CIE IGCSE Biology: 复习笔记：14.1.2 Types of Neurones

• 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