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unit 3 bio > 3.4- cells of the nervous system & neurotransmitters at synapses > Flashcards

3.4- cells of the nervous system & neurotransmitters at synapses Flashcards

1
Q

2 types of nerve cells in the nervous system

A

neurons

glial cells

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2
Q

what do neurons do?

A

receive and transmit electrical signals

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3
Q

3 things all neurons have

A

cell body

one axon

several dendrites

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4
Q

what are dendrites?

A

thread like extensions of the cytoplasm which are often referred to as nerve fibres

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5
Q

what do dendrites do?

A

receive nerve impulses and pass them towards a cell body

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6
Q

what is the cell body?

A

contains the nucleus and most of the cytoplasm

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7
Q

what is an axon and what do they do?

A

single nerve fibre that carries nerve impulses away from the cell body

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8
Q

direction of nerve impulses

A

dendrites - cell body - axon

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9
Q

where are myelin sheath found?

A

surrounding axons

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10
Q

2 functions of myelin sheath

A

insulate axon by surrounding them

increases the speed of impulse conduction

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11
Q

what is the effect of myelin sheath’s presence?

A

greatly increases the speed that impulses can be transmitted along the axon of a neuron

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12
Q

when does myelination take place?

A

continues from birth to adolescence

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13
Q

what effect does myelination have on responses to stimuli?

A

they aren’t as rapid or co-ordinated in the first 2 years as those of an older child or adult

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14
Q

what can happen to the myelin sheath in some diseases?

A

becomes damaged and destroyed causing a loss of muscular co-ordination

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15
Q

what do glial cells not do?

A

glial cells do not transmit nerve impulses

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16
Q

function of glial cells

A

some are responsible for the production of the myelin sheath

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17
Q

what are glial cells essential in?

A

glial cells are essential in providing neurons with physical support

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18
Q

what is a synapse?

A

gap between the end of one neuron and the beginning of another

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19
Q

how are synapses separated?

A

by a synaptic cleft

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20
Q

what do neurons connect with and where?

A

neurons connect with muscle fibres and endocrine gland cells at the synaptic cleft

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21
Q

what is the nerve cells before and after the synaptic cleft called?

A

presynaptic cleft

postsynaptic cleft

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22
Q

function of neurotransmitters on the synaptic cleft

A

neurotransmitters on the synaptic cleft relay impulses across the synaptic cleft

23
Q

4 steps in the action of neurotransmitters

A

neurotransmitters are stored in the vesicles in the axon endings of the presynaptic cleft

when a nerve impulse passes through the presynaptic neuron, it reaches the synaptic terminal and stimulates the vesicles

this causes the vesicles to discharge the neurotransmitters into the synaptic cleft

neurotransmitters then diffuse across the synaptic cleft and bind to receptors on the postsynaptic neurones membrane

24
Q

where are neurotransmitters stored?

A

neurotransmitters stored in the vesicles in the axon endings of the presynaptic cleft

25
Q

what does the neurotransmitter acetylcholine do?

A

acetylcholine binds to receptors causing membrane to open which allows an increased flow of ions through the membrane

26
Q

3 steps in the removal of neurotransmitters

A

neurotransmitters are removed from the synaptic cleft immediately following the passing of any impulse

if the neurotransmitter was left in the synaptic cleft, it would lead to continuous stimulation of the postsynaptic cleft

the system would not be able to responds to new signals making precise control impossible

27
Q

2 ways removal of neurotransmitters from the synaptic cleft is achieved

A

enzyme degradation

reuptake of neurotransmitters

28
Q

what happens during enzyme degradation?

A

some neurotransmitters are broken down by enzymes

non-active products are reabsorbed by the presynaptic membrane

29
Q

what happens in the reuptake of neurotransmitters?

A

in the reuptake of neurotransmitters they are taken back up directly by the presynaptic membrane

30
Q

what 2 things can signals be?

A

excitatory

inhibitory

31
Q

how is a signal determined to be excitatory or inhibitory?

A

the type of receptor involved in the bind to a neurotransmitter

32
Q

2 steps of filtering out weak stimuli

A

for a nerve impulse to be transmitted across a synapse and through the postsynaptic neuron it must first bring about the release of a certain minimum number of neurotransmitters

this number is needed to affect a sufficient number of receptor sites on the postsynaptic neurons membrane

33
Q

what it is called when the certain number of neurotransmitter molecules needed for a nerve impulse to be transmitted is achieved?

A

reaching the membranes threshold

34
Q

how do synapses filter out weak stimuli?

A

from the insufficient secretion of neurotransmitters

35
Q

what is summation and what happens?

A

summation is when several weak stimuli reach a target neuron together and their effect is summated

an impulse can be passed on

36
Q

example of summation

A

converging neural pathways can release enough neurotransmitter molecules to reach the threshold and trigger an impulse

37
Q

what are endorphins and how do they work?

A

chemicals that function like neurotransmitters and act as natural painkillers

do this by combining with receptors at synapses and blocking the transmission of pain signals

38
Q

where are endorphins produced?

A

hypothalamus

39
Q

4 things that increase production level of endorphins

A

physical and emotional stress

severe injury

lengthy periods of vigorous exercise

certain foods such as chocolate

40
Q

3 things that increases level of endorphins

A

prolonged exercise

sexual activity

eating favourite foods

41
Q

2 effects of dopamine

A

induces feelings of pleasure

reinforces particular behaviour by activating the reward pathway in the brain

42
Q

what does the reward pathway involve?

A

neurons that secrete or respond to dopamine

43
Q

how is the reward pathway activated?

A

activated by beneficial behaviour such as eating when hungry

44
Q

what is the active pathway associated with?

A

memory and learning

45
Q

what are agonists and what do they do?

A

agonists are chemicals that bind to and stimulate specific receptors

by mimicking the action of a neurotransmitter at a synapse

46
Q

what are antagonists and how do they work?

A

chemicals that bind to specific receptors preventing the normal neurotransmitter from acting on it

greatly reduces or halts the normal transmission of nerve impulses in the pathway

47
Q

2 ways other drugs act and their effect

A

inhibiting enzymes that degrade neurotransmitters

inhibiting reuptake of the neurotransmitter at the synapse causing an enhanced effect

48
Q

what do recreational drugs affect?

A

transmission of nerve impulses in the reward circuit in the brain

49
Q

4 things recreational drugs can alter in an individual

A

mood

cognitive thinking

perception

behaviour

50
Q

2 effects recreational drugs have on behaviour

A

stay awake longer

less inhibited

51
Q

what is a drug addiction and what is the cause?

A

chronic disease making one compulsively use drugs regardless of consequences

repeated use of drugs that act as antagonists

52
Q

how do antagonist drugs cause drug addiction?

A

block specific receptors causing the nervous system to compensate by increasing both the number and sensitivity of these receptors

53
Q

what is a drug tolerance and what is the cause?

A

when the intensity of an addictive drug is decreased compared to previous uses at the same concentration

repeated use of drugs that act as agonists

54
Q

how do agonist drugs cause drug tolerance?

A

stimulate specific receptors causing the nervous system to decrease them in both number and sensitivity

unit 3 bio (8 decks)

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