Long-Term Regulation of Arterial Pressure - Kidneys Flashcards
Long Tern Regulation of Arterial P
Regulation of extracellular fluid volume
Arterial P Control
1) Short Term Control - Negative Feedback Mechanisms (baroreceptors, chemoreceptors, atrial reflexes)
2) Long Term Control - Balance of fluid intake and output within the kidney (extrcellular fluid volume)
Effects of arterial P on urinary output
1) Inc in arterial P = inc in urinary output = PRESSURE DIURESIS
Inc in arteri P = inc in capillary P = inc in which force of urine is pushed out
Increases until P returns to normal
2) Inc in arterial P = inc in sodium output = PRESURE NATRIURESIS
2 Ways to affect longterm arterial P
1) Changes in renal function curve - rightward shift = higher P needed to secrete same amount of water and ions
2) Salt and Water Intake (inc = inc in arterial P)
Kidney sets ———– ———- AND Baroreceptors ————- ———–
Equilibrium arterial P point
Momentarily shifts arterial P from this point
Conditions that INCREASE long term arterial P
1) INC in renal vascular resistance
2) DEC in number of functional nephrons
BOTH - more P needed to excrete same water and sodium out of the cell
What happens to long-term arterial P if there is an inc in total peripheral resisitance BUT no change in renal resistance
Inc in urinary output, Dec in extracellular fluid volume = Inc arterial P
What happens to long-term arterial P if there is an inc in renal rsistance BUT no change in rtotal peripheral resisitance
Dec urinary output, Inc in extracellular fluid volume = INC arterial P
Hypertension
1) Idiopathic - Not caused by identifiable underlying disease (uncommon in dogs and cats)
2) Secondary - underlying identifiable cause
Secondary Hypertension
1) Primary Hyperaldosteronism
2) Hyperadrenocorticism
Primary Hyperaldosteronism
Retention of sodium and water in kidney
Vasocontriction and increase in total resistance
Prevelence of hypertension in cats with primary hypraldosterone
Incidence is low in dogs
Hyperadrenocorticism
One of the MOST COMMON ENDOCRINE DISORDERS in dogs but RARE in cats
Pituitary tumor secretes adrenocorticotropic hormone causing chronic excess of glucocorticoids
Intrinsic mineralocorticoid activity = acts like aldosterone
Activation of RAS - produces angiotensin II
Enhancement of inotropic and vasoconstrictor actions of agents
Suppression of vasodilators - nitric oxide
Hyperthyroidism
MOST COMMON FELINE ENDOCRINE DISEASE
RARE in dog
Excessive levels of circulating thyroxine
1) dec in vac resis w/ dec in diastolic BP
2) reflex inc in heart, stroke volume and cardiac output
Kidney - decline in renal profusion = stim release of renin
1) renal abs os sodium and water and inc in blood vol
2) inc in pulse P bc inc in systolic P and dec diastolic P
Kidney cannot
regenerate new nephrons
gradual —– of nephrons with age
decrease
