Neurons and synaptic transmission

Question 1

What are the three kinds of neurons present in the nervous system?

Answer 1

Sensory neurons
Motor neurons
Relay neurons

Question 2

Describe sensory neurons.

Answer 2

Location: PNS
Role: Carries nerve impulses from receptor cells, e.g. pain, heat in the PNS to the CNS
(long dendrites and short axons)

Question 3

Describe relay neurons.

Answer 3

Location: CNS and visual system
Role: Acts as a connector within the CNS carrying nerve impulses between the sensory neurons and motor neurons.
Structure: short dendrites and short axons

Question 4

Describe motor neurons.

Answer 4

Location: CNS and PNS
Role: Carries nerve impulses from the relay neuron (CNS) to an effector e.g. muscle or gland (PNS)
Structure: short dendrites and long axons

Question 5

Outline the process of synaptic transmission.

Answer 5

1. The presynaptic neuron contains vesicles filled with neurotransmitters. When an electrical impulse reaches the axon it causes the neurotransmitter to be released.
2. The neurotransmitters diffuse across the synaptic gap (from a high concentration to a low concentration) and then bind to the postsynaptic neuron receptors.
3. If there are more excitatory (+) neurotransmitters than inhibitory (-) neurotransmitters, the action potential threshold is reached due to the process of summation .This triggers an electrical impulse.