Biopsychology : neurons and synaptic transmission

Question 1

Define neuron

Answer 1

The basic building blocks of the nervous system - neurons are the nerve cells that process and transmit messages through electrical and chemical signals

Question 2

Define sensory neurons

Answer 2

They carry messages from the PNS (peripheral nervous system) to the CNS. They have long dendrites and short axons

Question 3

Define relay neuron

Answer 3

They connect the sensory neurons to the motor or other relay neurons. They have short dendrites and shirt axons

Question 4

Define motor neuron

Answer 4

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

Question 5

How many neurons are there in the human nervous system?

Answer 5

100 billion neurons
80% are located in the brain

Question 6

How do the neurons provide the nervous system with its primary means of communication?

Answer 6

By transmitting signals electrically and chemically

Question 7

What are the size variations of a neuron?

Answer 7

From less than a millimetre to a metre long

Question 8

Explain the structure of cell body in neuron?

Answer 8

Cell body / soma - includes nucleus (which contains genetic material of the cell.
from cell body

Question 9

What do dendrites do?

Answer 9

They carry nerve impulses from neighbouring neurons toward the cell body

Question 10

What does the axon do?

Answer 10

Carries the impulses away from the cell body down the length of the neuron

Question 11

What is the axon covered in and what does it do?

Answer 11

A fatty layer of myelin sheath - protects axon and speeds up electrical transmission of the impulse

Question 12

What are nodes of ranvier

Answer 12

They separate the myelin sheath which speeds up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon

Question 13

What is at the end of the axon and what do they do?

Answer 13

Terminal buttons : communicate with the next neuron in the chain across a gap, the synapse

Question 14

Where would the cell bodies of motor neurons be found?

Answer 14

In the CNS but they have long axons which form part of the PNS

Question 15

Where are sensory neurons located ?

Answer 15

Outside of the CNS , in the PNS in clusters known as ganglia

Question 16

Where are relay neurons found?

Answer 16

Within the brain and the visual system - they make up 97% of all neurons

Question 17

What happens when a neuron is in resting state ?

Answer 17

The inside of the cell is negatively charge pd compared to the outside

Question 18

What happens when a neuron is activated by a stimulus?

Answer 18

The inside of the cell becomes positively charged for a split second causing action potential to occur. This creates an electrical impulse that travels down the axon toward the end of the neuron

Question 19

What are the groups that neurons communicate within called?

Answer 19

Neural networks

Question 20

What are each neurons separated by?

Answer 20

Synapses

Question 21

How are signals within neurons transmitted?

Answer 21

Electrically

Question 22

How are signals between neurons transmitted between neurons?

Answer 22

Chemically accross the synapse

Question 23

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

Answer 23

It triggers the release of neurotransmitter from tiny sacs called synaptic vesicles

Question 24

What are neurotransmitters?

Answer 24

Chemicals which diffuse across the synapse to the next neuron in the chain

Question 25

What happens once a neurotransmitter crosses the gap?

Answer 25

It is taken up by a post synaptic receptor site on the dendrites of the next neuron (axons take signals to the synapse, dendrites take signals away)

Chemical message is converted back into an electrical impulse and the process of transmission begins again in the other neuron

Question 26

What is the direction of a neurotransmitter?

Answer 26

Only one way because they are released from the presynaptic neuron terminal and received by the post synaptic neuron (at the receptor sites)

Question 27

What does each neurotransmitter have?

Answer 27

It’s own specific molecular structure that fits perfectly into a postsynaptjc receptor site - similar to lock and key

Question 28

What else do neurotransmitters have?

Answer 28

Specialist functions
Eg : acetylcholine is found at each point where a motor neuron meets a muscle and upon release, it will cause muscles to contract

Question 29

What does neurotransmitters either have?

Answer 29

An excitatory or inhibitory effect on the neighbouring neuron

Eg: serotonin causes inhibition in the receiving neuron - resulting in the neuron becoming more negatively charged and less likely to fire

Question 30

What is summation?

Answer 30

Whether a postsynaptic neuron fires

Question 31

What happens in summation?

Answer 31

The excitatory and inhibitory influences are summed - if the net effect on the postsynaptic neuron is inhibitory , then the postsynaptic neuron is less likely to fire

Once the electrical impulse is created, it travels down the neuron

So , the action potential of the postsynaptic neuron is only triggered if the sum of the excitatory and inhibitory signals at any one time reaches the threshold

Question 32

Define synaptic transmission

Answer 32

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

Question 33

Define neurotransmitter

Answer 33

Brain chemicals released from synaptic vesicles which relay signals across the synapse from one neuron to another

They can be broadly divided into those that perform an inhibitory function and those which perform an excitably function

Question 34

Define excitation

Answer 34

When a neurotransmitter eg adrenaline increases the positive charge of postsynaptic neuron # increases likelihood that the postsynaptic neuron will pass on the electrical impulse

Question 35

Define inhibition

Answer 35

When a neurotransmitter such as serotonin increases the negative charge of the postsynaptic neuron - decreasing the likelihood that the postsynaptic neuron will pass on the electrical impulse