The Cells Of The Nervous System And Neurotransmitters At Synapses

Question 1

What are the three main structures of a neuron in the direction of an impulse?

Answer 1

Dendrites- pass nerve impulses towards the cell body
Cell body(nucleus,cytoplasm)
Axon-carries nerve impulses away from cell body

Question 2

What is an axon surrounded by

Answer 2

A myelin sheath

Question 3

What is the myelin sheath?

Answer 3

A fatty substance which acts to insulate the axon and increase the speed of the transmission of the impulse

Question 4

How is myelin formed?

Answer 4

During the process of myelination, this process continues from birth to adolescence
This is why responses to stimuli aren’t as rapid or coordinated during the first two years of life compared to adolescence and adulthood

Question 5

What can disease to the myelin sheath?

Answer 5

There are a number of diseases that can lead to the breakdown of the myelin sheath around the neurons
This can lead to a loss of coordination

Question 6

What are glial cells?

Answer 6

They’re cells that perform various functions to support neurons
They produce myelin
They support the neurons chemically

Question 7

What do neurons connect with?
What do they release at the synapse?

Answer 7

Other neurons or muscle fibres at a synaptic cleft
Here, they release neurotransmitters which relay impulses across the synaptic cleft

Question 8

What are the stages of when a nerve impulse arrives at the pre-synaptic neuron?

Answer 8

The nerve impulse arrives at the pre synaptic neuron
The vesicles in the axon endings of the pre synaptic neuron containing the chemical neurotransmitters are activated
These vesicles then release the neurotransmitters into the cleft
The neurotransmitters diffuse across the cleft and bind to the receptors on membrane of the post synaptic neuron
Nerve impulse is passed through the post synaptic neuron(if threshold is reached/if there’s enough)

Question 9

Why do neurotransmitters need to be removed after the nerve impulse is transmitted?

Answer 9

So that there’s not continuous stimulation of the post synaptic neuron

Question 10

How are the neurotransmitters removed?

Answer 10

Breakdown of the neurotransmitters by enzymes
Reuptake of neurotransmitters by vesicles in the pre synaptic neuron move

Question 11

What are the two types of signals generated at synapses?

Answer 11

Excitatory(increase or cause activity)
Inhibitory(slow down or stop activity)

Question 12

What does the type of signal generated depend on?

Answer 12

The type of receptor present on the post synaptic neuron
Some neurotransmitters can have an excitatory effect at one neuron and an inhibitory effect at the other

Question 13

What is needed in order for an impulse to be transmitted?

Answer 13

A minimum number of neurotransmitter molecules must attach to the receptors on the post synaptic membrane in order to reach the threshold to transmit the impulse

Question 14

What happens if the threshold is not reached?

Answer 14

This is rehearsed as a weak stimulus, in this case the synapse will filter out the weak stimuli

Question 15

What is summation?
What does it often happen in?

Answer 15

It describes the cumulative effect of a number of weak stimuli firing neurotransmitters simultaneously from a number of different pre synaptic nerouns
Convergent neural pathways can release enough neurotransmitters to reach the threshold and trigger an impulse

Question 16

What are neurotransmitters?

Answer 16

Chemicals that control all human processes, behaviours, feelings and mood

Question 17

What are endorphins?

Answer 17

They’re neurotransmitters that stimulate neurons involved in reducing the intensity of pain

Question 18

What at endorphins produced(in hypothalamus) in response to?

Answer 18

Sex
Severe injury
Certain foods
Prolonged and continuous exercise
Stress

Question 19

What is dopamine?

Answer 19

A neurotransmitter than induces feelings of pleasure
It reinforces particular behaviour by activating the reward pathway in the brain

Question 20

What does the reward pathway involve?
When is it activated?

Answer 20

Neurons which secrete or respond to dopamine
It’s activated when an individual engages in a behaviour that is beneficial to them
Example- eating when hungry

Question 21

What can many of the drugs used to treat neurotransmitter related disorders be classified as?

Answer 21

Agonists
Antagonists

Question 22

What are agaonists?

Answer 22

Chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse

Question 23

What are antagonists?

Answer 23

Chemicals that bind to specific receptors blocking the action of a neurotransmitter at a synapse

Question 24

What can recreational drugs also act as?

Answer 24

Agonists and antagonists
Therefore they can affect neurotransmission at synapses in the brain by altering an individuals mood, cognition,perception and behaviour

Question 25

What do many recreational drugs also affect?

Answer 25

Neurotransmission in the reward pathway of the brain Explains why they give feelings of euphoria and pleasure

Question 26

What is drug addiction caused by?

Answer 26

Repeated use of drugs that act as antagonists These antagonists block specific receptors causing the nervous system to increase both the number and sensitivity of these receptors This leads to sensitisation where the individual craves more of the drug to satisfy their needs

Question 27

What is drug tolerance cause by?

Answer 27

Repeated use of drugs that act as agonists They stimulate specific receptors chains the nervous system to decrease both the number and sensitivity of these receptors This leads to desensitisation where the person needs to take more of the drug to get an effect