Neurons & Synaptic Transmission

Explain the function and structure of sensory neurons

• connects PNS to CNS

• carries information from senses to brain / spinal cord

• have long dendrites and short axons

Explain the function and structure of motor neurons

• connected CNS to PNS

• carries information from brain / spinal cord to muscles and glands

• have short dendrites and long axons

Explain the functions and structure of relay neurons

• connect sensory neurons to motor neurons

• connect relay neurons to other relay neurons

• Process information

• Analyse sensations + decide how to respond

• Have short dendrites and short axons

Explain the difference between excitatory and inhibitory neurotransmitters

• Excitatory neurotransmitters

  • make neuron more positively charged

  • make post-synaptic neuron more likely to fire

• Inhibitory neurotransmitters

  • make neuron more negatively charged

  • make post-synaptic neuron less likely to fire

Explain the term ‘summation’ in relation to neural transmission, with reference to excitatory and inhibitory neurotransmitters

• total electrical energy = result of summation of the impact of excitatory and inhibitory neurotransmitters

• More excitatory neurotransmitters → increase chance of firing

• More inhibitory neurotransmitters → decrease chance of firing

• If: ‘result of summation > threshold’, neuron fires

What’s a synapse?

Microscopic gap between axon and dendrites of neurons

Explain the role of axons and dendrites in the process of synaptic transmission

• carry electrical signals

• They travel along the axon towards the synapse (pre-synaptic neuron)

• And along the dendrites away from the synapse (post-synaptic neuron)

Explain what happens at the synapse itself during synaptic transmission

1. Electrical signal reachers end of the axon of the pre-synaptic neuron

2. This triggers the release of neurotransmitter from synaptic vesicles

3. The neurotransmitters diffuse across the synapse

4. Then they bind to receptors on the post-synaptic membrane

5. Causing the electrical signal to continue along the dendrite

Explain why chemical transmission is a 1 way process

• vesicles are only on presynaptic nerve terminals

  • Only a vesicle can release a neurotransmitter

• Receptor sites are only on dendrites

  • Only a receptor can receive a neurotransmitter

Explain the mode of action of SSRIs in the brain

1. Block presynaptic vesicle

2. Selectively preventing reuptake / reabsorption of serotonin

3. More serotonin available at post-synaptic receptor

4. Increases circulating levels of serotonin

This reduces depression and OCD