Question

While snowboarding at Mammoth Mountain during Winter Break, a Swedish friend suggested the health benefits of sweating in a hot sauna followed by immersing in an ice-cold lake. As a student of physiology, you realized that the hot sauna would cause dilation of cutaneous blood vessels to dissipate body heat. However, when you jump into the cold lake, the same cutaneous vessels would constrict to preserve body heat, causing peripheral vascular resistance to increase abruptly. You were concerned whether your heart could maintain adequate cardiac output to prevent passing out and drowning. Despite your apprehensions, you tried the sauna/lake combination and experienced no harmful effects. Given that the process is safe and cardiac output from the right heart remains constant, answer the following questions:

a) From the left side of the heart, what is the immediate effect in increasing the peripheral resistance on the cardiac output?
b) What mechanisms in the heart makes up for the changes that occurred in part a?

Answer 1

Increasing peripheral resistance causes a decrease in cardiac output from the left side of the heart, but compensatory mechanisms in the heart help maintain an adequate cardiac output.

Step-by-step explanation:

The immediate effect of increasing peripheral resistance on cardiac output from the left side of the heart is a decrease in cardiac output. This is because increased peripheral resistance hinders the flow of blood from the left side of the heart to the rest of the body. As a result, less blood is being pumped out with each heartbeat.

However, the heart has compensatory mechanisms to make up for this decrease in cardiac output. One of these mechanisms is an increase in heart rate. When peripheral resistance increases, the heart rate increases to try to maintain an adequate cardiac output. Additionally, the heart may also increase the force of contraction to compensate for the reduced flow of blood.