Circulatory receptors and reflexes

Circulatory receptors and reflexes

This is a video on circulatory receptors and reflexes, mainly covering baroreceptors but also others.

ADDITIONAL TAGS:
Baroreceptor: ↑ blood pressure → activate stretch receptors → CNS → autonomic efferents → ↓ BP. Origins:
Aortic arch wall → efferent via vagus → tractus solitarius in medulla
Carotid sinuses (above carotid bifurcation in internal carotid) → small Hering’s nerves → glossopharyngeal nerve → tractus solitarius
Reflexes:
Response to low blood pressure:
Alpha-1 receptors → vasoconstriction
Both arteries (↑ SVR) and veins (↑ blood return to heart)
Beta-1 receptors → increase cardiac activity
Response high blood pressure:
Inhibit vasoconstriction center in medulla → ↓ peripheral resistance
Parasympathetic muscarinic receptors → ↓ HR and mildly ↓ cardiac contractility → ↓ CO
Abdominal compression reflex: baroreceptors → ↑ sympathetic output → constricting abdominal muscle vascular pools → ↑ venous return to the heart
Atrial volume reflex: ↑ atrial stretch → (1) dilation of afferent arterioles to the kidney, (2) ↓ antidiuretic hormone secretion from hypothalamus, and (3) ↑ atrial natriuretic hormone → ↑ loss of fluid via the kidneys.
Bainbridge reflex (atrial heart control reflex): Atrial stretch → sympathetic stimulation → ↑ increased heart rate and contractility
Bezold-Jarisch reflex: Stimulation of chemoreceptors and mechanoreceptors in the left ventricle → parasympathetic response → hypotension, bradycardia, and coronary artery dilation.
Chemoreceptor reflex: ↓ blood pressure and other factors (↓ partial oxygen pressure, ↑ hydrogen ion concentration, and ↑ carbon dioxide) → carotid body and aortic body receptors → glossopharyngeal and vagus nerves → vasomotor centers → ↑ respiratory drive, ↑ parasympathetic activity, and ↑ sympathetic activity if hypoxia is prolonged
Central nervous system ischemic response: Brain ischemia? → ↑ CO2 levels → ↑ sympathetic output → ↑ vasoconstrictor and cardiac function
If ischemia is caused by ↑ intracranial pressure → sympathetic → arterial baroreceptors → reflexive decrease in heart rate
Cushing’s reflex: ↑ ICP, ↑ BP, ↓ HR
Oculocardiac reflex: ↑ ocular pressure → stretch receptors → ciliary nerve, ophthalmic division of the trigeminal nerve, and then trigeminal nerve to the trigeminal ganglion → vagus nerve → ↑ parasympathetic → ↓ heart rate.