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Flashcards in Neurons Deck (91):
1

What are the two major divisions of the nervous system?

CNS - brain and spinal cord - surrounded by bone
PNS - nerves and neurons - not surround by bone

2

2 classes of cells

Glial cells and neurons

3

Glial cells are _____ of NS, 4 functions, *

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

4

Neurons are ____ of NS, 5 parts and functions

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

5

Where do neurons make connections

At synapses with one another

6

Synapse

Area where neurons communicate with another cell

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Presynaptic neuron

Neuron that sends msg

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Post synaptic neuron

Cell that receives msg

9

Synaptic cleft

Fluid filled gap separating pre and post synaptic membranes

10

3 different types of synapses

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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Agonist

Contraction for movement

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Antagonist

Action opposing agonist

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Synergist

Works with agonist

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Homonymous

Same muscle for sensory and contracting

15

Concentric

Muslce shortens

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Eccentric

Muscle lengthens

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Motor nerve - efferent or afferent?

Efferent

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Sensory nerve - efferent or afferent?

Afferent

19

Single axon rule

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

20

3 structural classification of neurons for mammalian

Pseudounipolar
Bipolar
Multipolar

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Pseudounipolar

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

22

Bipolar

Soma give rise to 2 processes - 1 actual axon
Special sense organs

23

Multipolar

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

24

3 functional classification of neurons

Sensory
Motor
Inter neurons

25

Sensory neurons - 2

respond to stimuli
input neurons of NS

26

Motor neurons

Sends signals to cells outside of NS
output neurons of NS

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Interneurons

Carry information between sensory and motor neurons

28

Cell membrane consists of? What’s selectivity?

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

29

What dictates the electrical signalling properties of neurons?

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

30

What exists across a neuron’s cell membrane?

Electrical potential

31

What is a potential difference?

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

32

Membrane potential

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

33

What ions are outside?

Sodium and chloride

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What ions are inside?

Potassium and aspartame

35

Neuron resting membrane potential

-65mV

36

Muscle cell RMP

-90mV

37

2 sources of alteration of membrane permeability

Activity of surround neurons - by neurontransmitters
Electrical current - lab

38

Why is RMP negative?

Inside of cell is negatively charged relative to the outside

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

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

40

What do inputs from other neurons do to the membrane

Depolarize Or hyperpolarize

41

Alteration in membrane permeability will alter

Membrane potential

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Depolarization

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

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Hyperpolarization

Stimulation makes membrane impermeable to Na - MP becomes more negative

44

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

Passive conduction and active propagation

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Passive conduction

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

Active progapation

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

47

Intracellular recording vs extracellular recording of AP

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

APs are generated when the cell membrane is?

Sufficiently depolarizer

49

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

We reach the membrane/firing threshold

50

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

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

51

Principle of neurons producing APs in response to excitatory synaptic inputs

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

52

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

Closing sodium ions - inhibitory stimulus

53

Events of depolarization

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

Neurophysiological perspective of an action potential

A standard brief pattern of change in membrane potential

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Functional perspective of action potential

Unit of information transmission within and amongst excitable tissues

56

5 essential principles of action potential

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

57

All or nothing

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

Initiated at only one site

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

59

Dynamic

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

60

Unidirectional
- how it is preserved

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

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

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

62

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

Larger than normal stimulus can initiate a new AP

63

Saltatory conduction
What would interfere with this?

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

Purpose of unmyelinated vs myelinated axons

Glandular control vs balance information

65

Once generated will the AP propagate through the entire axon?

Yes

66

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

Whether the axon is myelinated or not
Thickness of the axon - thicker means faster

67

AP velocity depends on neuron characteristics such as - 3

Neuronal fibre types, health of neuron, avg conduction velocity

68

Muscle spindle type and conduction velocity

Ia - 80-120m/s

69

Golgi tendon organ type and conduction velocity

Ib - 80-120 m/s

70

Muscle spindle type and conduction velocity

II 40-80m/s

71

Pressure receptor type and conduction velocity

III 5-30

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Nocireceptor type and conduction velocity

IV - 0.5-2m/s

73

How to calculate the velocity of conduction?

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

74

Skeletal muscle motor neuron type and conduction velocity

Alpha = 100m/s

75

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

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

76

Two outcomes of synaptic transmission

EPSP & IPSP

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EPSP

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

78

IPSP

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

79

Two ways of summing the effects of subthreshold potentials

Temporal summation and spatial summation

80

Temporal summation

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

Spatial summation

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

82

If you want more output, what would you increase?

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

83

Patterns of neural connectivity

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

Different populations of neurons connect to other population via two pathways

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

Feedforward connectivity

Information only moves forwards from input neurons to output neurons

86

2 types of feedback connectivity
- how does it happen?

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

87

Motor behaviour

Principle of skilled human movement

88

Learning

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

89

Motor development

Changes in movement resulting from maturation

90

Motor control

Regulated and coordinated movement from the info from receptors/perception

91

How many classes can a neuron fit into?

Any neuron falls into 1 and only 1 basic class