Cardio - Physio (Receptors, Circulation, Pressures, Regulation, & Exchange)

Question 1

What releases atrial natriuretic peptide, and in response to what?

Answer 1

Released from atrial myocytes in response to increased blood volume and atrial pressure

Question 2

What effects does atrial natriuretic peptide have?

Answer 2

Causes vasodilation and decreased Na+ reabsorption at the renal collecting tubule. Constricts efferent renal arterioles and dilates afferent arterioles via cGMP, promoting diuresis and contributing to “aldosterone escape” mechanism.

Question 3

What substance contributes to the “aldosterone escape” mechanism, and how?

Answer 3

Atrial natriuretic peptide; Constricts efferent renal arterioles and dilates afferent arterioles via cGMP, promoting diuresis and contributing to “aldosterone escape” mechanism.

Question 4

What releases B-type (brain) natriuretic peptide, and in response to what?

Answer 4

Released from ventricular myocytes in response to increased tension

Question 5

Compare/Contrast B-type (brain) natriuretic peptide (BNP) to atrial natriuretic peptide (ANP).

Answer 5

Similar physiologic action to ANP, with longer half-life

Question 6

What condition is BNP blood test used to diagnose? What is the predictive value of this test like?

Answer 6

BNP blood test used for diagnosing heart failure (very good negative predictive value)

Question 7

In what form does BNP used as a treatment of heart failure? What is the name of this form?

Answer 7

Available in recombinant form (nesiritide) for treatment of heart failure

Question 8

Draw the heart and some of the aortic branches, labeling the locations of: (1) Aortic baroreceptor (2) Aortic chemoreceptor (3) Carotid body chemoreceptor (4) Carotid sinus baroreceptor.

Answer 8

See p. 280 in First Aid 2014 for visual at top left

Question 9

What are 2 receptors related to the cardiovascular system and bp? Give the names, route of transmission, and trigger for each.

Answer 9

(1) Aortic arch transmits via vagus nerve to solitary nucleus of medulla (responds ONLY to high bp) (2) Carotid sinus (dilated region at carotid bifurcation) transmits via glossopharyngeal nerve to solitary nucleus of medulla (responds to low and high BP)

Question 10

Which baroreceptor responds to hypotension? What is the mechanism of action?

Answer 10

Hypotension - low arterial pressure => low stretch => low afferent baroreceptor firing => high efferent sympathetic firing and low efferent parasympathetic stimulation => vasoconstriction, increased HR, increased contractility, increased BP

Question 11

What is the mechanism of a carotid massage?

Answer 11

Carotid massage - Increased pressure on carotid sinus => Increased stretch => Increased afferent baroreceptor firing => Increased AV node refractory period => Decreased HR

Question 12

What is the triad of Cushing reaction?

Answer 12

Cushing reaction (triad of hypertension, bradycardia, and respiratory depression)

Question 13

What is mechanism by which baroreceptors contribute to Cushing reaction?

Answer 13

Contributes to Cushing reaction (triad of hypertension, bradycardia, and respiratory depression) - increased intracranial pressure constricts arterioles => cerebral ischemia and reflex sympathetic increase in perfusion pressure (hypertension) => increased stretch => reflex baroreceptor induced-bradycardia

Question 14

What are 2 types of peripheral chemoreceptors, and what stimulates them?

Answer 14

Peripheral - carotid and aortic bodies are stimulated by low PO2 (< 60 mmHg), high PCO2, and low pH of blood

Question 15

What stimulates central chemoreceptors? To what do they not directly respond?

Answer 15

Central - are stimulated by changes in pH and PCO2 of brain interstitial fluid, which in turn are influenced by arterial CO2. Do not directly respond to PO2

Question 16

Which organ has the largest blood flow? What percentage of cardiac output is it?

Answer 16

Lung; Organ with largest blood flow (100% of cardiac output)

Question 17

What organ has the largest share of systemic cardiac output?

Answer 17

Liver

Question 18

What organ has the highest blood flow per gram of tissue?

Answer 18

Kidney

Question 19

What organ has the largest arteriovenous O2 difference, and why? How does this effect the organ?

Answer 19

Largest arteriovenous O2 difference because O2 extraction is ~80%. Therefore increased O2 demand is met by high coronary blood flow, not by increased extraction of O2

Question 20

What is PCWP, and of what is it a good approximation?

Answer 20

PCWP - pulmonary capillary wedge pressure (in mmHg) is a good approximation of left atrial pressure

Question 21

How does the PCWP compare to the LV diastolic pressure in mitral stenosis?

Answer 21

In mitral stenosis, PCWP > LV diastolic pressure

Question 22

What instrument is used to measure PCWP? What is another name for this instrument?

Answer 22

Measured with pulmonary artery catheter (Swan-Ganz catheter).

Question 23

Draw the heart, including its chambers and major vessels and labeling their normal pressures. Also include the label of PCWP.

Answer 23

See p. 280 in First Aid 2014 for visual at bottom of page

Question 24

What is the value of PCWP?

Answer 24

< 12 PCWP

Question 25

What is the purpose of autoregulation?

Answer 25

How blood flow to an organ remains constant over a wide range of perfusion pressures

Question 26

What type of factors determine autoregulation of the heart? Give 3 examples of such factors.

Answer 26

Local metabolites (vasodilatory) - CO2, adenosine, NO

Question 27

What type of factors determine autoregulation of the brain? Give an example.

Answer 27

Local metabolites (vasodilatory) - CO2 (pH)

Question 28

What determines autoregulation of the kidney?

Answer 28

Myogenic and tubuloglomerular feedback

Question 29

What determines autoregulation of the lungs?

Answer 29

Hypoxia causes vasoconstriction

Question 30

What type of factors determine autoregulation of the skeletal muscle? Give 5 examples of such factors.

Answer 30

Local metabolites - lactate, adenosine, K+, H+, CO2

Question 31

What is the most important factor determining autoregulation of skin? What exactly does it control?

Answer 31

Sympathetic stimulation most important mechanism - temperature control

Question 32

What is the function of Starling forces? What are 4 types of Starling forces and the purpose of each?

Answer 32

Starling forces determine fluid movement through capillary membranes: (1) Pc = capillary pressure - pushes fluid out of capillary (2) Pi = interstitial fluid pressure - pushes fluid into capillary (3) pi c = plasma colloid osmotic pressure - pulls fluid into capillary (4) pi i - interstitial fluid colloid osmotic pressure - pulls fluid out of capillary

Question 33

What is the equation for net filtration pressure?

Answer 33

Net filtration pressure = P net = [(Pc - Pi) - (pi c - pi i)]

Question 34

What makes the pulmonary vasculature unique? How does this differ from other organs?

Answer 34

Note: The pulmonary vasculature is unique in that hypoxia causes vasoconstriction so that only well-ventilated areas are perfused. In other organs, hypoxia causes vasodilation.

Question 35

What is Kf? What property does it effect?

Answer 35

Kf = filtration constant (capillary permeability)

Question 36

What is Jv? What equation defines it?

Answer 36

Jv = net fluid flow = (Kf)(P net)

Question 37

What is edema? What are 4 common causes of it (as it relates to capillary fluid exchange)?

Answer 37

Edema - excess fluid outflow into interstitium commonly caused by: (1) High capillary pressure (increased Pc; heart failure) (2) Low plasma proteins (decreased pi c; nephrotic syndrome, liver failure) (3) High capillary permeability (high Kf; toxins, infections, burns) (4) High interstitial fluid colloid osmotic pressure (high pi i; lymphatic blockage)

Question 38

Give an example of a condition that involves edema due to high capillary pressure.

Answer 38

High capillary pressure (increased Pc; heart failure)

Question 39

Give 2 examples of conditions that involve edema due to low plasma proteins.

Answer 39

Low plasma proteins (decreased pi c; nephrotic syndrome, liver failure)

Question 40

Give 3 examples of conditions that involve edema due to high capillary permeability.

Answer 40

High capillary permeability (high Kf; toxins, infections, burns)

Question 41

Give an example of a condition that involves edema due to high interstitial fluid colloid osmotic pressure.

Answer 41

High interstitial fluid colloid osmotic pressure (high pi i; lymphatic blockage)