Cardiovascular Physiology Lab Questions

Describe the effect that pilocarpine had on the heart and why it had this effect. How well did the results compare with your prediction?

Pilocarpine decreased the heart rate. It had this effect because it mimics the action of acetylcholine and decreases the frequency of action potentials. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Ringer's solution contains which of the following?

cations, anions and electrolytes

When multiple stimuli were applied at 20 stimuli/sec, _______.

extrasystoles were produced

Modifiers that affect the force of contraction of the heart are _______.

inotropic

Calcium channel blockers block the movement of calcium _______.

into the cell and decrease heart rate

The total refractory period of cardiac muscle _______.

is longer than the total refractory period for skeletal muscle

A ___________________ drug increases the force of contraction of the heart.

positive inotropic

The autorhythmicity of cardiac pacemaker cells is made possible by the reduced permeability of _______.

potassium

The cardiac cell plasma membrane is most permeable to _______________________.

potassium

Which ion(s) at least initially lowered the frog heart rate in the activity you just performed?

potassium and sodium

The repolarization of cardiac muscle is due to _______.

potassium exiting the cell

Which of the following has the fastest rate of spontaneous depolarization?

the SA node

When vagus nerve stimulation was applied to the frog heart, _______.

the heart rate slowed and eventually stopped

Which part of the human body regulates temperature?

the hypothalamus

Which branch of the autonomic nervous system dominates after a large meal?

the parasympathetic branch

What part of your tracing illustrates vagal escape?

the part where the heart resumed beating

Heat-releasing mechanisms include which of the following?

vasodilation and sweating

Skeletal muscle is capable of which of the following?

wave summation and fused tetanus

Atropine is an acetylcholine antagonist. Does atropine inhibit or enhance the effects of acetylcholine? Describe your results and how they correlate with how the drug works. How well did the results compare with your prediction?

Atropine is an acetylcholine antagonist, meaning it inhibits the effects of ACh. Atropine increases the heart rate because it inhibits the parasympathetic vagus nerve.

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

Because the cardiac muscle is only able to depolarize after it repolarizes because of its long refractory period, so the extrasystole is not able to occur until the relaxation period.

Describe how calcium channel blockers are used to treat patients and why?

Calcium channel blockers play a role by blocking the movement of calcium. Because there is less calcium, there is a decreased rate of depolarization and a decreased force of contraction. This also means that the blood pressure will be lowered, so this can be used in patients with high blood pressure.

Distinguish between cholinergic and adrenergic chemical modifiers. Include examples of each in your discussion.

Cholinergic chemical modifiers bind to ACh receptors. Both pilocarpine and atropine are cholinernic chemical modifiers. Adrenergic chemical modifiers bind to adrenoceptors (for epinephrine and norepinephrine). The epinephrine in the experiment was an adrenergic chemical modifier.

Explain the effect that decreasing the temperature had on the frog heart. How do you think the human heart would respond? How well did the results compare with your prediction?

Decreasing the temperature slowed the heart rate of the frog. The same thing would most likely happen in a human. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Describe the benefits of administering digitalis.

Digitalis decreses heart rate and increases stroke volume and force of contraction. This can be helpful in a medical sense for people who are suffering from heart defects or heart failure. They need the maximum amount of time for venous return so that their hearts can keep up with the workload that the body is giving them. These patients would also benefit from increased contraction force so that their blood pressure doesn't get too low due to their weak heart.

What effect does potassium have on the resting membrane potential of the cardiac cell?

Increasing extracellular potassium causes the resting membrane potential to become more positive.

Describe the effect that increasing the calcium ions had on the heart in this activity. How well did the results compare with your prediction?

Increasing the calcium ions increased both the heart rate and the force of contraction. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Describe the effect that increasing the potassium ions initially had on the heart in this activity. Relate this to the resting membrane potential of the cardiac muscle cell. How well did the results compare with your prediction?

Intially, the effect of an increase in K+ ions was that the heart slowed significantly. It can be inferred that if the heart was exposed to a high enough concentration of potassium ions, it would stop. This is because potassium works against action potentials by making the membrane potential less polarized. (Usually potassium is in a higher concentration outside of the cells than inside the cells). ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Muscarine is a poison found in poisonous mushrooms. Muscarine binds to acetylcholine receptors and mimics its action. Which of the following describes the effect of muscarine?

Like pilocarpine, it decreases the heart rate.

Describe why Ringer's solution is required to maintain heart contractions.

Ringer's solution contains ions and electrolytes. When a heart taken out of the body is put in Ringer's solution, it will continue to beat for a little while longer until it runs out of energy because they allow action potentials to continue occuring.

Explain two ways that the heart can overcome excessive vagal stimulation.

The Purkinje fibers in the heart can initiate a heart rhythm in order to overcome excessive vagal stimulation. Sympathetic reflexes can also contribute to vagal escape.

Explain why the amplitude of the wave did not change when you increased the frequency of the stimulation. How well did the results compare with your prediction?

The amplitude did not change with frequency because the heart has a long stimulation refractory period. This prevents wave summation because if the heart did not have this refractory period then it could become tetanic and cramp up. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Explain the effect that increasing the temperature had on the frog heart. How do you think the human heart would respond? How well did the results compare with your prediction?

The effect of increasing the temperature was that the heart rate of the frog increased. It would most likely have the same effect on humans (such as the heart rate increasing when a human has a high fever). This is what I predicted would happen. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

If the human heart were experiencing hyperthermia, what do you think would be the effect on the heart rate?

The heart rate would increase.

Explain why the larger waves seen on the oscilloscope represent ventricular contraction.

The larger waves represent ventricular contraction because the ventricles of the heart are much stronger than the atria. The atria only have to pump blood a short distance away from them, while the ventricles are responsible for pumping blood all around the body. Therefore, they have to pump with more force.

What do you think would happen to the heart rate if the vagus nerve was cut?

The sinoatrial nerve would most likely take over its role. Because the vagus nerve is responsible for slowing the heart rate, the heart would beat faster after the vagus nerve is severed.

Describe how the sympathetic and parasympathetic nervous systems work together to regulate heart rate.

The sympathetic nervous system works to increase the heart rate because it is working during stressful times ("fight or flight" response situations). The parasympathetic nervous system works to relax and destress the body after the fight or flight situations, lowering the heart rate.

Explain why wave summation and tetanus are not possible in cardiac muscle tissue. How well did the results compare with your prediction?

Wave summation and tetanus are not possible in cardiac muscle tissue because cardiac cells have longer action potentials and a very long refractory period compared to other cells. This helps prevent the heart from cramping and seizing up. I had predicted that these were not possible in cardiac muscle. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

Explain the effect that extreme vagus nerve stimulation had on the heart. How well did the results compare with your prediction?

When the vagus nerve is stimulated, it decreases the heart rate. Because the stimulus was so frequent on the nerve, the heart rate continued to lessen until the heart stopped beating. ((Remember to put whether or not you predicted this correctly according to the questions in the virtual lab!))

When the ventricles beat rapidly in succession, _______.

a compensatory pause followed

Excessive vagal stimulation of the heart will result in _______.

a decrease in heart rate and, eventually, a temporary cessation of the heartbeat

Research shows that in the absence of neural and hormonal influences, the SA node generates action potentials at a frequency of about 100 times per minute. However, the resting heart rate is about 70 beats per minute. What would the approximate heartrate be if the vagus nerve were severed?

about 100 beats per minute

Which of the following decreases the rate of depolarization in the heart?

acetylcholine

The sinoatrial node has receptors for _______.

acetylcholine, epinephrine and norepinephrine

The doublet that results with more frequent stimulation of the frog heart represents _______.

an extrasystole and an extra contraction of the ventricles

An adrenergic drug that worked in opposition to epinephrine would _______.

be an antagonist and decrease heart rate

Beta blockers are used to treat high blood pressure (hypertension). Which receptors do you think are being blocked?

beta-adrenergic

Modifiers that affect heart rate are _______.

chronotropic

Delivering single shocks in succession to stimulate the frog heart _______.

did not increase the height of the ventricular systole wave

With respect to heart rate, which of the following worked in opposition to each other?

digitalis and atropine

With respect to heart rate, which of the following had the same effect?

digitalis and pilocarpine as well as atropine and epinephrine

For the frog heart, temperature and heart rate are _______.

directly proportional

Which of the following affect heart rate through the use of a cAMP (second messenger) system?

epinephrine and norepinephrine

Organisms that are poikilothermic _______.

have temperature fluctuations that coincide with the external temperature and lack internal homeostatic temperature regulatory mechanisms

The sinoatrial node is located _______.

in the right atrial wall of the human heart

The effect of the sympathetic nervous system on the heart is to _______.

increase the heart rate and increase the force of contraction

The movement of _______________ into the cardiac muscle cell depolarizes the cardiac muscle cell.

sodium and calcium

When the cardiac muscle cell is at rest, the concentration of _____________ is greater on the outside of the cell.

sodium and calcium