The nervous system and reflexes
Introduced| English | Meaning |
|---|---|
| nervous system/ˈnɜːvəs ˈsɪstəm/ | The network of nerve cells and supporting structures that detects information, coordinates responses and controls body functions. |
| reflex/ˈriːfleks/ | A fast automatic response not involving conscious thought. |
| central nervous system/ˈsentrəl ˈnɜːvəs ˈsɪstəm/ | The brain and spinal cord, which process information and coordinate responses. |
| spinal cord/ˈspaɪnl kɔːd/ | The part of the central nervous system inside the vertebral column that carries signals and coordinates some reflexes. |
| neurones/ˈnjuːrəʊnz/ | Nerve cells specialised to transmit information using electrical and chemical signals. |
| sensory/ˈsensəri/ | sensory |
| motor/ˈməʊtə/ | motor |
| effector/ɪˈfektə/ | A muscle, gland or other structure that carries out a response to a stimulus. |
Lightning-fast messages
- Touch something hot and your hand jerks back before you even feel pain.
- Your nervous system 神经系统 carries electrical messages at high speed — and reflexes 反射 are the fastest of all.
The central nervous system (CNS) consists of the:
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The CNS is the brain and spinal cord.
The nervous system
- The central nervous system 中枢神经系统 (CNS) is the brain and spinal cord 脊髓.
- Neurones 神经元 (nerve cells) carry electrical impulses to and from the CNS.
The brain coordinates the body through the nervous system
The reflex arc
A reflex is a fast, automatic response — the signal takes a short cut through the spinal cord.
A motor neurone carries impulses:
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Motor neurones go from the CNS to muscles or glands.
The neurone carrying impulses from a receptor to the CNS is the ______ neurone.
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Sensory neurones carry signals into the CNS.
Three types of neurone
- Sensory 感觉的 neurones carry impulses from receptors to the CNS.
- Relay neurones pass them on inside the CNS.
- Motor 运动的 neurones carry impulses from the CNS to effectors 效应器 (muscles/glands).
Put the reflex arc in order.
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Stimulus → receptor → sensory → relay → motor → effector → response.
A reflex action is fast and automatic, not consciously controlled.
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Reflexes protect the body before conscious thought.
The reflex arc
- A reflex is a fast, automatic response that protects the body.
- The impulse travels: stimulus → receptor → sensory → relay → motor → effector → response.
A reflex follows a fixed pathway — fast and automatic, bypassing conscious thought.
Reflexes don't wait for the brain to decide. The signal goes through the spinal cord and back, so the response happens before you consciously think — which is what makes reflexes so fast and protective.
You've got it
- the CNS = brain + spinal cord; neurones carry electrical impulses
- three neurones: sensory (in), relay (CNS), motor (out)
- a reflex arc: stimulus → receptor → sensory → relay → motor → effector → response