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Physiology I > Neurophysiology > Flashcards

Neurophysiology Flashcards

1
Q

What is a cell membrane composed of?

A

A phospholipid bilayer

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2
Q

What can cross a cell membrane?

A

Lipid-soluble molecules and gases diffuse through, water-soluble molecules pass with help

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3
Q

What does permeability of the membrane depend on?

A

Molecular size, lipid solubility, and charge

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4
Q

What is simple diffusion?

A

The movement of a substance down its concentration gradient using passive transport (no ATP)

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5
Q

What impacts the speed of diffusion?

A

The size of the concentration gradient. The larger the gradient, the faster the diffusion

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6
Q

What is facilitated diffusion?

A

Movement of molecules

down the concentration gradient across the membrane with the help of a carrier protein. Passive transport

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7
Q

What is saturated diffusion?

A

When the concentration of molecules exceeds the number of transport molecules

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8
Q

What transport types are passive? (No ATP)

A

Simple diffusion and facilitated diffusion

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9
Q

What is primary active transport?

A

The movement of molecules against the concentration gradient using ATP

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10
Q

What is secondary active transport?

A

Movement of molecules up its concentration gradient powered by the transport of another molecule down its gradient

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11
Q

How does active transport work?

A

Causes a conformational change in the membrane protein

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12
Q

What are pore loops?

A

Portions of a membrane protein that dangle inside the channel to create a selectivity filter based on size and charge

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13
Q

What is a ligand-gated channel?

A

The binding of a receptor with its ligand triggers a membrane event.

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14
Q

What is a voltage-gated channel?

A

Channels that open in response to changes in membrane polarity

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15
Q

What is the voltage sensing mechanism in voltage-gated channels?

A

The 4th transmembrane domain of the protein, S4 segment

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16
Q

How does the S4 segment function?

A

S4 segments are positively charged and stick out to the sides like wings. During resting potential the wings are held downwards, closing the channel.

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17
Q

What is endocytosis

A

inward pinching of the membrane to create a vesicle to capture proteins from the outside

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18
Q

What is exocytosis 1?

A

Kiss and run. Secretory vesicles dock and fuse at fusion pores and connect and disconnect several times before contents are emptied

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19
Q

What is exocytosis 2?

A

Complete fusion of the vesicle with the membrane, releasing the vesicle contents at once.

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20
Q

2 conditions for MPs?

A

1) create a concentration gradient with ATPases

2) Semi-permeable membrane to allow one ion species to move across more than another

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21
Q

Na+ / K+ pump

A

ATPase enzyme that moves 3 Na+ out and 2 K+ in for each ATP used

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22
Q

What contributes to resting membrane potential?

A

K+ has eq potential of -90mV and Na+ and Cl- diffusion make it -70mN instead

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23
Q

What is the concentration of ions inside and outside of the membrane?

A

Inside has more anions (proteins) and K+ and outside has more Cl- and Na+

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24
Q

How does depolarization occur?

A

Once membrane is depolarized to -55mV, S4 segments move up and Na+ gates open

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25
Q

What is an action potential?

A

A change in membrane potential that moves from -70mV to +30mV in cells with Na+ channels

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26
Q

Subthreshold stimuli

A

Below 15mV and open some Na+ channels but not enough to start action potentials

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27
Q

Suprathreshold stimuli

A

Produce more than enough to change to cause an action potential but don’t impact magnitude

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28
Q

Frequency coding

A

Information pertaining to stimulus intensity coded by changes in AP frequency

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29
Q

Refractory period

A

Period after an AP where some or all Na+ channels are inactivated

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30
Q

Relative refractory period

A

Some of the Na+ channels are reconfigured and can produce a smaller AP

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31
Q

What happens if more K+ is added outside the cell?

A

The K+ concentration gradient will be destroyed and the cell will stay depolarized

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32
Q

After-hyperpolarization

A

Allow Na+ channels to reconfigure fast enough to generate another AP. Both K+ leak channels and voltage-gated K+ channels are open to hyperpolarize the cell

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33
Q

Impulse conduction

A

When a patch of excitable membrane generates an AP, producing a depolarizing current for adjacent membrane.

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34
Q

How is lambda (length constant) improved?

A

1) increasing the diameter causes less resistance, less voltage lost
2) increasing membrane resistance causes less current to be leaked out

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35
Q

What is the Node of Ranvier?

A

Unmyelinated portions of the axon that have Na+ channels to generate action potentials

36
Q

Schwann cell function

A

Wrap around a single portion of one axon, squeezing out cytoplasm

37
Q

Oligodendrocyte function

A

Wrap around a whole bunch of axons individually

38
Q

Saltatory conduction

A

APs on one node can create a depolarizing current strong enough to last 5-10 nodes

39
Q

Remark bundle

A

Insulation in unmyelinated axons caused by Schwann cells and oligodendrocytes engulfing 5-30 axons without winding

40
Q

Electrical synapses

A

Electrical signals are transmitted from one cell to the next and don’t involve the release of neurotransmitters

41
Q

Chemical Synapse

A

Transmitter is released into the extracellular space between adjacent cells

42
Q

Vesicle release

A

Triggered by Ca++ ions that are released into the bouton in response to depolarizing AP currents

43
Q

Ionotropic effects

A

Ligand binds to an ion channel to directly produce a post-synaptic potential

44
Q

Ionotropic receptor ligands

A

Acetylcholine, glutamate, GABA (IPSPs) and glycine *can also act on metabotropic

45
Q

Metabotropic effects

A

Binding of the ligand to post-synaptic receptor to activate a G-protein coupled enzyme to activate a 2nd messenger

46
Q

Enzyme facilitation in 2nd messangers

A

cAMP, cGMP or InP3 is activates to activate phosphokinases to phosphorylate membrane proteins like Ca++ channels

47
Q

Beta-adrenoreceptor

A

Metabolic receptor for noradrenalin which activates adenylyl cyclase to increase cAMP production

48
Q

Post-synaptic potentials

A

Generated in inexcitable membranes such as dendrites and cell bodies to produce graded potentials

49
Q

PSP Summations

A

Many PSPs are needed to depolarize the trigger zone to -55mV and summation allows PSPs to be added

50
Q

Spatial Summation

A

Larger number of EPSPs occurring together in dendrites that overlap to be added on

51
Q

Temporal summation

A

Long EPSPs that allow successive inputs on any given synapse to generate other EPSPs to add onto pre-existing EPSPs

52
Q

Ihibitory IPSPs

A

Located between the EPSP generation site and trigger zone to stop depolarizing EPSP currents

53
Q

How do IPSPs work?

A

Involve the opening of Cl- channels to hyperpolarize the cell, clamping the MP

54
Q

Spike trains

A

EPSPs at the trigger zone generate an AP (spike). Caused by a long-lasting stimulus at the post-synaptic neuron

55
Q

Receptor potential

A

Change in MP due to the signal from an exterior sensory cue which causes depolarization

56
Q

How do receptor proteins function?

A

Function similar to PSPs and follow pathways similar to ionotropic and metabotropic

57
Q

Olfactory Receptor

A

A metabotropic receptor that produces currents similar to EPSPs

58
Q

Amplification

A

Occurs in metabotropic mechanisms and can make cells sensitive

59
Q

Sensory cell signal transmission

A

The branch point between different axons usually has the trigger zone and is depolarized by summation

60
Q

Sensory cell vesicles

A

Alone, the depolarizing current can cause an influx of Ca++, allowing vesicles to be released

61
Q

Slow adaptation

A

Slow decay of receptor potential for the duration of the stimulus. Magnitude based

62
Q

Rapid adaptation

A

When stimulus is constant, the receptor potential is zero and can elicit a response when stimulus is removed. Velocity of stimulus based.

63
Q

Habituation

A

Repeated identical stimuli in close succession elicits a weaker response each time

64
Q

Coding of stimulus intensity (graded potentials)

A

For graded potentials, greater stimulus intensity leads to greater receptor depolarization, releasing more transmitter

65
Q

Increasing stimulus intensity effect

A

Higher threshold sensory neurons are recruited

66
Q

What happens to APs when a stimulus is intense?

A

The frequency of APs increases

67
Q

Labeled line modality

A

Requires different receptors for qualities such as colours, texture, etc

68
Q

Population code

A

Specific stimuli are coded by the ratio of activity across a population of receptors. Ex, a stimulus activates one receptor stronger than others

69
Q

Receptive field

A

A spatial area each sensory neuron responds to. The more neurons, the higher the sensitivity

70
Q

Blood brain barrier function

A

Regulates the extracellular fluid in the neuronal environment

71
Q

Areas lacking the BBB

A

Hypothalamus and pituitary glans are connected to the bloodstream to secrete hormones. Circumventricular organs sense chemicals

72
Q

Brain encasings

A

Skull, meninges, reticular formation

73
Q

Meninges

A

1) Dura mater: sac containing the brain and spinal cord next to skull
2) arachnoid membrane
3) pia mater: lies on brain

74
Q

Reticular formation

A

Loose nerve cells that connect the brain to the spinal cord

75
Q

Subarachnoid space

A

Between the aracnoid space and pia matter. Filled with CSF to cushion the brain and also has blood vessels leading to the brain tissue

76
Q

BBB structure

A

Endothelial lining in blood vessels are tightly bound by gap junctions in the BBB but throughout the body have gaps

77
Q

Ventricles

A

Cavities in the brain filled with CSF

78
Q

CSF pathway

A

Lateral ventricle empties into the 3rd ventricle which connects to the 4th ventricle by the Aqueduct of Sylvius. 4th ventrical drains into the central canal into the spinal cord

79
Q

CSF drainage

A

Central canal > subarachnoid space > large venous sinus (midline) > venous system or arachnoid villi in dura matter

80
Q

Choroid plexus

A

Produces most CSF and is a network of capillaries

81
Q

CSF composition

A

Same osmolarity as blood but reduced K+, Ca++, Mg++

82
Q

How much CSF is there and how often is it replaced?

A

140ml volume (25ml in ventricles, 115ml in subarachnoid, 75ml in spinal cord) and is replaced 3x a day

83
Q

Astrocytes

A

Provide a bridge between neurons and blood vessels, wrap capillaries, produce lactate, remove neurotransmitters

84
Q

Local blood flow

A

Regulated by astrocytes to obtain more nutrients or less

85
Q

Prostaglandin (PGE2)

A

Triggered by glutamate synapses to release Ca++ in astrocytes to cause vasodilation

Physiology I (6 decks)

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