Urinary System Physiology 1 Flashcards
What vasculature of the kidney controls glomerular blood flow?
Afferent arteriole
What controls blood flow through peritubular capillaries?
Efferent arteriole
What happens with vasoconstriction of efferent arterioles?
Increased volume of blood into glomerulus –> increased glomerular hydrostatic pressure –> increase in filtration
What is the major role of peritubular capillaries?
Reabsorption
What is the tissue that regulates the concentration of the urine?
Vasa recta
What blood vessels bring blood back to circulation?
Renal venules
What collects the filtrate?
Bowman’s capsule
What part of the nephron is responsible for the majority of reabsorption?
The proximal tubule
Along with the vasa recta this part of nephron is important in controlling the concentration of urine?
The loop of Henle
Where in the nephron is filtrate monitored by osmoreceptors?
Late (convoluted) distal tubule
Which part of the nephron is impermeable to water?
Early/straight distal tuule
Which part of the nephron regulates body sodium and potassium?
Late/convoluted distal tubule
How does the body react to low Glomerular filtration rate?
(1) By causing vasodilation of the Afferent arteriole with release of vasodilator substances that bind to the afferent arteriole.
(2) By causing vasoconstriction of efferent arteriole by release of renin which leads to angiotensin II that binds to and causes vasoconstriction of the efferent arteriole.
What are the effects of angiotensin II?
(1) Local vasoconstrictor
(2) Promotes release of aldosterone
What stimulates renin production?
Decrease in Renal Blood Flow
Decrease in concentration of sodium. Renin is produced by the kidney to convert angiotensinogen to angiotensin II.
An indication of how effectively the kidneys clear or excrete individual substances in the blood is known as what?
Plasma clearance
What gives us a good estimate of GFR?
Plasma clearance of inulin. These substances are not secreted or reabsorbed by the kidney’s nephrons. Thus, GFR (liters of fluid filtered by the kidneys per minute) can be calculated.
Substances moving passively from blood into nephron is known as what?
Filtration
Substances moving actively from blood into nephron is known as what?
Secretion
Substances moving from nephron into blood is known as what?
Reabsorption
How is water reabsorbed?
Via osmosis
Where is most of the water reabsorbed?
Proximal tubule
What follows when sodium is actively reabsorbed?
Chloride
Where in the nephron does aldosterone exert its effect on potassium and sodium?
Convoluted/late distal tubule
Where is the majority of Na+, Cl- and K+ resorbed?
Proximal tubule
What injected substance is a good measure of Renal blood flow due to the fact that there is no resorption and 100% secretion?
PAH, para-aminohippuric acid
What are the effects of aldosterone?
Increased potassium secretion
Increased Sodium reabsorption
H+ excretion
Aldosterone ultimately is trying to increase water volume. Water follows sodium.
What are the major controls of aldosterone?
Angiotensin II
Increased Extracellular concentration of K+
Decreased Extracellular concentration of Na+
Why does measuring creatinine clearance give us an overestimated estimate of GFR?
100% of creatinine that is filtered gets excreted, no reabsorption. But also a small amount gets secreted into the nephron. So final excretion is 110% of what was filtered.
Where does ADH have its effect? What is its effect?
It acts on the late/convoluted distal tubule and collecting tubule by making them permeable to water by inserting water channels into the membrane.
How is dilute urine made?
Blood osmolality is measured by osmoreceptors and the amounts of ADH are controlled accordingly. Low osmolarity and the less ADH released and the more water excreted.
An increase in osmolarity causes what to be released?
ADH
What controls blood osmolality?
The concentration of sodium. Antidiuretic hormone (aka vasopressin) acts on the kidneys to reabsorb water to control the tonicity of fluids in the body.
How does the body respond to increase blood osmolality?
Increased blood osmolality is detected by osmoreceptors in the hypothalamus –> release of ADH and stimulation of thirst
When do we get a craving for salt?
With low blood osmolality. Low blood osmolality means that there’s fewer substances dissolved in the blood. This could be dangerous for the blood cells because the body will try to balance the concentration of solutes with osmosis. This will change the volume and thus shape of the blood cells. Therefore, the body will send signals to ingest more salt to increase that concentration and prevent this damage.
When do we get a desire to drink?
With increased blood osmolality
