Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A-level Aqa Biology > (15) nervous coordination > Flashcards

(15) nervous coordination Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

what are the components of neurones?

A

cell body
dendrons
axon
schwann cells
myelin sheath
nodes of ranvier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the role of the cell body?

A

(contains all usual cell organelles) contains nucleus and large amounts of RER
associated w production of proteins and neurotransmitters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the role of the dendrons?

A

extensions of cell body subdividing into dendrites (smaller branched fibres)
carry nerve impulses towards the cell body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the role of the axon?

A

(single long fibre) carries nerve impulses away from the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the role of the schwann cells?

A

wraps around the axon many times, protecting axon and providing insulation
carry out phagocytosis and play a part in nerve regeneration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the role of the myelin sheath?

A

forms covering to the axon and made up of membrane of schwann cells
rich in lipid called myelin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the role of the nodes of ranvier?

A

constrictions (gaps) between adjacent schwann cells where there is no myelin sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the definition of a nerve impulse?

A

self-propagating wave of electrical activity travelling across the membrane, it is a temporary reversal of the electrical potential difference between 2 states (resting n action potential)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is resting potential?

A

when a neurone is not conducting an impulse there is. a difference between the electrical charge inside and outside of the neurone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the value of resting potential?

A

-65mV (more positive Na+ and K+ ions outside compared to inside therefore inside is more negative)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the 3 ways that resting potential is maintained?

A

phospholipid bilayer: prevents Na+ n K+ ions from diffusing across it

channel proteins: have gates that can be opened or closed to let ions move through by facilitated diffusion

NaK pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does the sodium potassium pump maintain resting potential?

A

for every 3 Na+ ions that move out of the axon, 2 K+ ions move into the axons, creating an electrochemical gradient ( more Na+ ions in tissue fluid surrounding axon than in cytoplasm but there are more K+ ions in the cytoplasm than in the tissue fluid)

Na+ ions diffuse back naturally into the axon, K+ back out
(most gates for Na remain open but for K most remain close)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is an action potential?

A

when a stimulus (of sufficient size) is detected by receptor, it causes temporary reversal of charges -> inside of membrane becomes a positive charge of +40mV from -65mv

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is depolarisation?

A

the process by which the membrane potential of a neuron becomes less negative, leading to an action potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

generating an action potential: what happens during depolarisation?

A
  1. (resting potential) some K voltage-gated channels are open but Na VG C’s are closed
  2. energy of stimulus causes Na VG C’s to open (NA+ ions diffuse into axon through channels along electrochemical gradient)
  3. when threshold potential (-55mV) is reached, and Na VG C’s openT -> Na+ ions rapidly diffuse in
  4. when AP of +40mV is reaches, Na VG C’s close (prevents further influx of Na+ ions) and K VG C’s open
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

generating an action potential: what happens during repolarisation?

A
  1. K VG C’s are open, electrical gradient is reversed, more K channels open and more K+ ions diffuse out
  2. outward diffusion of K+ ions causes temporary overshoot of electrical gradient so axon s more negative than usual ( HYPERPOLARISATION)
  3. closable gates of K+ channels close and Na-K pump is in action -> action is REPOLARISED
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the refractory period?

A

when the inward movement of Na+ ions is prevented as the Na VG C’s are closed therefore action potentials cannot be generated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how does the refractory period ensure action potentials are propagated in one direction only?

A

AP’s pass from active to resting regions, cannot be propagated from a refractory region -> only moves in a forward direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how does the refractory period produce discrete impulses?

A

bc of refractory period, new AP cannot be formed immediately behind the first one -> ensures AP are separated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how does the refractory period limit the number of action potentials?

A

AP are separated from one another so it limits no of AP that can pass along the axon in a given time, limiting the strength of stimulus that can be detected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the all or nothing principle?

A

any stimulus below the threshold value of -55mV will fail to generate an AP (nothing)
any stimulus above threshold value will generate an AP and a nerve impulse will travel

20
Q

How can the size of a stimulus be determined?

A

by number of impulses passing in a given time: larger the stimulus, the more impulses generated

by having diff neurones w diff threshold values: brain interprets size

21
Q

what happens during the passage of an action potential along an unmyelinated axon?

A
  1. resting potential: conc of positive ions is greater outside than inside therefore axon is POLARISED
  2. stimulus causes influx of NA+ ions and a reversal of charge of axon membrane -> action potential and membrane is DEPOLARISED
  3. electrical currents by influx of NA+ ions cause NA VG C’s to open further along axon causing depolarisation
    behind region, NA VG C’s close and K VG C’s open so K+ ions leave axon along electrochemical gradient so DEPOLARISATION MOVES ACROSS THE MEMBRANE
  4. AP/ DEPOLARISATION is propagated in same way further along axon, outward movement of K+ ions continues so that axon membrane behind AP has be REPOLARISED (back to og state of positive outside negative inside)
  5. repolarisation of axon allows Na+ ions to be actively transported out returning to axon to resting potential ready for new stimulus
22
Q

what happens during the passage of an action potential along a myelinated axon?

A

the myelin sheath acts as electrical insulator and prevents AP from forming: AP occurs at the nodes of ranvier

through SALTATORY CONDUCTION: localised circuits arise between adjacent NoR , jumping from node to node

AP passed along myelinated axon faster than unmyelinated

23
Q

why does an action potential pass along a myelinated axon faster than unmyelinated?

A

bc in an unmyelinated neurone events of depolarisation have to take place all the way along the axon, taking more time

24
Q

what are the factors that affect the speed at which an action potential travels?

A

the myelin sheath
the diameter of the axon
temperature

25
Q

how does the myelin sheath affect the speed at which an action potential travels?

A

due to saltatory conduction (ap jumping from one node to another) increases speed of conductance

26
Q

how does the diameter of the axon affect the speed at which an action potential travels?

A

the greater the diameter, the faster the speed
due to less leakage of ions from a large axons (leakage makes membrane potentials harder to maintain)

27
Q

how does temperature affect the speed at which an action potential travels?

A

higher temp, faster impulse

affects rate of diffusion: energy comes from respiration which is controlled by enzymes that function rapidly at higher temperatures

28
Q

what is a synapse?

A

a junction between 2 neurones or between a neurone and an effector

29
Q

what are the components of a synapse?

A

synaptic cleft
presynaptic neurone
synaptic knob
synaptic vesicles

30
Q

what is the synaptic cleft?

A

the gap between cells at the synapse
(AP is transmitted across synaptic cleft)

31
Q

what is the presynaptic neurone?

A

the neurone that releases the neurotransmitter

32
Q

what is the synapatic knob?

A

the end of the axon of the presynaptic neurone: a swollen portion that contains many mitochondria (energy is needed to synthesis NTS) and ER

33
Q

what are the synaptic vesicles?

A

where the NTS are stored
(located in synaptic knob and fuse w presynaptic membrane to release NTS into synaptic cleft)

34
Q

what are the functions of synapses?

A
  • transmits info from one neurone to another, acting as junctions to
  1. allow a single impulse along one neurone to initiate new impulses at diff neurones at the synapse (allows a single stimulus to create a n of simultaneous responses)
  2. a number of impulses to be combined at the synapse ( allows nerve impulses from receptors reacting to diff stimuli to contribute to a single response)
35
Q

what are the different features of a synapse?

A

unidirectionality
summation (spatial and temporal)

36
Q

what is unidirectionality?

A

the way synapses can only pass info in one direction from PRESYNAPTIC NEURONE TO POSTSYNAPTIC NEURONE
synapses act as valves in this way

37
Q

what is summation?

A

low-frequency APs together lead to a release of NTS to trigger a new Ap in the postsynaptic neurone

38
Q

what is spatial summation?

A

diff presynaptic neurones together release enough NTS to exceed threshold value of postsynaptic neurone, triggering new AP

39
Q

what is temporal summation?

A

a single presynaptic neurone releases NTS many times over a short period to exceed the threshold value of the postsynaptic neurone, triggering new AP

40
Q

what is the role of excitatory neurotransmitters?

A

depolarise the postsynaptic membrane (inside more positive) firing an action potential of the threshold is reached

41
Q

what is the role of inhibitory neurotransmitters?

A

they hyperpolarise the postsynaptic neurone (inside becomes more negative) preventing it from firing an action potential

42
Q

how do inhibitory synapses operate?

A
  1. presynaptic neurone releases a type of neurotransmitter that binds to chloride ion protein channels on the postsynaptic neurone
  2. NT causes CL- ion protein channels to open
    and CL- ions move into postsynaptic neurone by facilitated diffusion
  3. the binding of the NTS cause opening of K+ protein channels, K+ ions move out of the postsynaptic neurone into the synapse
  4. combined effect of negative Cl- ions moving in and K+ ions moving out makes inside of postsynaptic membrane more negative and outside more positive
  5. hyperpolarisation: membrane potential increases to -80mV from -65mV -> less likely AP will be created as large influx of Na+ ions is needed
43
Q

what is the process of transmission across a cholinergic synapse?

A
  1. incoming AP causes depolarisation in the synaptic knob causing calcium channels to open and Ca2+ ions enter S knob by facilitated diffusion
  2. influx of Ca2+ ios into presynaptic neurone causes synaptic vesicles to fuse w synaptic membrane, releasing acetylcholine into synaptic cleft
  3. (diffusion pathway = short) acetylcholine molecules diffuse across cleft quickly and binds to receptor sites on Na+ protein channels in membrane of POSTSYNAPTIC neurone

-> causes Na+ channels to open and ions to rapidly diffuse in along a concentration gradient
GENERATES NEW AP IN POSTSYNAPTIC NEURONE

  1. acetylcholinease hydrolyses acetylcholine inot choline and ethanoic acid (diffuses back into presynaptic neurone)
    rapid breakdown of acetylcholine prevents new AP in postsynaptic neurone (discrete transfer of info)
  2. ATP released by mitochondria used to recombine choline and ethanoic acid into acetylcholine -> stored in synaptic vesicles
    then Na+ protein channels close in absence of acetylcholine
44
Q

what is the role of inhibitory neurotransmitters?

A

they hyperpolarise the post synaptic neurone (making inside of the membrane more negative) preventing it from firing an action potential

45
Q

drugs at synapses: what is the role of agonists?

A

they are the same shape as NTS and mimic the action of NTS so more receptors are activated -> triggering more action potentials

46
Q

drugs at synapses? what are the role of antagonists?

A

some drugs block the receptors on the Na/K ion channels post synaptic neurone so they cannot be activated by neurotransmitters meaning fewer (if any) can be activated

47
Q

what happens when drugs inhibit the release of neurotransmitters from the presynaptic neurone?

A

fewer receptors are activated

48
Q

what happens when some drugs inhibit the ENZYME that breaks down the neurotransmitter?

A

more neurotransmitters are available in the synaptic cleft to bind to receptors and they are there for longer

A-level Aqa Biology (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions