QUESTION 8 Which of the following is NOT a feature of cardiac muscle fibers? (1)

Question

QUESTION 8

Which of the following is NOT a feature of cardiac muscle fibers?

(1)They are usually multi-nucleated.

(2)They are very rich in myoglobin.

(3)They are rich in glycogen.

(4)They depend almost exclusively on aerobic respiration.

(5)They have huge mitochondria.

QUESTION 9

At an intercalated disc

(1)two cardiac muscle fibers are connected by gap junctions and desmosomes.

(2)the cell membranes of two cardiac muscle fibers are separated by a synaptic cleft.

(3)cardiac muscle fibers are fused together by tight junctions.

(4)adjacent sarcomeres within a myofibril are connected together.

(5)t-tubules unite the membranes of the adjoining cells.

QUESTION 10

The plateau is a feature of

(1)action potentials of all electrically-excitable cells.

(2)pacemaker cell action potentials.

(3)action potentials of autorhythmic cells.

(4)cardiac muscle and pacemaker action potentials.

(5)cardiac muscle fiber action potentials.

QUESTION 11

The tricuspid valve regulates the opening between

(1)the right atrium and the left atrium.

(2)the right atrium and the left ventricle.

(3)the left atrium and the left ventricle.

(4)the left ventricle and the right ventricle.

(5)the right atrium and right ventricle.

QUESTION 12

End-systolic volume represents the amount of blood in the ___________ at the end of _____________.

atrium; atrial contraction

(2)ventricle; ventricular ejection

atrium; isovolumetric relaxation

(4)ventricle, passive filling

(5)ventricle; ventricular filling

QUESTION 13

The pacemaker potential is a slow depolarization that begins with _________ through If channels.

(1)Na+ inflow.

K+ inflow.

(3)Ca2+ inflow.

(4)Na+ outflow.

QUESTION 14

The Frank-Starling law of the heart states that stroke volume is proportional to

(1)the end-systolic volume.

(2)the end-diastolic volume.

(3)the afterload.

the heart rate.

(5)contractility.

QUESTION 15

Contractility of cardiac muscle increases when the __________________.

(1)intracellular potassium level rises

sarcomeres reach their optimum length

(3)calcium channels are blocked

(4)intracellular calcium level rises

(5)intracellular sodium level rises

QUESTION 16

(1)If the papillary muscles of the heart fail to contract

the AV valves will not open.

(3)the ventricles will not pump blood.

(4)the semilunar valves will not open.

(5)the AV valves will not close properly.

(6)the atria will not pump blood.

QUESTION 17

Which of these is not part of the cardiac conduction system?

the sinoatrial (SA) node

the tendinous cords (TC)

the atrioventricular (AV) node

the atrioventricular (AV) bundle (bundle of His)

(5)the Purkinje fibers

QUESTION 18

Which of the following describes the effect of end-diastolic volume on stroke volume?

(1)A decrease in end-diastolic volume allows cardiac muscle to relax, conserving energy for the next contraction, thereby increasing stroke volume of that next contraction.

(2)An increase in end-diastolic volume stretches ventricular muscle cells to lengths greater than optimum, decreasing the strength of contraction and thereby decreasing stroke volume.

A decrease in end-diastolic volume allows ventricular muscle cells to relax more during diastole, allowing more blood to return to the heart increasing stroke volume.

A decrease in end-diastolic volume creates a vacuum drawing more blood into the ventricle increasing stroke volume.

(5)An increase in end-diastolic volume stretches ventricular muscle cells to lengths closer to optimum, increasing the strength of contraction and thereby increasing stroke volume.

QUESTION 19

The following is a list of vessels and structures that are associated with the heart:

1. aorta

2. left atrium

3. left ventricle

4. pulmonary trunk

5. pulmonary veins

6. right atrium

7. right ventricle

8. vena cavae

What is the correct order for the flow of blood entering from the systemic circuit? Start with the vessels that carry the blood back to the heart from the systemic circuit.

(1)8,6,7,4,5,2,3,1

(2)1,8,6,7,4,5,2,3

(3)8,6,7,5,4,2,3,1

(4)5,2,3,1,8,6,7,4

8,7,6,4,5,3,2,1

QUESTION 20

Rapid repolarization occurs in cardiac muscle cells and pacemaker cells when

(1)potassium channels open and potassium ions leave the cell.

(2)sodium ions are pumped out of the cell.

potassium channels open and potassium ions enter the cell.

(4)calcium ions are pumped into the sarcoplasmic reticulum.

(5)calcium channels open and calcium ions leave the cell.

QUESTION 21

Which of these is the correct sequence of events of the cardiac cycle?

(1)ventricular filling isovolumetric relaxation isovolumetric contraction ventricular ejection

(2)ventricular filling isovolumetric relaxation ventricular ejection isovolumetric contraction

(3)ventricular filling isovolumetric contraction isovolumetric relaxation ventricular ejection

(4)ventricular filling isovolumetric contraction ventricular ejection isovolumetric relaxation

(5)ventricular filling ventricular ejection isovolumetric contraction isovolumetric relaxation

QUESTION 22

_____________ increase(s) stroke volume.

(1)High arterial blood pressure

(2)Negative inotropic agents

Increased venous return

Increased afterload

(5)Dehydration

QUESTION 23

________________ cause an increase in the contractility of cardiac muscle.

(1)Negative chronotropic agents

(2)Negative inotropic agents

(3)Positive inotropic and positive chronotropic agents

(4)Positive inotropic agents

(5)Positive chronotropic agents

QUESTION 24

What happens when pressure in the aorta exceeds pressure in the left ventricle?

(1)There is no relationship between pressures in these chambers because they are not directly connected to each other.

(2)AV valve opens

(4)AV valve closes

(5)semilunar valve opens

(6)semilunar valve closes

QUESTION 25

Friction between membranes of the heart is reduced by

(1)the epicardium.

(2)a cushion of air that surrounds the heart.

(3)serous fluid in the pericardial cavity.

(4)fluid between the epicardium and the myocardium.

(5)a blood-filled sinus called the pericardium.

QUESTION 26

The sac around the heart is the

(1)myocardium.

(2)pericardium.

(3)pleural sac.

(4)peritoneum.

(5)epicardium.

QUESTION 27

The first heart sound is heard when the

(1)AV valves close.

atria contract.

(3)semilunar valves close.

(4)AV valves open.

(5)blood enters the aorta.

QUESTION 28

Which of the following would shorten the pacemaker potential and accelerate heart rate?

(1)inhibiting the opening of If channels

(2)opening more K+ channels

(3)inhibiting the opening of Na+ channels

(4)opening more Ca2+ channels

(5)hyperpolarizing the cell

QUESTION 29

About 2/3 of the volume of blood that enters the ventricles during ventricular filling occurs

(1)during atrial diastole.

(2)during atrial systole.

(3)during isovolumetric relaxation.

(4)during ventricular systole.

(5)when the AV valve is closed.

QUESTION 30

As blood leaves the left ventricle, it passes

(1)into the pulmonary trunk.

(2)into the right atrium.

(3)through the aortic semilunar valve.

(4)through the bicuspid valve.

(5)into the right ventricle.

QUESTION 31

The fibrous skeleton serves as electrical insulation between the ______________.

(1)atria and ventricles

(2)sinoatrial node and atrioventricular node

(3)left and right ventricles

(4)left and right atria

QUESTION 32

The left ventricular wall of the heart is thicker than the right wall in order to:

(1)pump blood through a smaller valve.

(2)accommodate a greater volume of blood.

pump blood with greater pressure.

(4)expand the thoracic cage during diastole.

(5)receive blood that is under higher pressure.

QUESTION 33

Isovolumetric contraction:

(1)occurs only in people with heart valve defects.

(2)occurs while the AV valves are open.

(3)refers to the short period during ventricular systole when the ventricles are completely closed chambers.

(4)produces the stroke volume as blood is ejected from the ventricles into the great vessels.

(5)occurs immediately after the semilunar valves close.

QUESTION 34

The opening and closing of the atrioventricular and semilunar valves is driven by _________.

(1)contraction of the ventricles and atria that pull the valve cusps into place.

(2)differences in pressure in the compartments on each side of the valve.

(3)constriction and dilation of the opening by the fibrous skeleton.

(4)contraction and relaxation of the valve.

(5)contraction of muscles attached to the valves.

QUESTION 35

If the vagal nerves (carrying parasympathetic signals) to the heart were cut, the result would be that:

(1)the heart would stop, since the vagal nerves trigger the heart to contract.

(2)the heart rate would increase to its intrinsic rate.

(3)heart rate would decrease.

(4)the AV node would become the pacemaker of the heart.

QUESTION 36

Conduction of the electrical signal slows down as it passes through the _______________.

(1)AV bundle

(2)Purkinje fibers

(3)bundle branches

(4)fibers of the AV node

(5)internodal pathways

QUESTION 37

In the contractile fibers of the myocardium, the depolarization phase of the action potential is the result of

(1)decreased membrane permeability to sodium ions.

(2)increased membrane permeability to chloride ions.

(3)increased membrane permeability to sodium ions.

(4)increased membrane permeability to sodium and calcium ions.

(5)increased membrane permeability to potassium ions.

QUESTION 38

The coronary circulation receives its blood supply from vessels that arise from the

base of the aorta

left atrium

pulmonary trunk

right ventricle

left ventricle

(1)They are usually multi-nucleated.

(2)They are very rich in myoglobin.

(3)They are rich in glycogen.

(4)They depend almost exclusively on aerobic respiration.

(5)They have huge mitochondria.

Explanation / Answer

Answers:

1). Cardiac muscle is very unique muscle fiber that plays a key role in blood pumping. This muscle fiber has special characteristics such as,

Cardiac muscle is uninucleated.

Cardiac muscle utilizes the huge amount of ATP for their proper function so they need more number of mitochondria’s. In addition, to make ATP by aerobic respiration and the short term energy source is glycogen.

Hence, the final answer is option 1 they are usually multi-nucleated.

2). At an intercalated disc..

Tight junctions fuse cardiac muscle fibres together.

The cell membranes of two cardiac muscle fibres are separated by a synaptic cleft.

Gap junctions and desmosomes connect two cardiac muscle fibres.

3). The plateau is a feature of cardiac muscle fibre action potentials.( there is no plateau phase occurs in pacemaker cells

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