Neurones
Biology: Cambridge International A Level, topic 15.1.1
Types of Neurone
Neurones are cells that transmit information from receptors to effectors. There are three main types of neurones:
Sensory neurones
- Sensory neurones carry nervous impulses from receptors (e.g. pressure receptors) into the Central Nervous Systems (CNS).
Motor neurones
- Motor neurones carry impulses from the CNS to effector organs (e.g. muscles or glands).
Relay neurones
- Relay neurones are intermediate neurones.
- Relay neurones receive impulses from a sensory neurone and relay them to motor neurones.
Structure of Neurones
Neurones transmit information from receptors to effectors. The structure of neurones is important in ensuring this information is transmitted correctly and efficiently.
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Basic structure
- Neurones can be myelinated or non-myelinated but all neurones have the following basic structures:
- Dendrites - carries nervous impulses towards a cell body.
- Axons - carries nervous impulses away from the cell body.
- Cell body - where the nucleus is normally located.
Myelinated motor neurones
- Motor neurones in vertebrates are usually myelinated.
- Schwann cells are wrapped around the axon of the neurone. These cells form the myelin sheath.
- Gaps between adjacent Schwann cells are called nodes of Ranvier.
- Myelin increases the speed of the electrical impulse travelling along neurons.
Test yourself on Neurones
Where do motor neurones carry impulses?
Which of these are NOT a feature of neurones?
Which of the following statements about neurones are true?