5.1.3- Neuronal Communication Flashcards

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1
Q

what are sensory receptors?

A

specialised cells that detect stimuli

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2
Q

what are sensory receptors known as and why?

A

ENERGY TRANSDUCERS
they convert different forms of energy into electrical energy

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3
Q

what are the 4 types of sensory receptors and what is their stimulus?

A

1- Mechanoreceptor- pressure and movement
2-Chemoreceptors- chemicals
3-Thermoreceptors- heat
4- Photoreceptors- light

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4
Q

what is an example of a mechanoreceptor?

A

Pachinian Corpuscle, in the skin

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5
Q

what is an example of a chemoreceptor?

A

Olfactory receptor in the nose

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6
Q

what is an example of a thermoreceptor?

A

End-bulbs of Kraus, in the tongue

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7
Q

what is an example of a photoreceptor?

A

Cone cells in the eye

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8
Q

what is the function of a sensory neurone?

A

carry impulses from receptors to the CNS

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9
Q

what is the function of a relay neurone?

A

connect the sensory and motor neurone, present in the CNS

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10
Q

what is the function of a motor neurone?

A

carry impulses from CNS to effectors

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11
Q

when in resting potential, what is the neurone cell membrane described as?

A

polarised

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12
Q

what is resting potential?

A

the potential difference across the neurone cell mebrane while the neurone is at rest

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13
Q

what happens during resting potential of neurones?

A

-3 sodium ions are transported out
-2 potassium ions are transported in
-the sodium-potassium pump controls this
-the sodium ion channels are closed so that sodium cannot come back into the neurone, while the potassium ion channels remain open so they can move back out
-this leads to the inside being negative and the outside being positive, with a difference of around -70mV

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14
Q

what is action potential?

A

the depolarisation of the neurone cell membrane, so the inside is more positive than the outside, occurring when the cell is active

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15
Q

what happens during action potential of neurones?

A

-sodium ion channels open, and potassium ion channels close
-this causes a rush of sodium ions into the neurone, causing the flip of charge
-the change becomes around +40 mV

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16
Q

what occurs during repolarisation of neurones?

A

-the Na ion channel closes but the K ion channels open, which leads to a flood of K entering the neurone
-however, this can lead to overpolarisation, as the inside will become too negative
-therefore, the sodium-potassium pump works to get it back to normal

17
Q

what is a pacinian corpsucle?

A

a specific sensory receptor that detects mechanical pressure

18
Q

how does a pacinian corpuscle convert mechanical pressure into a nervous impulse?

A

-normal state, PC has a resting potential
-stretch-mediated sodium channels in sensory neurones membrane are too narrow to allow Na ions to pass through
-pressure is applied, so the PC changes shape, membrane stretches
-Na ion channels widen so Na ions diffuse in
-membrane becomes depolarised, resulting in a generator potential
-generator potential if reaching threshold potential creates an action potential

19
Q

what is generator potential?

A

the transmembrane potential difference produced by activation of a sensory receptor

20
Q

what is habituation?

A

-body gets used to a particular ‘feeling’ if the body receives the stimulus over a long period of time.
—> less stimulation of corpuscle over time

21
Q

what is a nerve impulse?

A

a wave of depolarisation followed by a wave of repolarisation

22
Q

how is a nerve impulse transmitted?

A

-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)

23
Q

how is a nerve impulse transmitted?

A

-when an action potential is set up, the influx of sodium ions set off the transmission along the neurone
-the increase of these ions set up a local current
-these ions then diffuse sideways along the neurone, causing voltage-gated sodium channels to open further down the neurone, setting off another action potential
-local current moves down as a wave of depolarisation, followed by the nerve impulse (wave of repolarisation)

24
Q

what does a more intense stimulus mean in terms of frequency?

A

a high frequency of nerve impulses

25
Q

what is a myelinated neurone?

A

when a neurone has a fatty sheath wrapped around it, providing electrical insulation, along side layers of membrane, Schwann cells, nodes of ranvier

26
Q

what is the speed of conduction of a myelinated neurone?

A

FAST= 120m/s
known as saltatory conduction

27
Q

what is a unmyelinated neurone?

A

when several neurones share one lossely wrapped schwann cell, no nodes of ranvier and no fatty sheath, and so action potential moves along in a wave with no jumping

28
Q

what is the speed of conduction of an unmyelinated neurone?

A

SLOW= 20m/s

29
Q

what is the advantages of myelinated neurones?

A

-action potential is transmitted more quickly
-rapid response
-saltatory conduction (AP jumps from node to node)
-insulated parts stay resting

30
Q

what is a synapse?

A

the junction between two neurones (pre-synpatic and post-synpatic)

31
Q

what allows nerve impulses to cross the synpatic cleft?

A

neurotransmitters

32
Q

what is a cholinergenic synapse?

A

a synapse which makes and releases acetylcholine.

33
Q

describe the movement of nerve impulses across a synapse in
8 steps?

A

1- AP moves down neurone until synpase is reached
2-Within the synpatic knob, acetylcholine is released and transported in vesicles
3- Calcium ions diffuse into the neurone, causing the vesicles to move towards the pre-synaptic membrane.
4-The vesicles then fuse with the membrane (exocytosis), and so acetylcholine diffuses acrosss the synapse towards the post-synaptic membrane
5-the sodium ion channels are attached to a receptor, and these open , allowing the ions to diffuse in
6-Acetylcholine binds to the receptor.
7-This means that the enzyme, acetylcholinesterase is left within the synaptic cleft
8-The enzyme breaks down, with choline moving back into the pre-synaptic neurone, where it then combines with acetylcoenzymeA to create acetylcholine.

34
Q

what are the two types of summation?

A

-spatial= occurs when a number of pre- connect with one post-, so neurotransiters build up high enough to trigger AP in post-.
-tempora;= occurs when a single pre- releases neurotransmitter to AP over a short period of time, so it builds up in synpase until sufficient to trigger an AP