Neurons Flashcards

1
Q

What are the two major divisions of the nervous system?

A

CNS - brain and spinal cord - surrounded by bone

PNS - nerves and neurons - not surround by bone

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2
Q

2 classes of cells

A

Glial cells and neurons

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3
Q

Glial cells are _____ of NS, 4 functions, *

A
Structural units like glue 
Firmness and structure 
Form myelin
Provide nutrients to neurons 
Scavengers - remove debris
* no function in electrical transmission
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4
Q

Neurons are ____ of NS, 5 parts and functions

A

Functional units/basic signaling units of NS
Dendrites/branching - input mechanism
Cell body/soma - integrative centre of neurons
Axon hillock - site of action potential generation
Axon/conducting unit - myelin and nodes of ranvier to have signals go faster
Terminal branch - output mechanism from collaterals

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5
Q

Where do neurons make connections

A

At synapses with one another

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6
Q

Synapse

A

Area where neurons communicate with another cell

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7
Q

Presynaptic neuron

A

Neuron that sends msg

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8
Q

Post synaptic neuron

A

Cell that receives msg

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9
Q

Synaptic cleft

A

Fluid filled gap separating pre and post synaptic membranes

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10
Q

3 different types of synapses

A

Axo dendritic synapse - between axon of presynaptic neuron and dendritic branch of postsynaptic neuron
Axo somatic - between axon of presynaptic neuron and cell body of postsynaptic neuron
Axo axonic - between axon of presynaptic neuron and axon of postsynaptic neuron

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11
Q

Agonist

A

Contraction for movement

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12
Q

Antagonist

A

Action opposing agonist

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13
Q

Synergist

A

Works with agonist

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14
Q

Homonymous

A

Same muscle for sensory and contracting

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15
Q

Concentric

A

Muslce shortens

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16
Q

Eccentric

A

Muscle lengthens

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17
Q

Motor nerve - efferent or afferent?

A

Efferent

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18
Q

Sensory nerve - efferent or afferent?

A

Afferent

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19
Q

Single axon rule

A

If a neuron has an axon, then it has only one

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20
Q

3 structural classification of neurons for mammalian

A

Pseudounipolar
Bipolar
Multipolar

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21
Q

Pseudounipolar

A

Single process emerges from soma, splits into two processes
Goes to periphery and spinal cord
Sensory neuron that travels to the dorsal root ganglia

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22
Q

Bipolar

A

Soma give rise to 2 processes - 1 actual axon

Special sense organs

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23
Q

Multipolar

A

Most common
Single axon and many dendritic branches
Motor neurons controlling skeletal muscles

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24
Q

3 functional classification of neurons

A

Sensory
Motor
Inter neurons

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25
Q

Sensory neurons - 2

A

respond to stimuli

input neurons of NS

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26
Q

Motor neurons

A

Sends signals to cells outside of NS

output neurons of NS

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27
Q

Interneurons

A

Carry information between sensory and motor neurons

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28
Q

Cell membrane consists of? What’s selectivity?

A

Lipd/protein belayer to separate intra/extra cellular environments, semipermeable to some ions

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29
Q

What dictates the electrical signalling properties of neurons?

A

Relative concentration of ions between intra and extra cellular environments - membrane potential

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30
Q

What exists across a neuron’s cell membrane?

A

Electrical potential

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31
Q

What is a potential difference?

A

Difference in electrical potential across the membrane where electrical potential reflects ionic concentration (Na, K, Cl, Ca)

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32
Q

Membrane potential

A

Voltage value describing the potential difference across the membrane at any point of time

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33
Q

What ions are outside?

A

Sodium and chloride

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34
Q

What ions are inside?

A

Potassium and aspartame

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35
Q

Neuron resting membrane potential

A

-65mV

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36
Q

Muscle cell RMP

A

-90mV

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37
Q

2 sources of alteration of membrane permeability

A

Activity of surround neurons - by neurontransmitters

Electrical current - lab

38
Q

Why is RMP negative?

A

Inside of cell is negatively charged relative to the outside

39
Q

At rest what is the membrane imperable to? How does it make it negative?

A

Na, more K leak channels making the inside negative at -65mV, then pumps regulate that

40
Q

What do inputs from other neurons do to the membrane

A

Depolarize Or hyperpolarize

41
Q

Alteration in membrane permeability will alter

A

Membrane potential

42
Q

Depolarization

A

Stimulation leads to influx of Na - membrane potential becomes more positive - depolarization

43
Q

Hyperpolarization

A

Stimulation makes membrane impermeable to Na - MP becomes more negative

44
Q

Neurons send signals to other neurons via their axons in 2 ways

A

Passive conduction and active propagation

45
Q

Passive conduction

A

Charged particles move to equalize potential difference, this will continue to do so as long as potential difference exists - but this cant go far because distance matters

46
Q

Active progapation

A

Process that requires metabolic energy
Involves voltage gated ion channels
Action potential - cellular ATP

47
Q

Intracellular recording vs extracellular recording of AP

A

Microelectrode to see the potential difference across the membrane
Extracellular recording of AP uses two electro heads outside of the axon and see the potential difference between electrodes - starting from 0 because there is not resting membrane electrode

48
Q

APs are generated when the cell membrane is?

A

Sufficiently depolarizer

49
Q

Membrane potential will change in response to stimulus, but it will return to rest values unless …

A

We reach the membrane/firing threshold

50
Q

At a given membrane potential/threshold, membrane respons with? Different threshold for neurons and muscles?

A

Sudden change in potential
Neurons = -55mV
Muslce cells = -75mV

51
Q

Principle of neurons producing APs in response to excitatory synaptic inputs

A

Stimulus that moves membrane potential closer to threshold increases probability for AP firing known as excitatory stimulus so the sodium can rush in.

52
Q

What does a hyperpolarizing stimulus work and what is it always on known as?

A

Closing sodium ions - inhibitory stimulus

53
Q

Events of depolarization

A

Signal generated near axon hillock
Sodium channels open and depolarization happens, it goes up to 30mV, sodium channel closes and K channels open to depolarize - keep on going until less than -65mV which all voltage gates close

54
Q

Neurophysiological perspective of an action potential

A

A standard brief pattern of change in membrane potential

55
Q

Functional perspective of action potential

A

Unit of information transmission within and amongst excitable tissues

56
Q

5 essential principles of action potential

A
All or nothing 
Initiated only at one site 
Dynamic 
Unidirectional propagation 
Velocity depends on neuron characteristics
57
Q

All or nothing

A

Each AP looks the same, it either gets created or not
All APs produced in the particular neuron all reach the same max value, thus, they are either generated as a whole (ALL) or they are not generated at all (nothing) because the number of channels would be the same like firing a gun

58
Q

Initiated at only one site

A

APs are generated only at the axon hillock where there is a high density of Na channels

59
Q

Dynamic

A

APs are dynamic and travel along the neuron axon/muslce fibre

60
Q

Unidirectional

- how it is preserved

A

AP propagation is unidirectional and travel away from soma (ORTHODROMIC)
Refractory period of axon (inactive Na channels post AP firing)
Varying levels of excitability along axon (due to density of Na channels)

61
Q

Absolute refractory period - when is that and could an AP be generated?

A

Na open then close and K opens - hyperpolarizes and no AP can be generated

62
Q

Can you have initiate an AP during the relative refractory period?

A

Larger than normal stimulus can initiate a new AP

63
Q

Saltatory conduction

What would interfere with this?

A

High density Na channels at the nodes of ranvier which allows them to “jump” and increase conduction velocity - we dont have to generate as many APs as it flows passively under the myelin sheath
Demyelination disease reduce/block conduction and current leaks out the previously insulated axons

64
Q

Purpose of unmyelinated vs myelinated axons

A

Glandular control vs balance information

65
Q

Once generated will the AP propagate through the entire axon?

A

Yes

66
Q

2 characteristics of the neuron that are largely responsible for differences in propagation speed

A

Whether the axon is myelinated or not

Thickness of the axon - thicker means faster

67
Q

AP velocity depends on neuron characteristics such as - 3

A

Neuronal fibre types, health of neuron, avg conduction velocity

68
Q

Muscle spindle type and conduction velocity

A

Ia - 80-120m/s

69
Q

Golgi tendon organ type and conduction velocity

A

Ib - 80-120 m/s

70
Q

Muscle spindle type and conduction velocity

A

II 40-80m/s

71
Q

Pressure receptor type and conduction velocity

A

III 5-30

72
Q

Nocireceptor type and conduction velocity

A

IV - 0.5-2m/s

73
Q

How to calculate the velocity of conduction?

A

V=(s2-s1)/(t2-t1)

74
Q

Skeletal muscle motor neuron type and conduction velocity

A

Alpha = 100m/s

75
Q

Muslce spindle and the 2 types of neurons and their conduction velocity

A

Beta: 50m/s
Gamma: 20m/s

76
Q

Two outcomes of synaptic transmission

A

EPSP & IPSP

77
Q

EPSP

A

Excitatory post synaptic potential : Depolarization - membrane becomes more permeable to Na

78
Q

IPSP

A

Inhibitory post synaptic potential - membrane becomes less permeable to Na = hyperpolarization

79
Q

Two ways of summing the effects of subthreshold potentials

A

Temporal summation and spatial summation

80
Q

Temporal summation

A

Sum effects of several APs from same synapse
- EPSPs are superimposed, leading to larger EPSP, several APs arrive successively at presynaptic membrane before it gets back to its resting levels

81
Q

Spatial summation

A

Several APs (stimuli) from diff synapses arrive simultaneously - AP generated

82
Q

If you want more output, what would you increase?

A

AP firing frequency which is increased by stimulus durationm but not intensity

83
Q

Patterns of neural connectivity

A

Neurons can be connected directly to each other or connected via other neurons
Monosynaptic - two neurons directly connected
Disynaptic - 2 neurons connected via intermediate neuron
Trisynaptic - 2 connected via 2 intermediate neurons/polysynaptic

84
Q

Different populations of neurons connect to other population via two pathways

A

Convergence - multiple neurons in source population connect to smaller number in target population - one postsynaptic cell from multiple presynaptic cells - intermediate neurons consolidate the info into one msg.

Divergence - fewer neurons in source population connect to a larger number in target population - one presynaptic cell that makes the message to multiple postsynaptic

85
Q

Feedforward connectivity

A

Information only moves forwards from input neurons to output neurons

86
Q

2 types of feedback connectivity

- how does it happen?

A

Feedback excitation - presynaptic excites postsynaptic
Fdbk inhibition - neg fdbk which maintains homeostasis
There’s a collateral that goes back to the presynaptic cell

87
Q

Motor behaviour

A

Principle of skilled human movement

88
Q

Learning

A

Internal processes associated with practice/experiment that lead to changes in capability for movement

89
Q

Motor development

A

Changes in movement resulting from maturation

90
Q

Motor control

A

Regulated and coordinated movement from the info from receptors/perception

91
Q

How many classes can a neuron fit into?

A

Any neuron falls into 1 and only 1 basic class