Chapter 12 - Neurophysiology Flashcards

1
Q

Electrical signals

A

only travel along membranes (axolemma & sarcolemma); membranes carry electrical signals

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2
Q

Ions involved in generation of electrical signals

A
  1. Na+
  2. K+
    when they go thru a membrane they change. they charge across membrane & generate electrical signals
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3
Q

axolemma & sarcolemma

A

phospholipid; ions have a hard time crossing membranes; protein channels allow ions thru

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4
Q

ion channels

A

places on the membrane that allows a specific ion thru & it begins to generate signals

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5
Q

Types of Ion channels

A
  1. Leakage channels
  2. Gated channels
    a. ligand-gated i.c.
    b. mechanically gated i.c.
    c. voltage gated i.c.
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6
Q

Leakage channels

A

ions leak thru a little at a time & it’s not regulated

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7
Q

Gated channels

A

when gate is open, ion can move thru; when closed, there is no movement; responds to stimulus to open or close

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8
Q

Ligand-gated ion channels

A

respond to special chemicals (neurotransmitters);
ligand = specific chemical that binds;
acetylcholine-specific binding that opens after it binds & ions can go thru & charge across membrane changes;
can only produce graded potentials;
located–plasma membrane of dendrites or cell body

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9
Q

Mechanically gated ion channels

A

responds to physical force (pressure, touch, stretching) & signal generated;
can only produce graded potentials;
located–plasma membrane of dendrites or cell body

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10
Q

Voltage gated ion channel

A

if voltage changes it can open the ion channel; responds to changes in membrane potential;
voltage = charge difference;
only one to produce action potentials;
located-axolemma & sarcolemma

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11
Q

Membrane potential

A

charge difference across a membrane

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12
Q

Volt meter

A

can measure charge difference across membrane

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13
Q

Resting membrane potential

A

no signal is being generated;

approx: -70 mV (million volts); cell at rest; charge on inside is more negative than outside of cell

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14
Q

Explanation of why inside of cell is more negative outside of cell

A

Na+ K+ pump–pumps ions from low to high; pumps Na+ out of cell & K+ into cell; exists in every single cell’s membrane; fluid outside cell has lots of Na; for every 3 Na+ out in pumps 2 K+; so more charges are on outside; inside has fewer positive charges, so more negative on inside

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15
Q

Electrical Signals (2 types)

A
  1. Graded potentials

2. Action potentials

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16
Q

Graded potentials

A

caused by decreasing w/distance; short distance electrical signals; ligand-gated or mechanically gated i.c.

17
Q

Electrical signals

A

move resting membrane potential to more positive position

18
Q

Action potentials

A

voltage-gated channels; only occurs on axolemma & sarcolemma; long-distance electrical signals; do not decrease effect over long distance, signal stays just as strong

19
Q

Action Potentials (characteristics)

A
  1. Long distance electrical signal
  2. Transient reversal of membrane potential; flips membrane potential to neg on inside to pos on inside; depolarization, repolarization, hyperpolarization
  3. Mediated by movement of ions
  4. All-or-none event - either 100% or 0%
  5. Fast - travels quickly so our NS responds quickly
20
Q

threshold

A

certain membrane potential that must be reached in order for action potential to start; very important #; ex. if it doesn’t reach threshold, nothing happens

21
Q

3 Phases of Action Potentials

A
  1. Depolarization
  2. Repolarization - returns to resting
  3. Hyperpolarization
22
Q

Polarized

A

negative

23
Q

Action Potentials:

Phase / Caused by / Membrane potential

A
  1. Phase: Depolarization
    Caused by: Na+ channel opens; Na+ enters cell;
    Membrane potential: more positive
  2. Phase: Repolarization
    Caused by: K+ channel opens; K+ leaves cell
    Membrane potential: more negative
  3. Phase: Hyperpolarization
    Caused by: K+ channels close slowly;
    Membrane potential: more neg than resting
24
Q

Action potentials occur…

A

at axon hillock; all we need is threshold for action potential to start; goes away from cell body to axon terminal

25
Q

Refractory period

A

action potentials don’t go backwards; explains why action potentials move forward; it can’t respond backwards

26
Q

Factors affecting rate of Action potentials

A
  1. Diameter of axon - thick axon travels faster; increase diameter, increase rate
  2. Increase temp, increase rate
  3. Increase amount of myelination, increase rate
27
Q

Myelinated axon move faster than unmyelinated axons bc

A

action potentials jump over schwann cells to next node; saltatory conduction–faster than continuous conduction bc you are skipping spots

28
Q

fastest moving action potential in body

A

very thick & myelinated; travels 300 mph by saltatory conduction

29
Q

Synapses

A

junction between 2 neurons or between a neuron & an effector cell; how neurons talk to other neurons; how signal gets to another cell