Final Exam Notes Flashcards
Peritubular capillaries
Surround the nephron so that you can do exchanges between the filtrate that is in the nephron and the blood
Vasa Recta
Peritubular capillaries that surround the loop of Henle
Glomerular Filtration Rate
GFR
Typically about 115-125 ml/min; thats all of them together; that’s how much filtrate you are making per minute
How do you increase your glomerular filtration rate?
By vasodilating the afferent arteriole to have higher blood pressure in blood capillary; you don’t have as much as a pressure drop in the blood vessel; so if you want to increase your GFR you want to increase your blood flow so you dilate the afferent arteriole
How much filtrate gets reabsorbed in the proximal tubule?
About 65% of GFR
What is the job of the distal tubule?
To regulate the salt content of filtrate
The pumping in the proximal tubule is predominantly
A sodium pump
What is the function of the Loop of Henle?
To create a concentration gradient so that the interstitial has a greater osmotic concentration as you move down the tubule. It does not concentrate the fluid
If we are hydrated what do we want for the walls of our collecting duct?
You want them to be impermeable to water so you can get rid of the excess fluid
If we are dehydrated what do we want for the walls of our collecting duct?
We want to save our fluids so we will make the walls of the collecting duct as permeable as possible
How do we adjust the permeability of the collecting duct?
We use the Antidiuretic Hormone
Comes from the Posterior Pituitary Gland
The neurons carry axons down to the pituitary
Antidiuretic causes you to retain water; makes the collecting duct more permeable so water moves out. If the osmotic concentration falls, that inhibits ADH secretion. If the osmotic concentration of your blood rises, that means you lost water, that means your blood is more concentrated than it should be, so you stimulate the production of ADH secretion. If you are dehydrated the ADH won’t make you hydrated again, it will just help you hold onto your water.
How does the Loop of Henle set up a concentration gradient?
The thick ascending limb is impermeable to water and solutes & there’s all types of mitochondria in these cells and ion pumping; sodium ions being pumped out. The thin descending limb of loop of henle is permeable to solutes and water. Fluids primarily will leave the filtrate, making the inside more concentrated. About 20% of the fluid that you produce from the glomerulus is reabsorbed as the filtrate goes through the loop of henle
Job of the Distal Convoluted Tubule
Job is to regulate salt; sodium in the body
Are active transport pumps that pump out sodium
Na+/K+ coupled pump
Hormone Aldosterone
Regulates ion pumping in the distal tubule. Without aldosterone 80% of the remaining Na+ is reabsorbed. With aldosterone 100% of the remaining Na+ can be reabsorbed & potassium will be secreted from the blood to the filtrate. In order to get rid of excess potassium, you need some aldosterone. Also good when your sodium levels are low. Secreted by Adrenal Cortex. Stimulated by high blood [K+], low sodium does NOT stimulate adrenal cortex. Is stimulated by angiotensin II.
Granular Cells
Secrete renin. Do this when the blood flow becomes too low in the afferent arteriole. The cells act like stretch receptors. If the cells are not stretched enough (e.g. low flow, low cardiac output), the granular cells will secrete renin
Angiotensinogen
A plasma protein produced by the liver that is always present in the blood. Is converted into Angiotensin I by Renin
Angiotensin II
An active enzyme in the walls of the pulmonary vessels. Acts on the adrenal cortex & acts as a vasoconstrictor. Causes aldosterone to be secreted which increases sodium pumping leading to more water to be reabsorbed so blood volume will go back up again.
Atrial Natriuetic Hormone
From right atrium. Is in response to an increase in stretching (ie: too much blood volume). It is going to help you get fluid from the body. Helps in fluid removal. Inhibits ADH so dilute filtrate just comes out. Inhibits renin & aldosterone because in combination they help bring sodium from the filtrate and water follows by osmosis and you already have too much water. Increases glomerular capillaries permeability so GFR increases. Greater filtration, greater fluid loss
Juxtaglomerular Apparatus
It is half distal tubule and half afferent arteriole. Within the afferent arterioles are granular cells which secrete renin. Within the distal tubule are macula densa cells
Granular cells
Within the afferent arterioles. Secrete renin
Macula Densa Cells
Within the distal tubule. Are responsive to sodium concentration. They inhibit the granular cells from secreting renin if the sodium concentration is too high
We secrete renin when blood volume is…
When blood volume is low you secrete renin
In our lab what happened when we drank the distilled water?
You diluted your blood by drinking distilled water. The osmotic concentration fell. Hypothalamus sensed a reduction in osmotic concentration, there inhibiting ADH secretion. You want copious quantities of dilute water that you secrete. In the heart it will cause an excess of blood volume, stretching the atria and inhibits ADH, renin, and aldosterone sequence
What happened in the lab if we had the isotonic saline
We did not alter the osmotic concentration. ADH wouldn’t immediately be affected because you didn’t change osmotic concentration but blood volume would increase which would inhibit ADH and the system. You increase copious amounts of dilute urine. The blood volume then comes back normal but without getting rid of the salts your osmotic concentration begins to rise. High sodium filtrate, sensed by macula densa cells, which inhibits renin