Unit 5: Energy, Exercise and CoordinationRevision Notes

Topic 7Run for Your Life

Muscles & MovementLigaments hold bones together and restrict their movements at joints. Theyre made of elastic connective tissueTendons are non-elastic fibrous, cord-like tissue which attach muscle to bone

Muscles & MovementKnee joint is a synovial joint:

Tendon joins muscle to boneMuscleLigament joins bone to bone, strong & flexibleSynovial Membrane secretes synovial fluidSynovial Fluid Acts as lubricantBoneCartilage absorbs synovial fluid, acts as shock absorberCartilage Pad gives extra shock protectionFibrous capsule encloses the joint

Muscles & MovementSkeletal muscles are usually in antagonist pairs. These are pairs of muscles which pull in opposite directionsFlexors contract to flex or bend a joint (biceps)Extensors contract to extend or straighten a joint (triceps)

Muscles & MovementThe structure of skeletal muscles are shown right.Myofibrils are made up of fibrous proteins: actin (thin filaments) and myosin (thick filaments)Sarcolemma is the cell surface membrane of a muscle cellSarcoplasmic Reticulum is a specialised ER. It stores and releases Ca+ ions.Sarcoplasm is cytoplasm inside a muscle cell.

Connective TissueBundle of muscle fibresOne muscle fibreMyofibril

One SarcomereNeuromuscular Junction is the specialised synapse between neurones and muscle cells.

Muscles & MovementThe sliding filament theory of music contraction is given most simply by a diagram (R)Myosin filaments have flexible heads that can change orientation, bind to actin and hydrolyse ATP using ATPaseActin filaments are associated with 2 other proteins: Troponin & Tropomyosin which control binding of myosin heads to actin filaments.

1 sarcomereMyosinActinArrangement of filaments when relaxedArrangement of filaments when contracted

Muscles & MovementWhen a nerve impulse arrives at a neuromuscular junction, Ca+ ions are released from sarcoplasmic reticulum. The process below then occurs:

ActinActinTropomyosinTroponinCa2+ binding siteADP + PiMyosin binding site blocked by tropomyosin. Myosin head cannot bind.Ca2+ attaches to troponin (on the actin) causing it to move together with threads of tropomyosinMyosin binding siteADP + PiCa2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Ca2+Myosin binding sites of actin are exposed so myosin form cross-bridges with actin filamentADP + PiADP + Pi ReleasedMyosin heads release ADP and Pi and change shape are a result. This is the POWER STROKE.ATP binds to myosin head causing it to detach from the actin.ATP BINDSATPATPase causes ATP hydrolysisMyosin head returns to upright position.ADP + Pi

Muscles & MovementThere are 2 types of muscle fibres - Fast Twitch and Slow Twitch

Slow TwitchFast TwitchSpecialised for slower sustained contraction. Can cope with long periods of exercise.Specialised to produce rapid, intense contractions in short bursts.Many mitochondria - ATP comes from aerobic respiration (in E.T.C.)Few mitochondria - ATP comes from anaerobic respiration (in glycolysis)Lots of myoglobin (gives it a darker colour) to store O2 and lots of capillaries to store O2. Little myoglobin and few capillaries. The muscle has a light colour.Fatigue resistant.Fatigue quickly.Low glycogen contentHigh Glycogen contentlow levels of creatine phosphatehigh levels of creatine phosphate

Energy SystemsAerobic respiration:glucose + oxygen carbon dioxide + water + energyC6H12O6 + 6O2 6CO2 + 6H2O + ~30ATPAnaerobic respiration:glucose lactic acid + energyC6H12O6 3C3H6O3 + 2ATPATP provides energy to cells. Energy is need to add a third phosphate bond to ADP (which creates ATP). When the bond is broken by hydrolysis, the energy released can be used in processes in the cell which need energy.

Energy Systems - GlycolysisGlucose (hexose) (6C)hexose phosphate (6C)hexose biphosphate (6C)2x triose phosphate (3C)intermediates2x pyruvate (3C)ATPATP2ATP2H2ATP2NAD2 Reduced NADGlycolysis=Gluco (sugar) + lysis (splitting)

Energy Systems -Anaerobic RespirationGlucose Pyruvate 2H reduced NAD NAD 2H Lactate 2ADP + 2Pi2ATPLactate Pathway

Glycolysis doesnt need molecular O2. Instead, a constant NAD supply is required.In anaerobic respiration, NAD is made by e.t.c. The reduced NAD must be oxidised to NAD.During anaerobic respiration, this must come from elsewhere.

In animals, pyruvate gets reduced into lactate, and NAD is formed.The anaerobic respiration allows animals to make a small amount of ATP. The process is not very efficient, but its fast and delivers ATP to muscle cells when O2 isnt delivered fast enough.Lactate forms Lactic Acid in solution. This reduces the pH which can inhibit enzymes and cause muscle cramp if allowed to build up.Once aerobic respiration resumes most lactate is converted back into pyruvate. It is oxidised via the Krebs cycle into CO2 and H2O. Extra oxygen needed for this is the Oxygen debt, which must be paid back.

Investigating Rate of Respiration - Core PracticalRate of aerobic respiration can be determined using a respirometer by measuring rate of oxygen absorbed by small organisms.Any CO2 produced is absorbed by the soda lime, so that Oxygen absorbed by the organisms results in the coloured liquid moving towards the organism in the tube.There is problems with pressure changes in the apparatus, which can be solved by the syringe if necessary.

Aerobic RespirationAerobic respiration takes place in 2 stages:First pyruvate is oxidised into Carbon Dioxide, and Hydrogen (accepted by NAD and FAD). This takes place in the matrix of mitochondria and involved the Krebs cycle.In the 2nd stage, most of the ATP made in aerobic respiration is synthesised by oxidative phosphorylation associated in electron transport chain (e.t.c.). This involves chemiosmosis and ATPase. It takes place in the cristae of the mitochondria.

Cytoplasm

The Link Reaction: Preparing for the Krebs cycle.Pyruvate from glycolysis2HAcetyl (2C) Co-enzyme ACO2NAD or FADReduced NAD or FADTo Krebs CycleEach glucose provides 2 Pyruvate from Glycolysis. This means the link reaction happens twice per glucose, so 2 Acetyl are made.Taken up byHydrogenacceptors.Inside Matrix

The Krebs CycleAcetyl (2C) Co-enzyme A6C Compound5C Compound4C CompoundCO22HCO2ATP2H2H2HNADReduced NADNADReduced NADNADReduced NADFADReduced FADEach molecule of the 2C Acetyl coenzyme A from the link reaction is used to generate:three molecules of reduced NADone molecule of reduced FADtwo molecules of CO2one molecule of ATP by substrate-level phosphorylation (synthesised directly from the energy released by reorganising chemical bonds).one molecule of a 4-carbon compound which is regenerated to accept an acetyl group and start the cycle again.

As each glucose molecule makes 2 pyruvate = 2 Acetyl = 2 turns around carbon cycle.

Oxidative phosphorylation, chemiosmosis and the electron transport chainVast majority of ATP generated in aerobic respiration comes from the electron transport chain...

electroncarrierelectroncarrierelectroncarrierH+H+H+NADReduced NADH2OO2H+ADP+PiATPIntermembrane Spaceinner mitochondrial membranemitochondrialmatrixReduced NAD (coenzyme) carries H+ and e- to e.t.c. on inner mitochondrial membrane.

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6Electrons 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.

2Protons (H+) move across the inner membrane mitochondrial membrane creating high H+ concentrations in the intermembrane space.

3H+ diffuse back into the matrix down electrochemical gradient.

4H+ diffusion allows ATPase to catalyse ATP synthesis

5Electrons & H+ ions recombine to form hydrogen atoms which then combine with oxygen to create water. If supply of oxygen stops, e.t.c. and ATP synthesis will also stop.

6Majority of ATP generated by aerobic respiration comes from the activity of the e.t.c. in the cristae (inner membrane of the mitochondria)

Aerobic respiration -The overall reaction can be summarised as 1) splitting and oxidation of a respiratory substance (glucose) to release CO2 as a waste product.2) reuniting hydrogen with oxygen which releases a large amount of energy in the form of ATP.

summaryThe diagram (right) shows how many ATP molecules are generated by substrate level phosphorylation and oxidative phosphorylation (via e.t.c.)

Control of cardiac cycleThe impulse to contract the heart originates from the heart itself. Hence the heart is myogenic.

RARVLVLAsinoatrial node (SAN)atrioventricular node (AVN)non-conducting layer in heart wall between atria and ventricles

Purkyne fibresElectrical impulses from the SAN spread across the atria walls, causing contraction. ATRIAL SYSTOLE.

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4Impulses pass to the ventricles via the AVN after a short delay to allow time for the atria to finish contracting.

2Impulses pass down the Purkyne fibres to the heart apex.

3The impulses spread up through the ventricle walls causing contraction from the apex upwards. Blood is squeezed into arteries. VENRTICULAR SYSTOLE.

4After systole the heart goes into diastole, where the cardiac muscles relax. Returning blood fills atria.

Measuring electrical changes in the heartElectrical currents caused by wave of depolarisation when the impulse spreads can be detected using an ECG.

ECG resultsP WaveT WaveST segmentQ SRPR interval1 SecondThe P wave is the time of atrial systole.The QRS complex is the time of ventricular systole.The T wave is causing repolarisation of ventricles during diastoleYou can work out heart beat by measuring time interval between 1 P wave and next (1 cycle) and working out rate per minute.

Regulation of cardiac outputcardiac output (dm3min-1) = stroke volume (dm3) x heart rate (min-1) stroke volume is volume of blood leaving the left ventricle with each beatthe heart rate can be affected by hormones (eg adrenaline) and nervous control.the Cardiovascular Control Centre in the medulla of the brain controls the sinoatrial node via nerves.the Sympathetic Nerve speeds up the heart rate in response to falls in the pH in the blood due to CO2 and lactate levels rising, increases in temperature and mechanical activity in joints.Impulses carried by vagus nerve (Parasympathetic) slows down heart rate when the demand for O2 and CO2 reduces.

Regulation of ventilation rateventilation rate = tidal volume x number of breaths per minuteTidal volume - volume of air breathed in or out of lungs per breathVital capacity - max volume of air that can be forcibly exhaled after a max intake of airThe ventilation centre in the medulla controls the rate and depth of breathing in response to impulses from chemereceptors in the medulla and arteries which detect the pH and concentration of CO2 in the blood.Impulses are sent from the ventilation centre to stimulate muscles involved in breathing.A small increase in CO2 concentration causes a large increase in ventilation.It also increases in response to impulses from the motor cortex and from stretch receptors in tendons and muscles involved in movement.We also have some voluntary control over breathing.

SpirometerA person using a spriometer breathes in and out of an airtight chamber causing it to move up & down and leaving a trace on a revolving drum.

The volume of O2 absorbed in a given time by measuring differences in volume between troughs (labelled A + B) in the diagram and dividing by the time between A + B.

HomeostasisHomeostasis is the maintenance of a stable internal environment. A homeostatic system requires:

receptors to detect the change away from the norm value (stimulus)a control mechanisms that can respond to the information. The control mechanism uses the nervous system or hormones to switch effectors on or offeffectors to bring about the response. Muscles and glands are effectors.InputReceptorsControl MechanismEffectorsOutputFeedback

Homeostasis -Negative feedback helps to keep the internal environment constant. A change in the internal environment will trigger a response that counteracts the change. For negative feedback to occur there must be a norm value (set point).

negative feedbackConditions controlled by homeostasis fluctuate about the norm value.norm valueCondition is controlled by negative feedback.norm valuerise abovenormfall below normchange from norm detectedeffectors act to return the condition to the set pointtime

Homeostasis The increased respiration rate not only produces a lot of CO2 and/or lactate but the energy transfers also release a lot of heat energy. It can be as much as 1C rise every 5-10 mins is the heat cant be dispersed.The control of core body temperature through negative feedback is called thermoregulation.Thermoreceptors in the skin detect changes in temperature, as well as thermoreceptors in the hypothalamus which can detect changes in the core blood temperature.If a rise in temperature is detected above the norm value the heat loss centre will stimulate effectors to increase heat loss from the body (usually through skin)

and exercise

Homeostasis This can be summarised in the diagram below:

and exerciseset point(norm)detected byreceptorsheat losscentre inhypothalamuseffectorsreactset point(norm)set point(norm)

detected byreceptorsheat gaincentre inhypothalamuseffectorsreactTemperature RisessendsimpulsessendsimpulsesTemperature FallsTemperature FallssendsimpulsessendsimpulsesTemperature RisesHeat Loss CentreStimulates: -sweat glands to secrete sweat

Inhibits:- contraction of arterioles in skin (dilates capillaries)- hair erector muscles.- liver (reduces metabolic rate.- skeletal muscles (relax - no shivers) Heat Gain Centre

Stimulates: -arterioles in the skin to contsrict-hair erector muscles to contract- liver to raise metabolic rate- skeletal muscles to contract in shivering

Inhibits:- sweat glandsAbove and below certain temperatures makes homeostasis fail. Instead Positive feedback may occur resulting in a higher temperature continuing to rise or low temperature falling still.This may lead to death.

Medical Technology & SportKeyhole surgery uses fibre optics. This makes it possible for surgeons to repair damaged joints (inc. ligaments in knee) which precision and little damage. Only a small incision is made = less blood & damage to joint - recovery is much quicker.

Prostheses are artificial body parts designed to help the patient regain relatively normal function and/or appearance. The design of prostheses has improved over the years so many disabled athletes can compete at high levels. (eg dynamic response feet literally provide a spring in their step). Damaged joints (eg knee) can be repaired with small prosthetic implants to replace damaged bone ends. This restores mobility and free the patient from a life of pain.

Too Little ExerciseOver prolonged periods of time, too little exercise can have side effects:

reduced physical endurance, lung capacity, stroke volume and maximum heart rate.increased resting heart rate. blood pressure and storage of fat in the body.increased risk of CHD, type 2 diabetes, some cancers, weight gain and obesity.impaired immune response due to lack of natural killer cells.increased LDL levels and reduced HDL levels.reduced bone density = higher risk of osterperosis.

Too Much ExerciseOvertraining can lead to chronic fatigue and poor athletic performanceIt can also lead to increased wear and tear on joints. Damage to cartilage in synovial joints can lead to inflammations and a form of athritis. Ligaments also damage. Bursae the cushion joint parts become inflamed and tender

Also, there is correlation between intense exercise and the risk of infections like colds and sore throats. It could be caused by increased pathogen exposure or a suppression of the immune system.There is some evidence that the number and activity of some cells of the immune system may be decrease in post vigorous exercise recovery. It may also be true that damage to muscles and release of hormones (eg adrenaline) during exercise may cause an inflammatory response which could also suprpress the immune system.

Effect of Drugs on GenesSome drugs (eg anabolic steroids) are closely related to natural steroid hormones.They can pass directly through cell membranes and be carried into the nucleus bound to a receptor molecule.These hormone/receptor complexes act as transcription factors. They bind to the promoter region of a gene allowing RNA polymerase to start transcription.As a result more protein synthesis takes place in the cells.EXAMPLE: Testosterone increases protein synthesis in muscle cells, increasing the size & strength of muscle tissue. Peptide hormones dont enter cell directly but they bind with receptors on the CSM which starts a process that results in the activation of a transcription factor within the nucleus.EXAMPLE: Erythropoietin (EPO) stimulates the production of red blood cells. THis means that blood carries more oxygen, which is good for an athlete.

Effect of Drugs on GenesRNA polymerasePromoter region (site for RNA polymerase attachment)

GeneDNATranscription factors

transcriptioninitiation complexRNA SynthesisGenes are switched on by successful formation and attachment of transcription initiation complex to the promoter region.Genes remain switched off by the failure of the transcription initiation complex to form and attach to the promoter region. This is due to absence of protein transcription factors or action of repressor molecules.

Performance Enhancing Drugs & EthicsSome athletes feel the need to use illegal performance-enhancing substances to pursue excellence. Others may feel the need to follow suit, in order to keep up.Ethical frameworks can be used on both sides of the argument:- right and duties- maximising the amount of good in the world- making decisions for yourself- leading a virtuous lifeEXAMPLE - doping could be not acceptable because of athletes right to a fair competition. However, it could equally be considered that athletes have a right to exercise autonomy, to achieve their best performance.

Performance Enhancing Drugs & EthicsIn order to maintain if something is ethical or not, a reasonable argument needs to be executed.Ethical Absolutists see things as very clear cut, black and white. They would take one of two stances: - It is never acceptable for athletes to use such substances even if legal or - It is always acceptable for athletes to use any substance available to them to compete effectively, even if there are health risks.Ethical Relativists would realise that people and circumstances may be different- EXAMPLE It is wrong for athletes to use performance enhancing substances but there may be some occasions when it is acceptable.

Topic 8Grey Matter

Responding to the EnvironmentAnimals have a fast acting nervous systems which contain neurones (nerve cells) that carry information in the form of impulses.In mammals, sensory neurones carry impulses from receptors to a central nervous system (CNS) which consists of the brain & spinal crd.The CNS incorporates relay neurones, and processes info from lots of sources and sends the via motor neurones to effector organs (eg. muscles and glands)

The Pupil ReflexThe iris contains antagonistic muscles (radial and circular) which control iris size under the influence of the autonomic nervous system (involuntary)

Radial Muscles RelaxCircular muscles contractRadial Muscles ContractCircular muscles relaxPupil ConstrictedPupil DilatedIn bright light photoreceptors (eg rods) in the retina cause nerve impulses to pass along the optic nerver to a group of nerve cells in the brain.These cells then send impulses along the parasympathetic motor neurones to the circular muscles of the iris.The muscles contact, reducing the diameter of the pupil so less light enters the eye which prevents retinal damage.

In low light situations, fewer impulses reach the retina, hence fewer reach coordinating centre in the brain.Impules are sent down sypathetic motor neurones to radial muscles of the iris.This causes radial muscles to contract and the pupil become dilated.This allows more light in.

Converts toReverts quickly in Far Red LightPRreverts slowly in the dark as relatively unstablemay trigger a range of different photoperidic responsesPlant Sensitivity - PhotoperiodismPlants flower and their seeds germinate in response to changes in day length. The photoreceptor here is Phytochrome (blue-green pigment), and comes in two forms : Red(PR) and Far-red(PFR)

PFRAbsorbs natural (red) lightInactiveActive

Plant Sensitivity - PhototropismTropisms are growth responses in plants, where direction of growth is determined by the direction of external stimulus. If a plant grows towards a stimulus, it is a positive trophic response.In plant shoots, light and auxins have an effect:

With illumination from all sides, an even distribution of auxins moves down from the shoot tip and causes elongation of cells across the zone of elongationAuxins are broken down by enzymesWhen light comes from just one side, auxins move along the shaded side of the shoot, elongating them which bends to tip towards the light.

Comparison of communication and coordination methods in plants and mammals

Nervous system in mammalsEndocrine system in mammalsTropisms in plantsElectrochemical changes giving an electrical impulse. Chemical neurotransmitters used at most synapses.Chemical hormones from endocrine glands carried in blood plasma around circulatory system.Chemical growth substances (eg auxins) diffusing from cell to cell. Some may go in phloemrapid actingslower actingslower actingUsually associated with short term changes (eg muscle contraction)Can control long term responses (eg growth). Some involved in homeostasis (eg blood sugar levels). Some can be relatively fast (eg adrenaline response)Controls long term growth responses (eg cell elongation)Response is very localised and specific to (eg) muscle cell or glandResponse can be widespread or targeted to specific cells.Response may be widespread but normally restricted to cells within a short distance of the growth substance being released.

Structure of NeuronesDendrites conduct impulses towards cell body.Axons conduct impulses away from cell body.Neurones can carry waves of action potentials (electrical activity) over long distances. The membranes are polarised.Myelin sheath wrapped is a fatty insulating layer. This increases the speed of conduction through SALTATORY CONDUCTION:Schwann cells wrap around the neurone go nourish and protect it and produce myelin sheath.There are small gaps left uncovered called nodes of Ranvier.Action potentials jump from one node of Ranvier to the next, increasing conduction speed.

Nucleuslipid layer made by schwannAxonSchwann CellCell BodyDendritesNucleusAxonSchwann cellnode of RanvierTerminal BranchesMotor NeuroneCell BodySchwann cellDendritesAxonSensory NeuroneRelay NeuroneCell BodyAxonDendritesseveral axons held together making a moveNerve

Transmission of a nerve impulseIn a resting neurone, there are more sodium (Na+) ions outside the cell membrane than inside, and more potassium (K+) inside that outside.The inside of resting neurone has a negative charge in comparison, due to presence of chloride ions and -ve charged proteins = p.d. of about -70mV. This is resting potential. The membrane is called Polarised.The sodium-potassium pump creates concentration gradients across the membrane (Na+ move out, K+ in).Potassium ion channels allow facilitated diffusion of K+ out of the membrane (down concentration gradient) which creates that uneven charge.

Transmission of a nerve impulseIf a neurone cell is stimulated by an impulse, voltage dependant Na+ channels open and Na+ diffuse in.This increases the positive charge inside the cell = charge across membrane is reversed.The membrane now carries a p.d. of +40mV. This is the action potential and the membrane is said to be polarised.As the charge reverses, the Na+ channels shut and voltage-dependant K+ ions channels open so more potassium ions leave the axon, which repolarises the membrane.The membrane can become hyperpolarised, when the p.d. drops below the resting potential. Voltage-dependant K+ channels close. K+ diffuses back into the axon to recreate the resting potential.

Transmission of a nerve impulseMovement of ions in and out of membrane during an action potential.

Propagation of a nerve impulse along an axonHigh Na+High K+axonAt resting potential, there is a positive charge on the outside, and negative charge inside, which high Sodium concentration outside and high Potassium concentration inside.When stimulated, voltage dependant Na+ channels open and Na+ flow into axon = depolarisation. Localised electric currents are generated in the membrane. Na+ move into adjacent polarised (resting) region causing a change in charge across this part of membrane1st Action PotentialNa+Na+stimulationlocalised electric current

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3The change in p.d. in the membrane adjacent to the 1st action potential initiates a second action potential.At the site of the first action potential, the voltage dependant Na+ ion channels close and voltage dependant K+ channels open. K+ leave the axon, repolarising the membrane. The membrane is hyperpolarised

4A 3rd action potential is initiated by the 2nd. In this way local electric currents cause the nerve impulse to move along the axon.At the site of the 1st, K+ move back into axon, restoring action potential.2nd Action PotentialNa+Na+K+K+3rd Action PotentialNa+Na+K+K+Refractoryperiodprogress of impulseAction potentials are all or nothing. A bigger stimulus increases the frequency of action potentials - NOT the strength.

A threshold stimulus must be applied to produce an action potential.Right after an action potential there is a refractory period. This is where a new action potential cannot be generated as Na+ channels cant reopen.This ensure that action potentials are kept as separate signals, and are UNIDIRECTIONAL

SynapsesA synapse it the point where one neurone meets another.At the tip of an axon, an impulse opens up Calcium ion (Ca+) channel, then triggers the release of a chemical neurotransmitter from synaptic vesicles.The neurotransmitter can diffuse across the gap between neurones (synaptic cleft) and bind to receptors of postsynaptic membrane.If the neurotransmitter comes from a excitatory neurone, it may open Na+ channels on the post synaptic membrane which will trigger a new action potential in the postsynaptic neurone.Some neurotransmitters are inhibitory, and may open Chloride ion channels on the post synaptic membrane, causing it to be hyperpolarised and therefore harder to get an above-threshold response needed to trigger the new action potential.

SynapsesAn enzyme is often present in the synaptic cleft to hydrolyse the neurotransmitter to avoid the response from repeating.The neurotransmitter may be taken back into presynaptic membrane to be reused.As receptors are only on the postsynaptic membrane, the signal can only be unidirectional. Synapses also act as junctions and allow nerve impulses to converge or diverge because one neurone can meet many others at a single synapse.

SynapsesAxonSynaptic VesicleNeurotransmitterPresynaptic MembranePostsynaptic MembraneSynaptic CleftCa2+Na+An action potential arrives

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1The membrane depolarises. Calcium ions channels open.Calcium ions enter the neurone.

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2Calcium ions cause synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane.

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3Neurotransmitter is released into the synaptic cleft.

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4Neurotransmitter binds with receptors on the postsynaptic membrane. Cation channels open. Sodium ions flow through the open channels.

5Membrane depolarises and initiates an action potential

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6When released the neurotransmitter will be taken up across the presynaptic membrane (whole or after being broken down), or it can diffuse away & be broken down

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Vision & Human PhotoreceptorsHuman eyes have 2 types of photoreceptor cells found in our retinas. 1) Cones allow colour vision in bright light and are clustered in the centre of the retina.2) Rods only provide black and white vision, but are much more sensitive than cones and work in dim light conditions.

Vision & Human PhotoreceptorsLight energy is absorbed by rhodopsin which splits into retinal and opsin.The opsin binds to the membrane of the outer segment of the cell and this causes sodium ion channels to close.The inner segment continues to pump sodium ions out of the cell and the membrane becomes hyperpolarised.This means that glutamine will not be released across the synapse.Glutamine usually inhibits the neurones which connect the rod cells to the neurones in the optic nerve.When there is less inhibition an action potential forms and is transmitted to the brain.The info from the optic nerve is processed by the brain in the visual cortex.

darklightOuterSegmentInnerSegmentNa+ diffuse through open cation channelsNa+Na+Na+ move down concentration gradientNa+ actively pumped outMembrane slightly depolarised -40mVNeurotransmitter is released and binds to bipolar cell preventing it depolarisingBipolar NeuroneLight breaks down rhodopsin to retinal and opsinOpsin binds to the membrane causing a series of reactions which result in the Na+ channels being closedNa+ actively pumped outMembrane hyperpolarisedNo Neurotransmitter is releasedNa+Cation channels in bipolar cell open and membrane becomes depolarised, generating an action potential in the optic nerve neurone.

The CerebrumThe cerebral cortex (cerebrum) is the largest part of the brain.Its divided into 2 hemispheres connected by a band of white matter called the Corpus Callosum. The cerebrum is associated with advanced mental activity like language, memory, calculation, processing info from eyes & ears, emotion and controlling all voluntary activities.

The CerebrumFrontal Lobe Parietal Lobe OccipitalLobeTemporal Lobe CerebullumFrontal Lobe Concerned with the higher brain functions, like decision making, reasoning, planning & consciousness of emotion.Also, its concerned with forming associations and with ideas.It includes the primary motor cortex which has neurones that connect directly to the spinal cord and brain stem (and onto the muscles).Parietal Lobe Concerned with orientation, movement, sensation, calculation, some times of recognition & memory.Occipetal Lobe concerned with processing info from eyes, including vision, colour, shape recognition and perspectiveTemporal Lobe concerned with processing auditory info, ie hearing, speech, recognition and also involved in memory.Next Slide for more on Cerebellum

The CerebellumSpinal CordMedulla OblongataCerebellumCerebrumMidbrainPituitary GlandBasal GangliaCorpus CallosumHypothalalmusThalamusHypothalamuscontrols thermoregulationCerebellumimportant for balance & coordinating movementsMedulla Oblongatacontrols many body processes such as heart rate, breathing and blood pressure

Critical WindowsCritical Windows (or critical periods) for development are those periods of time where it is though that the nervous system needs specific stimuli in order to properly develop.Evidence for critical windows have come from medical observationsEXAMPLE: A child under 10 days who develops cataracts may suffer from permanent visual damage even if cataracts are removed at a later dateAnimal models are also used; EXAMPLE: Hubel and Wiesel used kittens and monkeys as models to investigate the critical window in visual development because of the similarity of their visual systems to that of humans.The animals were deprived of stimulus of light into one eye (monocular deprivation) at different stages of development and for different lengths of time.It found that kittens deprived of light in 1 eye at age 4 weeks were effectively permanently blind in that eye.Monocular deprivation before 3 weeks and after 3 months had NO effect.

Eye deprived of light during critical periodEye that remains open during critical periodAxons do not pass nerve impulses to cells in the visual cortexAxons pass nerve impulses to cells in the visual cortexInactive synapses eliminatedSynapses used by active axons are strengthenedEye has no working connection to the visual cortex and is effectively blind, even though the cells of the retina and optic nerve work normally when exposed to lightSynapses only present for axons coming from the light-stimulated eye. So the visual cortex can only respond to this eye.

Animal Rights IssuesThe use of animals in scientific study is a controversial topic.Animal Rights activists who hold an absolutist view think it is NEVER right to used animals in medical research.Medical Researchers hold a more relativist view, that humans should keep animals well and minimise harm and suffering as much as possible. The emphasis is on animal welfare (rights to food, drink, vets and normal behaviours). Its very similar to EU law.This all assumes that animals can suffer and experience pleasure.A utilitarian ethical framework allows certain animals

Nature, Nurture & Brain developmentNature: Many of our characteristics develop solely under the influence of our genes with little help from our environment or learning (eg blood group)Nurture: Many Characteristics are learnt or heavily influenced by our environment (eg hair length)

Nature, Nurture & Brain developmentMost characteristics are determined by nature and nurture, or nature via nurture.We are the result of a mix of genetic and environmental factors.Human behaviours, attitudes and skills may have an underlying genetic basis, but are modified (eg by experience etc)EXAMPLE: the chance of developing some cancers has a genetic basis where are gene (or several) interact to confer susceptibility to the disease with environmental factors contributing to the risk of development.

Nature, Nurture & Brain developmentEvidence for the relative roles of nature and nurture in brain development come from a variety of different sources:The abilities of newborn babies: The innate abilities that babies exhibit suggest that genes help form the brain & some behaviours before the baby is born.Studies of patients with damaged brain areas: Some pxs who have suffered brain damage show the ability to recover some of their brain function, which demonstrates that some neurones have ability to change.Animal experiments: eg Hubel and Weisels experiments on critical windows for sight, suggesting that stimulation is important in brain development.Twin Studies: Identical twins obviously share all the same genes. Fraternal (non-identical) twins share the same number as any other sibling would. Twin studies can estimate the relative contribution of genes and the environment. Any differences between identical twins must be due to environmental effects.Identical twins raised apart in comparison to those raised together are particularly useful for study. EXAMPLE: If there is a greater difference between those twins raised apart than twins raised together it suggests some environmental influence. However, twins raised apart may not have completely different environments and twins raised together may develop different personalities due to a desire to be different. In general if genes have a strong influence on the development of a characteristic, then the closer the genetic relationship, the stronger the correlation will be between individuals for that trait.Cross-cultural studies: Investigations into the visual perceptions of groups from different cultural backgrounds support the idea that visual cures for depth perception are at least partially learnt.

HabituationHabituation is a very simple type of learning which involves the loss in response to a repeated stimulus which fails to provide any form of reinforcement (reward or punishment).It allows animals to ignore unimportant stimuli so they can concentrate of reinforce stimuli.

Habituation InvestigationsThis practical measures the time a snail spends withdrawn into its shell when you tap its head (between the eyes).Initially the snail tends to hide for a significant length of time, but as the tapping continues, the time interval decreases.The snail becomes habituated to the tap.Ethical and Safety concerns need to be addressed here as animals are used.

Core Practical

Animal ModelsInvertebrates make for useful animal models for the inner working of the nervous system. Here, Sea Slugs have been used to investigate habituation.Gill withdraws siphon when stimulated by water jetSiphonWater JetAfter several minutes of repeated stimulation of the siphon the gill no longer withdraws.SiphonWater JetWith repeated stimulation, Ca2+ channels become less responsive so less Ca2+ crosses the presynaptic nerve

1Less neurotransmitter released.

2There is less depolarisation of postsynaptic membrane, so no action potential is triggered in motor neurone.

3Ca2+sensory neurone from siphonmotor neurone to the gillGill withdrawalGill

Dopamine & ParkinsonsParkinsons disease is associated with the death of a group of dopamine secreting neurones in the brain (midbrain). This results in the reduction of dopamine levels in the brain.Dopamine is a neurotransmitter which is active in neurones in the frontal cortex, brain stem and spinal cord. It is associated with the control of movement & emotional responses.Treatments for Parkinsons are varied, with most aiming to increase the concentration of dopamine in the brain.Dopamine cannot move into the brain from the bloodstream but the L-Dopa molecule, which is used to make dopamine, can which could help to relieve symptoms. The symptoms of Parkinsons are:muscle tremorsmuscle stiffness & slow movementpoor balance and walking problemsdifficulties with speech and breathingdepression

Serotonin & DepressionSerotonin is another neurotransmitter, but this time its linked to feelings of reward & pleasure. Clinical depression (prolonged feelings of sadness, anxiety, hopelessness, loss of interest, restlessness, insomnia... etc...) is attributed to low serotonin levels. Treatments for depression often involve drugs which can increase serotonin concentration in synapses.EXAMPLE: Prozac is a Selective Serotonin Reuptake Inhibitor (SSRI) that blocks the process which removes serotonin from the synapse.

Drug effects on synapsesSome drugs affect the synthesis, or storage, of neurotransmitters. (eg L-dopa used in the treatment of Parkinsons disease is converted into dopamine, increasing the concentration of dopamine to reduce the symptoms of the disease)Some drugs may affect the release of the neurotransmitter from the presynaptic membrane.Some drugs may affect the interaction between the neurotransmitter and the receptors on the postsynaptic membrane~ some may be stimulatory by binding to the receptors and opening the sodium ion channels - eg dopamine agonists (mimic dopamine due to shape, used in Parkinsons treatment) bind to dopamine receptors and trigger action potentials.~ some may be inhibitory, blocking the receptors on the postsynaptic membranes and preventing the neurotransmitters binding.Some drugs prevent the reuptake of the neurotransmitter back into the presynaptic membrane - eg Ecstasy (MDMA) prevents the reuptake of Serotonin. The effect is the maintenance of a high serotonin concentration in the synapse which brings about moods changes in MDMA users. One of the side effects of MDMA is depression as a result of the loss of serotonin from neurones, due to lack of reuptake. Prozac is a SSRI that blocks the reuptake of serotonin in the treatment of depression.Some drugs may inhibit enzymes involved in breaking down the neurotransmitter in the synaptic cleft, resulting in maintenance of a high concentration of the neurotransmitter in the synapse and therefore repeated action potentials (or inhibition) of the presynaptic cleft.

Drug effects on synapsesPresynaptic membranePostsynaptic membraneNeurotransmitter synthesis & storageNeurotransmitter releaseNeurotransmitter receptor bindingNeurotransmitter reuptakeNeurotransmitter breakdown

Drug developmentWe now know that chemicals which affect membrane-bound proteins or mimic the effect of naturally occurring neurotransmitters can have a significant effect on defective or normal neural pathways. The more we know about the specific proteins (and their shapes) active in cells, the more likely we can find complementary chemicals with the same effect.Traditionally most medicines come from existing plant-based chemicals. However, info from the human genome project could help develop drugs that are highly specific so that they can be effective in lower doses with fewer side effects. Pharmacogenomics links pharmaceutical expertise with the knowledge of the genome project. New drugs have to go through rigorous testing before they go to market (see unit 2)

Brain Imaging TechniquesMagnetic Resonance Imaging (MRI) scans use a strong magnetic field and radio waves to make images of soft tissues (like the brain). They align hydrogen nuclei to the magnetic field. MRI scans can be used in the diagnosis of tumours, strokes, brain injuries and infections. They can also track progress of degenerative diseases like Alzheimer's by comparing scans over a period of time.Functional MRI (fMRI) scan are a modified MRI technique which allows you to see the brain in action doing live tasks, as it detects activity in the brain, followed by oxygen uptake in active bran areas.Computerised axial tomography (CAT or CT) scans use 1000s of narrow collimated x-ray beams rotated around the px. Like MRI they only capture a snapshot in time, so only look at structures and damage rather than functions. The resolution is worse than MRI so small structures in the brain cannot be distinguished. X-rays are ionising, so have potential to harm.

Drug development & The Human Genome ProjectA genome is ALL the DNA of an organism. The Human Genome Project (HGP) was an international project which determined the base sequence of the human genome. Many new genes have been identified, inc. some which are responsible for inherited diseases.In addition, new drug targets have been identified. Info about a pxs genome may help Drs to prescribe the correct drug at the correct dose. The HGP may also allow some prevention of diseases. If the genes you carry are known, then you may understand what disease youre at risk from.The HGP also provides info about evolution and increases our knowledge of physiology and cell biology. The HGP has also noted other animals and plants genome.

The Human Genome Project & Ethical IssuesHere are some ethical questions about the HGP:Who owns the information? Some groups have applied for patents on genetic sequences, so they have ownership, or have to be paid for any treatments developed using the knowledge of that sequence.Who is entitled to know the information about YOUR genome if it is sequenced? Should insurance companies know? Employers?Will genetic screen lead to the genetic selection of humans (eugenics) and designer babies?Who will pay for the development of new therapies and drugs? Many possible highly specialised treatments are expensive and will only be suitable for a few people.

Use of GM to make drugsGM plants may be useful for the production of edible drugs (eg vaccines) that can easily be transported and stored in plant products (eg bananas or potatoes).Useful genes can be transferred into crop plants by using a vector, gene guns (pellets coated with DNA) or a virus.Restriction enzymes are used to cut DNA at specific sequences and DNA Ligase (enzyme) can stick DNA pieces together. These make it possible to insert specific DNA sequences in to the GM organism. Large numbers of identical GM plants can easily be produced.

Transgenic Animals (animals with a human gene added) can be used to produce drugs that can be harvested from their milk or semen. Liposomes and viruses are vectors used to insert genes into animal cells. Drugs produces from transgenic animals include the blood clotting factors used to treat haemophilia.

Microorganisms such as bacteria are the most common target for genetic modification as the are relatively easy targets for gene transfer and can be grown rapidly in large quantities in fermenters. The drugs made can be extracted and purified using downstream processing. Insulin to treat type II diabetes is an eg of a drug produced from GM micro-organisms.

Genetically Modified PlantsBacteriaPlasmid carrying desired gene & antibiotic resistance gene(marker gene) ChromosomeDNA gunPellets coated in DNABulletororinsertion of new geneVirus DNAgenes incorporated into the plant DNA of some cells.incubation in growth medium, with antibioticonly cells with the new genes surviveplant growth substances stimulate shoot and root growthMicropropagation: cells grow in sterile culture medium, with sucrose, amino acids, inorganic ions and plant growth substances.transgenic plant - all cells contain new geneplantlets separated and grown into full size plants

Concerns over GMOsgenetic pollution through cross-pollinationantibiotic resistance genes are used to identify GM bacteria, which could lead to antibiotic resistance in other microbesGM crops could out-compete other plants and resist herbicides - Become Super-weeds. They could damage natural food chains, resulting in damaged environment, because they would encourage farms to use selective herbicides to kill everything but the cropGM crops may not produce fertile seeds. This prevents farmers collecting seed and replanting, so may need to return to biotech company to buy new seeds for each planting - this could increase the price.