Regulation of BP Flashcards
Which two parameters are closely regulated that are involved in blood pressure and volume homeostasis?
- ECF volume
2. Extracellular osmolality
Which ion is the major determinant of ECF volume? Which organ regulates this?
Na+ content is controlled by the kidney
What do low pressure sensors monitor? Where are they located?
They monitor the effective circulating volume (the blood that is perfusing tissues). They are located in the pulmonary artery, atrial/venous input junctions, in the atria and ventricles, afferent arterioles of the kidneys, in the liver, and in the CNS.
Name the four pathways of circulatory volume regulation.
- Renin-angiotensin-aldosterone system
- Sympathetic stimulation
- ADH/AVP
- ANP
Which is more sensitive: high pressure receptors or low pressure receptors?
Low pressure receptors
Describe the renin-angiotensin-aldosterone system.
JG cells in the kidneys make renin in response to low BP –> cleavage of angiotensinogen (made by liver) –> angiotensin I.
Angiotensin I is cleaved by ACE (made by lungs) –> angiotensin II
Angiotensin II acts on the hypothalamus (thirst and ADH), adrenal glands (aldosterone), and kidneys (decreased sodium and water excretion), and peripheral vessels (vasoconstriction).
What does SNS stimulation do to the kidneys that increase BP?
- Increased vascular resistance –> decreased GFR, decreased Na+ excretion.
- Stimulates renin release
- Activates a-adrenergic receptors on the renal tubule to increase Na+ reabsorption.
What does ADH aka arginine vasopressin (AVP) do?
Acts on cells in the collecting duct to express aquaporin channels and reabsorb water.
What does ANP do?
Promotes natriuresis (sodium excretion by the kidneys) to lower BP.
What happened when they abruptly gave that dude 150 mmol of sodium per day?
His urinary Na+ excretion gradually increased until it matched the intake, and his total body sodium content did not increase further. He gained 1 kg of weight in water to keep his ECF osmolality the same despite having more total body sodium (this ECF expansion is what told the kidney to excrete more Na+).
Where are osmoreceptors located? What do they do?
They are in the hypothalamus. They are stimulated when there is increased plasma [Na+], and they tell the supraoptic nuclei in the hypothalamus to make more ADH/AVP –> increase water reabsorption by the collecting duct –> decreased ECF osmolality.
There is also a second group of osmoreceptors that trigger thirst.
What is glomerotubular balance?
The balance between reabsorption of solutes and glomerular filtration, which must be as constant as possible. If the glomerular filtration rate rises or falls, the rate of tubular reabsorption must rise or fall proportionally.
Compare what really happens to sodium excretion as GFR rises above, and falls below the ideal glomerulotubular balance line.
As GFR increases above the ideal level, sodium excretion rises disproportionally higher. As GFR decreases below the ideal level, sodium excretion drops disproportionally.
What happens to heart rate when you have depleted effective circulating volume? What about when you have increased circulating volume? What receptors are responsible for each reflex?
Depleted volume: tachycardia is induced from decreased stretch of high-pressure arterial receptors (callbed the Baroreceptor reflex).
Increased volume: tachycardia is induced from increased stretch of low-pressure atrial receptors (called the Bainbridge reflex).
The majority of cases of hypertension in the U.S. are classified as ________, meaning that there is no discernible cause.
essential
