Cardio - Physio (Receptors, Circulation, Pressures, Regulation, & Exchange) Flashcards
Pg. 279-281 in First Aid 2014 Sections include: -Atrial natriuretic peptide -B-type (brain) natriuretic peptide -Baroreceptors and chemoreceptors -Circulation through organs -Normal pressures -Autoregulation -Capillary fluid exchange
What releases atrial natriuretic peptide, and in response to what?
Released from atrial myocytes in response to increased blood volume and atrial pressure
What effects does atrial natriuretic peptide have?
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.
What substance contributes to the “aldosterone escape” mechanism, and how?
Atrial natriuretic peptide; Constricts efferent renal arterioles and dilates afferent arterioles via cGMP, promoting diuresis and contributing to “aldosterone escape” mechanism.
What releases B-type (brain) natriuretic peptide, and in response to what?
Released from ventricular myocytes in response to increased tension
Compare/Contrast B-type (brain) natriuretic peptide (BNP) to atrial natriuretic peptide (ANP).
Similar physiologic action to ANP, with longer half-life
What condition is BNP blood test used to diagnose? What is the predictive value of this test like?
BNP blood test used for diagnosing heart failure (very good negative predictive value)
In what form does BNP used as a treatment of heart failure? What is the name of this form?
Available in recombinant form (nesiritide) for treatment of heart failure
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.
See p. 280 in First Aid 2014 for visual at top left
What are 2 receptors related to the cardiovascular system and bp? Give the names, route of transmission, and trigger for each.
(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)
Which baroreceptor responds to hypotension? What is the mechanism of action?
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
What is the mechanism of a carotid massage?
Carotid massage - Increased pressure on carotid sinus => Increased stretch => Increased afferent baroreceptor firing => Increased AV node refractory period => Decreased HR
What is the triad of Cushing reaction?
Cushing reaction (triad of hypertension, bradycardia, and respiratory depression)
What is mechanism by which baroreceptors contribute to Cushing reaction?
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
What are 2 types of peripheral chemoreceptors, and what stimulates them?
Peripheral - carotid and aortic bodies are stimulated by low PO2 (< 60 mmHg), high PCO2, and low pH of blood
What stimulates central chemoreceptors? To what do they not directly respond?
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
Which organ has the largest blood flow? What percentage of cardiac output is it?
Lung; Organ with largest blood flow (100% of cardiac output)
What organ has the largest share of systemic cardiac output?
Liver
What organ has the highest blood flow per gram of tissue?
Kidney
What organ has the largest arteriovenous O2 difference, and why? How does this effect the organ?
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
What is PCWP, and of what is it a good approximation?
PCWP - pulmonary capillary wedge pressure (in mmHg) is a good approximation of left atrial pressure
How does the PCWP compare to the LV diastolic pressure in mitral stenosis?
In mitral stenosis, PCWP > LV diastolic pressure
What instrument is used to measure PCWP? What is another name for this instrument?
Measured with pulmonary artery catheter (Swan-Ganz catheter).
Draw the heart, including its chambers and major vessels and labeling their normal pressures. Also include the label of PCWP.
See p. 280 in First Aid 2014 for visual at bottom of page
What is the value of PCWP?
< 12 PCWP
What is the purpose of autoregulation?
How blood flow to an organ remains constant over a wide range of perfusion pressures
What type of factors determine autoregulation of the heart? Give 3 examples of such factors.
Local metabolites (vasodilatory) - CO2, adenosine, NO
What type of factors determine autoregulation of the brain? Give an example.
Local metabolites (vasodilatory) - CO2 (pH)
What determines autoregulation of the kidney?
Myogenic and tubuloglomerular feedback
What determines autoregulation of the lungs?
Hypoxia causes vasoconstriction
What type of factors determine autoregulation of the skeletal muscle? Give 5 examples of such factors.
Local metabolites - lactate, adenosine, K+, H+, CO2
What is the most important factor determining autoregulation of skin? What exactly does it control?
Sympathetic stimulation most important mechanism - temperature control
What is the function of Starling forces? What are 4 types of Starling forces and the purpose of each?
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
What is the equation for net filtration pressure?
Net filtration pressure = P net = [(Pc - Pi) - (pi c - pi i)]
What makes the pulmonary vasculature unique? How does this differ from other organs?
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.
What is Kf? What property does it effect?
Kf = filtration constant (capillary permeability)
What is Jv? What equation defines it?
Jv = net fluid flow = (Kf)(P net)
What is edema? What are 4 common causes of it (as it relates to capillary fluid exchange)?
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)
Give an example of a condition that involves edema due to high capillary pressure.
High capillary pressure (increased Pc; heart failure)
Give 2 examples of conditions that involve edema due to low plasma proteins.
Low plasma proteins (decreased pi c; nephrotic syndrome, liver failure)
Give 3 examples of conditions that involve edema due to high capillary permeability.
High capillary permeability (high Kf; toxins, infections, burns)
Give an example of a condition that involves edema due to high interstitial fluid colloid osmotic pressure.
High interstitial fluid colloid osmotic pressure (high pi i; lymphatic blockage)
