Coordination systems and neurones
Introduced| English | Meaning |
|---|---|
| endocrine system/ˈendəʊkraɪn ˈsɪstəm/ | The glands and tissues that release hormones into the blood to coordinate body functions. |
| nervous system/ˈnɜːvəs ˈsɪstəm/ | The network of nerve cells and supporting structures that detects information, coordinates responses and controls body functions. |
| neurone/ˈnjuːrəʊn/ | Nerve cells specialised to transmit information using electrical and chemical signals. |
| axon/ˈæksɒn/ | A long projection of a neuron that carries electrical impulses away from the cell body. |
| sensory neurone/ˈsensəri ˈnjuːrəʊn/ | A nerve cell carrying impulses from a receptor toward the central nervous system. |
| motor neurone/ˈməʊtə ˈnjuːrəʊn/ | A nerve cell carrying impulses from the central nervous system to an effector. |
| effector/ɪˈfektə/ | A muscle, gland or other structure that carries out a response to a stimulus. |
| reflex arc/ˈriːfleks ɑːk/ | The neural pathway connecting a receptor to an effector in a reflex response. |
Control and coordination
- The body has two coordination systems.
- The endocrine system 内分泌系统 sends chemical hormones in the blood.
- The nervous system 神经系统 sends fast electrical signals along nerve cells.
A neurone that carries impulses from a receptor to the CNS is a:
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Sensory neurones carry signals into the CNS.
Nervous vs endocrine
| Feature | Nervous | Endocrine |
|---|---|---|
| signal | electrical impulse | chemical hormone |
| transport | along nerve cells | in the blood |
| speed | very fast | slower |
| lasts | short | longer |
Compared with the endocrine system, the nervous system is:
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Nervous signals are fast electrical impulses with short-lived effects; hormones are slower and longer-lasting.
The nervous system gives a faster but shorter-lasting response than the hormonal (endocrine) system.
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Electrical impulses are quick and brief; hormones travel in the blood — slower, but their effects last longer.
Neurones 神经元
- A neurone is a nerve cell, with a long fibre (the axon 轴突) the impulse travels along. Three kinds:
- sensory neurone 感觉神经元 — carries impulses from a receptor towards the brain/spinal cord.
- motor neurone 运动神经元 — carries impulses out to an effector 效应器 (e.g. a muscle).
- intermediate (relay) neurones — connect sensory to motor neurones.
A motor neurone: dendrites, a cell body, and a long myelinated axon carrying the impulse to a muscle
Real neurones stained brown under the microscope, showing their cell bodies and processes
Explore a motor neurone
Tap each part. The impulse travels from the cell body down the long axon to the terminals, jumping between the myelin gaps.
A motor neurone:
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Motor neurones carry impulses from the CNS out to effectors; sensory neurones carry them in.
Match each neurone or part to its job.
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Sensory in, motor out, relay between; the myelin sheath makes the impulse travel faster.
The reflex arc 反射弧
- A sensory receptor detects a stimulus and starts an impulse.
- The reflex arc: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.
A reflex arc: stimulus → receptor → sensory → relay → motor → effector
Put the reflex arc in order.
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Stimulus → receptor → sensory → relay → motor → effector → response.
A sensory receptor:
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A receptor detects the stimulus (e.g. chemicals in a taste bud) and triggers an action potential.
You've got it
- nervous = fast electrical impulses, short-lived; endocrine = slower hormones, longer-lasting
- sensory neurone → towards CNS; motor → out to effector; relay connects them
- a receptor detects a stimulus and starts the impulse
- reflex arc: stimulus → receptor → sensory → relay → motor → effector → response