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Physiology > CNS And Action Potentials > Flashcards

CNS And Action Potentials Flashcards

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

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

A

Outward

Farther

Takes time to get from synapse to the axon hillock

24
Q

Why does the signal degrade (eventually to nothing)

A

Electrical resistance in the cytoplasm

The cell membrane is leaky to ions

25
Q

Explain action potentials

A

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
Q

Explain the ionic basis of the action potential

A 
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
Q

What causes repolarization

Or hyperpolarization

A

When K leaves the cell

28
Q

What is the absolute refractory phase

What is the relative refractory phase

A

Rising and falling phase

Recovery phase

29
Q

How will changes in extracellular K influence transmission of action potentials

Hyperkalemia
Hypokalemia

A

Hyperkalemia

  • RMP is depolarized
  • smaller stimulus will bring cell to threshold

Hypokalemia

  • RMP is hyperpolarized
  • requires larger stimulus to bring cell to threshold
30
Q

The action potential is conducted from the ___ to the ___

A

Soma

Terminals

31
Q

What is local current flow (unmylenated axons)

A

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
Q

Initial state of unmylenated action potentials

A

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
Q

What is the trigger zone on an unmylenated axon

A

Axon hillock

34
Q

Once the initial state of AP on unmylenated axons occur what happens

A

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
Q

How does the depolarization occur on an unmylenated axon

A

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
Q

Na enters the axon causing depolarization and this depolarizes ____ to the threshold

A

The adjacent segment

37
Q

Myelin is formed from concentric layers of _____ cell membrane and they are excellent __

A

Glial

Insulators

38
Q

What does Mylen do for the axon

A

Increases electrical efficiency of the axons

39
Q

What are the Mylenations separated by

A

Nodes of ranvier

40
Q

What are found at the nodes of ranvier

A

Very high density Na channels

K channels are found nearby

41
Q

What type of conduction do AP travel on mylenated axons

A

Saltatory conduction

42
Q

What does saltatory conduction mean

A

The action potential travels by jumping node to node (instead of travelling like a wave)

43
Q

What are demylenated diseases (what happens)

A

Degeneration of the mylen sheath

Conduction slows when the current leaks out

44
Q

What are the two ways to speed up velocity of AP along an axon

A

Increase axon diameter

Mylenation

45
Q

How does increasing the axon diameter help AP move faster

A

Increases velocity because as the axon radius becomes larger internal resistance decreases

46
Q

How does mylenation make AP move faster

A

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
Q

What is demyelination disease

A

Multiple sclerosis

Guillain barre syndrome

48
Q

What is multiple sclerosis

A

Autoimmune disease
Unknown cause
Demyelination of CNS axons
Multiple patterns of progression

49
Q

What are symptoms of multiple sclerosis

What are treatments

A

Loss of balance loss of speech loss of vision abnormal pupil reflexes numbness pain

Immunosuppressants and other drugs as indicated by symptoms

50
Q

What is guillain barre syndrome

A

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
Q

What are symptoms of guillain barre syndrome

A

Tingling weakness pain in hands and feet

Inability to speak paralysis and respiratory distress

52
Q

What are treatments of guillain barre syndrome

A

Plasmapheresis (to remove antibodies from blood) and immunoglobulin G to inactivate circulating antibodies

Most people survive but recovery may take months to years

53
Q

What is fugu poisoning

A

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
Q

What other anesthetic also block voltage gated Na channels

A

Lidocaine

Benzocaine

Physiology (15 decks)

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