What homeostasis is, the parts of a control system, neurones, synapses and the reflex arc.
What you will learn
- Say what homeostasis is and name receptors, coordination centres and effectors
- Describe what sensory, relay and motor neurones do
- Explain how an impulse crosses a synapse
- Describe a reflex arc and explain why reflexes are fast
Keeping conditions steady
Your cells only work well when the conditions around them stay within narrow limits: body temperature, blood glucose concentration and water level all have to be held steady.
Keeping internal conditions within set limits is homeostasis, and it happens automatically.
Every control system has three parts:
- Receptors detect a stimulus (a change inside or outside the body).
- A coordination centre (the brain, the spinal cord or an organ such as the pancreas) processes the information and decides on a response.
- Effectors (muscles or glands) carry out the response.
The body sends the messages in two ways: as electrical impulses along neurones (the nervous system) or as hormones in the blood (the endocrine system).
Receptors detect and effectors respond. A muscle or a gland is always an effector, never a receptor.
The rest of this lesson and its 11 practice questions are locked.
In this lesson
- Keeping conditions steady
- Neurones and the nervous system
- The reflex arc
- Try it: How fast is an impulse?
11 practice questions, marked as you go; about 25 minutes in all.
Key terms
Homeostasis, Receptors, Coordination centre, Effectors, Central nervous system, Sensory neurone, Relay neurone, Motor neurone, Synapse, Reflex
In this unit: Homeostasis and response
How the nervous and hormonal systems keep the body's internal conditions steady: reflexes and reaction time, blood glucose and diabetes, reproductive hormones and contraception, the brain, eye, temperature and kidneys, and plant hormones.