Cells of nervous system, neurotransmitters at synapses

Question 1

Nerve cells

Answer 1

Neurons - adapted to carry electrical impulses from one place to another

Question 2

Parts of neurons

Answer 2

Axon - single fibre that carries nerve impulses away from cell body which is insulated by a fatty (myelin) sheath

Dendrites - branched nerve fibres which receive nerve impulses and pass them towards cell body

Question 3

Axon - fatty myelin sheath function

Answer 3

Insulated by fatty (myelin) sheath which increases speed of nerve impulses along neuron

Question 4

Myelination

Answer 4

process of developing myelin around axon fibres, it continues from birth to adolecense

Question 5

Multiple sclerosis and poliomyeltis

Answer 5

Cause myelin sheath to be destroyed - damage to motor neurons which means muscles no longer receive signals from brain or spinal cord. Results in loss of strength and co-ordination in the limbs.

Question 6

Myelin sheath is produced by what kind of cells?

Answer 6

Glial cells

Question 7

Glial Cells

Answer 7

DO NOT transmit nerve impulses. Instead they maintain homeostasis, form myelin and provide support and protection for neurons. Glial cells also remove any debris by phagocytosis

Question 8

Synapse

Answer 8

Where 2 neurons meet - small gap called synapse

The plasma membranes of each neuron are in very close contact and are seperated by a narrow space called synaptic cleft.

Question 9

Mechanism for electrical impulse to cross gap

Answer 9

1. electrical nerve travels along axon of 1st neuron (presynaptic neuron)
2. when nerve impulse reaches dendrites at end of axon, chemical messenger called neurotransmitters are released
3. these chemicals diffuse across synaptic cleft. Chemicals bind with receptors molecules on membrane of second neuron (postsynaptic neuron)
4. receptor molecules on second neuron can only bind to specific neurotransmitters released from first neuron.
5. binding of neurotransmitter to receptors stimulates 2nd neuron to transmit an electrical impulse along its axon. Signal is therefore been carried from one neuron to the next.

Question 10

neurotransmitters are stored where?

Answer 10

inside vesicles which are found in presynaptic neuron

Question 11

between impulses transmitter molecules are rapidly removed from synaptic cleft to prevent continuous stimulation of postsynaptic neurons - what are 2 types of removal?

Answer 11

Re-uptake - the neurotransmitter is reabsorbed back into presynaptic neuron and restored inside vesicle ready to be used again - e.g. noradrenaline

Enzyme degradation - neurotransmitters broken down by an enzyme into smaller inactive product which are then reabsorbed by presynaptic neuron and resynthesied into active neurotransmitter.

Question 12

Receptors on the postsynaptic membrane determines whether the signal received is?

Answer 12

Excitatory - increases contraction of muscle fibres

Inhibitory - decreases contraction of muscle fibres

Question 13

A critical number of neurotransmitter molecules is needed for what?

Answer 13

In order to affect enough receptors on the postsynaptic membrane

A nerve impulse is only transmitted across synapse if enough neurotransmitters is released.

Question 14

Weak stimuli

Answer 14

Doesn’t reach critical number of neurotransmitter molecules to generate an impulse. This filters out weak stimuli.

Question 15

Summation

Answer 15

A series of weak stimuli combine, increasing amount of neurotransmitters released. This means enough being diffused across the synaptic cleft to trigger the impulse in the postsynaptic neuron.

Question 16

Endorphins

Answer 16

Neurotransmitters that stimulate neurons involved in reducing intensity of pain.

Connected to feeling of pleasure

Question 17

Endorphins arise from activities such as

Answer 17

prolonged exercise, eating and sex

Question 18

endorphin production increases in response to…

Answer 18

severe injury

prolonged and continuous exercise

stress

certain foods

Question 19

increased endorphines can in turn stimulate the release of…

Answer 19

dopamine

Question 20

Dopamine can bring around other responses such as…

Answer 20

Euphoria

Apetite regulation

Release of sex hormones

Question 21

Dopamine

Answer 21

Neurotransmitter that indices feeling of pleasure and is involved in reinforcing particular behaviour as part of reward pathway (neurons which secrete or respond in increased levels of dopamine)

reward pathway = eating when hungry

Question 22

Alzheimer’s disease

Answer 22

Linked to low levels of neurotransmitters acetylcholine which results in decline in signals between brain and cells

Question 23

Parkinson’s disease

Answer 23

Low levels of dopamine affect part of brain controlling movement causing it to not work properly.

Question 24

Drug treatments for neurotransmitter linked diseases?

Answer 24

Either agonists or antagonists

Question 25

Agonists

Answer 25

Chemicals that mimic the neurotransmitter effect. Agonists bind to and stimulate receptors, triggering the same response as the neurotransmitter

Question 26

Example of agonists

Answer 26

Morphine

Question 27

Antagonsists

Answer 27

Block neurotransmitters from binding to and stimulating receptors.

Question 28

Example of antagonsits

Answer 28

Antihistamines - blocking or inhibiting histamine receptors that the allergy triggered.

Question 29

Antagonists other treatments available may affect uptake of neurotransmitters by either…

Answer 29

Inhibiting enzymes which degrade them or inhibiting the reabsorption.

Question 30

Recreational drugs

Answer 30

Affect neurotransmitters in reward pathway. Act as either agonists or antagonists. Can also stimulate release of neurotransmitters or inhibit their uptake.

Question 31

Recreational drugs cause changes in…

Answer 31

mood
awareness
perception
behaviour

Question 32

Agonist recreational drugs

Answer 32

Repeated use results in tolerance

Stimulate specific receptors which decreases number and sensitivity of receptors. As sensitivity decreases the individual must take more drugs to trigger receptors and therefore feel effect.

Question 33

Antagonist recreational drugs

Answer 33

Repeated use leads to addiction

Block specific receptors which increases both number and sensitivity of receptors. As result sensitisation leads to individual craving more of the drug.