contact between objects and energy transfer from one to another
what is convection
air lying next to the sin will be warmed by the body and will expand and rise or is moved away by air currents. it will be replaced by cooler air → energy loss by bulk movement is called convection
what is evaporation
energy required to evaporate sweat is drawn from the body
what are hormones
hormones are chemical messengers released into the blood from endocrine glands
each hormone only affects specific target cells, modifying their activity
how are hormones released
- endocrine glands don’t have ducts
- most hormones are produced in an inactive form or packaged within secretory vesicles by the golgi so that they arent affected by their products
- vesicle fuses with cell membrane and release contents by exocytosis
what does the pituitary gland release
growth hormone-> stimulates growth
follicle stimulating hormone -> controls testes and ovaries
antidiuretic hormone -> causes reabsorption of water in kidneys
what does the thyroid gland release
thyroxine-> raises basal metabolic rate
what does the adrenal gland release and what does this hormone do
adrenaline-> raises basal metabolic rate, dilates blood vessels, prepares the body for action
what does the pancreas release
insulin
lowers blood glucose conc
what does the ovary release and what does that hormone do
oestrogen
promotes development of ovaries and female secondary sexual characteristics
what does the testis release
testosterone
promotes development of male secondary sexual characteristics
what do transcription factors do
- proteins called transcription factors control the transcription of genes
- transcription factors bind to DNA sites near the start of genes and increase or decrease the rate of transcription
- hormones can affect the activity of transcription factors
what are activators and repressors
- factors that increase the rate of transcription are called activators
- factors that decrease the rate of transcription are called repressors
how can hormones work inside cells
some hormones can cross the cell membrane, enter the nucleus and bind to transcription factors to alter gene transcription
how can hormones be used to regulate body temperature at normal temps
- at normal body temperature the thyroid hormone receptor (which is a transcription factor) binds to DNA at the start of a gene
- this decreases the transcription of a gene coding for a protein that increases metabolic rate
how can hormones be used to regulate body temperature at cold temps
- at cold temperatures, thyroxine is released which binds to the thyroid hormone receptor which causes it to act as an activator
- the transcription rate increases, producing more protein
- the protein increases the metabolic rate → causing an increase in body temp
why cant some hormones work from inside the cell
some hormones e.g protein hormones cant cross the cell membrane as they arent lipid soluble
however they can still affect the activity of transcription factors
how do hormones work from outside the cell membrane
- they bind to receptors in the cell membrane which activates messenger molecules in the cytoplasm of the cell
- these messenger molecules activate enzymes such as protein kinases which trigger a cascade ( a chain of reactions) inside the cell
- during the cascade transcription factors can be activated → these then effect the transcription of genes in the cell nucleus
what happens if you do too much exercise
- doing more than your body can physically tolerate with inadequate rest to allow for recovery may lead to immune suppression and increased wear and tear on joints
- immune suppression could lead to more frequent infections
- increased wear and tear on joints may need surgical repair
what kind of infections is athletes more prone to
- athletes that are engaged in heavy training programmes are more prone to infection than normal
- sore throats, flu-like symptoms (upper respiratory tract infections) are more common
what is the suggested relationship between risk of infection and amount of exercise? sketch the shape to show this relationship on a graph
some scientists have suggested that there is a U-shaped relationship between risk of infection and amount of exercise
what are the two main factors have been suggested as contributing to higher infection rates when doing too much exercise
exposure to pathogens
suppressed immunity
why does exposure to pathogens contribute to higher infection rates in athletes
- the location of competitions and and any necessary travel may expose the athlete to a greater a greater range of infected people and unfamiliar organisms
- participants in team sports will also bring players into close contact with others → increases the chance of transmission of infection
what is the effect of moderate exercise on immunity
moderate exercise increases the number and activity of natural killer cells
natural killer cells are activated in several ways e.g by cytokines and interferons
what are natural killer cells
- is a type of lymphocyte
- found in blood and lymph
- they don’t use specific antigen recognition unlike B and T cells
- they provide non specific immunity against cells invaded by viruses and cancerous cells
how do natural killer cells work
- they release perforin which makes pores in the membrane of the targeted cell
- these pores allow other molecules such as protease to enter and cause apoptosis
what is the effect of vigorous exercise on the immune system
- research shows that during recovery after prolonged high intensity exercise, the number and activity of some cells in the immune system falls. these include:
- natural killer cells
- phagocytes
- B cells
- T helper cells
therefore the specific immune system is temporarily depressed
what is the effect of a decrease in T helper cells which occurs due to vigorous exercise
- the dec in T helper cells reduces the amount of cytokines available to activate lymphocytes
- therefore the number of antibodies produced falls
why may vigorous exercise reduce the available non specific immune response against upper respiratory tract infections
suggested that an inflammatory response occurs in muscles due to damage to muscle fibres caused by heavy exercise
this may reduce the available non-specific immune response against upper respiratory tract infections
physical exercise and psychological stress cause secretion of hormones such as adrenaline and cortisol which are known to suppress the immune system
recall some advantages of getting enough exercise
- lowers BP due to increased vasodilation → reduce risk of CHD and stroke
- increases HDL levels in the blood and reduces LDLs
- balance between energy input and output → healthy weight
- reduces likelihood of developing type 2 diabetes due to increased sensitivity of muscles to insulin which improves blood glucose regulation
- increases bone density and reduces its loss during old age
- improves wellbeing
what are the effects of too little exercise
- obesity → leads to high BP and high LDL levels
- increase risk of CHD and stroke, diabetes (type 2)
- high glucose levels due to eating sugar rich foods can reduce the sensitivity of cells to insulin resulting in type 2 diabetes
- the body doesn’t produce enough insulin and body cells don’t respond to the insulin that is produced
- so blood sugar levels cant be controlled
- decreased absorption of glucose from the blood → cells break down fatty acids and proteins instead leading to weight loss
how are joints damaged by exercise
- high forces generated on the joints
- repeated forces on joints can lead to wear and tear of one or more parts of the joint
- many joint disorders are associated with such overuse and can also result from ageing
these disorders are typically associated with pain, inflammation and restricted movement of the join
what are the treatments for wear and tear on joints
treatment usually involves rest, ice, compression and elevation, anti-inflammatory pain killers or surgical repair
what injuries can occur to the knees due to wear and tear
athiritis
patellar tendonitis
damage to ligaments
how can athiritis occur
articular cartilage covering the surfaces of bones wears away → bones may grind on each other → cause damage that can lead to inflammation and a form of arthritis
how can paellar tendonitis occur
kneecap doesn’t glide smoothly across the femur due to damage of the articular cartilage on the femur
how can damage to ligaments occur
sudden twisting/ abrupt movement of the knee joints often results in damage to the ligaments
why were surgical operations painful and recovery takes a long time
- main reason for this was due to large incisions needed to remove or repair very small structures
- a large hole had to be made to allow access for the surgeons hands and instruments + also to let in enough light to let the surgeon see what they’re doing
what is keyhole surgery
- with keyhole surgery, using fibre optics or minute video cameras this has changed
- it is possible to repair damaged joints or remove diseased organs through small holes
- keyhole surgery on joints is called arthroscopy
how is keyhole surgery carried out
one or two small incisions made. a camera and light source are inserted and if surgery is required then miniature instruments are also inserted
what is the advantages of keyhole surgery
- since only a small incision is made, recovery after keyhole surgery can be rapid and only a short stay in the hospital is needed
- patients lose less blood and have less scarring as they don’t involve big incisions
- makes it easier for the patient to return to normal activities
what is an example of a common sports injury
damaged cruciate ligaments
can be fixed by keyhole surgery
what is the cruciate ligament and how can they be treated
cruciate ligaments are found in the middle of the knee connecting your thigh bone to your lower leg bone
- they can be removed and replaced with a graft
- the graft is likely to be from a tendon in the patients leg or from a donors tendon
what can protheses be used for
- it can be possible to replace the damaged or missing body parts with a prosthesis
- can be used to replace whole limbs or parts of limbs
how do prothesis work
- some prostheses include electronic devices that operate the prosthesis by picking up information sent by the nervous system
- these make it possible for people with some disabilities and certain injuries to participate in sport
how can damaged knee joints be treated
- damaged knee joints can be replaced by prosthetic joins
- a metal device is inserted into the knee to replace damaged cartilage and bone
- the knee joint and the ends of the leg bones are replaced to provide a smooth knee joint
- cushioning in the new joint helps to reduce the impact on the knee
- it allows people with serious knee problems to move around and participate in low impact sports such as walking, swimming
what are some examples of performance enhancing drugs
anabolic steroids
stimulants
narcotic analgesics
what do anabolic steroids do
increase strength
speed
stamina by increasing muscle size
allow athletes to train harder
they also increase aggression
what do stimulants do
speed up reactions
reduce fatigue
increase aggression
what do narcotic analgesics do
reduce pain, so injuries don’t affect performance
what happens if youre caught taking performance enhancing drugs in sports competition
- hese are banned in most sports
- can be tested for these at any time
- if they’re caught they can be banned from competing and stripped of any medals
what are the arguments for the use of performance-enhancing drugs
- up to each individual → athletes should have the right to make their own decisions to take the drugs and whether they’re worth the risk
- drug free sports isn’t fair and different athletes have access to different training facilities, coaches, equipment etc so the use of these drugs can overcome these inequalities
- athletes that wants to compete at a higher level may only be able to by using these drugs
what are the arguments against using performance enhancing drugs
- some of these drugs are illegal
- competitions become unfair if some people take drugs as people gain an advantage by taking them rather than through training and hard work
- serious health risks associated with them e.g high BP and heart problems
- athletes may not be fully informed of the health risks of the drugs they take
what is the synovial membrane
secretes synovial fluid which acts as a lubricant
allows the joints to move
synovial fluid acts as a shock absorber and acts as a lubricant to reduce friction between the bones
what happens to the muscles in the arm when the arm is lowered
when arm is lowered
bicep relaxes
triceps contract
what is the structure of the synovial joint and the functions of its structures
recall the different types of joints
gliding joint present in the vertebrate
pivot joint present at the top of the joint
hinge joint present in elbows
ball and socket present in the hips
what is the gliding joint
two flat surfaces slide over one another
what is the hinge joint
convex surface fits into a concave shape
allows for movement in two directions
what is the pivot joint
part of the bone fits into a ring shapes structure
allows rotation
joint at the stop of the spine
what is the ball and socket joint
a round head fits into a cup shaped socket
allows for omni directional movement
what is the structure of the tendon
it is tough and non elastic
what is the importance of the tendon linked to the bone
the contraction of muscle pulls bone. the tendons are joined to the muscle and then bones
how does the texture of the synovial fluid help in this role
it is a thick and viscous. this makes it hard to compress an d therefore good at absorbing shocks and makes it a good lubricant
what is the role of the fibrous joint capsule
contains the synovial fluid
the capsule tells you that it must be a moveable synovial joint
what is meant by articulating surface
are the points of contact between bones
they fit together closely but dont normally touch due to synovial fluid present within the joint capsule
the degree of movement at a joint is determined by the shape of the articulating surfaces
what is the appearance of the ligament
white and shiny
smooth and reasonably firm but not as hard as bone
why are ligaments slightly elastic
to allow some movement of bones around a joint
What does EPO do
stimulates formation of red blood cells
Performance enhancing drug
allows the body to transport more oxygen to muscles and therefore increase stamina and performance
