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Tissues BDS1 > Neurons > Flashcards

Neurons Flashcards

1
Q

what are neurons?

A

nerve cells

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2
Q

where are neurons?

A

in the nervous system

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3
Q

what are neurons specialised for?

A

communication

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4
Q

what do neurons connect with?

A

other neurons and with other excitable cells

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5
Q

what are the different parts of the neuron?

A

dendrites, cell body, axon and axon terminals

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6
Q

where do the inputs go into in the neuron?

A

dendrites

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7
Q

where do the signal outputs come from in the neuron?

A

axon terminals

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8
Q

name the 6 different types of neurons

A

purkinje cell, spinal interneuron, sensory neuron, pyramidal cell, motor neuron and bipolar cell

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9
Q

what is the resting membrane potential?

A

a potential difference across the membrane of all cells

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10
Q

what is the value for the resting membrane potential?

A

20-90mV

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11
Q

comment on the polarity of the membrane

A

polarised

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12
Q

comment on the positive and negative charges on each side of the membrane

A

approximately equal numbers but not distributed evenly with the ICF negative to the ECF

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13
Q

are sodium ions higher in the ECF or ICF

A

ECF

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14
Q

are potassium ions higher in the ECF or ICF

A

ICF

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15
Q

are chlorine ions higher in the ECF or ICF

A

ECF

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16
Q

where does the resting membrane potential arise from?

A

the separation of charges on either side of the membrane

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17
Q

what is the resting membrane potential determined by?

A

The diffusion of K+ from cell interior through K+ channels. The sodium potassium pump (3Na+ out and 2K+ in)

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18
Q

how is the membrane potential altered?

A

applying an electric current to the cell

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19
Q

what does a hyperpolarising current do?

A

moves the MP further from 0

20
Q

what does a depolarising current do?

A

moves the MP nearer to 0

21
Q

what happens if the MP is raised to -55mV

A

a large depolarisation occurs

22
Q

what is the action potential?

A

large change in MP

23
Q

what is the first action potential step?

A

stimulus applied, depolarisation and MP moves towards 0mV

24
Q

what is the second step of action potential?

A

MP reaches about -55mV, voltage-gated Na+ channels open, MP moves towards 0mV

25
Q

what is the third action potential step?

A

Na+ diffuse inwards through voltage-gated channels

26
Q

why does action potential occur?

A

the entry of Na+

27
Q

what is the fourth action potential step?

A

when MP reaches about +35mV the Na+ channels shut and K+ channels open for K+ to leave the cell making the MP more negative

28
Q

what is the fifth action potential step

A

after a small overshoot (hyperpolarisation) the MP returns to original resting level

29
Q

is the amplitude of the action potential dependent or independent of the stimulus?

A

independent

30
Q

what happens at the threshold of the action potential?

A

voltage-gated Na+ channels open and Na+ diffuse in (depolarisation)

31
Q

what happens at the peak of the action potential?

A

Na+ channels close, voltage-gated K+ channels open and K+ diffuse out (repolarisation)

32
Q

how do local anaesthetics stop nerve conduction?

A

by blocking the Na+ channels

33
Q

what is the refractory period?

A

the neuron cannot generate another AP until the first one has ended - the period of inexcitability

34
Q

what is the refractory period due to?

A

the inactivation of voltage-gated sodium channels

35
Q

what is AP propagation?

A

the AP in one section of the axon depolarises adjacent resting parts of the axon. The AP is regenerated further along the axon

36
Q

how do action potentials travel along the axon?

A

as waves of depolarisation

37
Q

what increases the AP propagation

A

the axon diameter

38
Q

do large or small axons conduct more rapid impulses?

A

large axons

39
Q

how is rapid conduction achieved?

A

only with very large axons

40
Q

what does myelination do?

A

greatly increases the AP conduction speed

41
Q

what is myelin

A

a fatty layer

42
Q

what is myelin formed by?

A

wrapping the membranes og glial cells round the axon

43
Q

what does myelin do?

A

insulates the axon and improves conduction

44
Q

what are nodes of ranvier?

A

interruptions in the myelin sheath

45
Q

what occurs at the nodes of ranvier

A

ion flow can occur

Tissues BDS1 (10 decks)

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