After a heart transplant, there is no direct connection between the nervous syst

Question

After a heart transplant, there is no direct connection between the nervous system and the heart. However, the cardiac output of patients with heart transplants can vary in response to changes in metabolic demand (for example, cardiac output will increase during exercise).

a. How could this be possible? Explain.

b. Would you expect this regulation of cardiac output to be as efficient as in an
individual who has not had a heart transplant (someone who still has a direct
connection between the nervous system and the heart)? Explain why or why not.

Explanation / Answer

a. Cardiac muscle or heart muscle is a striated muscle formed in the process of myogenesis. So Cardiac muscle is Myogenic (originates from muscle tissue rather than from nerve impulse).

Imp points to be known: The peak oxygen intake presents reduced value in transplanted individuals, related to the surgical technique employed, among factors such as: systolic and diastolic dysfunction, muscular atrophy, metabolic abnormalities as result of the heart failure (that remain after transplant), use of medicine reduce the exercise capacity and sympathetic stimulation as result of the use of immunosuppressive agents. However, the regular physical activity may improve the oxygen intake.

The post-transplantation rest heart rate is high when compared to healthy individuals of same gender and age. However, a progressive delay both to reach maximal heart rate and to its reduction in the recovery period is observed during the exercise. during progressive exercise, the inadequate increase in the heart rate through the release of the surrounding catecholamines leads to the increase in the cardiac output

The cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important indicator of how efficiently the heart can meet the demands of the body.

b. Yes, we expect this regulation of cardiac output to be as efficient as in an
individual who has not had a heart transplant (someone who still has a direct
connection between the nervous system and the heart).

In healthy individuals, cardiac output can increase from 5 to approximately 20 L/min. At rest, man’s cardiac output is approximately 5 L/min . Such an increase can occur in response to maximal metabolic demand by large working muscles during extremely vigorous exercise, as would occur if one was running to escape mortal danger or competing in an especially intense sporting event. In healthy individuals, metabolic rate and cardiac output are closely correlated. The peripheral muscular and metabolic alterations have a substantial impact on the aerobic exercise capacity in Heart Transplanted recipients and that they may have a greater impact than cardiac limitations.

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