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-neuroneThe 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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