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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

(72 cards)

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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
electric potentials
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
26
resting membrane potential
no net flow of ions (neuron not in excited state) about -70 mV (-90 to -60 mV) maintained by the electrochemical gradient
27
what is the electrochemical gradient?
the ion concentration (chemical) gradient and electrical gradient determine the ion concentration across the membrane
28
what is the ion concentration (chemical) gradient and what does it do?
unequal distribution of ions with more ions concentrated inside the cell more potassium inside, more calcium, sodium, and chloride outside
29
what is the electrical gradient and what does it do?
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
what 3 factors maintain the resting membrane potential?
chemical gradient, electrical gradient, and passive diffusion of ions
31
what is the flow of ions in and out of the cell using leak channels (passive diffusion)?
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
is energy expended to maintain the resting membrane potential?
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
what are local potentials?
environment acts on neuron or neuron acts on neuron creating a local signal depolarization or repolarization, no hyperpolarization receptor and synaptic
34
what are receptor potentials?
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
what are synaptic potentials?
one neuron to another
36
what is a passive electrical signal?
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
what is an active electrical signal?
more stimulus=more APs threshold exceeded stim strength affects # of APs travel more reliably
38
what is temporal summation of local potentials?
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
what is spacial summation of local potentials?
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
action potentials
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
upstroke
opening
42
downstroke
closing
43
what is a refractory period?
period occurring during and after APs are fired lasts a few milliseconds limits max frequency of APs (longer period=lower frequency)
44
what is the difference b/w absolute and relative refractory periods?
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
properties of APs
all or none events threshold (around 15 mV positive to resting) exceeded constant amplitude increased strength=increased frequency
46
how are axon potentials rejuvenated along unmyelinated axons?
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
how do currents flow along myelinated axons?
Na2+ and K+ channels are only concentrated where there's no myelination (nodes of Ranvier)
48
what are nodes of Ranvier?
areas of no myelination on myelinated axons only place on myelinated axons that can produce APs
49
is myelinated or unmyelinated propogation faster and why?
myelinated propogation is faster bc it skips segments allowing the current to flow faster
50
myelin sheaths ____ conduction and ____ resistance
decrease; increase
51
how does axon diameter affect speed of AP transmission?
larger diameter axons increase conduction velocity of APs bc larger axons have more room for ions to flow without hitting the exoskeleton
52
what axons have the fastest transmission speed?
large diameter myelinated axons
53
afferent neurons
towards the CNS (from periphery (DRG) to CNS (dorsal horn)) peripheral sensory neurons pseudounipolar and some bipolar neurons
54
efferent neurons
away from CNS (AP from ventral horn of SC to muscle at NMJ)
55
interneurons
connect afferents and efferents as well as among themselves projection neurons most abundant neurons multipolar neurons
56
what is orthodromic conduction?
an AP flows from the soma to the axon natural propagation of APs same direction as anterograde
57
what is antidromic conduction?
an AP flows from the axon to the soma E stim same direction as retrograde
58
what is the antidromic conduction flow of sensory neurons?
dorsal horn to the DRG (CNS to periphery)
59
what is convergence of neurons?
one neuron getting lots of info from multiple neurons can help identify what an object is somatosensory cortex in the brain
60
what is divergence of neurons?
one neuron synapsing on different neurons one stimulation can result in multiple responses painful stimulus
61
what is the role of glia?
support and signaling, but not directly involved in conduction
62
what are the different types of macroglia?
astrocytes, oligodendrocytes, satellite cells, Schwann cells, and ependymal cells
63
astrocytes
CNS neurotrophic factors, signaling among themselves, and act as phagocytes taking up ions outside the neuron
64
oligodendrocytes
form myelin sheath in CNS
65
satellite cells
PNS cover the soma nutrients
66
Schwann cells
forms myelin sheath in PNS secrete neurotrophic factors, especially when injury is present
67
ependymal cells
CNS secretes CSF
68
microglia
known to be essential in normal healing in the CNS
69
CNS demyelination
MS
70
PNS demyelination
peripheral neuropathy and Guillan Barre
71
positive neuroinflammation
reorganization, increased plasticity, tissue repair, and neuroprotective immune surveillance, memory, learning, development, and injury induced remodeling
72
negative neuroinflammation
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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