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45 Cards in this Set
- Front
- Back
What is the physiologic definition of hypertension?
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sustained diastolic pressure > 89mmHg
sustained systolic pressure > 139mmHg |
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What is the equation to calculate mean arterial pressure?
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CO x TPR
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What factors alter stroke volume?
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1. contractility
2. afterload 3. preload |
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What factors alter cardiac output?
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1. Heart rate
2. Stroke volume |
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What alters heart rate?
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Autonomic Nervous System
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What is the formula to calculate cardiac output?
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CO = HR x SV
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What determines total peripheral resistance? what is the most important factor?
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1. vessel radius <--- most important
2. vessel length 3. viscosity |
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How do you alter vessel radius?
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1. circulating regulators (angiotensin II, catecholamines)
2. direct innervation (alpha-1, beta-2 receptors) 3. local regulators (N.O., endothelin, hydrogen ion, oxygen/CO2, adenosine, prostaglandins) |
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What alters blood viscosity?
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Hematocrit, inc. hematocrit causes inc. viscosity
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What mechanism do baroreceptors detect in vessels?
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stretch
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Where are the high pressure baroreceptors located in the body? what do they respond to?
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High pressure baroreceptors are located at the carotid sinus and the aortic arch
detect increases in "stretch" of the vessel |
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What effect does increasing "stretch" have on baroreceptors/mechanoreceptors?
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Causes an increased number in AP generation rate in these baroreceptors
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Where are low-pressure baroreceptors located? what do they respond to?
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In low-pressure sites such as the atria
Respond to "fullness" of the circulation due largely to an increase in venous return |
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Where do afferent APs generated by the carotid sinus/body travel through?
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The sinus nerve which joins the glossopharyngeal trunk (CNIX)
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Where do afferent APs generated by the aortic arch/body travel through?
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The vagus nerve (CNX) which joins the superior laryngeal nerve => or inferior ganglion of the vagus
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Where is the pressure coordinating center?
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Medulla
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What area of the medulla receives input from afferent neural pathways and sends neural projections via interneurons to the vagal PNS, vasomotor areas, cardioacceleratory areas?
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Nucleus tractus solitarius
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Where does the nucleus tractus solitarius send interneurons?
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sends neural projections via interneurons to the vagal PNS, vasomotor areas, cardioacceleratory areas
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What areas contain the cell bodies of the efferent vagal PNS cardiac nerves?
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Excitatory interneurons to cardioinhibitory or cardiac decelerator areas
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What cell bodies do inhibitory neurons to vasomotor areas contain?
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A1 and C1 areas that contain cell bodies of efferent SNS nerves that innervate the heart and arterioles/veins
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What cell bodies do inhibitory interneurons to cardioacceleratory areas contain?
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At the dorsal medulla that contain neurons that innervate the heart,
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What does activation through inhibitory interneurons to cardioacceleratory nerves do?
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Inhibits the cardiac accelerator which is responsible for speeding up HR and increasing contractility through the SNS
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What does activation through the inhibitory interneurons to vasomotor areas do? where are these areas?
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A1 and C1 areas; responsible for vasoconstriction of arteries and veins through the SNS
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What do excitatory interneurons to cardioinhibitory or cardiac decelerator areas do?
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contain vagal PNS cardiac nerves, this activates the cardiac decelerator which inhibits the SA node
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What effect would hypovolemia have on baroreceptors? what would be the response?
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hypovolemia => dec arterial pressure => dec stretch of high pressure baroreceptors => dec firing of high pressure baroreceptors => dec sinus nerve activity => dec NTS activity => less inhibition of vasomotor and cardioacceleratory areas => inc. SNS 1=> NE:beta1 in SA increasing HR. 2=> NE:beta1 in AV => inc. conduction velocity through AV/Bundle of HIS. 3=> NE:beta1 in ventricular smooth muscle => inc. cardiac contractility. 4=> NE:alpha1 in arteries => vasoconstriction => inc. TPR. 5=> veins and venules constrict => inc. venous return => inc. preload
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What effect does tachycardia and inc contractility have on the heart?
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increases cardiac output
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What effect does vasoconstriction have on resistance?
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increases TPR
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What effect does increased cardiac ouput and increased TPR have on pressure?
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increases pressure
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What effect does inc sympathetic activity to the splanchnic venoconstriction/vasoconstriction have?
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vasoconstriction => displacement of blood from veins in gut, liver, etc => inc. stressed blood volume => inc. venous return => inc. preload => inc. SV => inc. CO => inc. arterial pressure
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What is released from the adrenal medulla as a result of SNS activity?
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epinephrine
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What effect does increased SNS activity have on renal arterioles?
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Inc. SNS activity leads to vasoconstriction of renal arterioles, dec. renal blood flow and urine output
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What effect does arteriolar vasoconstriction have on diffusion?
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decreases capillary pressure => osmotic reabsorption of interstitial fluid => inc. blood volume
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What effect do angiotensin II and aldosterone have?
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ANGII: increases resistance by contributing to vasoconstriction
Ald: promotes salt/water reabsorption => corrects hypovolemia |
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What do peripheral chemoreceptors detect?
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Changes in PO2, PCO2 and pH
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What nerve do peripheral chemoreceptors send impulses to the NTS through?
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CN IX (glossopharyngeal)
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When do peripheral chemoreceptors increase their firing rate to the NTS?
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1. dec. PO2
2. dec. pH 3. inc. PCO2 |
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What is the primary effect of peripheral chemoreceptors?
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Inc. NTS stimulation => inhibition of SNS, activation of PNS => dec. HR
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What effect does hypocapnia (dec. CO2 in blood) have on chemoreceptors? increased lung stretch?
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decreases firing rate of APs to the NTS => inc. HR
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What is the secondary effect of peripheral chemoreceptors?
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Excite respiratory centers in the medulla; which increases respiratory activity => dec. PCO2 / inc. stretch of pulmonary stretch receptors
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What will be the effect on the NTS if breathing is blocked?
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Significant bradycardia will result
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Where are central chemoreceptors located? what do they sense?
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Located in the medulla and sense low brain pH
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What does activation of central chemoreceptors do?
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Increases rate and depth of respirations => dec. PCO2 and inc. stretch of pulmonary stretch receptors => inhibits cardiac PNS/vagal centers in medulla => inc. HR
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What is the effect of combined excitation of peripheral and central chemoreceptors?
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Increased HR
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What is the primary effect of peripheral chemoreceptors if respiratory activity drops? what nerve conducts the info?
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Bradycardia via the vagus nervce
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What is the secondary effect of peripheral chemoreceptors if the pt suddenly starts breathing?
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Tachycardia b/c if the pt starts breathing the primary effect of peripheral chemoreceptors will be canceled out
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