Coordination systems and neurones · ⁨协调系统与神经元⁩

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.

Nervous vs endocrine

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

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

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