Neurons and Synaptic Transmission

Question 1

What is a neuron?

Answer 1

• Basic building blocks of the nervous system.
• Nerve cells that process and transmit messages through electrical & chemical signals

Question 2

How many neurons are in the body?

Answer 2

100 billion and 80% are in the brain

Question 3

What is the function and structure of the sensory neuron?

Answer 3

Function = carry message from the PNS to CNS

Structure = long dendrites & short axons

Question 4

What is the function and structure of the relay neuron?

Answer 4

Function = connect sensory neurons to motor neurons or other relay neurons

Structure = short dendrites

Question 5

What is the function and structure of the motor neuron?

Answer 5

Function = connect the CNS to effectors

Structure = short dendrites & long axons

Question 6

What does the axon do on a neuron?

Answer 6

carries impulses away from the cell body
- covered in the fatty layer of the myelin sheath which protects it and speeds up the electrical transmission

Question 7

What does the dendrites do on a neuron?

Answer 7

branch-like structures which carry nerve impulses from neighbouring neurons towards the cell body

Question 8

What is the gap between the myelin sheath called?

Answer 8

nodes of ranvier

Question 9

What is electrical transmission (firing of a neuron)?

Answer 9

• When in the resting state the inside of the cell is negatively charged compared to the outside
• When it is activated by a stimulus, the inside becomes positively charged for a split-second causing an action potential

Action potential = creates an electrical impose that travels down the axon to the end of the neuron

Question 10

What is a synaptic transmission?

Answer 10

Process in which neighbouring neurons communicate with each other by sending chemical messages across the gap that separates them

Question 11

What is a neurotransmitter?

Answer 11

• Chemicals that diffuse across the synapse to the next neuron
  
  • Taken up by the postsynaptic receptors (dendrites)
  • Then transferred back to an electrical message

Question 12

What is excitation?

Answer 12

When a neurotransmitter increases the positive charge of the postsynaptic neuron, it increases the likelihood that the neuron will fire up and pass on the electrical impulse

Question 13

What is an example of excitation?

Answer 13

Adrenaline is both a hormone and a neurotransmitter.

Question 14

What is inhibition?

Answer 14

When a neurotransmitter increases the negative charge of the postsynaptic neuron,it decreases the likelihood that the neuron will fire up and pass on the electrical impulse

Question 15

What is an example of inhibition?

Answer 15

Serotonin

Question 16

What is summation

Answer 16

Whether a post-synaptic neuron fires is decided by summation.
That means how the excitatory and inhibitory influences are summed

– if the net effect on the post-synaptic neuron is inhibitory, it is less likely to fire.

-If the net effect on the post-synaptic neuron is excitatory, it is likely to fire as it will become positively charged and travel down the neuron.

Question 17

What happens during synaptic transmission?

Answer 17

1. electrical impulse reaches a presynaptic neuron (end)
2. triggers release of neurotransmitters via synaptic vesicles
3. neurotransmitter is taken up by postsynaptic receptor site
4. transferred back to an electrical transmission