5.2 The nervous system and neurones
7 exam questions worth 17 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which structures make up the central nervous system?
Choose one answer.
Correct Not quite: the answer is Brain and spinal cord
Mark scheme
A (brain and spinal cord)
Model answer
A: the brain and spinal cord.
Name the type of neurone that carries impulses from the CNS to an effector.
Mark scheme
motor (neurone)
Model answer
A motor neurone.
Name two types of effector and describe how each responds.
Mark scheme
- muscles, which contract (1)
- glands, which secrete (chemicals / hormones) (1)
Model answer
Muscles respond by contracting, and glands respond by secreting chemicals such as hormones.
Explain how the myelin sheath helps a motor neurone to carry out its function.
Mark scheme
- (myelin sheath) insulates the axon (1)
- so impulses travel faster / impulses jump between gaps in the sheath (1)
Model answer
The myelin sheath is a fatty layer that insulates the axon, so the electrical impulse travels along it much faster.
Explain how the structure of a motor neurone is adapted to its function.
Mark scheme
- long axon (1) so it can carry impulses a long distance from the CNS to the effector / muscle (1)
- myelin sheath (1) insulates / speeds up the impulse (1)
- many dendrites (1) so it can receive impulses from / connect with many other neurones (1)
- branched nerve endings (1) to pass impulses to many muscle fibres / connect to an effector (1)
Max 4: one mark for a feature, one for linking it to its function
Model answer
A motor neurone has a long axon so it can carry impulses all the way from the CNS to a muscle. The axon is covered in a myelin sheath, which insulates it so impulses travel faster. It has many dendrites so it can receive impulses from many relay neurones, and branched nerve endings that pass the impulse to many muscle fibres.
A student sees a ball thrown towards her and catches it.
Describe how her nervous system brings about this response.
Mark scheme
- receptors in the eye / retina detect the stimulus (light) (1)
- impulses travel along sensory neurones to the brain / CNS (1)
- the brain / CNS coordinates the response (1)
- impulses travel along motor neurones to the effector / muscles (1)
- muscles contract (to catch the ball) (1)
Max 4
Model answer
Light receptors in her eyes detect the ball. Electrical impulses travel along sensory neurones to her brain, which processes the information and coordinates a response. Impulses then travel along motor neurones to the muscles in her arms and hands, which contract so she catches the ball.
Compare the structure and job of a sensory neurone with a motor neurone.
Mark scheme
- sensory carries impulses from receptors to the CNS; motor carries impulses from the CNS to effectors (1)
- sensory neurone has a (long) dendron; motor neurone has many dendrites on the cell body / no dendron (1)
- the cell body of a sensory neurone is part-way along / to the side; in a motor neurone it is at one end (in the CNS) (1)
- allow: both have a myelin sheath / axon / nerve endings (1)
Max 3
Model answer
Both have a myelinated axon and nerve endings. A sensory neurone carries impulses from a receptor to the CNS, and it has a long dendron with its cell body part-way along. A motor neurone carries impulses from the CNS to an effector; its cell body is at one end, in the CNS, with many dendrites.
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