Exam 1 Review:  Chapter 19:  Vasomotor Tone and Vascular Reflexes

vasomotor nerves - The diffuse collection of autonomic sympathetic nerves which originate in the lateral horns of thoraco-lumbar spinal segments, pass through the autonomic nerve plexuses, e.g., the sympathetic chain ganglia and the ganglia located in the walls of the great vessels and which deliver sympathetic impulses and release norepinephrine (NE) to the smooth muscle in the walls of all blood vessels.

vasomotor tone - The degree of tension of the smooth muscle within the walls of blood vessels, particularly in the arterial tree, which is controlled by the sympathetic nervous system which releases norepinephrine to stimulate appropriate α and β receptors, and in response to a variety of vasoactive factors (hormones (ADH = antidiuretic hormone and epinephrine=adrenalin), local hormones, and metabolites).

carotid sinus - A dilated area located at the bifurcations of the carotid arteries which contain baroreceptors that function in the control of blood pressure by mediating changes in the heart rate and chemoreceptors (see carotid body definition below) which monitor various parameters of blood such as pH, acidity, and H+ levels.

carotid sinus reflex - One of the autonomic reflexes involved in the regulation of cardiac output and blood pressure; baroreceptors in the carotid sinus are stimulated by the stretching of the walls of carotid artery when blood pressure (and possibly blood volume increase); this sensory information is routed to the parasympathetic cardioinhibitory center within the cardiovascular center of the medulla oblongata which integrates this information to decrease the rate of the heartbeat and the muscular tension in the blood vessels by sending parasympathetic impulses via parasympathetic preganglionic neurons through the vagus nerve (X), the preganglionic neurons synapse with parasympathetic postganglionic neurons which reside near the sino-atrial node and relay the impulses to the sino-atrial node where their neurotransmitter, acetyl choline, directly stimulates the heart to decrease cardiac output to return the circulatory system to a resting homeostasis after the end of episodes of increased muscular activity or fight-or-flight emergencies.

aortic reflex  - One of the autonomic reflexes involved in the regulation of cardiac output and blood pressure; baroreceptors in the aortic sinus are stimulated by the stretching of the walls of carotid artery when blood pressure (and possibly blood volume increase); this sensory information is routed to the parasympathetic cardioinhibitory center within the cardiovascular center of the medulla oblongata which integrates this information to decrease the rate of the heartbeat and the muscular tension in the blood vessels by sending parasympathetic impulses via parasympathetic preganglionic neurons through the vagus nerve (X), the preganglionic neurons synapse with parasympathetic postganglionic neurons which reside near the sino-atrial node and relay the impulses to the sino-atrial node where their neurotransmitter, acetyl choline, directly stimulates the heart to decrease cardiac output to return the circulatory system to a resting homeostasis after the end of episodes of increased muscular activity or fight-or-flight emergencies.

Marey's law of the heart - The blood pressure in the carotid arteries leading to the brain is inversely proportional to heart rate; thus if carotid artery pressure falls heart rate will rise in an attempt to return adequate blood flow to the brain.

right heart (atrial) reflex = Bainbridge reflex - One of the autonomic reflexes involved in the regulation of cardiac output and blood pressure; baroreceptors detect  increased pressure in the right atrium which is relayed to the cardiovascular center in the medulla, then, specifically, the cardioaccelerator center sends sympathetic impulses along the autonomic nerve plexuses, e.g., the sympathetic chain ganglia and the ganglia located in the walls of the great vessels, to release norepinephrine at the SA node which increases heart rate and force of contraction.

carotid body - The structure containing a group of chemoreceptors located near the bifurcations of the carotid arteries which monitor changes in the oxygen and CO2 content and pH of the blood and relay that sensory information to the hypothalamus and brain stem to help them control cardiovascular and respiratory functions; other cells in the carotid body respond to blood temperature and to certain chemicals, e.g., nicotine and cyanide.

aortic body - The structure containing a group of chemoreceptors located in the arch of the aorta which monitor changes in the oxygen and CO2 content and pH of the blood and relay that sensory information to the hypothalamus and brain stem to help them control cardiovascular and respiratory functions.

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