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Physiology > CNS And Action Potentials > Flashcards

CNS And Action Potentials Flashcards

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1
Q

What are specialized for communication in the nervous system

A

Neurons

Glia

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2
Q

The nervous system consists of ____ and____

A

The peripheral nervous system

The central nervous system

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3
Q

The peripheral nervous system consists of what

A

Sensory division

Efferent division

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4
Q

Sensory division sends ____

Efferent division takes ___

A

Information to the CNS through afferent neurons

Information from the CNS to target cells via efferent neurons

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5
Q

Define neurons

A

Specialized to carry electrical signals and communicate with other cells

High density of ion channels

Special transport mechanisms to move materials from one end to the other

Secrete signalling molecules (neurotransmitter and neurohormones)

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6
Q

What are the four types of neurons

A

Pseudounipolar (sensory neurons)
Bipolar (sensory neurons)
Anaxonic (interneurons)
Multipolar (efferent and interneurons)

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7
Q

What are the types of glia in the CNS

A

Oligodendrocytes

Ependymal cells

Microglia

Astrocytes

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8
Q

What are the types of glia in the PNS

A

Satellite cells

Schwann cells

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9
Q

Oligodendrocytes

A

Myelinate axons

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10
Q

Line ventricles and make neural stem cells

A

Ependymal cells

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11
Q

What are the immune cells of the CNS

A

Microglia

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12
Q

Astrocytes

A

Blood brain barrier

Trophic factors

Take up excess water and K

Neural stem cells

Pass lactate to neurons

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13
Q

What do Schwann cells do

A

Myelinate axons

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14
Q

What do satellite cells do

A

Trophic factors

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15
Q

Membrane potential will change if ion channels _____ and allow _____

A

Open

Ions to move across the cell membrane

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16
Q

How are ion channels on neurons classified according to

A

Ions they carry

Where on the cell they are located

Gating mechanisms

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17
Q

What are the 5 ion channel gating mechanisms

A

1) voltage gated ion channel
2) receptor channels
3) phosphorylation gated
4) stretch gated
5) temperature gated

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18
Q

What are voltage gated ion channels

A

Changes in membrane potential open the channel

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19
Q

What are receptor channels

A

(Ligand gated ion channels)

Gate when they bind a ligand

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20
Q

Opening and closing of ion channels causes ___

A

Rapid changes in membrane potential

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21
Q

Explain graded potentials

A

Signals communicated from one neuron to the next are graded potentials

Small subthreshold changes in membrane potential

Can be depolarizing or hyperpolarizing

Passive

Proportional to the size of the stimulus

Caused by the flow of ions through a few ion channels

Gradually dissipate as they travel through a cell

Can be summed

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22
Q

Postsynaptic potentials

Study These Flashcards
A

Signals communicated from one neuron to the next are graded potentials

23
Q

The graded potential travels like a ripple on a pond and it moves ____ from the source and degrades as it moves ___ away

Study These Flashcards
A

Outward

Farther

Takes time to get from synapse to the axon hillock

24
Q

Why does the signal degrade (eventually to nothing)

Study These Flashcards
A

Electrical resistance in the cytoplasm

The cell membrane is leaky to ions

25
Explain action potentials
Wave of depolarization that propagates across neuronal membrane (regenerative) All of one FAST (often called a spike AP) Large amplitude about 100 mV Always depolarizing Requires the membrane be depolarized past a threshold There is a refractory period CANNOT BE SUMMED In neurons site of AP generation is the axon hillock
26
Explain the ionic basis of the action potential
``` Starts at RMP (-70) Cell is depolarized by graded potential Membrane depolarizes to threshold (-55) - voltage gated Na channels open quickly and Na enters - voltage gated K channels open slowly The rapid Na entry depolarized the cell Na channels stop and K channels open fully K Leaves the cell K channels hyperpolarizes the cell K closes and Na recoverers ```
27
What causes repolarization | Or hyperpolarization
When K leaves the cell
28
What is the absolute refractory phase What is the relative refractory phase
Rising and falling phase Recovery phase
29
How will changes in extracellular K influence transmission of action potentials Hyperkalemia Hypokalemia
Hyperkalemia - RMP is depolarized - smaller stimulus will bring cell to threshold Hypokalemia - RMP is hyperpolarized - requires larger stimulus to bring cell to threshold
30
The action potential is conducted from the ___ to the ___
Soma | Terminals
31
What is local current flow (unmylenated axons)
A section of axon depolarizes Positive charges move by local current flow into adjacent sections of the cytoplasm On the extracellular surface current flows towards the depolarized region
32
Initial state of unmylenated action potentials
Normal ion gradients RPM -80 Very high density of Na channels at the axon hillock Voltage gated Na and K channels distributed along the axon
33
What is the trigger zone on an unmylenated axon
Axon hillock
34
Once the initial state of AP on unmylenated axons occur what happens
Voltage gated Na channels open and Na enters the axon (causing depolarization) Positive charge flows into adjacent sections of the axon by local current flow Local current flow from the active region causes new sections of the membrane to depolarize
35
How does the depolarization occur on an unmylenated axon
Some Na is attracted to the nearby areas (LOCAL CURRENT FLOW) This causes depolarization of the nearby axon to its threshold (the hillock is now refractory)
36
Na enters the axon causing depolarization and this depolarizes ____ to the threshold
The adjacent segment
37
Myelin is formed from concentric layers of _____ cell membrane and they are excellent __
Glial Insulators
38
What does Mylen do for the axon
Increases electrical efficiency of the axons
39
What are the Mylenations separated by
Nodes of ranvier
40
What are found at the nodes of ranvier
Very high density Na channels K channels are found nearby
41
What type of conduction do AP travel on mylenated axons
Saltatory conduction
42
What does saltatory conduction mean
The action potential travels by jumping node to node (instead of travelling like a wave)
43
What are demylenated diseases (what happens)
Degeneration of the mylen sheath Conduction slows when the current leaks out
44
What are the two ways to speed up velocity of AP along an axon
Increase axon diameter Mylenation
45
How does increasing the axon diameter help AP move faster
Increases velocity because as the axon radius becomes larger internal resistance decreases
46
How does mylenation make AP move faster
Increases velocity because insulted areas mean less leakage of Na and K Also means less ATP used Mylenation allows axons to be smaller so you can fit more into a space
47
What is demyelination disease
Multiple sclerosis | Guillain barre syndrome
48
What is multiple sclerosis
Autoimmune disease Unknown cause Demyelination of CNS axons Multiple patterns of progression
49
What are symptoms of multiple sclerosis What are treatments
Loss of balance loss of speech loss of vision abnormal pupil reflexes numbness pain Immunosuppressants and other drugs as indicated by symptoms
50
What is guillain barre syndrome
Autoimmune days after a seemingly minor GI or lung infection May also be associated with chronic illness such as lupus HIV Demyelination of sensory and motor and autonomic axons (PNS) Slowing or loss of AP conduction
51
What are symptoms of guillain barre syndrome
Tingling weakness pain in hands and feet | Inability to speak paralysis and respiratory distress
52
What are treatments of guillain barre syndrome
Plasmapheresis (to remove antibodies from blood) and immunoglobulin G to inactivate circulating antibodies Most people survive but recovery may take months to years
53
What is fugu poisoning
Kills 30-100 people a year Tetrodotoxin comes from pufferfish and several other species Fugu is a very specific antagonist of voltage gated Na channels Prevents entry of Na into cells Prevents AP in neurons and muscles
54
What other anesthetic also block voltage gated Na channels
Lidocaine | Benzocaine

Physiology (15 decks)

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