Page 12, History of Cardiovascular Physiology, Dr. D. Penney

Evidence of the Cardiovascular System:

The cardiovascular system is one system which is plainly evident to us without the use of sophisticated instruments. This contrasts, for example, with the endocrine system. Without dissection, one would not know where the thyroid or pituitary gland is located, or even that it exists.

We can feel our pulse at the radial artery in the wrist or at the carotid artery in the neck. We often sense the heart 'skipping' a beat, usually due to the failure of conduction and the loss of a ventricular contraction. The pause is not so much sensed as is the much stronger contraction following the pause. We have all felt our pulse (= heart rate) racing when we are anxious or while we are exercising.

Graying out or blacking out when one stands up, known as orthostatic hypotension, is a common experience and is normal when it occurs occasionally. We can see the superficial or cutaneous veins in our body, and the way in which they can be 'pumped up' to stand out more clearly, as by flexing a muscle. The jugular, the largest vein in the body stands out in the neck when we do the Valsalva maneuver. Blushing is an emotional reaction, due to the dilatation of cutaneous vessels.

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