Animal Responses Flashcards
(a) Discuss why animals need to respond to their environment;
Animals respond to their environments, both externally and internally, to increase their chances of survival. This is achieve via nervous and hormonal coordination, to control responses ranging from muscle actions to running away from a predator, to fine control of balance, posture and temperature regulation.
They respond to changes of an internal environment to make sure that the conditions are always optimal for their metabolism (all of the chemical reactions being sustained inside for life).
Animals respond to their environments, both externally and internally, to increase their chances of survival. This is achieve via nervous and hormonal coordination, to control responses ranging from muscle actions to running away from a predator, to fine control of balance, posture and temperature regulation.
They respond to changes of an internal environment to make sure that the conditions are always optimal for their metabolism (all of the chemical reactions being sustained inside for life).
Animals respond to their environments, both externally and internally, to increase their chances of survival. This is achieve via nervous and hormonal coordination, to control responses ranging from muscle actions to running away from a predator, to fine control of balance, posture and temperature regulation.
They respond to changes of an internal environment to make sure that the conditions are always optimal for their metabolism (all of the chemical reactions being sustained inside for life).
(b) Outline the organisation of the nervous system in terms of central and peripheral systems in humans;
The nervous system is divided into the central nervous system and the peripheral nervous system.
- The central nervous system (CNS) is composed of the brain and the spinal cord.
- The peripheral nervous system consists of the nerves which run between the CNS and the rest of the body; from receptors to effects. Sensory and motor neurones.
The peripheral nervous system has two components:
The somatic nervous system; includes all sensory neurones and also the motor neurones that run to skeletal muscles; control conscious activities, voluntary muscles. Myelinated. Looks white.
The autonomic nervous system; consists of two sets of motor neurones carrying impulses to effectors other than skeletal muscles, such as glands and the muscles of the gut and heart. Controls unconscious activities. Non myelinated. Looks grey.
The autonomic nervous has two components:
The sympathetic nervous system gets the body ready for action; the ‘fight or flight’ system. Sympathetic neurones release the neurotransmitter noradrenaline.
The parasympathetic nervous system calms the body the fuck down. It’s the ‘rest and digest’ system. Parasympathetic neurones release the neurotransmitter acetylcholine (#STANDARD)
(c) Outline the organisation and roles of the autonomic nervous system;
Sympathetic Nervous System
• Very short pre-ganglion neurones
• Long post-ganglion neurone
• Ganglion is right near CNS, just outside spinal cord
• Post-ganglion neurone secretes noradrenaline at the synapse
• Most active in times of stress
• Effects of action include: increased heart rate, pupil dilation, increased ventilation rate, orgasm.
Parasympathetic Nervous System
• Long pre-ganglion neurone
• Short-post ganglion neurone
• Neurones of a pathway are linked at a ganglion within the target tissue themselves, in the wall of the target organ.
• Post-ganglion neurone secretes acetylcholine at the synapse
• Most active in sleep and relaxation
• Effects of action include: decreased heart rate, pupil dilation decreased ventilation rate, sexual arousal.
(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;
Cerebrum
• Largest part of the brain, located at the front, most recognisable part
• Consists of two hemispheres joined by the corpus callosum
• Responsible for all higher order processes, such as memory, language, emotions, thinking, planning, personality, imagination, reasoning, vision, hearing, learning.
• Associated with what makes us ‘human’
Cerebellum
• Located underneath the cerebrum, also has a folded cortex.
• Control and coordination of movement and posture, including balance, co-ordination and fine movement; fine control of muscular movements such as walking, cycling, driving and playing a musical instrument.
• Contains over half of all nerve cells of the brain; processes sensory information from the retina, balance organs in the inner ear, spindle fibres in muscles that give information about muscle tension, and the joints.
Medulla oblongata
• Located at the base of the brain, at the top of the spinal cord.
• Controls non-skeletal muscles; cardiac and involuntary, such as control of breathing, heart rate and smooth muscle of the gut.
• Effectively in control of the autonomic nervous system; connected to; regulatory centres include the cardiac centre and the respiratory centre.
Hypothalamus
• Located just beneath the middle part of the brain.
• Controls the autonomic nervous system.
• Responsible for most of the body’s homeostatic systems; automatically maintains body temperature at the normal level etc.
• Controls much of the endocrine function of the body (endocrine glands) by regulating the pituitary gland.
• Also contains the thermoregulatory centre and osmoreceptors; sensory input from temperature receptors and osmoreceptors are received by the hypothalamus which leads to the initiation of automatic responses that regulate body temperature and blood water potential.
(e) Describe the role of the brain and nervous system in the co-ordination of muscular movement;
The sensory areas of the cerebrum receive sensory information from receptors which then send impulses to association areas (areas of the cerebrum which compare input from previous experiences in order to interpret what the input means and judge an appropriate response). Impulses then pass to motor areas, and from there to effectors, so that skeletal muscles contract. In the association area concerned with planning actions and movements, the brain integrates these sensory inputs and motor outputs to ensure that muscular movement is coordinated and appropriate. This requires the controlled action of skeletal muscles about joints.
The conscious decision to move voluntarily is initiated in the cerebellum. Neurones from the cerebellum carry impulses to the motor areas so that motor output to the effectors can be adjusted appropriately in these requirements
(f) Describe how co-ordinated movement requires the action of skeletal muscles about joints, with reference to the movement of the elbow joint;
Coordinated and appropriate movement requires the controlled action of skeletal muscles about joints. A muscle can only exert force by contracting, working antagonistically with its pair attached across a joint, the latter relaxing.
This can be seen in the movement of the elbow joint (a type of hinge joint, allowing movement in only one plane):
- The bones of the lower arm are attached to a bicep and a tricep muscle via tendons (inelastic, muscle to bone; ligaments are elastic connecting bone to bone to allow joint movement)
- The bicep and the tricep work together as an antagonistic pair; when the bicep contracts, the tricep relaxes, with your arm coming towards you; bicep is a flexor muscle. When the tricep contracts, the bicep relaxes, straightening the joint and extending the arm; an extensor muscle.
Joints at which two bones can move significantly with respect to one another are synovial joints; the ends of the bone are covered in cartilage (acts as a shock absorber), and the movement is lubricated by synovial fluid.
- Ball and socket joints allow rotary movement; e.g. the shoulder
- Gliding joints allow a wide range of movement due to the action of small bones gliding over one another; e.g. the wrist
- Hinge joints allow movement in one plane only.
(g) Explain, with the aid of diagrams and photographs, the sliding filament model of muscular contraction;
- Myosin (thick) and actin (thin) filaments slide over one another to make the sarcomeres (the smallest contractile unit of muscle consisting of thick and thin filaments responsible for muscular contraction; and is the span between one Z-line to the next Z-line, repeating unit) contract; the myofilaments themselves do not contract.
- The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract.
- Sarcomeres return to their original length as the muscle relaxes.
- An action potential from a motor neurone stimulates a muscle cell, depolarising the sarcolemma (the cell surface membrane of the muscle fibre).
- Depolarisation spreads down the inturned T-tubules, with the action potential reaching the sarcoplasmic reticulum.
- Depolarisation of the sarcoplasmic reticulum membrane makes it permeable to its enclosed calcium Ca2+ ions.
- Ca2+ ions flood into the sarcoplasm, and bind to the troponin protein, pulling the attached tropomyosin protein out of the actin-myosin binding site into the actin filament, exposing the binding site for the myosin head to bind.
- Myosin head groups attach to the surrounding actin filaments forming an actin-myosin cross bridge
- The myosin head group then moves and bends, pulling the actin filament (thin) along in a rowing action; the power stroke, such that they overlap more, pulled towards the centre of the sarcomere. ADP and Pi are released, from the breakdown of ATP (by the enzyme ATPase activated by calcium ions) to provide the energy required for muscle contraction.
- The actin-myosin cross bridge is broken, from energy from ATP binding to the head, hydrolysed to ADP and Pi, allowing myosin and actin to separate.
- The myosin head group then tilts back to its original position, to form new actin-myosin cross bridges to a different binding site further along the actin (thin) filament. This continuously occurs, causing the actin (thin) filaments to slide past the myosin (thick) filaments, decreasing the length of the I-band and H-zone. The cycle continues as long as Ca2+ ions are present and bound to troponin.
(h) Outline the role of ATP in muscular contraction, and how the supply of ATP is maintained in muscles;
Role
Energy from the hydrolysis of ATP into ADP and Pi is required for the power stroke to occur, and to break the actin-myosin cross-bridge (allowing myosin and actin to separate) to re-set the myosin head group forwards. The hydrolysis of ATP and the power stroke do not occur at the same time. When excitation ceases, ATP is used for the active transport of Ca2+ ions back into the sarcoplasmic reticulum.
Maintenance
- Via oxidative phosphorylation in mitochondria; during aerobic respiration
- Via glycolysis of ATP in the sarcoplasm; anaerobic respiration (leads to formation of lactic acid; toxic; this enters the blood to stimulate increased blood supply to the muscles)
- Via the conversion of the ADP produced from muscle contraction back to ATP by transferring a phosphate group from creatine phosphate in the sarcoplasm by the action of the enzyme phosphotransferase. Only limited supply of creatine phosphate; must be replenished using ATP from respiration.
(i) Compare and contrast the action of synapses and neuromuscular junctions;
Neuromuscular junction:
- Impulse arrives at the neuromuscular junction, causes vesicles to move and fuse with the pre-synaptic membrane, releasing acetylcholine into the cleft (gap).
- Acetylcholine binds to receptors on the muscle fibre membrane (sarcolemma), causing a depolarisation wave.
- Depolarisation wave travels down T-tubules
- T-system depolarisation leads to Ca2+ ion release from stores in the sarcoplasmic reticulum (specialised endoplasmic reticulum)
- The Ca2+ ions bind to proteins in the muscle, leading to contraction
- Acetylcholinesterase in the cleft rapidly breaks down acetylcholine so that contraction only occurs when impulses arrive continuously.
- The postsynaptic membrane of the synapse is the cell surface membrane of a neurone; the postsynaptic membrane at a neuromuscular junction is the cell surface membrane (sarcolemma) of a muscle (at nicotinic cholinergic receptors)
- The neurotransmitter may be acetylcholine, noradrenaline, glutamate or another at the synapse; the neurotransmitter is just acetylcholine for neuromuscular junctions.
- The depolarisation of the postsynaptic membrane of a synapse may be stimulatory or inhibitory; the depolarisation of the postsynaptic membrane of a neuromuscular junction is only stimulatory.
- In both, neurotransmitter is secreted, diffuses across a cleft, binds to receptors in the postsynaptic membrane and is finally broken down.
(j) Outline the structural and functional differences between voluntary, involuntary and cardiac muscle;
- Voluntary muscle is striated (striped), involuntary muscle is unstriated (non-striped/smooth) and cardiac muscle is semi-striated.
- Voluntary muscle has cylindrical cells that are multinucleate; involuntary muscle has spindle-shaped cells that each has a single nucleus; cardiac muscle has cylindrical cells, each with a single nucleus, branched and connected with other cells.
- Voluntary muscles are skeletal (attached to the bone); involuntary muscles are found in the walls of tubular structures (e.g. gut, blood vessels and ducts); cardiac muscles are only found in the heart.
- Voluntary muscles are controlled by the somatic nervous system (conscious); involuntary muscles are controlled by the autonomic system (muscle contraction is unconscious); cardiac muscles are also controlled by the autonomic nervous system (muscle contraction is unconscious – myogenic, contracting on its own)
- Voluntary muscles contract quickly, fatiguing quickly; involuntary muscles contract slowly, fatiguing slowly, cardiac muscles contract spontaneously (rhythmically) without fatigue.
(k) What are responses to environmental stimuli in mammals co-ordinated by?
Responses to environmental stimuli in mammals are co-ordinated by both the nervous and endocrine systems.
(l) Explain how, in mammals, the ‘fight or flight’ response to environmental stimuli is co-ordinated by the nervous and endocrine systems.
Nervous System
- Sensory neurones of the somatic nervous system carry impulses from receptors to the sensory areas of the cerebrum of the brain, giving information about the danger in the environment.
- Nerve impulses pass to association areas of the cerebrum of the brain, giving information about the danger and the environment.
- Nerve impulses in the sympathetic nerves of the autonomic nervous system, from the brain to the sinoatrial node (SAN) of the heart increase the pulse rate and stroke volume of the heart.
- Impulses in sympathetic nerves from the brain to the adrenal glands cause secretion of adrenaline from the adrenal medulla.
Endocrine System
Adrenaline is secreted into the bloodstream, having a number of effects including:
- Stimulation of the heart, with the same effects as stimulation by sympathetic nerves
- Increase in blood pressure, by constriction of blood vessels to the skin and gut
- Increase air flow to the lungs
- Increased breakdown of glycogen in the liver
- Decreased sensory threshold and increased mental awareness.
The actions of adrenaline provide an increased flow of oxygenated blood carrying glucose. With the body prepared in this way for the needs of muscles, which may work hard for the organism to escape from or cope with source of danger, a decision is made about how to respond.
- Nerve impulses from the association area in the frontal love of the cerebrum (the prefrontal association complex), concerned with planning actions and movements, pass to motor areas.
- From there, motor neurones of the somatic nervous system carry impulses to muscles, to produce the chosen action.
