Biopsychology: Neurons and synaptic transmission

Question 1

What are the 3 types of neurons?

Answer 1

1) Sensory
2) Relay
3) Motor

Question 2

What is the sensory neuron responsible for?

Answer 2

• Carries messages from the PNS to CNS.
• Long dendrites and short axons.
• Carries nerve impulses from sensory receptors to the brain and spinal cord.

Question 3

What is the relay neuron responsible for?

Answer 3

• Connects the sensory neurons to the motor or other relay neurons.
• Short dendrites and short axons.

Question 4

What is the motor neuron responsible for?

Answer 4

• Connects the CNS to effectors such as muscles and glands
• Short dendrites and long axons.
• Takes impulses from relay neuron to muscles around the body.

Question 5

In what order do the neurons come?

Answer 5

1) Sensory
… then …
2) Relay
… then …
3) Motor
… then …

Question 6

What is in the structure of a neuron?

Answer 6

• Cell body
• Dendrites
• Axon
• Myelin sheath

Question 7

What is a cell body?

Answer 7

• Includes a nucleus which contains the genetic material of the cell.

Question 8

What does a dendrite do?

Answer 8

• Branches carrying nerve impulses from other neurons towards the cell body.

Question 9

What does an axon do?

Answer 9

• Carries electrical impulse away from the cell body down the length of the neuron.
• Covered in a fatty layer of the myelin sheath that protects the axon.
• Gaps in the axons called nodes of Ranvier speed up the transmission of the impulse.

Question 10

What are neurtransmitters?

Answer 10

Chemical substances play an important role in the workings of the NS by transmitting nerve impulses across a synapse.

Question 11

What is a synapse? (synaptic cleft)

Answer 11

The small gap between two neurons, where nerve impulses are relayed by a neurotransmitter from the axon of a presynaptic (sending) neuron to the dendrite of a postsynaptic (receiving) neuron.

Question 12

What is the process of synaptic transmission?

Answer 12

Refers to the process by which a nerve impulse passes across the synaptic cleft from one neuron to another.

1) Action potential (impulse) travels down the axon through the dendrites to the axon terminal where synaptic vesicles (presynaptic neuon) triggers the release of neurotransmitters.

2) Neurotransmitters diffuse across the synaptic cleft from the presynaptic neuron to the postsynaptic neuron.

3) Once across, the neurotransmitters bind to receptors of the postsynaptic neuron.

Question 13

What happens when a neuron is activated by a stimulus?

Answer 13

• The inside of the cell becomes positively charged for a split second, causing an action potential to occur
  = electrical impulse, moving it down the axon

Question 14

(i) How are signals within neurons transmitted?

(ii) How are signals between neurons transmitted?

Answer 14

(i) Electrically

(ii) Chemically

Question 15

What happens when the electrical impulse reaches the end of the neuron (presynaptic terminal)?

Answer 15

• Triggers the releases of neurotransmitters from synaptic vesicles.

Question 16

What happens when the neurotransmitter crosses the synaptic cleft?

Answer 16

It is taken up by the postsynaptic receptor sites on the next neuron.

Question 17

In terms of synaptic transmission, what are neurotransmitters? Give an example of a neurotransmitter and what it’s responsible for.

Answer 17

• Chemicals that diffuse across the synapse
• Serotonin - affects mood and social behaviour.

Question 18

What is inhibition? Give an example of inhibitory neurotransmitter

Answer 18

• Increases the negative charge of the postsynaptic neuron, making it less likely the neuron will fire.
• e.g. Serotonin

Question 19

What is excitation? Give an example of a excitatory neurotransmitter

Answer 19

• Increases the positive charge of the postsynaptic neuron, making it more more likely the neuron will fire.
• e.g. Adrenaline.

Question 20

What is somation?

Answer 20

Both inhibitory and exhibitory neurons cross to reach the postsynaptic neuron, whatever neuron reaches this the most will depend on whether they fire or not.