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Predict the effects of a reduced rate of cardiac musclecontraction on the duration of the isovolumic contraction phase ofthe cardiac cycle. What would be the likely effects of hypertensionon the duration of of the isovolumic phase?

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Jamar Ferry
Jamar FerryLv2
28 Sep 2019

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Related questions

Match the following terms describing the physical/mecahnical events with the correct phases of the cardiac cycle. Each phase may be used more than once.

- A. B. C. D.

All 4 cardiac valves are closed and all 4 chambers are relaxed during this phase.
- A. B. C. D.

The maximum amount of blood is in the ventricles at the end of this phase.
- A. B. C. D.

The pressure in the ventricles is higher than in the atria, but lower than in the arteries, during this phase.
- A. B. C. D.

The semilunar valves are open and the AV valves are closed during this phase.
- A. B. C. D.

The atria contract at the end of this phase.
- A. B. C. D.

The pressure in the ventricles is higher than the pressure in both the atria and the arteries during this phase.
- A. B. C. D.

Systole begins with this phase.
A.

isovolumetric relaxation
B.

ventricular ejection
C.

isovolumetric contraction
D.

ventricular filling

Question 5. Dr. Campbell used an elliptical trainer for 40 minutes at the gym. Although the workload remained constant, Dr. Campbell’s heart-rate rose to 150 beats per minute during the first 5 minutes, stayed at that level for the next 25 minutes and then started to rise. It was 180 beats per minute at the end of the exercise period.

What was the time interval between QRS complexes when Dr. Campbell’s heart rate was 180 beats per minute?

a. 3.3 ms

b. 33 ms

c. 333 ms

d. 3333 ms

Question 6. In the question 5 above, Dr. Campbell’s heart rate is most likely to have risen during the last 10 minutes of exercise because his:

a. lungs were becoming congested

b. atrial cells were fatigued

c. extracellular Ca2+ concentration had increased

d. hematocrit increased due to sweating

Question 7. A Physiology student is sitting still in a cold igloo. After 30 minutes, she stands up, walks slowly around the igloo, and suddenly starts to shiver.

The student preserved their core temperature while they were sitting by:

a. depressing their Frank-Starling mechanism

b. decreasing the extracellular Ca2+ concentration

c. relaxing smooth muscles in their peripheral circulation

d. increasing the resistance of arterioles in their arms and legs

Question 8. In the question 7 above, the student started to shiver soon after walking because:

a. their atria started to fibrillate

b. their ventricles started to fibrillate

c. blood moved to the periphery, became cold, and chilled the core when it returned to the chest

d. the ATP concentration in their skeletal muscles had dropped to zero

Please use the following scenario for answering the questions 9 and 10.

A newly discovered drug binds to myosin molecules in cardiac muscle (and nowhere else) and increases the probability that myosin molecules in ventricular cells will bind to actin filaments when the intracellular Ca2+ concentration rises. The drug is being tested as a potential therapy for patients with heart failure.

Question 9. This drug might help people who have low cardiac output by:

a. increasing peripheral resistance

b. increasing the force developed by ventricular cells

c. increasing the isovolumic contraction time

d. increasing heart rate

Question 10. The increased binding of cardiac myosin molecules to actin might prevent the drug from being a useful treatment by:

a. slowing ventricular relaxation

b. decreasing the duration of systole

c. decreasing resistance of capillaries

d. slowing heart rate

Effects of electrical stimulation of ventricle at various time points during a Frog cardiac cycle:

1. at which time points of the cardiac cycle can an electrical stimulation induce extra systole?

2. explain how the extra systole can appear during this manipulation in terms of the refractory period of the ventricular action potential.

3. Stannius ligature experiment: what will happen to the beating rate of the two atria (right and left) versus the ventricle during the ligature?)

4. explain how these changes occur in the beating rate during the stannius ligature.

5. now the heart is completely devoid of neural or hormonal input. What will happen to the beating rate of all three chambers? What about the chamber’s beating rate when they are surgically separated? explain possible mechanisms for the changes in the beating rate for each chamber.)

6. describe the effects of the following drugs on the heart rate and the force of ventricular contraction:
acetylcholine(1%), atropine (0.5%), Pilocarpine (2.5%), nicotine (0.2%), Epinephrine (0.1%), Isoproterenol (0.1%)

also, explain how each of the 6 chemicals above either mimic or inhibit the cardiac function

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