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Biology A2 > Organisms Response to Change - Nervous Coordination > Flashcards

Organisms Response to Change - Nervous Coordination Flashcards

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1
Q

what is a potential difference?

A

difference in electrical potential between 2 points

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2
Q

define a polarised cell

A

a cell with an electrical difference across its membrane

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3
Q

what is a leakage channel protein?

A

an ion channel in plasma membranes, where the permeability is constant

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4
Q

what is a voltage gated channel protein?

A

an ion channel in plasma membranes that open and close as a cell’s polarisation changes

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5
Q

what is a protein pump?

A

proteins involved in the active transport of substances across a membrane

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6
Q

why can’t ions pass directly through a membrane?

A

the charges can’t pass through the hydrophobic tails

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7
Q

how are neurons polarised in a resting state?

A

inside is negative, outside is positive

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8
Q

what is the potential difference of a neuron in the resting state?

A

-65mv

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9
Q

why is a neuron polarised at resting state?

A

there are more positive ions outside the cell than inside

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10
Q

which ions are present and where in a neuron at resting potential?

A

sodium ions - outside

potassium ions - inside

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11
Q

what maintains the resting potential of a neuron?

A

sodium-potassium pump

leakage channel proteins

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12
Q

how does the sodium-potassium pump help maintain the resting potential in a neuron?

A

actively transports sodium ions out of the cell and potassium ions into the cell

this is done in the ratio of 3 sodium ions out for 2 potassium ions in

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13
Q

how do leakage channels help to maintain the resting potential of a neuron?

A

sodium leakage channels closed - prevents sodium ions diffusing into the cell

potassium leakage channels open - potassium ions can diffuse out of the cell

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14
Q

what is an impulse?

A

wave of excitation caused by an action potential

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15
Q

what causes an action potential?

A

a stimulus reaching a neuron

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16
Q

what are the stages of an action potential?

A

stimulus

depolarisation

repolarisation

hyperpolarisation

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17
Q

what happens in the stimulus stage of an action potential?

A

stimulus causes voltage gated sodium channels to open

sodium ions diffuse into neuron, making inside less negative

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18
Q

what happens in depolarisation?

A

if there is a large enough stimulus the threshold is reached

more voltage gated sodium channels open until the cell is +40mv and an action potential occurs

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19
Q

what voltage is the threshold in action potential?

A

-55mv

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20
Q

what happens in repolarisation?

A

voltage gated sodium channels close, voltage gated potassium channels open

allows potassium to diffuse out of the cell

cell becomes more negative

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21
Q

what happens in hyperpolarisation?

A

neuron now too negative

voltage gated potassium ions shut

sodium-potassium pump restores resting potential

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22
Q

what is the refractory period?

A

period of time after an action potential when it is impossible for another action potential to occur

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23
Q

what happens during the refractory period?

A

voltage gated sodium channels are closed and cannot be opened

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24
Q

what is the importance of the refractory period?

A

ensures action potential only happens in 1 direction

produces discrete impulses

limits number of action potentials

25
Q

why is it important that the no. action potentials fired is limited?

A

too many can cause siezures

26
Q

why is it important that the impulses are discreet?

A

so 2 different action potentials can be distinguished

27
Q

what is the all or nothing principle?

A

the principle where:

action potential will only occur once threshold is reached

once threshold reached, all action potentials that occur are the same, no matter size of stimulus

28
Q

what factors can affect rate of impulse transmission?

A

myelin sheath

diameter of axon

temperature

29
Q

how does the myelin sheath affect the rate of impulse transmission?

A

myelinated neurons transmit impulses faster

30
Q

how does the diameter of an axon affect rate of impulse transmission?

A

larger diameter = faster impulse due to less leakage of ions

31
Q

how does temperature affect the rate of impulse transmission?

A

higher temperature = faster impulse as ions can diffuse quicker

32
Q

what is the myelin sheath made up of?

A

schwann cells and myelin membranes wrapped around neurons

33
Q

what is the node of ranvier?

A

breaks in the myelin sheath

34
Q

how are voltages propagated through non-mylenated neurons?

A

stimulus causes voltage gated sodium channels to open, reaching threshold so an action potential occurs

localised electric currents established by influx of sodium ions causes voltage gated sodium channels to open further along the axon, so AP passed down

35
Q

how are action potentials propogated in myelinated neurons?

A

voltage gated Na and K channels only found at nodes of ranvier so AP only occurs here

AP jumps from one node to the next

36
Q

label this diagram of a synapse

A
37
Q

describe how impulses travel along a cholinergic synapse

A

Action potential arrives at presynaptic membrane

gated Ca channels open and Ca ions enter synaptic knob, causing synaptic vesicles to fuse with presynaptic membrane

Acetylcholine diffuses across and binds to Na ion channels

Na ions diffuse into postsynaptic neuron

Action potential generated in postsynaptic neuron

acetylcholine hydrolysed and diffuses back across the cleft to presynaptic membrane

ATP used to reform acetylcholine.

38
Q

what hydrolyses acetylcholine?

A

acetylcholinerase

39
Q

what is acetylcholine hydrolysed into?

A

acetyl / ethanoic acid

choline

40
Q

what are the types of summation?

A

spatial

temporal

41
Q

how do inhibitory synapses transmit impulses?

A

neurotransmitters bind to chloride ion channels on post synaptic membrane

causes chloride channels to open and chloride ions diffuse into cell

also causes potassium channels to open and potassium ions leave the cell

42
Q

what is spatial summation?

A

lots of neurons releasing signals to one neuron

43
Q

what is temporal summation?

A

repeated stimuli from one neuron in quick succession

44
Q

what is the role of a transducer?

A

converting one form of energy to another

eg converting energy of stimulus into electrical impulse

45
Q

what are 3 different types of receptors?

A

pacinian corpusle

rods

cones

46
Q

what is the stimulus for a pacinian corpusle?

A

pressure on skin

47
Q

where are pacinian corpusle receptors located?

A

skin, joints, ligaments, tendons

48
Q

how is an action potential caused in a pacinian corpusle?

A

pressure causes pacinian corpusle to be stretched and stretch mediated sodium channels to widen

sodium ions diffuse into neuron

neuron becomes depolarised creating a generated potential, leading to an action potential

49
Q

what are the layers in the structure of the retina?

A

optic nerve fibre

ganglion cells

bipolar neurons

rod/cone cells

pigment epithelium

50
Q

what is the stimulus for rods?

A

low intensity light

51
Q

where are rod cells found?

A

retina

52
Q

where are cone cells found?

A

retina

53
Q

how is an action potential propogated in rod cells?

A

light strikes cell

rhodopsin breaks down to form retinal and opsin

causes rod cell to depolarise

generator potential occurs, leading to action potential

54
Q

what is the stimulus for cone cells?

A

bright light

55
Q

how is an action potential propogated in a cone cell?

A

light strikes cell

iodopsin breaks down

cone cell depolarises

generated potential occurs, leading to action potential

56
Q

what are the properties of rod cells?

A

temporal summation

low visual activity

sensitive to low levels of light due to rhodopsin’s sensitivity

black and white vision

57
Q

what are the properties of cone cells?

A

spatial summation

high visual activity

respond to high light only

different cones for different wavelengths of light - so coloured vision

58
Q
A

Biology A2 (15 decks)

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