Which of the following would cause a DECREASE in cardiac out

Which of the following would cause a DECREASE in cardiac output (CO)?

1.decreasing thyroid function (thyroxine)

2.suddenly standing up from a supine position

3.heightened use of skeletal muscle

Solution

Answer: DECREASE in cardiac output (CO) would be caused by 1. decreasing thyroid function (thyroxine)

Explaination: Cardiac output (CO), is defined as the volume of blood that is pumped by a heart (by a left or right ventricle) in a minute. The CO values are expressed as dm³/min OR L/min.

Thyroid is an endocrine gland, responsible for the secretion of thyroid hormones (T3: triiodothyronine and T4: thyroxine). In addition the thyroid hormones play a wide range of role for the normal functioning of human body. Among all, one role is for the proper functioning of cardiovascular system. Thyroxine is responsible for the increasing the resting heart rate and contractility of the left ventricular. During hypothyroidism (low level of thyroid hormones i.e. T4) heart rate is decreased and resulting to the reduced CO.