CIE IGCSE Biology: 复习笔记：14.1.2 Types of Neurones
CIE IGCSE Biology: 复习笔记：14.1.2 Types of Neurones
Neurone Diagrams
- There are three main types of neurone: sensory, relay and motor
- Sensory neurones carry impulses from sense organs to the CNS (brain or spinal cord)
- Relay neurones are found inside the CNS and connect sensory and motor neurones
- Motor neurones carry impulses from the CNS to effectors (muscles or glands)
- Neurones have a long fibre (axon)
- This means that less time is wasted transferring the impulse from one cell to another
- The axon is insulated by a fatty sheath with small uninsulated sections along it (called nodes)
- This means that the electrical impulse does not travel down the whole axon, but jumps from one node to the next
- Their cell body contains many extensions called dendrites
- This means they can connect to many other neurones and receive impulses from them, forming a network for easy communication
Identifying the types of neurone:
The three types of neurone
- Sensory neurones are long and have a cell body branching off the middle of the axon
- Relay neurones are short and have a small cell body at one end with many dendrites branching off it
- Motor neurones are long and have a large cell body at one end with long dendrites branching off it
Exam Tip
A way to remember which neurone is which:
Sensory neurones connect a sense organ eg. eye, nose, tastebuds to the CNS
Motor neurones result in a response, which is often movement; think of a moving motorbike
转载自savemyexams
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