Structure and Function of Sensory, relay and motor neurons, Process of Synaptic transmission

Question 1

What is the structure of a Neuron?

Answer 1

• Cell Body
• Dendrites
• Axon
• Myelin Sheath

Question 2

What is the function of the cell body?

Answer 2

• Contains the nucleus (chromosomes)

Question 3

What is the function of the dendrites?

Answer 3

• Extend from the cell body
• They carry electrical impulses from other neurons towards the cell body

Question 4

What is the function of the Axon?

Answer 4

• An extension of the neuron
• It carries the impulses away from the cell
• It is covered by the Myelin Sheath

Question 5

What is the function of the Myelin Sheath?

Answer 5

• A fatty substance which increases the speed at which impulses propagate

Question 6

What are Sensory Neurons?

Answer 6

• Neurons which carry nerve impulses from the sensory receptors (e.g. vision, taste, touch) to the Central Nervous System
• They have long dendrites and short axons

Question 7

What are Relay Neurons?

Answer 7

• Neither sensory nor motor but sit somewhere in between - allowing the two other types to communicate
• Carries information through the spinal cord/brain (from sensory neurons –> motor)

Question 8

What are Motor Neurons ?

Answer 8

• Responsible for directly or indirectly controlling muscles
• Carries impulses from the Central Nervous System to effectors (e.g. muscles or glands)
• They have short dendrites and long axons

Question 9

What are neurotransmitters?

Answer 9

• The molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles

-They allow the transfer of signaling messages between brain cells

Question 10

Where are neurotransmitters located and stored?

Answer 10

• They are located in a part of the neuron called the axon terminal
• They are stored within thin-walled sacs called synaptic vesicles

Question 11

Where does communication between two neurons happen?

Answer 11

• In the synaptic cleft

Question 12

What are 2 examples of neurotransmitters?

Answer 12

• Dopamine
• Seretonin

Question 13

What does too high dopamine cause?

Answer 13

Schizophrenia

Question 14

What does too low serotonin cause?

Answer 14

Depression

Question 15

What is Synaptic transmission?

Answer 15

The process by which a nerve impulse passes across the synaptic gap from a pre- synaptic neuron to a post-synaptic neuron.

Question 16

Explain the 7 stage process of Synaptic Transmission

Answer 16

• Information is passed down the axon of the neuron as an electrical impulse known as action potential. Once it reaches the end of the axon it needs to be transferred to another neuron or tissue
• It must cross over the synaptic gap between the pre-synaptic neuron and post-synaptic neuron
• At the end of the neuron (in the axon terminal) are the synaptic vesicles, which contain chemical messengers, known as neurotransmitters
• When the electrical impulse (action potential) reaches these synaptic vesicles, it triggers (by opening up the calcium channels) the vesicles to move towards the membrane and release neurotransmitters into the synaptic cleft (called exocytosis)
• Neurotransmitters then carry the signal across the synaptic cleft. They bind to receptor sites on the post-synaptic cell, thereby completing the process of synaptic transmission
• The neurotransmitters makes it either more likely or less likely that the post-synaptic neuron will fire
• Neurotransmitters that don’t bind are either absorbed/broken down by enzymes or get re-uptaken back into the pre synaptic neuron

Question 17

What is summation?

Answer 17

Add up of both excitatory and inhibitory inputs determines whether the cell fires

Question 18

Explain the term excitation

Answer 18

• Neurotransmitter which increases the likelihood that an excitatory signal is sent to the post-synaptic cell, making it more likely that the neuron will ‘fire’

Question 19

Explain the term inhibition

Answer 19

• A neuron which decreases the likelihood of a neuron ‘firing’

Question 20

Give an example of Excitatory neurotransmitters taking action

Answer 20

Noradrenaline, act as the nervous system ‘on switches’ and they make it more likely that a post-synaptic neuron will ‘fire’, and a behavior will occur

Question 21

Give an example of Inhibitory neurotransmitters taking action

Answer 21

GABA, are the nervous system’s ‘off switches’ in that they decrease the likelihood that a post-synaptic neuron will ‘fire’, and make it less likely that a behavior will occur