Neurons And Synaptic Transmission

Question 1

Dendrites function

Answer 1

Carry nerve impulses from neighbouring neurons towards the cell body

Question 2

Axon

Answer 2

Carries the nerve impulse away form the cell body

Question 3

Myelin Sheath

Answer 3

A fatty layer around the axon which protects and insulates the axon and speeds up electrical transmission of the impulse.

Question 4

Nodes of Ranvier

Answer 4

Gaps in the myelin sheath which speed up the transmission by forcing it to “jump” across gaps in the axon.

Question 5

What are the three types of neurons?

Answer 5

Motor, relay and sensory

Question 6

What is the role of the sensory neuron?

Answer 6

To carry messages from the PNS to the CNS. They have long dendrites and short axons

Question 7

What is the role of the motor neuron?

Answer 7

To connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons.

Question 8

What is the role of the relay neuron?

Answer 8

To connect the sensory neurons to the motor neurons or other relay neurons. They have short dendrites and short axons. NO MYELIN SHEATH

Question 9

What is synaptic transmission?

Answer 9

The process by which a nerve impulse passes across the synaptic cleft from the presynaptic neuron to the postsynaptic neuron

Question 10

What is excitation?

Answer 10

When a neurotransmitter increases the positive charge of the postsynaptic neuron, increasing the likelihood that the neuron will fire. E.g. adrenaline

Question 11

What is inhibition?

Answer 11

When a neurotransmitter makes the charge of the postsynaptic neuron more negative, decreasing the likelihood that the neuron will fire. E.g. Serotonin

Question 12

What is a neurotransmitter?

Answer 12

A chemical messenger that helps transfer the electrical impulse across the synapse from the presynaptic to the postsynaptic neuron

Question 13

What is summation?

Answer 13

The net result of adding up the excitatory and inhibitory neurotransmitters binding to the receptors- determines whether or not the neuron fires

Question 14

Describe the process of synaptic transmission

Answer 14

x Nerve impulse travels down axon of presynaptic neuron and then reaches the terminal button.
x At the end of the axon, there are a number of sacs known as synaptic vesicles. These contain neurotransmitters.
x The synaptic vesicles release neurotransmitters which transfer electrical impulses into chemical messages.
The neurotransmitters diffuse across the synapse and bind to receptors on surface of postsynaptic neuron- has either inhibitory or excitatory effect
x Likelihood of cell firing determined by summation