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DPT 503 > Physical and Electrical Properties of Cells in the NS > Flashcards

Physical and Electrical Properties of Cells in the NS Flashcards

1
Q

what is the main job of the neuron?

A

to transmit info

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2
Q

what are the 4 basic functions of a neuron?

A

receive, integrate, transmit, and transfer info

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3
Q

what is the soma and what does it do?

A

the cell body that integrates info

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4
Q

what are dendrites and what do they do?

A

projections from the soma that receive info

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5
Q

what is the axon hillock?

A

the connection b/w the soma and axon

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6
Q

what is the axon and what does it do?

A

long projection out of the soma that transmits info via the electric voltage potential that runs down the axon to the terminal

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7
Q

what is the axon terminal?

A

the end of the axon that forms a synapse with another neuron’s dendrites

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8
Q

what is myelin?

A

fatty and protein sheath that wraps around the axon

prevents current flow across axonal membrane

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9
Q

what maintains the shape of the neuron?

A

cytoskeleton proteins such as microtubules, neurofilaments, and microfilaments

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10
Q

what is axoplasmic transport?

A

old and new proteins transported up and down the axon

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11
Q

what is anterograde transport

A

new materials brought from the soma to the axon

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12
Q

what is retrograde transmission

A

old materials brought from the axon up to the soma

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13
Q

what is a unipolar neuron?

A

one projection from the soma

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14
Q

what is a bipolar neuron?

A

2 projections from the soma (dendrite and axon)

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15
Q

what is a pseudounipolar neuron?

A

a single projection from the soma that divides into two branches (one is dendrite, other is axon)

most sensory neurons (cell body in DRG, dendrite in organs, axons synapse in dorsal horn SC)

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16
Q

what is a multipolar neuron?

A

more than 2 projections from the soma (multiple dendrites and 1 axon

Purkinje cells

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17
Q

how are membrane channels classified?

A

the mechanism that opens them and the ions they conduct

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18
Q

leak channels

A

open and close at random

considered to be open all the time

contribute to the resting membrane potential

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19
Q

what are the 3 types of gated channels?

A

voltage-gated channels

ligand-gated channels

modality-gated channels

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20
Q

voltage-gated channels

A

opened by a change in the voltage

sodium, calcium, and chlorine move in

potassium moves out

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21
Q

what ions are concentrated outside the membrane?

A

sodium, calcium, and chlorine

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22
Q

what ions are concentrated inside the membrane?

A

potassium

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23
Q

ligand-gated channels

A

a molecule binds to the receptor and opens it

NT receptor can allow more than 1 ion through at a time

can be opened by a molecule inside or outside the cell

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24
Q

modality-gated channels

A

opens/closes in response to mechanical forces (stretch, acidity, chemical, etc)

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25
Q

electric potentials

A

difference in electrical charge on each side of the membrane with the inside being more negative than the outside

rapid changes in the electrical charge transmits info along the axon

resting, local, and action

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26
Q

resting membrane potential

A

no net flow of ions (neuron not in excited state)

about -70 mV (-90 to -60 mV)

maintained by the electrochemical gradient

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27
Q

what is the electrochemical gradient?

A

the ion concentration (chemical) gradient and electrical gradient determine the ion concentration across the membrane

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28
Q

what is the ion concentration (chemical) gradient and what does it do?

A

unequal distribution of ions with more ions concentrated inside the cell

more potassium inside, more calcium, sodium, and chloride outside

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29
Q

what is the electrical gradient and what does it do?

A

inside cell is more negative than outside the cell

organic anions (neg ions) trapped inside the cell

chemical and electrical gradients are equal and opposite forces at resting membrane potential

30
Q

what 3 factors maintain the resting membrane potential?

A

chemical gradient, electrical gradient, and passive diffusion of ions

31
Q

what is the flow of ions in and out of the cell using leak channels (passive diffusion)?

A

sodium leaks in and potassium leaks out because there is more sodium outside and more potassium inside and ions will flow from more to less

32
Q

is energy expended to maintain the resting membrane potential?

A

yes, ATP is used to reverse the pattern of leak channels (sodium potassium pump pushes sodium out and potassium in against their concentration gradients)

3 sodium out, 2 potassium in

33
Q

what are local potentials?

A

environment acts on neuron or neuron acts on neuron creating a local signal

depolarization or repolarization, no hyperpolarization

receptor and synaptic

34
Q

what are receptor potentials?

A

outside environment is producing a signal on the neuron from peripheral receptors

outside signal stimulates receptor, membrane potential goes up, sodium channels open to make it more positive inside (depolarization).

35
Q

what are synaptic potentials?

A

one neuron to another

36
Q

what is a passive electrical signal?

A

higher stimulus=higher response

has a direct relationship b/w stim strength and stim response

local potentials

don’t last long and don’t produce APs

37
Q

what is an active electrical signal?

A

more stimulus=more APs

threshold exceeded

stim strength affects # of APs

travel more reliably

38
Q

what is temporal summation of local potentials?

A

1 neuron constantly sending synaptic potentials

a series of consecutive potentials sent onto a neuron summates to get past the threshold and fire APs

39
Q

what is spacial summation of local potentials?

A

many neurons connected to 1 neuron send signals to that 1 neuron

gets past threshold to fire APs

need more than 1 source of input

40
Q

action potentials

A

transient changes in membrane permeability

rapid and brief Na+ permeability
(sodium influx and depolarization)
- can react to slight changes in membrane potential

delayed and prolonged K+ permeability (K+ leaves the cell and repolarization occurs then as it keeps leaving the cell hyperpolarization occurs)
- needs a larger change in voltage than sodium

41
Q

upstroke

A

opening

42
Q

downstroke

A

closing

43
Q

what is a refractory period?

A

period occurring during and after APs are fired

lasts a few milliseconds

limits max frequency of APs (longer period=lower frequency)

44
Q

what is the difference b/w absolute and relative refractory periods?

A

during absolute refractory periods, no AP is possible due to the voltage inactivation of Na+ channels

during relative refractory period, an AP is possible with a greater than normal stimulus

45
Q

properties of APs

A

all or none events

threshold (around 15 mV positive to resting) exceeded

constant amplitude

increased strength=increased frequency

46
Q

how are axon potentials rejuvenated along unmyelinated axons?

A

Na2+ influx, K+ efflux=AP

Na2+ and K+ channels are all along the axon

current spreads back and forward

refractory period doesn’t allow the axon length behind the current fire AP

47
Q

how do currents flow along myelinated axons?

A

Na2+ and K+ channels are only concentrated where there’s no myelination (nodes of Ranvier)

48
Q

what are nodes of Ranvier?

A

areas of no myelination on myelinated axons

only place on myelinated axons that can produce APs

49
Q

is myelinated or unmyelinated propogation faster and why?

A

myelinated propogation is faster bc it skips segments allowing the current to flow faster

50
Q

myelin sheaths ____ conduction and ____ resistance

A

decrease; increase

51
Q

how does axon diameter affect speed of AP transmission?

A

larger diameter axons increase conduction velocity of APs bc larger axons have more room for ions to flow without hitting the exoskeleton

52
Q

what axons have the fastest transmission speed?

A

large diameter myelinated axons

53
Q

afferent neurons

A

towards the CNS (from periphery (DRG) to CNS (dorsal horn))

peripheral sensory neurons

pseudounipolar and some bipolar neurons

54
Q

efferent neurons

A

away from CNS (AP from ventral horn of SC to muscle at NMJ)

55
Q

interneurons

A

connect afferents and efferents as well as among themselves

projection neurons

most abundant neurons

multipolar neurons

56
Q

what is orthodromic conduction?

A

an AP flows from the soma to the axon

natural propagation of APs

same direction as anterograde

57
Q

what is antidromic conduction?

A

an AP flows from the axon to the soma

E stim

same direction as retrograde

58
Q

what is the antidromic conduction flow of sensory neurons?

A

dorsal horn to the DRG (CNS to periphery)

59
Q

what is convergence of neurons?

A

one neuron getting lots of info from multiple neurons

can help identify what an object is

somatosensory cortex in the brain

60
Q

what is divergence of neurons?

A

one neuron synapsing on different neurons

one stimulation can result in multiple responses

painful stimulus

61
Q

what is the role of glia?

A

support and signaling, but not directly involved in conduction

62
Q

what are the different types of macroglia?

A

astrocytes, oligodendrocytes, satellite cells, Schwann cells, and ependymal cells

63
Q

astrocytes

A

CNS

neurotrophic factors, signaling among themselves, and act as phagocytes taking up ions outside the neuron

64
Q

oligodendrocytes

A

form myelin sheath in CNS

65
Q

satellite cells

A

PNS

cover the soma

nutrients

66
Q

Schwann cells

A

forms myelin sheath in PNS

secrete neurotrophic factors, especially when injury is present

67
Q

ependymal cells

A

CNS

secretes CSF

68
Q

microglia

A

known to be essential in normal healing in the CNS

69
Q

CNS demyelination

A

MS

70
Q

PNS demyelination

A

peripheral neuropathy and Guillan Barre

71
Q

positive neuroinflammation

A

reorganization, increased plasticity, tissue repair, and neuroprotective

immune surveillance, memory, learning, development, and injury induced remodeling

72
Q

negative neuroinflammation

A

collateral damage, depression, anxiety, cognitive impairment, reduced plasticity, and neural damage

CNS injury, repeated social deficit stress, aging, TBI, neurodegenerative disease.

DPT 503 (22 decks)

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