Neurons & synaptic transmission

Question 1

What is a neuron?

Answer 1

nerve cells that transfer information throughout the body (electrically & chemically)

Question 2

What is the function of sensory neurons?

Answer 2

• also known as afferent neurons
• located in the PNS
• Carry sensory information from PNS to the CNS
• long dendrites, short axons

Question 3

What is the function of relay neurons?

Answer 3

• also know as interneurons
• located in the CNS (within brain)
• connect the sensory neuron to the motor neurons
• short axons, short dendrites

Question 4

What are the functions of motor neurons?

Answer 4

• also known as efferent neurons
• located in the CNS
• Carry impulses from CNS towards effectors e.g. muscles/ glands
• short dendrites, long axons

Question 5

What is the function of dendrites?

Answer 5

• branch-like structures
• carry nerve impulses from other neurons towards cell body

Question 6

What is the function of axons?

Answer 6

• long slender structure
• carries nerve impulses (action potential) away from cell body towards axon terminal
• surrounded by myelin sheath which speeds up electrical transmission

Question 7

What is the function of the axon terminal? (buttons)

Answer 7

• Connects neurons to other neurons via synaptic transmission

Question 8

What is the function of the cell body(soma)?

Answer 8

• contains nucleus with ‘genetic material’ of cell

Question 9

What is the function of the nodes of Ranvier?

Answer 9

• gaps in myelin sheath
• re-charges action potential to help impulses travel faster

Question 10

What are neurotransmitters?

Answer 10

• chemical messengers, located in the synaptic vesicles of a neuron

Question 11

What happens in the reflex arc?

Answer 11

1. sense organs in PNS detects a stimulus e.g. change in temp
2. sensory neuron sends the electrical impulse from PNS to relay neuron in brain/CNS
3. Relay neurons connect sensory neurons to motor neurons (involved in analysis of sensations, what it means, how to respond etc)
4. Motor neurons send electrical impulses to an effector
5. effector produces a response e.g. muscle contracts

Question 12

Explain the firing of a neuron

Answer 12

neuron in resting state = cell negatively charged
activated by stimulus= cell positively charged = causing an action potential to occur
» electrical impulse travels down axon

Question 13

Explain the process of synaptic transmission

Answer 13

1. electrical impulse arrives at the end of presynaptic neuron to the terminal buttons
2. triggers release of neurotransmitters from synaptic vesicles of presynaptic neuron into the synapse
3. neurotransmitters diffuse chemically across the synapse and bind to receptor sites on postsynaptic neuron
   (any not picked up are broken down or reabsorbed through process of reuptake)
   4.impulse converted back into electrical impulse

Question 14

What is the role of inhibitory neurotransmitters?

Answer 14

• Serotonin, GABA
• increases negative charge of postsynaptic neuron
• postsynaptic neuron is less likely to fire an impulse

Question 15

What is the role of excitatory neurotransmitters?

Answer 15

• Adrenaline, dopamine
• increases positive charge in postsynaptic neuron
• postsynaptic neuron is more likely to fire an impulse

Question 16

What is summation?

Answer 16

• the addition of positive and negative postsynaptic potentials
• whether a postsynaptic neuron fires is decided by the process of summation

Question 17

If the net effect on the postsynaptic neuron is inhibitory then it is __ likely to fire

Answer 17

less

Question 18

If the net effect on the postsynaptic neuron is excitatory then it is__ likely to fire

Answer 18

more