Exam 4

Question 1

Why are Potassium channels in the heart called inward rectifying K+ channels?

Answer 1

The inward movement of cations (Ca++ and Na+) is what causes the potassium channels to close

Question 2

Is the left or right ventricular sub endocardium more prone to ischemia or infarct and why?

Answer 2

Left ventricle sub endocardium
-sub endocardium is furthest from the coronary arteries the supply the epicardial area. First to suffer with decreased blood flow.
-Left ventricle has higher o2 demand pumping blood out systemically so decreased o2 causes this area to be more vulnerable

Question 3

Closer to surface of the heart _____ likely ischemia will be.

Answer 3

least

Question 4

Ventricular myocyte also considered

Answer 4

ventricular muscle cell/ Purkinje fiber

Question 5

R Vagus innervates

Answer 5

SA node

Question 6

L Vagus innervates

Answer 6

AV node

Question 7

Parasympathetic innervation is mainly at the __________ areas of the heart.

Answer 7

pacemaker

Question 8

Sympathetic innervation of the heart is more ________.

Answer 8

widespread

Question 9

SNS primary catecholamine of the heart

Answer 9

Norepinephrine

Question 10

What parts of our body do NOT conduct electricity very well?

Answer 10

Fat tissue
air, copd (lower qrs complex)

Question 11

where do you see the most voltage in the depolarization of the tissue?

Answer 11

Half of the tissue is resting and half is depolarized, you’ll see the most voltage/ electrical current.

Question 12

Arrow pointing to the left

Answer 12

negative deflection

Question 13

Arrow pointing to the right

Answer 13

positive deflection

Question 14

Towards the positive lead denotes a

Answer 14

positive deflection in the meter

Question 15

Away from the positive lead denotes a

Answer 15

negative deflection in the meter

Question 16

P wave is the depolarization of the

Answer 16

atria

Question 17

QRS is depolarization of the

Answer 17

ventricles

Question 18

T wave is __________ repolarization

Answer 18

ventricular

Question 19

Why does the T wave show up as a positive deflection on the EKG? explain.

Answer 19

The ventricles have an opposite order of depolarization and repolarization. They depolarize one way and repolarize in the opposite way.
- Action potential starts in the deep areas of the ventricle and make their way further to the surface. inside depolarizes 1st. outside depolarizes 2nd.

Question 20

The ________ repolarizes before the endocardium in the ventricles.

Answer 20

epicardium

Question 21

Where is the conduction system of the ventricles located?

Answer 21

Deep in the heart wall

Question 22

The ventricle is _________ isolated from the atria

Answer 22

electrically

Question 23

___________ does not allow the resetting of cells after action potential.

Answer 23

Ischemia

Question 24

Usually an abnormal current of injury can be located where?

Answer 24

In an area where we should not have any current.

Question 25

Why is the SA node considered the pacemaker of the heart?

Answer 25

Tissue at the SA node depolarizes and reaches threshold potential faster than any other tissue in the heart

Question 26

Normal HR produced at the SA node?

Answer 26

72 BPM

Question 27

HCN channels are non specific for ________.

Answer 27

Cations

Question 28

HCN stands for?

Answer 28

Hyperpolarization + Cyclic nucleotide

Question 29

Explain HCN channels in the SA node and how they contribute to physiologic antagonism in this area of the heart?

Answer 29

HCN channels are tied to the beta adrenergic activity in the heart. when norepinephrine binds to beta adrenergic receptors they cause an increase in Cyclic Adenosine monophosphate (CAMP), which increases the amount of HCN channels during phase 4 slope of the action potential. More HCN channels helps get to threshold potential faster with the influx of cations (Na+/ Ca++) into the cell. Muscarinic Ach- R are also located at the heart and cause an increase in resting membrane potential with the Efflux of potassium out of the cell, making it harder to reach threshold potential and lowering the HR.

Question 30

Beta adrenergic activity tends to _______ ________ the potassium channels tied to muscarinic Ach receptors.

Answer 30

shut down

Question 31

How does ECF calcium affect HR and Vrm?

Answer 31

Hypercalemia–> increases threshold potential (more +) and slows down HR
Hypocalcemia–> decreases threshold potential (more -) and increases HR

Question 32

What is the pathophysiology on how calcium affects Vrm?

Answer 32

It is unknown