Neurones

• Dendrites receive signals from other cells to be carried across the neurone
• The cell body keeps the cell functional
• The cell membrane protects the cell
• the node of ranvier allows the diffusion of ion across the neurone
• The axon transfers signals from other cells and organs
• The myelin sheath increases the speed of the electrical signal
• The axon terminal forms junctions with other cells
• Motor neurones carry signals from the CNS to effectors (Muscles/Glands)
• Motor neurones have short dendrites and long axons with the cell body at the top
• Relay neurones connect sensory neurones to motor neurones
• Relay neurones have short dendrites and short axons with the cell body in the middle
• Sensory neurones carry signals from receptor sites to the CNS
• sensory neurones have long dendrites and short axons with the cell body to the side
• Synaptic transmission is when an electrical impulse reaches the end of a neurone meaning it must travel across the synaptic gap to the next neurone via neurotransmitters
• Stages of synaptic transmission

  1. An action potential (electrical impulse) travels along the axon of the transmitting neurone to the dendrites
  2. This triggers the pre-synaptic neurone to release neurotransmitters from the vesicles
  3. Neurotransmitters diffuse across synaptic gap and bind with receptor sites on the post-synaptic neurone
  4. This stimulates the post-synaptic neurone to transmit an electrical impulse
  5. Reuptake; some neurotransmitter left in synaptic gap is reabsorbed by the pre-synaptic neurone
• Neurotransmitters can be excitatory or inhibitory
• Summation is how likely a neurone is to fire based on whether neurotransmitters are excitatory or inhibitory
• EGs of neurotransmitters; adrenaline, dopamine, serotonin