Exam 3- CV phys

Question 1

The heart’s ability to trigger its own contractions is called

Answer 1

autorhythmicity

Question 2

autorhythmicity occurs because

Answer 2

the plasma membrane in cardiac pacemaker cells has reduced permeability to potassium ions but still allows sodium and calcium ions to slowly leak into the cells

Question 3

depolarization causes voltage gated sodium channels in the cell membrane to open
this increases the flow of sodium into the cell

Answer 3

Phase 0

Question 4

open sodium channels begin to inactivate

at the same time voltage-gated potassium channels close and voltage gated calcium channels open

Answer 4

Phase 1

Question 5

potassium channels are closed
Long lasting L calcium channels stay open
lasts about .2 sec

Answer 5

Phase 2

Question 6

a second set of potassium channels open allowing a significant amount of potassium to flow out of the cell
Calcium channels close

Answer 6

Phase 3

Question 7

all voltage gated channel are closed

Answer 7

Phase 4

Question 8

the reason tetanus occurs in skeletal muscle

Answer 8

sk muscle has a relatively short absolute refractory period

Question 9

which is true of the cardiac myocyte action potential

Answer 9

it is longer than skeletal muscle cell action potential

Question 10

the total cardiac action potential lasts

Answer 10

250-300 milliseconds

Question 11

the period of time when cardiac muscle is incapable of reacting to any stimulus is

Answer 11

absolute refractory period

Question 12

when you increased the frequency of stimulation the amplitude of the ventricular systole wave

Answer 12

did not change

Question 13

When you delivered 20 stimuli/sec to the heart you saw

Answer 13

neither wave summation nor tetanus

Question 14

an extrasystole is also a(n)

Answer 14

extra ventricular contraction

Question 15

which contributes to the inability of the cardiac muscle to be tetanized

Answer 15

the long refractory period of the cardiac action potential

Question 16

the amplitude of the ventricular systole did not change with the more frequent stimulation because

Answer 16

a new contraction could not begin until the relaxation phase

Question 17

why is it important that cardiac muscle NOT reach tetanus?

Answer 17

the heart must relax fully to allow blood to enter

Question 18

why is it only possible to induce an extrasystole during relaxation?

Answer 18

prior to relaxation the heart is in its absolute refractory period

Question 19

explain why wave summation and tetanus are not possible in cardiac muscle

Answer 19

Cardiac muscle has a long plateau phase with a long associated absolute refractory period. A contraction can not begin until the ARF has ended-until relaxation. So wave summation and tetanus are impossible, treppe though, is possible

Question 20

At rest both the SNS and PNS are working but the ______branch is more active

Answer 20

PNS

Question 21

the _________nerve carries the parasympathetic signal to the heart

Answer 21

vagus

Question 22

select the 2 factors that contribute to vagal escape

Answer 22

initiation of a rhythm by purkinje fibers

sympathetic reflexes

Question 23

according to the introduction of activity 2 PEX 6 in the absence of parasympathetic stimulation , sympathetic stimulation, and hormonal controls, the SA node generates action potentials _____times per minute

Answer 23

100

Question 24

When you applied multiple stimuli to the heart by indirectly stimulating the vagus nerve

Answer 24

the heart rate decreased

Question 25

After vagal nerve stimulation in activity 6 we saw vagal escape this was

Answer 25

he response that resumed the normal heart rate after multiple vagal nerve stimulation

Question 26

In the absence of neural and hormonal influences the SA node generates action potentials at a predetermined frequency . The resting HR is approximately 30 bpm lower. This suggests that

Answer 26

the parasympathetic system has more control over the resting HR

Question 27

If the vagus nerve was cut how you would expect the HR to change

Answer 27

without vagal stimulation you would expect the resting HR to be closer to 100

Question 28

humans are _____ which means that the human body maintains an internal body temperature within 35.8-38.2 degrees C range even though the external temperature is changing

Answer 28

homeothermic

Question 29

when you decreased the temperature of the ringer's solution the frog heart rate

Answer 29

decreased

Question 30

you would expect the Heart rate of a person with a temperature of 100.4F=38C to be

Answer 30

increased compared to someone with a temperature of 37C

Question 31

if the frog heart was in distilled water and not in ringer's solution

Answer 31

spontaneous cardiac action potentials would not develop

Question 32

norepinephrine and epinephrine increase the frequency of action potentials in the heart by binding to ____adrenergic receptors embedded in the plasma membrane

Answer 32

beta 1

Question 33

"Working through a _______2nd messenger mechanism, binding of the ligand (NE) opens sodium and calcium channels, increasing the rate of depolarization and shortening the period or repolarization"

Answer 33

cAMP

Question 34

agonist

Answer 34

produces the same response as the initial neurotransmitter of hormone

Question 35

antagonist

Answer 35

blocks the effect of the initial neurotransmitter or hormone

Question 36

Pilocarpine is an acetylcholine agonist that you applied to the frog heart in activty 4 this lead to a(n)

Answer 36

decrease in HR

Question 37

Atropine is an acetylcholine antagonist that you applied to the frog heart in activity 4 this lead to a(n)

Answer 37

increase in HR

Question 38

uses for calcium channel blockers are

Answer 38

treat hypertension | treat abnormal HRs

Question 39

greater concentration outside the resting cell

Answer 39

Ca2+, Cl-, Na+

Question 40

greater concentration inside the resting cell

Answer 40

K+

Question 41

effect of digitalis on the heart

Answer 41

decrease the HR, it also strengthens the contraction force to increase Stroke volume

Question 42

Phase 0 rapid depolarization

Answer 42

Na+ enters

Question 43

Phase 1 small repolarization

Answer 43

decrease in Na+ movement

Question 44

Phase 2 plateau

Answer 44

K+ movement out decreases Ca2+ enters the cell

Question 45

phase 3 repolarization

Answer 45

K+ leaves the cell Ca2+ movement decreases

Question 46

Phase 4 resting potential

Answer 46

K+ moves out little sodium or Ca2+ moves in

Question 47

the effect of increasing Na+ outside the heart was

Answer 47

negative chronotrope and negative inotrope

Question 48

A calcium channel blocker such as verapamil is a

Answer 48

negative chronotrope and negative inotrope

Question 49

pilocarpine is an acetylcholine agonist. Besides its effect on the heart select three other possible responses

Answer 49

increase perspiration increase GI activity- loose stool contract the pupil

Question 50

digitalis is

Answer 50

positive inotrope

Question 51

the effect of increasing Ca2+ outside the heart was

Answer 51

positive chronotrope and positive inotrope

Question 52

hyperkalemia is expected to

Answer 52

decrease HR

Question 53

hypoxia, or worse anoxia, to cells results in cell death. When there is decreased blood flow to cardiac cells this leads to cardiac cell death. When cells die the empty their contents. Remember, there is more potassium inside a cell then outside. Thus the microenvironment around a recently killed cell may be high in potassium. How might this affect the resting membrane potential of the still viable neighbor cells?

Answer 53

the hyperkalemia may decrease the resting membrane potential decreasing the strength of their contraction

Question 54

the addition of most ions on the frog heart lead to

Answer 54

an erratic HR

Question 55

affect of calcium channel blockers on smooth muscle found in blood vessels is to

Answer 55

decrease entry of calcium and thus lower vasomotor tone and vasodilate, decrease BP

Question 56

the phase of the cardiomyocyte action potential when calcium channels are open and potassium channels are closed is called the

Answer 56

plateau phase

Question 57

the initial effect of hyperkalemia is as

Answer 57

negative inotrope and negative chronotrope

Question 58

ion with the most profound change on the heart rate was

Answer 58

K+