Chapter 12 - Neurophysiology

Question 1

Electrical signals

Answer 1

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

Question 2

Ions involved in generation of electrical signals

Answer 2

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

Question 3

axolemma & sarcolemma

Answer 3

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

Question 4

ion channels

Answer 4

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

Question 5

Types of Ion channels

Answer 5

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

Question 6

Leakage channels

Answer 6

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

Question 7

Gated channels

Answer 7

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

Question 8

Ligand-gated ion channels

Answer 8

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

Question 9

Mechanically gated ion channels

Answer 9

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

Question 10

Voltage gated ion channel

Answer 10

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

Question 11

Membrane potential

Answer 11

charge difference across a membrane

Question 12

Volt meter

Answer 12

can measure charge difference across membrane

Question 13

Resting membrane potential

Answer 13

no signal is being generated;

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

Question 14

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

Answer 14

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

Question 15

Electrical Signals (2 types)

Answer 15

1. Graded potentials

2. Action potentials

Question 16

Graded potentials

Answer 16

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

Question 17

Electrical signals

Answer 17

move resting membrane potential to more positive position

Question 18

Action potentials

Answer 18

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

Question 19

Action Potentials (characteristics)

Answer 19

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

Question 20

threshold

Answer 20

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

Question 21

3 Phases of Action Potentials

Answer 21

1. Depolarization
2. Repolarization - returns to resting
3. Hyperpolarization

Question 22

Polarized

Answer 22

negative

Question 23

Action Potentials:

Phase / Caused by / Membrane potential

Answer 23

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

Question 24

Action potentials occur…

Answer 24

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

Question 25

Refractory period

Answer 25

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

Question 26

Factors affecting rate of Action potentials

Answer 26

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

Question 27

Myelinated axon move faster than unmyelinated axons bc

Answer 27

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

Question 28

fastest moving action potential in body

Answer 28

very thick & myelinated; travels 300 mph by saltatory conduction

Question 29

Synapses

Answer 29

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