Cardiopulmonary Reflexes

They are located in carotid sinus REF: Ganong’s 22nd edition chapter-14, http://en.wikipedia.org/wiki/Low_pressure_receptor_ zones

Baroreceptors can be divided into two categories: high-pressure arterial baroreceptors and low-pressure baroreceptors (also known as cardiopulmonary or volume receptors)

Drinking is regulated by plasma osmolality and ECF volume in much the same fashion as vasopressin secretion. Water intake is increased by increased effective osmotic pressure of the plasma, by decreases in ECF volume

ECF volume also affects vasopressin secretion. Vasopressin secretion is increased when ECF volume is low and decreased when ECF volume is high. There is an inverse relationship between the rate of vasopressin secretion and the rate of discharge in afferents from stretch receptors in the low- and high-pressure portions of the vascular system.

A Bainbridge Reflex is a positive feedback mechanism in which there is a compensatory increase in heart rate, due to a rise in right atrial pressure. It is commonly referred to as an Atrial Reflex.

• Atrial stretch receptors are responsible for this.
• Afferent signals: are carried through the vagus nerves to the medulla of the brain.
• Efferent signals are transmitted back through vagal and sympathetic nerves to increase heart rate and strength of heart contraction.

• Type A receptors react primarily to heart rate but adapt to long-term changes in atrial volume. 
• Type B receptors increase their discharge during atrial distension. 
• C fibers arise from receptors scattered through the atria; these discharge with a low frequency and respond with increased discharge to increase in atrial pressure.