Control Of Cardiac Output & Arterial Pressure

Front 1

What is the physiologic definition of hypertension?

Back 1

sustained diastolic pressure > 89mmHg
sustained systolic pressure > 139mmHg

Front 2

What is the equation to calculate mean arterial pressure?

Back 2

CO x TPR

Front 3

What factors alter stroke volume?

Back 3

1. contractility
2. afterload
3. preload

Front 4

What factors alter cardiac output?

Back 4

1. Heart rate
2. Stroke volume

Front 5

What alters heart rate?

Back 5

Autonomic Nervous System

Front 6

What is the formula to calculate cardiac output?

Back 6

CO = HR x SV

Front 7

What determines total peripheral resistance? what is the most important factor?

Back 7

1. vessel radius <--- most important
2. vessel length
3. viscosity

Front 8

How do you alter vessel radius?

Back 8

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)

Front 9

What alters blood viscosity?

Back 9

Hematocrit, inc. hematocrit causes inc. viscosity

Front 10

What mechanism do baroreceptors detect in vessels?

Back 10

stretch

Front 11

Where are the high pressure baroreceptors located in the body? what do they respond to?

Back 11

High pressure baroreceptors are located at the carotid sinus and the aortic arch

detect increases in "stretch" of the vessel

Front 12

What effect does increasing "stretch" have on baroreceptors/mechanoreceptors?

Back 12

Causes an increased number in AP generation rate in these baroreceptors

Front 13

Where are low-pressure baroreceptors located? what do they respond to?

Back 13

In low-pressure sites such as the atria

Respond to "fullness" of the circulation due largely to an increase in venous return

Front 14

Where do afferent APs generated by the carotid sinus/body travel through?

Back 14

The sinus nerve which joins the glossopharyngeal trunk (CNIX)

Front 15

Where do afferent APs generated by the aortic arch/body travel through?

Back 15

The vagus nerve (CNX) which joins the superior laryngeal nerve => or inferior ganglion of the vagus

Front 16

Where is the pressure coordinating center?

Back 16

Medulla

Front 17

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?

Back 17

Nucleus tractus solitarius

Front 18

Where does the nucleus tractus solitarius send interneurons?

Back 18

sends neural projections via interneurons to the vagal PNS, vasomotor areas, cardioacceleratory areas

Front 19

What areas contain the cell bodies of the efferent vagal PNS cardiac nerves?

Back 19

Excitatory interneurons to cardioinhibitory or cardiac decelerator areas

Front 20

What cell bodies do inhibitory neurons to vasomotor areas contain?

Back 20

A1 and C1 areas that contain cell bodies of efferent SNS nerves that innervate the heart and arterioles/veins

Front 21

What cell bodies do inhibitory interneurons to cardioacceleratory areas contain?

Back 21

At the dorsal medulla that contain neurons that innervate the heart,

Front 22

What does activation through inhibitory interneurons to cardioacceleratory nerves do?

Back 22

Inhibits the cardiac accelerator which is responsible for speeding up HR and increasing contractility through the SNS

Front 23

What does activation through the inhibitory interneurons to vasomotor areas do? where are these areas?

Back 23

A1 and C1 areas; responsible for vasoconstriction of arteries and veins through the SNS

Front 24

What do excitatory interneurons to cardioinhibitory or cardiac decelerator areas do?

Back 24

contain vagal PNS cardiac nerves, this activates the cardiac decelerator which inhibits the SA node

Front 25

What effect would hypovolemia have on baroreceptors? what would be the response?

Back 25

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

Front 26

What effect does tachycardia and inc contractility have on the heart?

Back 26

increases cardiac output

Front 27

What effect does vasoconstriction have on resistance?

Back 27

increases TPR

Front 28

What effect does increased cardiac ouput and increased TPR have on pressure?

Back 28

increases pressure

Front 29

What effect does inc sympathetic activity to the splanchnic venoconstriction/vasoconstriction have?

Back 29

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

Front 30

What is released from the adrenal medulla as a result of SNS activity?

Back 30

epinephrine

Front 31

What effect does increased SNS activity have on renal arterioles?

Back 31

Inc. SNS activity leads to vasoconstriction of renal arterioles, dec. renal blood flow and urine output

Front 32

What effect does arteriolar vasoconstriction have on diffusion?

Back 32

decreases capillary pressure => osmotic reabsorption of interstitial fluid => inc. blood volume

Front 33

What effect do angiotensin II and aldosterone have?

Back 33

ANGII: increases resistance by contributing to vasoconstriction

Ald: promotes salt/water reabsorption => corrects hypovolemia

Front 34

What do peripheral chemoreceptors detect?

Back 34

Changes in PO2, PCO2 and pH

Front 35

What nerve do peripheral chemoreceptors send impulses to the NTS through?

Back 35

CN IX (glossopharyngeal)

Front 36

When do peripheral chemoreceptors increase their firing rate to the NTS?

Back 36

1. dec. PO2
2. dec. pH
3. inc. PCO2

Front 37

What is the primary effect of peripheral chemoreceptors?

Back 37

Inc. NTS stimulation => inhibition of SNS, activation of PNS => dec. HR

Front 38

What effect does hypocapnia (dec. CO2 in blood) have on chemoreceptors? increased lung stretch?

Back 38

decreases firing rate of APs to the NTS => inc. HR

Front 39

What is the secondary effect of peripheral chemoreceptors?

Back 39

Excite respiratory centers in the medulla; which increases respiratory activity => dec. PCO2 / inc. stretch of pulmonary stretch receptors

Front 40

What will be the effect on the NTS if breathing is blocked?

Back 40

Significant bradycardia will result

Front 41

Where are central chemoreceptors located? what do they sense?

Back 41

Located in the medulla and sense low brain pH

Front 42

What does activation of central chemoreceptors do?

Back 42

Increases rate and depth of respirations => dec. PCO2 and inc. stretch of pulmonary stretch receptors => inhibits cardiac PNS/vagal centers in medulla => inc. HR

Front 43

What is the effect of combined excitation of peripheral and central chemoreceptors?

Back 43

Increased HR

Front 44

What is the primary effect of peripheral chemoreceptors if respiratory activity drops? what nerve conducts the info?

Back 44

Bradycardia via the vagus nervce

Front 45

What is the secondary effect of peripheral chemoreceptors if the pt suddenly starts breathing?

Back 45

Tachycardia b/c if the pt starts breathing the primary effect of peripheral chemoreceptors will be canceled out