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A2 biology 5.4.2
OCR biology - animal responses
| Question | Answer |
|---|---|
| Describe structure of cerebrum | largest area of human brain, left and right hemispheres, joined by corpus callosum, cerebral cortex = outermost layer of cerebrum folded into gyri and sulci 2.5m2. Sensory, association, motor areas |
| Describe function of cerebrum | Controls higher brain functions: conscious thought, emotional responses, ability to override reflexes, reasoning and judgement, Broca's (speech production), Wernicke's area (language comprehension). Sensory, association, motor areas |
| Describe structure of cerebellum | Contains over half of neurones in human brain, at base of brain |
| Describe function of cerebellum | Controls balance, posture, coordination of fine movement. Receives sensory input: retina, inner ear, spindle fibres, joints. Sends impusles to motor areas in cerebrum: maintain balance, judge position of tools/limbs, manipulate tools, antagonistic muscle |
| Describe function + location of medulla oblongata | Brain stem. Controls autonomic functions, controls cardiac and involuntary (smooth) muscle, contains respiratory centre (controls rate and depth of breathing), contains cardiac cenrre (controls heart rate) |
| Describe function + location of hypothalamus | Midbrain. Controls homeostasis - receives sensory input from temperature receptors and osmoreceptors so controls thermoregulation and osmoregulation via negative feedback. Controls most of endocrine system as it controls the pituitary gland |
| Describe organisation of nervous system | NS -> central (brain + spinal cord) + peripheral. PNS -> sensory (transmit impulses from receptors to sensory areas in cerebrum) + motor neurones. Motor neurones -> somatic + autonomic. Autonomic -> sympathetic NS and parasympathetic NS |
| Describe somatic motor neurones | Carry impulses to skeletal muscle, mainly myelinated, voluntary control, usually only 1 nerve between CNS and effector |
| Describe autonomic motor neurones | Preganglionic neurone carries impulse to ganglion in CNS, then motor neurone -> effector. Cardiac + involuntary (smooth) muscle e.g. gut wall, glands. Mainly unmyelinated, involuntary control, homeostasis and stress responses |
| Describe parasympathetic nervous system | Active during sleep and relaxation. Ganglion located in target tissue so preganglionic neurones vary in length. acetylcholine. effects: decreases heart rate and breathing rate, constricts pupils, sexual arousal |
| Describe sympathetic nervous system | Active during stress, Ganglion located just outside spinal cord so preganglionic neurones are short. Noradrenaline. Increases heart + breathing rate, sexual orgasm, dilates pupils |
| describe the structure+ function of involuntary muscle | Autonomic NS, involuntary, cells are short, spindle shaped, interlocking, 1 central nucleus. contracts + fatigues slowly, no striations. peristalsis gut wall. iris: contraction of circular muscles=constriction. Arterial walls: pressure, temperature, shunt |
| describe the structure + function of cardiac muscle | Autonomic NS, SAN/cardiovascular centre/adrenaline.Branched fibres, 1 central nucleus, intercalated discs, gap junctions, functional syncytium, contracts quickly, doesn't fatigue, striated, can't respire anaerobically.Controls speed of blood flow+pressure |
| describe the structure of skeletal muscle | Somatic NS, voluntary, endomysium, sarcolemma (T tubules, receptors), sarcoplasm (mitochondria, SR, myofibrils, nuclie), sarcomere -> myofibril -> unbranched fibres (NO separate cells), motor unit, striated, contracts + fatigues quickly |
| describe the structure of the sarcomere | H zone= space between actin filaments in 1 sarcomere. I band = space between myosin filaments in adjacent sarcomeres. A band = length of myosin in 1 sarcomere. Z line holds actin in place, M line holds myosin in place |
| Continued | Thin filament: 2 strands of actin wound around each other, tropomyosin coiled around actin, each tropomyosin is associated with 1 troponin complex (3 polypeptides). Thick filament: bundles of myosin, 2 heads (ADP + Pi) + 1 tail |
| What is the function of skeletal muscle? | Connected to skeleton, allows coordinated, voluntary movement OF BONE (!!!!!!) at joints |
| What are the similarities and differences between ligaments and tendons? | Similarities: connected to periosteum of bone, made of collagen fibres. Differences: ligaments connects bones together to prevent dislocation, tendons connect skeletal muscle to bone |
| What must be true for movement at a joint? | Coordinated action of at least 2 muscles, antagonistic or synergistic |
| What is a synovial joint? | Large degree of movement is required e.g. elbow. Ligament holds bones together to prevent dislocation, cartilage reduces friction between bones as they move, synovial membrane produces synovial fluid which lubricates the joint |
| What is the neuromuscular junction? Describe the sequence of events that happen there | Motor neurone reaches muscle fibres. AP arrives at axon terminal, opens V-gated Ca2+ channels, influx, vesicles dock to membrane, ACh exocytosis, binds to receptors on sarcolemma, depolarisation down T tubules -> SR, Ca2+ release, acetylcholinesterase |
| What are the similarities between neuromuscular junction and synapse? | Vesicles of neurotransmitter in axon terminal, Ca2+ influx through voltage gated channels causes release of neurotransmitter, neurotransmitter diffuses across gap and causes depolarisation of next membrane, enzymes degrade neurotransmitter |
| What are the differences between the neuromuscular junction and the synapse? | Neurone to neurone vs neurone to muscle fibre. Excitatory or inhibitory vs excitatory only. AP in post synaptic neurone vs muscle contraction |
| How would you investigate contraction in isolated muscles? | Extract a frog calf muscle with nerve still attached, attach to spring loaded pins and datalogger, immerse in ringers solution |
| Describe the difference between twitch, summation and tetanus | 1 electrical stimulus of sufficient strength=twitch, muscles contract quickly then relax immediately, increasing stimulus strength increases force up to maximal response. 2 stimuli in quick succession are summated, many cause tetanus (powerful/sustained) |
| What does a sarcomere look like in relaxed state? | 2.5 μm, H zone is large, troponin bound to tropomyosin and actin, myosin head has ADP and Pi attached |
| Describe the sequence of events involved in muscle contraction | Sliding filament model. Ca2+ binds to troponin, conformational shape change, tropomyosin moves, exposes binding sites, myosin head binds, cross bridge, power stroke: ADP +Pi are ejected, myosin head moves, pulling actin filament along... |
| Continued | ATP binds to myosin head breaking cross bridge, ATPase enzyme hydrolyses ATP -> ADP + Pi, myosin head returns to original state, millions of cross bridges are made +broken while sarcolemma is depolarised so actin filaments move deeper into a band |
| What does a sarcomere look like in contracted state? | Sarcomere shorter, H zone shorter (may disappear completely in a forceful contraction), Z lines closer together, A band the same |
| What are the uses of ATP in muscle contraction? | Breaking cross bridges in power stroke, active transport of Ca2+ back into SR for relaxation, synthesis of creatine phosphate (creatine + ATP -> creatine phosphate + ADP), protein synthesis of new muscle fibres |
| What are the sources of ATP in muscles? | Aerobic respiration, anaerobic respiration (low energy yield, lactate), creatine phosphate: Pi from creatine phosphate is transferred to ADP by creatine phosphotransferase to form ATP, energy surge supports muscle contraction for a further 2-4 s |
| What is the fight or flight response? | Response to situations of perceived danger, coordinated by nervous and endocrine systems, prepares organism to confront danger directly or escape, heightened activity of the sympathetic nervous system |
| What physiological changes occur in the stress response? | Increased rate of respiration (rate/depth of breathing increase, gluconeogenesis, glycogenolysis, increased speed of blood flow), pilo-erection, dilates pupils, increased mental awareness, blood shunting, more sweat, endorphins |
| Describe the sequence of events in the stress response | Sensory receptors detect stressor, period of heightened activity, cerebrum sends impulses to hypothalamus, 1) increased activity of sympathetic NS, adrenaline released fomr adrenal medulla, 2) hypothalamus releases corticotropin-releasing factor... |
| Continued | Anterior pituitary gland releases adreno-corticotropic hormone, causes release of corticosteroids (mineralocorticoids, glucocorticoids) from adrenal cortex which help body resist stressors |
| Define stressor | A stimulus that causes the fight or flight response, damages mental and physical health |
| What is PTSD and why does it occur? | Where traumatic flashbacks active the fight or flight response unnecessarily. The hypothalamus cant distinguish between the cerebral judgement of real and imagined threats |
| What are some of the physiological effects of stress? | digestive system problems (sympathetic nervous system, toxins, constipation, colon cancer), mental health problems, weakened immune system, myocardial infarction and agina, high blood pressure - kidney failure |
| What is grey matter vs white matter? | Grey matter = cell bodies, dendrites. White matter = axons (myelin sheath) |
| Why must animals respond to their environment? | To find food/ mates and escape danger. In mammals, responses are coordinated by the nervous AND endocrine systems |
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