Final answer:
During exercise, there is an increase in cardiac output due to an increase in heart rate and stroke volume. Activation of the sympathetic nervous system and the release of hormones contribute to these changes. Blood flow is selectively directed to certain organs while reduced to others.
Step-by-step explanation:
During exercise, there are several changes that occur in the cardiovascular system. One of the major changes is an increase in cardiac output, which is the amount of blood pumped by the heart per minute. This increase is achieved through an increase in heart rate and stroke volume.
Specific efferent mechanisms that account for the changes in cardiac output include the activation of the sympathetic nervous system. The sympathetic nerves release norepinephrine, which increases heart rate and contractility, leading to an increase in stroke volume. Another mechanism is the release of hormones such as epinephrine and norepinephrine from the adrenal glands, which further increase heart rate and contractility.
Additionally, during exercise, there is selective vasodilation in the skeletal muscles, heart, lungs, liver, and integument, which increases blood flow to these organs. At the same time, vasoconstriction occurs in the vessels leading to the kidneys and most of the digestive and reproductive organs, reducing blood flow to these organs.