Long term control of blood pressure/hypertension Flashcards
How can hypotension be defined in general? What about hypertension? How can you get transient elevations and chronic elevations of arterial pressure?
Low BP of systolic less than 90; sustained elevated arterial pressure of 140/90 or greater;
transient: fever, physical exertion, emotional upset
chronic: heart failure, vascular disease, renal failure, stroke
Define what mediates fast, intermediate, and slow changes in arterial blood pressure
Baroreceptor reflex: cardiac and vascular;
renal actions: PVR;
renal salt and water excretion
What is the predominant mechanism for feedback gain at optimal pressure?
RAA system
How do kidneys act directly and indirectly to maintain long-term blood pressure?
Direct: alter blood volume; RAA system (JGA)
What causes release of renin? What does angiotensin II help stimulate in terms of secretion? What does this product help with in terms of release?
Lowered blood pressure;
aldosterone;
ADH release
How can the RAA system act (2 ways)?
Locally and globally
What determines renin secretion?
- Neural baroreceptors through renal sympathetics to granular cells in JGA
- Intra-renal baroreceptors in aa
- NaCl delivery to macula densa of JGA (too much would inhibit renin secretion)
What can lead to afferent arteriole resistance going down? What can lead to efferent arteriole resistance going up? What do these both promote?
decreased NaCl at macula densa;
Increased renin and A II;
Increased glomerular filtration pressure
What does A II do for PVR, GFR, and blood volume? How can it ultimately affect renin production negatively?
Vasoconstriction (increase PVR);
Constrict mesangial cells and reduce surface area, reducing GFR;
stimulates aldosterone secretion and prox Na-H exchange to increase blood volume;
binds on granular cells (AT-receptor) to lower IC Ca, inhibiting renin
What in the short term maintains a BP setpoint? Long-term?
Baroreceptor reflex;
kidneys
What four “organs” help maintain blood pressure?
Name the factors influencing blood pressure
Heart, bv’s, kidney, brain;
CO, PR, blood volume;
BP = CO x PVR = SV x HR x PVR
What do Na and water do with respect to volume of blood and vascular system?
Adjust the volume of blood to fit vascular system
What determines ECF, and how much does Na make up this substance?
Total osmotic content; 90%
What is the major player in controlling Na content? What else contributes?
A II; some symp nerve activity, ADH, and ANP
On graph of intake or output vs. arterial pressure, what is the 100 mm Hg mark called? What happens with e.g. increased volume or salt?
Equilibrium point; you have negative state where you return towards “normal”
What is the main trigger for reduction in plasma and ECF volume?
Increased blood pressure and increased afferent arteriolar pressure (aim to decrease A II and later increase GFR)
What major factor controls aldosterone? What does it help stimulate in cortical tubules and CD?
A II levels, with minor help from plasma K concentration and ANP;
stimulate Na reabsorption, or about 2% of total filtered sodium
What is ultimately the result of increased renal arterial pressure and increased pressure in the glomerular capillaries on the afferent arterioles?
Constriction, leading to decreased renal blood flow, as well as inhibiting the increase in glomerular capillary pressure
What do natiuretic peptides do? Examples?
What things can enhance Na reabsorption, or decrease it?
Inhibit release of renin, relax afferent arteriole, can help diagnose e.g. CHF;
cortisol, estrogen, GH, TH, insulin;
glucagon, progesterone, PTH
What do baroreceptors assess? Osmoreceptors?
What two components control water excretion and how do they do it?
Vascular fullness vs. plasma osmolality;
proximal (regulate ECF based on BP) and distal (ADH determines)
In the case of change in plasma volume vs decreased osmolality, which wins out?
Plasma volume (ie effects of baroreceptors will trounce effects of osmoreceptors since the priority is VOLUME retention)
What is the primary determinant of long term blood pressure? How do prox nephron and distal nephron differ in their handling of salt and water? What regulates ADH secretion?
Sodium content via its effects on ECF volume;
affects Na and water together in prox, vs. Na by aldosterone and water by ADH in distal;
Baroreceptors vs. osmoreceptors (BP vs. plasma osmolality)
Hypothesis for hypertension is…
abnormal renal sodium handling could result in HTN
What condition can lead to hypernatremia and hypokalemia?
Primary hyperaldosteronism
What can obesity lead to that would result in HTN?
Hyperinsulinemia (smooth muscle proliferation and vasoconstriction; kidneys with more Na reabsorption; heart with greater cardiac output due to SNS)
