Neural regulation of blood pressure - baroreceptor and chemoreceptor reflexes
Date Uploaded: 10/11/2019
Tags: homeworkclinic.com Homework Clinic HWC Neural regulation of blood pressure baroreceptor chemoreceptor aortic arch carotid sinus glossopharyngeal nerves baroreceptors medulla oblongata parasympathetic impulses heart rate myocardial contractility venous tone Vasoconstriction sensory nerve Sympathetic impulses hypoxia hypercapnia
• The nervous system regulates blood pressure with two reflex arcs: baroreceptor and chemoreceptor. ■ Baroreceptors (pressure) and chemoreceptors (chemical) are located in the carotid sinus and aortic arch. • Carotid sinus reflex helps maintain normal blood pressure in brain. • Baroreceptors are stimulated by the changes in the stretch of the carotid sinus wall; nerve impulses propagate from the baroreceptors over glossopharyngeal nerves to the CV center in the medulla oblongata. • Aortic reflex maintains general systolic blood pressure. • Baroreceptors in the wall of the ascending aorta and the aortic arch send impulses over vagus nerves. • If MABP drops, there is less stretch and fewer signals sent to the brain stem. • CV center sends out more sympathetic and fewer parasympathetic impulses. • Decrease in parasympathetic impulses increases heart rate and CO. • Increase in sympathetic impulses increases heart rate, myocardial contractility, venous tone, and CO. • Vasoconstriction of small arteries and arterioles increases SVR. • Increases in both CO and SVR cause MABP to rise back toward normal. • Reflexes also work in the opposite direction. • If MABP increases stretch then sensory nerve impulses increase. • Sympathetic impulses decrease; parasympathetic impulses increase. • Decreases in both CO and SVR cause MABP to lower back toward normal. • Receptors in carotid and aortic bodies detect chemical changes (O2, CO2, and H+') in blood level. • Such conditions as hypoxia (lowered O2), acidosis (increased H+), or hypercapnia (excess CO2) stimulate receptors to send impulses to CV center. • CV center increases sympathetic stimulation to arterioles and veins. • Increases in SVR, CO and venous tone cause MABP to rise back toward normal.
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