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biology a level OCR > neuronal communication > Flashcards

neuronal communication Flashcards

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1
Q

what is the reflex arc

A

stimulus -> receptor -> sensory neurone -> CNS -> relay neurone -> motor neurone -> effector (muscle or gland)

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2
Q

name 4 receptors

A
  • baroreceptors
  • chemoreceptors
  • proprioceptors
  • thermoreceptors
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3
Q

what is cell signalling

A

the process by which, cells communicate with one another, where chemicals from one cell bind to receptors on another cell e.g. neurotransmitters.

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4
Q

what are found at the end of sensory neurones

A

pacienion corpuscles

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5
Q

what is habituation

A

grow more sensitive, due to to exposure leading to oversensitivity

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6
Q

what is a nerve

A

an enclosed cable like bundle of neurones

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7
Q

what is the spinal cord

A

a column of nervous tissue, running down the back. Neurones feed into and come out of it:

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8
Q

what is grey matter

A
  • synapses -unmyelinated relay neurones
  • many cell bodies
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9
Q

what is white matter

A
  • myelinated axons
  • relatively few cell bodies
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10
Q

nerve impulses, are said to be?

A

all or nothing responses

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11
Q

what is the threshold value

A

-55Mv

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12
Q

what has to be reached in order to generate an action potential

A

the firing threshold (-55mv)

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13
Q

what is the threshold value

A

the minimum receptor potential needed to generate an action potential.

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14
Q

what is the generator potential

A

the change in electrical potential of membrane, generated in response to a stimulus (e.g. pressure)

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15
Q

what do Pacinian corpuscles respond to

A

a change in pressure

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16
Q

what is the function of a thermoreceptor

A
  • to respond to a change in body temperature
  • found in the skin and hypothalamus
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17
Q

what is the function of a baroreceptor

A
  • to respond to a change in blood pressure
  • found in the carotid artery
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18
Q

what is the function of a osmoreceptor

A
  • respond to a change in blood water potential
  • found in the hypothalamus
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19
Q

page 13 know the summary

A

yes or no

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20
Q

what do reflexes allow the body to do

A
  • to make involuntary adjustments to changes in the external environment to help control the internal environment
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21
Q

what is a monosynaptic reflex

A

when a sensory neurone, directly links to a motor neurone ( i.e. 1 synapse

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22
Q

what is a dendron

A

the part of the neurone responsible for transmitting electrical impulses towards the cell body. only found in sensory and relay neurones

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23
Q

what are axons

A

singular, elongated nerve fibres that transmit impulses away from the cell body.

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24
Q

what is a motor neurones

A

neurones that carry an action potential from the CNS to the effector (muscle or gland)

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25
Q

what is the myelin sheath

A

an insulating fatty layer around a neurone that consist of several layers on membrane an thin cytoplasm from a Schwan cell.

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26
Q

what is the neuromuscular junction

A

the structure at which a nerve meets the muscle, similar in action to a synapse

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27
Q

what is neurone

A

a specialised cell which transmits impulses in the form of action potentials

28
Q

what are relay neurones

A

neurones within the CNS that allow sensory neurones to communicate with motor neurones. they are never myelinated

29
Q

what are sensory neurones

A

neurones that carry an action potential from the sensory receptor to the CNS

30
Q

what is a transducer

A

a cell that converts one form of energy into another - in the case of sensory receptors, to an electrical impulse.

31
Q

what are sodium ion channels

A

protein channels in cell membranes that actively transport sodium ions out of a cell and potassium ions into the cell

32
Q

myelination

A

myelinated neurones are insulated by an individual myelin (fatty) sheath

33
Q

what keeps the myelin sheath alive

A

Schwan cells

34
Q

how long is a Schwan cell

A

about 1mm

35
Q

what is the function of the myelin sheath

A

to prevent ion movement across the neuron membranes so movement can only occur at the node of ranvier.

36
Q

what is the function of myelinated neurones

A

carry action potential over long distances quickly.

37
Q

what is the function of non myelinated neurones

A

involved in coordination actions, where speed is less important e.g. digestion

38
Q

what can be said about the diameter of an axon

A
  • the greater the diameter, the faster the transmission
  • if narrower, there is an increased resistance to flow of ions (so slower)
39
Q

what is the conduction speed of myelinated neurones

A

up to 120 m/s

40
Q

what is the conduction speed of nonmyelinated neurones

A

up to 0.5 m/s

41
Q

what are the nodes of Ranvier

A

gaps in the myelin sheath at intervals of 1-3 mm

42
Q

what can be said about a resting axon

A

that there is a slightly negative electrical potential on the inside compared to the outside.

43
Q

when is the neurone said to be at rest

A

when it is not transmitting an action potential, but it is in fact actively pumping ion using the sodium/potassium pump.

44
Q

how many sodium ions are pumped out and how many potassium ions are pumped in.

A
  • 3 sodium pumped out
  • 2 potassium pumped in
45
Q

what is an action potential

A

a brief reversal of the potential across the membrane of a neurone causing a peak of +40mV compared to the resting potential of -60mv.

46
Q

describe the resting potential

A
  • membrane, is polarised i.e. a potential difference is -65mv, inside relative to the outside.
  • the generation of an action potential is due to the stimulation of receptors or synaptic transmission
47
Q

what is depolarisation

A
  • sodium channels open and sodium diffuses into the axon and it becomes more negative/positive and reaches the threshold potential (-55mv)
  • voltage gated sodium sodium channels open and many sodium ions influx. therefore, the inside becomes increasingly positive compared to the outside and the potential difference reaches 40Mv
48
Q

what is repolarisation

A
  • voltage gated sodium channels close and volage gated potassium channels open, therefore potassium ions move out of the neuron via diffusion and the potential difference is restored
  • more negative inside than outside.
49
Q

what is hyperpolarisation

A

the potential difference overshoots (to -70mv) making the cell hyperpolarised, i.e. more potassium ions, have excited the cell than is necessary.

50
Q

what is the redistribution of ions

A

the sodium and potassium pump, restores the normal distribution of ions, to return the cells to its normal resting potential (-65/-70 mv)

51
Q

what can be said about the all or nothing law

A
  • if the stimulus is below a certain threshold, there is no response, because no action potential is generated.
  • if the stimulus intensity, exceeds the threshold, an action potential is therefore generated.
52
Q

what can be said about the strength of a given stimulus

A

the strength of a stimulus, is determined by the brain and by the frequency of impulses along the neurone, as well as the number of neurones carrying the action potential

53
Q

how do we determine the nature of the stimulus

A

it is determined by the position of the receptors and the sensory neurone bringing the information

54
Q

know the action potential summary on page 30

A
  • 1 - shit
  • 2 - alright
  • 3 - average
  • 4 - good
  • 5 - perfect
55
Q

after an axon has transmitted an impulse, it cannot transmit another straight away because:

A
  • membrane, has to be repolarised from + 40mv -> -65 Mv.
  • resting distribution of NA+ + k+ ions is restored.
56
Q

what is the absolute refractory period

A

no additional stimulus, no matter how strong is able to produce an action potential. NA+ concentration is high in an axon + NA+ channels must return to resting.

57
Q

what is the relative refractory period

A

only more intense stimulus, can produce an action potential, this is during repolarisation and hyperpolarisation period.

58
Q

what is the importance of the refractory period

A
  1. The action potential is propagated forwards, towards a region which is not in refractory period -> impulses, travels in one direction only.
  2. it separates action potential as by the time the second action potential is generated, the first has passed further down line.
59
Q

transmission of the action potential in a nonmyelinated neurone

A
  1. voltage gated sodium channels open and sodium ions diffuse in
  2. a localised increase in sodium inside (AP = 40MV)
  3. the sodium ions, diffuse along the axon dendrite, a short distance from a high to low concentration
  4. causes a slight depolarisation, therefore voltage gated sodium channels, further along the neurone open (NA+ in +40MV)
60
Q

know the saltatory conduction on page 37

A
  • 1 - shit
  • 2 - alright
  • 3 - average
  • 4 - good
  • 5 - perfect
61
Q

what is excitatory post synaptic potential

A

where the membrane potential, of the post synaptic neurone moves closer to the threshold value, due to a small depolarisation as a neurotransmitter causes opening of channels, which allow positive (Na+) charges to enter the post synaptic neurone.

62
Q

what is inhibitory post synaptic potential

A

where the membrane potential of the post synaptic neurone moves away from the threshold due to a small hyperpolarisation as a neurotransmitter causes opening of channels, which allow negative charges (Cl-) to enter the post synaptic neurone and or positive charges (k+) to leave the post synaptic neurone.

63
Q

what is the role of synapses

A
  • allow neurones to communicate
  • ensure one way transmission between neurones
  • divergence
64
Q

give an example of divergence

A

In a reflex, one post synaptic neurone, may carry out the response and another post synaptic neurone, informs the brain on what happened.

65
Q

what is spatial summation

A

simultaneous EPSPs from multiple neurones bring the trigger zone to threshold

66
Q

what is temporal summation

A

Successive EPSPs bring the trigger zone to threshold

biology a level OCR (32 decks)

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