Phys 1

Question 1

What is the state of the Na+ channel in: resting, activated, inactivated?

Answer 1

1. Activation gate is closed, inactivation gate is open
2. Activation gate is open, inactivation gate is open
3. Activation gate is open, inactivation gate is closed

Question 2

What is the order of the Conduction System?

Answer 2

1. Sa Node
2. AV Node
3. Bundle of His
4. Right/Left Bundle Branches
5. Purkinje Fibers

Question 3

The SA Node works to…

Answer 3

create an AP that spreads throughout the atria to elicit their contraction (usually right a little bit ahead of the left)

Question 4

Atrial myocytes and Ventricular myocytes are…

Answer 4

separated from each other. This means that a depolarization of the SA Node to the atrial myocytes should not spread to the ventral myocytes (AP must go through AV Node to reach ventricular myocytes).

Question 5

Are Purkinje fibers or myocytes larger? Why does this matter?

Answer 5

1. PF
2. The PFs/Bundle of His will conduct the AP at a faster rate

*the larger the fiber, the faster the AP transmission

Question 6

The cells that ____ last are the first to ____.

Answer 6

depolarize, repolarize

Question 7

How does depolarization/repolarization differ in what layers they move through first/second?

Answer 7

1. Depolarization: interior (endo) to exterior (epi)

2. Repolarization: exterior (epi) to interior (endo)

Question 8

Rank these fastest to slowest for AP Transmission:

AV Node, Atrial/Ventricular muscle, PFs

Answer 8

1. PFs
2. Atrial/Ventricular muscle
3. AV Node

Question 9

What is the purpose of the delay of the AV Node (why it’s the slowest)?

Answer 9

It allows the atria to have extra time to contract, and to “top off” the ventricles; meaning ventricles reach peak volume of blood

Question 10

What cells can make an AP? At what pace?

Answer 10

SA Node > AV Node > PFs

Question 11

What is the RMP of Ventricle? Atrium? SA Node

Answer 11

1. -90 +/- -5
2. -90 +/- -5
3. -65 +/- -5

Question 12

Na+ (m)

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 12

1. +30mV
2. Membrane potential crosses threshold
3. Opens
4. 0, 1
5. Very fast generation of depolarization then automatically closes allowing partial repolarization

Question 13

K+ (a)

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 13

1. -90mV
2. Cell depolarizes
3. Opens
4. 1
5. Very rapid partial repolarization

*Transient outward current

Question 14

Ca2+

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 14

1. +40mV
2. Cell depolarizes
3. Opens
4. 2, 3
5. Slow to open and remains open for a determined amount of time then opens helping with phase 3

*L type

Question 15

K+ (b)

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 15

1. -90mV
2. Cell depolarizes
3. Closes
4. 2, 3
5. Slow to close and remains closed for a determined amount of time then opens helping with phase 3 (special rectifiers)

Question 16

K+ (c)

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 16

1. -90mV
2. Remains open
3. Remains open
4. 4
5. Leak channel which maintains resting potential

Question 17

Na+ (f)

1. Ek
2. Activated when
3. Action
4. Phase
5. Special Features

Answer 17

1. +30mV
2. SA or AV Node depolarize
3. Opens
4. 4
5. Specific to SA/AV Node where it causes slow depolarization during resting phase

Question 18

Kd

Answer 18

• volatage gated channels
• all phase 3 events involved

*NOT K+ leak channels

Question 19

What channels did he mention are sensitive to acetylcholine?

Answer 19

Kb channels (has a parasympathetic effect)

Question 20

Phase 3 is essentially a ____ of phase 1.

Answer 20

reversal

Question 21

What is equilibrium potential?

Answer 21

it equals a little less than RMP

Question 22

What phase is the plateau phase?

Answer 22

2 –> purpose is to prolong contraction, and is fundamentally different than skeletal muscle

Question 23

Conduction velocity usually relates to…

Answer 23

your phase 0 slope

Question 24

AV Block

Answer 24

AV node damage that further delays conduction

Question 25

Arrhythmias

Answer 25

Purkinje fiber damage that disrupts the natural conduction and contraction of ventricles

Question 26

Relative Refractory Period

Answer 26

AP can be generated, but will have an abnormal conduction (phase 0 is tipped to not propogate the next AP at the same speed)

Question 27

Supranormal Period

Answer 27

the cell is more excitable than normal

Question 28

Chronotropic

Answer 28

-effect changes rate of depolarization of SA node, and therefore HR + --> increased HR - --> decreased HR (slowed Na+ f channels during phase 4; hyper polarization by increasing outward K+ current via K+ Ach channel)

Question 29

Dromotropic

Answer 29

-effect is speed of condition + --> faster conduction - --> slower conduction (reduced Ca2+ inward current; increased outward K+ current via K+ Ach)

Question 30

Inotropic

Answer 30

effect changes the strength of muscular contraction | + --> heart contracts more forcefully

Question 31

Lusitropic

Answer 31

effect changes the rate of muscular relaxation

Question 32

What regions get parasympathetic innervation?

Answer 32

- SA node and AV node - acetylcholine goes to receptors M2 or M3 - leads to decreased HR

Question 33

Which has a longer Relative refractory period: neurons or cardiac cells?

Answer 33

cardiac

Question 34

What is the purpose of the refractor period?

Answer 34

to prevent arrhythmias