Neurobiology Unit 3 KA 4

Question 1

What are Neurons?

Answer 1

Neurons are nerve cells which receive and transmit nervous impulses

Question 2

What makes up Neurons? (3)

Answer 2

1) Several Dendrites
2) A cell body
3) One axon

Question 3

What direction does a nervous impulse travel down a Neuron?

Answer 3

Dendrites -> Cell body -> Axon

Question 4

What does the cell body of a Neuron contain? (3)

Answer 4

1) The nucleus
2) Most of the cytoplasm
3) Ribosomes

Question 5

What does the cell body of a Neuron do?

Answer 5

The cell body of a neuron is the control centre of the cells metabolism

Question 6

What is an Axon?

Answer 6

An Axon is a single nerve fibre that carries nerve impulses away from a cell body and towards the next neuron/muscle/gland

Question 7

What surrounds an Axon?

Answer 7

The Myelin sheath surrounds an Axon

Question 8

What does the Myelin sheath do?

Answer 8

The Myelin sheath insulates the Axon and increases the speed of impulse conduction

Question 9

What does Multiple sclerosis (MS) do to the Myelin sheath?

Answer 9

Multiple sclerosis destroys the Myelin sheath and causes a loss of co-ordination and muscle control is severely impaired

Question 10

What do Glial cells do? (2)

Answer 10

1) Produce the Myelin sheath
2) Physically support neurons

Question 11

What is a Synapse?

Answer 11

A Synapse is the tiny region between the axon end of one neuron and the dendrite end of the next neuron

Question 12

What is the Neuron before a Synaptic cleft called?

Answer 12

The neuron before a Synaptic cleft is called the pre-synaptic neuron

Question 13

What is the Neuron after a Synaptic cleft called?

Answer 13

The neuron after a Synaptic cleft is called the post-synaptic neuron

Question 14

What happens to a Neurotransmitter (NT) at a synapse? (5)

Answer 14

1) The impulse travels down the axon of the pre-synaptic neuron
2) The impulse arrives at vesicle
3) NT’s stored in vesicles are released into the cleft
4) NT’s diffuse across the cleft
5) NT’s bind to the receptors on the membrane of the post-synaptic neuron

Question 15

What do Receptors determine?

Answer 15

Receptors determine whether the signal is excitatory or inhibitory

Question 16

Why do Vesicles containing Neurotransmitters occur on only one side of a synapse?

Answer 16

Vesicles containing Neurotransmitters only occur on one side of a synapse because it ensures that the nerve impulses are transmitted in only one direction

Question 17

Why must Neurotransmitters be removed from the synaptic cleft after the impulse has been transmitted?

Answer 17

Neurotransmitters must be removed from the synaptic cleft after the impulse has been transmitted to prevent the continuous stimulation of post-synaptic neurons

Question 18

How can Neurotransmitters be removed from a synaptic cleft? (2)

Answer 18

1) Enzyme degradation
2) Re-uptake

Question 19

What is Enzyme degradation?

Answer 19

Enzyme degradation involves breaking down the NT into non-active products which are reabsorbed by the pre-synaptic neuron and resynthesized into the active neurotransmitter (requires energy)

Question 20

What is Re-uptake?

Answer 20

Re-uptake is when Neurotransmitters are reabsorbed directly by the pre-synaptic membrane that secreted it and is stored in the vesicle ready for use

Question 21

What does an Excitatory effect do to a muscle?

Answer 21

An Excitatory effect causes a muscle to contract

Question 22

What does an Inhibitory effect do to a muscle?

Answer 22

An Inhibitory effect causes a muscle contraction to release

Question 23

What must happen in order for an impulse to be transmitted?

Answer 23

In order for an impulse to be transmitted, a minimum number of Neurotransmitter molecules must attach to receptors to reach the minimum threshold on the post-synaptic neuron

Question 24

What happens when the secretion of Neurotransmitters is insufficient?

Answer 24

If the secretion of Neurotransmitters is insufficient it allows the synapses to filter out the weak stimuli

Question 25

Why are **Mitochondria** present in a Neuron?

Answer 25

Mitochondria are present in a Neuron to ensure there is enough **energy** for reabsorption of NTs from the synaptic cleft

Question 26

What is **Summation**?

Answer 26

Summation is when a series of weak stimuli can release enough NT to trigger an impulse

Question 27

What are **Endorphins**?

Answer 27

Endorphins are NTs that stimulate neurons involved in reducing the sensitivity of pain (natural painkillers)

Question 28

What increases **Endorphin** production? (4)

Answer 28

1) Severe injury 2) Prolonged and continuous exercise 3) Stress 4) Certain foods (chocolate)

Question 29

Increased levels of **Endorphins** are linked to feelings of pleasure gained from what three activities?

Answer 29

1) Eating 2) Sex 3) Prolonged exercise

Question 30

What is **Dopamine**? What does it activate?

Answer 30

Dopamine is a NT that induces the feeling of pleasure and reinforces that particular behaviour by activating the **Reward pathway** in the brain

Question 31

What does the **Reward pathway** involve?

Answer 31

The Reward pathway involves neurons which secrete or respond to **dopamine**

Question 32

How is the **Reward pathway** activated?

Answer 32

The reward pathway is activated when an individual engages in behaviour that is beneficial to them (eating when hungry)

Question 33

Name two NT related disorders -

Answer 33

1) **Alzheimers** disease (loss of neurons that synthesise Acetylcholine) 2) **Parkinson's** disease (loss of neurons that synthesise dopamine)

Question 34

What do **Antagonistic** drugs do?

Answer 34

Antagonistic drugs contain chemicals that bind to specific receptors **blocking** the action of the neurotransmitter at a synapse

Question 35

What do **Agonist** drugs do?

Answer 35

Agonist drugs contain chemicals that bind to and stimulate specific receptors **mimicking** the action of the neurotransmitter at a synapse

Question 36

What do **Recreational drugs** affect?

Answer 36

Recreational drugs affect the transmission of nerve impulses in the reward circuit of the brain

Question 37

What can **Recreational drugs** change? (4)

Answer 37

1) **Mood** (happy/confident/aggressive) 2) **Cognition thinking**(Poorer at problem solving and decision making) 3)** Perception** (misinterprets stimuli- colour, sound, time) 4)** Behaviour **(stay awake longer, talk endlessly)

Question 38

What causes drug **Addiction**?

Answer 38

Drug Addiction is caused by the repeated use of **Antagonists** - Antagonists block specific receptors increasing their sensitivity and the person craves more of the drug

Question 39

What causes drug **Tolerance**?

Answer 39

Drug Tolerance is cause by the repeated use of **Agonists** - Agonists stimulate specific receptors decreasing their sensitivity and the person must take more of the drug to get an effect