Human Phys 2.3

Question 1

Depolarization

Answer 1

mV moves up into positives

Question 2

Hyperpolarization

Answer 2

mV moves down into negatives

Question 3

Undershoot

Answer 3

Goes below resting potential before going back up to resting potential (K+ channels closing)

Question 4

Repolarization

Answer 4

When the action potential is moving back to resting after depolarization (due to K+ leaving cell)

Question 5

Excitability

Answer 5

Ability of membrane to change mV (repolarize and depolarize)

Question 6

Threshold

Answer 6

Certain mV that if it’s crossed there will be an action potential generated

Question 7

Action potential steps

Answer 7

1. If the threshold is reached voltage gated Na+ channels are opened and Na+ pours into the cell the membrane depolarizations and then the inactivation gate closes stopping Na+
2. K+ channels then open which repolarizes the cell bringing it back to the resting membrane potential

Question 8

Action potential

Answer 8

Regenerating depolarization of membrane potential that propagates along an excitable membrane

Question 9

Propagates

Answer 9

Conducted without decrement

Question 10

Excitable

Answer 10

Capable of generating action potentials

Question 11

What are the properties of action potentials?

Answer 11

All or none event

Initiated by depolarization

Have constant amplitude

Have constant conduction velocity

Question 12

All or none event

Answer 12

Action potential either happens or it doesn’t

Question 13

Initiated by depolarization

Answer 13

Action potentials can be induced in nerve and muscle by extrinsic stimulation

Question 14

Have constant amplitude

Answer 14

Information is coded by frequency not amplitude (do not summate)

Question 15

Have constant conduction velocity

Answer 15

True for given fiber

Question 16

What type of fiber conducts faster?

Answer 16

Fiber with a large diameter

Question 17

Action potential summary

Answer 17

During upstroke of action potential Na+ permeability increases due to opening of Na+ channels

During downstroke of action potential Na+ permeability decreases due to inactivation of Na+ channels and K+ permeability increases due to opening of K+ channels

After hyperpolarization the mV may drop below where it was due to delayed closure of K+ channels

Question 18

Is there a specific direction of propagation?

Answer 18

No

Question 19

What happens due to the presence of inactivation gates and refractory periods?

Answer 19

Backward propagation is prevented

Question 20

How does lidocaine work?

Answer 20

Binds to voltage gates Na+ channels and inactivates them

Question 21

What are axons surrounded by?

Answer 21

Myelin sheath

Question 22

What is responsible for myelination?

Answer 22

Schwann cells

Question 23

Node of ranvier

Answer 23

Break in myelin sheath every 1-3mm

Question 24

Where are most of the Na+ channels located?

Answer 24

At the node of ranvier

Question 25

Saltatory conduction

Answer 25

Current travels along axon under myelin sheath due to insulation and is amplified at the nodes of ranvier by the voltage gated Na+ channels

Question 26

Why is myelinated faster than unmyelinated?

Answer 26

You need less action potentials

Question 27

Multiple sclerosis

Answer 27

Auto immune disorder that causes demylination in 1 per 1000 people (causes decreased coordination)

Question 28

Overshoot

Answer 28

Peak of action potential