Animal Responses

Animal ResponsesBy Daniella Di-FonzoSpecification(a) discuss why animals need to respond to their environment; (b) outline the organisation of the nervous system in terms of central and peripheral systems in humans; (c) outline the organisation and roles of the autonomic nervous system; (d) describe, with the aid of diagrams, the gross structure of the human brain, and outline the functions of the cerebrum, cerebellum, medulla oblongata and hypothalamus; (e) describe the role of the brain and nervous system in the co-ordination of muscular movement; (f) describe how co-ordinated movement requires the action of skeletal muscles about joints, with reference to the of the elbow joint; (g) explain, with the aid of diagrams and photographs, the sliding filament model of muscular contraction; (h) outline the role of ATP in muscular contraction, and how the supply of ATP is maintained in muscles; (i) compare and contrast the action of synapses and neuromuscular junctions; (j) outline the structural and functional differences between voluntary, involuntary and cardiac muscle; (k) state that responses to environmental stimuli in mammals are co-ordinated by nervous and endocrine systems; (l) explain how, in mammals, the fight or flight response to environmental stimuli is coordinated by the nervous and endocrine systems.

animals need to respond to their environmentAnimals increase their survival chances by responding to the changes in their external environmentThey also respond to changes in their internal environment to ensure optimum conditions for metabolic processesAny change in either environment is a stimulus and usually elicits a responsethe nervous systemReceptors detect stimuli and effectors bring about a response. Effectors include muscles cells and cells in glandsReceptors communicate with effectors via the nervous or hormonal systems, and sometimes both

The central nervous system; made up of the brain and spinal cord- most neurones here are intermediate neurones and have short dendritesthe autonomic nervous systemDifferent from somatic ns: most the neurones in ANS are non-myelinatedSNS connections to effectors consist of one neurone as opposed to two in ANSAutonomic motor neurones can be sympathetic or parasympatheticThe sympathetic and parasympathetic systems are antagonisticParasympatheticsympatheticMost active in times of sleep and relaxationMost active in times of stressThe neurones of the pathway are linked at a ganglion within the target tissue. Pre-ganglionic neurones vary in lengthThe neurones are linked at a ganglion just outside the spinal cord so pre-ganglionic neurones are very shortPost-ganglionic neurones secrete acetylcholine between the neurone and effectorPost-ganglionic neurone secrete noradrenaline at the synapse between the neurone and effectorEffects include: decreased heart rate, pupil constriction, decreased ventilation rateEffects include: increased heart rate, pupil dilation, increased ventilation rate

External and internal environments are being constantly monitored by sensors in the endocrine and nervous systemResponses are coordinated and balanced to ensure survival. E.g., short term homeostatic mechanisms or long term like mating behaviourThe coordination is mainly the result of the brain assessing the most appropriate response. The brain also regulates endocrine responses through the hypothalamus and its control of the pituitary glandthe fight or flight responseThe perception of a threat leads to a number of physiological changes These are caused by the sympathetic nervous system being activatedPhysiological changes include:Increased heart rate to pump blood around the body fasterMuscles in bronchioles relax allowing for deeper breathsGlycogen is converted to glucose so there can be more respirationArterioles in the digestive system constrict and blood is diverted to the heart, lungs and skeletal muscles, where the arterioles have dilated.

**norepinephrine is another name for noradrenaline and epinephrine is adrenaline

the functions of the cerebrum, cerebellum, medulla oblongata and hypothalamus;cerebellum-Underneath the cerebrum and has a folded cortex-Important for muscle coordination, balance and posture.Hypothalamus-Controls body temp, etc (homeostasis)-Found beneath middle part of brain-Produces hormones that control the pituitary glandCerebrum-Largest part of brainDivided into two hemispheres-Thin outer layer called cerebral cortex which is highly folded-Controls vision, hearing, learning, thinking.Medulla oblongata-At the base of the brain: top of the spinal cord-Controls non-skeletal muscles-Automatically controls breathing and heart ratethe structural and functional differences between voluntary, involuntary and cardiac muscle;Voluntary (skeletal ) muscleInvoluntary (smooth) muscleCardiac (heart) muscleConsciousUnconsciousMyogenic (unconscious)Many muscles with many nucleiEach muscle fibre only has one nucleusEach muscle fibre only has one nucleusRegular cross striations (striped pattern)No striped appearanceSome cross striations but not as much as voluntary muscleFound around jointsFound in gut/ arteriolesFound in heartMany cms longSpindle shaped 0.2mm longCylindrical, connected by intercalated discs, each fibre is branchedSome contract slowly for endurance and posture. Fatigue slowlyContract slowly, fatigue slowlyContract rhythmically and dont fatiguedescribe the role of the brain and nervous system in the co-ordination of muscular movementThe CNS receives sensory information and decides what kind of response is neededIf the response is movement, the CNS sends signals, via neurones, telling muscles to contract

Skeletal muscles and joints Skeletal muscles are attached to bones by tendonsLigaments attach bone to other bones (they hold them together)The type of joint between bones determines the type of movement possibleBall & socket joints (e.g., shoulder) allow movement in all directionsGliding joints (e.g., wrist) allow a wide range of movement because small bones can glide over each otherHinge joints (e.g., elbow) allow movement in only one plane, like up and down

Your elbow

Bones of your lower arm are attached to biceps and triceps muscles by tendonsAs one muscle contracts, the other relaxes- this moves your armTriceps are the extensor muscle, whilst biceps are the flexor muscleMuscles work in antagonistic pairs The elbow joint is a synovial joint. This contains fluid allowing for smooth movementthe sliding filament model of muscular contractionThin filaments are mainly two strands of the protein actin coiled together. Each strand has globular subunits. Tropomyosin ( a rod shaped protein) reinforces the structure. A troponin complex is attached to each Tropomyosin molecule and is made of three polypeptides. One binds to actin, another to calcium and the final to Tropomyosin, holding the complex in place. The actin binding site is blocked by Tropomyosin while restingThick filaments are made of the protein myosin. Each myosin has a tail and two protruding heads (one a binding site for actin, the other a binding site for ATP). Each thick filament has many myosin molecules with heads sticking out at opposite endsWhen a muscle contracts, the I-bands and H-zones shorten, while the A-bands remain the same length

SarcomereI- bandI- bandA- bandH-zoneThick filament (myosin)Thin filament (mainly actin)

4) When the muscle stops being stimulated, the calcium ions move back into sarcoplasmic reticulum via active transport. Troponin returns to their original shape and Tropomyosin moves to block binding sites again. Muscles arent contracted because there are no cross bridges, so the actin filaments slide back to their original positions, this lengthens the sarcomere The power stroke

1) Action potentials depolarise the sarcolemma and it spreads down the T-tubules into the sarcoplasmic reticulum, causing Calcium ions to be released into the sarcoplasm. These bind to Troponin and cause it to change shape, pulling Tropomyosin out of the binding site, which then allows myosin to bind to an actin filament and form a cross bridge3) ATP also provides energy to break the cross bridge so the myosin head detaches from the actin filament after its moved. The myosin head then reattaches to a different site and forms a new cross bridge. This cycle repeats causing the muscle to contract. The cycle continues as long as there is enough ATP and calcium levels in the sarcoplasm is high2) Calcium ions also activate the enzyme ATPase, which hydrolyses ATP to ADP +Pi, to provide the energy for muscle contraction. This energy moves the myosin head which pulls the actin filament along with a rowing actionATP and PCr provide energy for muscle contractionATP gets used up very quickly by muscles (its needed to break cross bridges and reset the myosin heads) so needs to be continually; this happens in three main ways:Aerobic respiration: most ATP is generated by oxidative phosphorylation in the cells mitochondria. Aerobic respiration only works when theres oxygen so its good for long, low-intensity exercise e.g., joggingAnaerobic respiration: ATP is made rapidly by glycolysis. Unfortunately, lactate is produced and this builds up quickly and causes muscle fatigueATP- phosphocreatine system (PCr) system: ATP is made by phophorylating ADP. PCr is stored inside cells and this system can produce ATP very quickly . Its good nfor short bursts of vigorous exercise e.g., tennis serve. Its anaerobic and doesnt produce lactate compare and contrast the action of synapses and neuromuscular junctions; A neuromuscular junction is a synapse between a motor neurone and a muscle cell. Neuromuscular junctions use acetylcholine (a neurotransmitter) which bind to nicotinic cholinergic receptors. The neurotransmitter triggers depolarisation in the postsynaptic cellNeuromuscular junctionsSynapses (between neurones)NeurotransmitterAcetylcholineVariousPostsynaptic receptorsNicotinic cholinergic receptorsvariousNumber of postsynaptic receptorsLotsFewerPostsynaptic cellMuscle cellNeuronePostsynaptic membraneHas clefts containing AChESmoothEffect of neurotransmitter binding to receptorsMuscle cell always contractsAction potential may or may not fire in the next neuroneRemoval of neurotransmitterBroken down by AChEDepends on neurotransmitterGood luck with your exams