Neurons and synaptic transmission

Question 1

Outline the structure of a generic neuron.

Answer 1

Dendrites receive signals from other neurons or sensory receptors and connected to cell body. Axon carries impulse to axon terminals (could be a synapse). Myelin sheath - insulating layer.

Question 2

What are the three types of neuron?

Answer 2

Sensory, relay and motor neurons.

Question 3

What is the function of sensory neurons?

Answer 3

Carry nerve impulses from the sensory receptors to the brain and spinal cord. Convert sensory information into a neural impulse.

Question 4

What is the function of relay neurons?

Answer 4

Lie wholly in the CNS and allow sensory and motor neurons to communicate with each other.

Question 5

What is the function of motor neurons?

Answer 5

Conduct signals from the CNS to effector organs (e.g. muscles). Form synapses with muscles - stimulated motor neurons release neurotransmitters that triggers the muscle to contract.

Question 6

Are motor neurons in the CNS or peripheral nervous system?

Answer 6

Start in CNS, long axons extend out of the CNS to the PNS.

Question 7

What is the first stage of synaptic transmission?

Answer 7

Action potential arrives at pre-synaptic membrane causes vesicles (containing neurotransmitter) to fuse with the pre-synaptic membrane.

Question 8

What is the second stage of synaptic transmission?

Answer 8

Vesicle fused to pre-synaptic membrane release their contents into the synaptic gap by exocytosis.

Question 9

What is the third stage of synaptic transmission?

Answer 9

Neurotransmitter diffuses across the synaptic gap, down the concentration gradient. Binds to complementary receptors on post-synaptic membrane.

Question 10

What is the fourth stage of synaptic transmission?

Answer 10

Receptors produce either an excitatory or inhibitory effect. Resulting action potential transmits along post-synaptic neurone.

Question 11

What is re-uptake and what does it determine?

Answer 11

Neurotransmitter is taken up again by the pre-synaptic neurone. Speed of this determines how prolonged the effects will be.

Question 12

What are excitatory neurotransmitters?

Answer 12

Increase potential difference across post-synaptic membrane, which increases the likelihood that an action potential will be generated.

Question 13

Give an example of an excitatory neurotransmitter.

Answer 13

Dopamine.

Question 14

What are inhibitory neurotransmitters?

Answer 14

Reduce potential difference across post-synaptic membrane, which decreases the likelihood that an action potential will be generated.

Question 15

Give an example of an inhibitory neurotransmitter.

Answer 15

Serotonin.

Question 16

What is summation?

Answer 16

A calculation involving adding the excitatory and inhibitory synaptic input that indicates whether it was excitatory or inhibitory - determining if action potential induced.