Coordination systems and neurones
Control and coordination
- The body has two coordination systems.
- The endocrine system sends chemical hormones in the blood.
- The nervous system sends fast electrical signals along nerve cells.
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 |
Practice
Compared with the endocrine system, the nervous system is:
Nervous signals are fast electrical impulses with short-lived effects; hormones are slower and longer-lasting.
Neurones
- A neurone is a nerve cell, with a long fibre (the axon) the impulse travels along. Three kinds:
- sensory neurone — carries impulses from a receptor towards the brain/spinal cord.
- motor neurone — carries impulses out to an effector (e.g. a muscle).
- intermediate (relay) neurones — connect sensory to motor neurones.
Practice
A motor neurone:
Motor neurones carry impulses from the CNS out to effectors; sensory neurones carry them in.
The reflex arc
- A sensory receptor detects a stimulus and starts an impulse.
- The reflex arc: stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response.
Practice
Put the reflex arc in order.
Stimulus → receptor → sensory → relay → motor → effector → response.
Practice
A sensory receptor:
A receptor detects the stimulus (e.g. chemicals in a taste bud) and triggers an action potential.
You've got it
Key idea
- 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