Responding to the Environment - Animal Responses

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  • Created by: mia
  • Created on: 22-04-13 15:05

(a)

discuss why animals need to respond to their environment

Animals need to respond to their environment to stay alive. This is done using nerves and hormones, to control responses ranging from muscle actions to run away from a predator, control of balance, posture and temperature regulation.

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(b)

outline the organisation of the nervous system in terms of central and peripheral systems in humans

Nervous system

  • Central Nervous System
  • Peripheral Nervous System
    • Somatic Nervous System
    • Autonomic Nervous System
      • Sympathetic Nervous System
      • Parasympathetic Nervous System
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(c)i

outline the organisation and roles of the autonomic nervous system

Sympathetic Nervous System

  • Most active in times of stress
  • The neurones of a pathway are linked at a ganglion just outside of the spinal cord.
  • Pre-ganglion neurones are very short
  • Post-ganglion neurones secrete noradrenaline at the synapse between neurone and effector

Effects of action include

  • Increased heart rate
  • Pupil dilation
  • Increased ventilation rate
  • Orgasm
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(c)ii

Parasympathetic Nervous System

  • Most active in sleep and relaxation
  • The neurones of a pathway are linked at a ganglion within the target tissue, so pre-ganglion neurones vary in length
  • Post ganglion neurones secrete acetylcholine as the neurotransmitter at the synapse between neurone and effector

Effects of action include:

  • Decreased heart rate
  • Pupil dilation
  • Decreased ventilation rate
  • Sexual arousal
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(d)i

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

Control of all higher order processes such as memory, language, emotions, thinking and planning

Cerebellum

Control and coordination of movement and posture

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(d)ii

Medulla Oblongata

Control of breathing, heart rate and smooth muscle of the gut

Hypothalamus

Control of the autonomic nervous system and some endocrine glands

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(e)

describe the role of the brain and nervous system in the co-ordination of muscular movement

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

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(f)i

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. This can be seen in the movement of the elbow joint

1. Impulses arriving at the neuromuscular junction cause vesicles to fuse with the presynaptic membrane and to release acetylcholine into the gap

2. Acetylcholine binds to receptors on the muscle fibre membrane (sarcolemma) causing depolarisation

3. Depolarisation wave travels down tubules (T system)

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(f)ii

4. T system depolarisation leads to Ca2+ release from stores in sarcoplasmic reticulum

5. Ca2+ binds to proteins in the muscle, which leads to contraction

6. Acetylcholinesterase in the gap rapidly breaks down acetylcholine so that contraction only occurs when impulses arrive continuously

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(g)

explain, with the aid of diagrams and photographs, the sliding filament model of muscular contraction

1. Myosin head groups attach to the surrounding actin filaments forming a cross bridge

2. The head group then bends, forming the thin filament to be pulled along and so overlap more with the thick filament. This is the power stroke. ADP and Pi are released

3. The cross bridge is broken as new ATP attaches to the myosin head

4. The head group moves backwards as ATP is hydrolysed to ADP and Pi. It can then form a cross bridge with the thin filament along and bend again.

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(h)

outline the role of ATP in muscular contraction, and how the supply of ATP is maintained in muscles

Role

  • Energy from ATP is required to break the cross bridge connection and re-set the myosin head forwards

Maintenance

  • Aerobic respiration in mitochondria
  • Anaerobic respiration in sarcoplasm
  • Transfer of phosphate group from Creatine Phosphate to ADP in sarcoplasm
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(i)

compare and contrast the action of synapses and neuromuscular junctions

Synapse

  • Post synaptic membrane is the cell surface membrane of a neurone
  • Neurotransmitter may be ACh, noradrenaline, glutamate or another transmitter
  • Depolarisation of the post synaptic membrane may be stimulatory or inhibitory

Neuromuscular Junction

  • Post synaptic membrane is the cell surface membrane of a muscle
  • Neurotransmitter is ACh
  • Depolarisation of post synaptic membrane is stimulatory

Both: Neurotransmitter is secreted, diffuses across a cleft, binds to receptors in the postsynaptic membrane and is finally broken down

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(j)

outline the structural and functional differences between voluntary, involuntary and cardiac muscle

Voluntary

  • Striated
  • Cylindrical cells are multinucleate
  • Found attached to bone
  • Controlled by the somatic nervous system
  • Contracts quickly; tires easily
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(j)i

outline the structural and functional differences between voluntary, involuntary and cardiac muscle

Voluntary

  • Striated
  • Cylindrical cells are multinucleate
  • Found attached to bone
  • Controlled by the somatic nervous system
  • Contracts quickly; tires easily
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(j)ii

Involuntary

  • Unstriated
  • Spindle-shaped cells each have a single nucleus
  • Found in the walls of tubular structures, such as the gut, blood vessels and ducts
  • Controlled by the autonomic nervous system
  • Contracts slowly; fatigues slowly
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(j)iii

Cardiac

  • Semi-striated
  • Cylindrical cells, each with a single nucleus, branch and connect with other cell
  • Found only in the hearts
  • Controlled by the autonomic nervous system
  • Contracts spontaneously without fatigue
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(k) state that

responses to environmental stimuli in mammals are co-ordinated by nervous and endocrine systems

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(l)

explain how, in mammals, the ‘fight or flight’ response to environmental stimuli is co-ordinated by the nervous and endocrine systems

Nervous

  • Sensory neurons from 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 in the cerebrum
  • Nerve impulses in sympathetic nerves of the autonomic nervous system, from the brain to the sinoatrial node of the heart, increase pulse rate and the stroke volume of the heart
  • Impulses in sympathetic nerves from the brain to the adrenal glands cause secretion of adrenaline from the adrenal medulla
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(l)i

explain how, in mammals, the ‘fight or flight’ response to environmental stimuli is co-ordinated by the nervous and endocrine systems

Nervous

  • Sensory neurons from 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 in the cerebrum
  • Nerve impulses in sympathetic nerves of the autonomic nervous system, from the brain to the sinoatrial node of the heart, increase pulse rate and the stroke volume of the heart
  • Impulses in sympathetic nerves from the brain to the adrenal glands cause secretion of adrenaline from the adrenal medulla
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(l)ii

Hormonal

  • Adrenaline is secreted into the blood then has a number of responses, including
    • Stimulation of the heart, increasing stroke volume and pulse rate
    • Increase in blood pressure, by constriction of blood vessels in the skin and gut
    • Increase in air flow to the lungs
    • Increased breakdown of glycogen in the liver
    • Decreased sensory threshold
    • Increased mental awareness
  • These responses provide an increased flow of oxygenated blood carrying glucose. This prepares the body for the needs of the muscles, which may work hard for the organisms to escape from, or cope with a source of danger.

A decision is then made about how to respond

  • Nerve impulses pass from the association areas in the frontal lobe of the cerebrum (concerned with planning actions and movements) to motor areas
  • From there, motor neurones of the somatic nervous system carry impulses to the muscles to produce the chosen action
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