CONTROL OF THE HEART
Understanding the concepts presented in this chapter will enable the student to:
Describe the origin and distribution of sympathetic and parasympathetic
nerves to the heart and circulation.
Know the location and function of alpha- and beta-adrenoceptors and
muscarinic receptors in the heart and blood vessels.
Describe the location and afferent connections from the carotid sinus, aortic
arch, and cardiopulmonary baroreceptors to the medulla oblongata.
Describe how carotid sinus baroreceptors respond to changes in arterial pres-
sure (mean pressure and pulse pressure), and explain how changes in barore-
ceptor activity affect sympathetic and parasympathetic outflow to the heart
Describe (a) the location of peripheral and central chemoreceptors; (b) the way
they respond to hypoxemia, hypercapnia, and acidosis; and (c) the effects of
their stimulation on autonomic control of the heart and circulation.
List the factors that stimulate the release of catecholamines, renin, aldosterone,
atrial natriuretic peptide, and vasopressin.
Describe how sympathetic nerves, circulating catecholamines, angiotensin II,
aldosterone, atrial natriuretic peptide, and vasopressin interact to regulate
arterial blood pressure.
Autonomic nerves and circulating hormones
serve as important mechanisms for regulating
cardiac and vascular function. These mechanisms
are controlled hy sensors that monitor blood
pressure (baroreceptors), blood volume (volume
receptors), blood chemistry (chemoreceptors),
and plasma osmolarity (osmoreceptors). Periph-
eral sensors such as baroreceptors are found in
arteries, veins, and cardiac chambers. They have
afferent nerve fibers that travel to the central
nervous system, where their activity is monitored
and compared against a “set point” for arterial
pressure. Deviations from the set point result in
selective activation or deactivation of neurohu-
moral efferent control systems. Sensors located
within the central nervous system (e.g., central
chemoreceptors and osmoreceptors) also interact
with regions within the brain that control neuro-
humoral status. The sensors work together with
the neurohumoral mechanisms to ensure that
arterial blood pressure is adequate for perfusing
otgans. Although the following sections describe
several individual neurohumoral mechanisms,
note that these mechanisms interact together to
ensure cardiovascular homeostasis.
AUTONOMIC NEURAL CONTROL
Autonomic Innervation of the
Heart and Vasculature
Autonomic regulation of cardiovascular func-
tion is controlled by the central nervous sys-
tem. The medulla oblongata located within