Intro to Renal Physiology Lecture Sep 18

Question 1

What are the roles of the renal system?

Answer 1

Regulate extracellular fluid volume and blood pressure

Regulate osmolarity

Maintain ion balance

Regulate pH

Excrete waste (urea is the big one)

Produce hormones (such as erythropoeitin)

The first part are involved in homeostasis

Question 2

What are the organs involved in the urinary system?

Answer 2

kidneys

ureters

bladder

Question 3

What is the functional cell of the kidney?

Answer 3

the nephron

Question 4

Describe the basic anatomy of a kidney

Answer 4

It is surounded by a capsul

THe next inner layer is the cortex where the nephron glomerulus are

Beneath the cortex is the medulla where the tubules are located

THe tubules dump into the renal pelvis which dumps into the ureter

Question 5

Where does filtration occur in the nephron?

WHere does reabsorption occur in the nephrone?

In other words, wha tis the general anatomy of a nephron?

Answer 5

Filtration occurs through the glomerulus in bowman’s capsule.

Reabsoprtion occurs through the tubules, including the proximal tubule, the loop of henle (descending and ascending), the distal tubule, and the collecting duct

Question 6

The glomerulus has an afferent arteriole (bringin blood in) and an efferent arteriole (bringing blood out). What will happen to filtration if the afferent arteriole is constricted? WHat will happen to filtration if the efferent arteriole is constricted?

Answer 6

If the afferent arteriole constricts, filtration will decrease because the blood flow to the kidney goes way down.

If the efferent arteriole constricts, the blood builds up in the glomerulus and filtration increases.

Question 7

WHat happens to blood after it is filtered in the glomerulus?

Answer 7

THe blood will enter a portal system within the renal medulla and participates in the reabsorption of fluid from the tubules and loop of henle.

Question 8

WHere are most ions and salts reabosrbed from the filtrate?

What part of the nephron has the MOST water reabsoprtion?

Answer 8

Na+ and other ions are mostly reabsorbed in the proximal tubule

THe collecting duct is where most of the water is reabsorbed

Question 9

What is the urine production rate?

Answer 9

Glomerular filtration rate - tubular reabsoprtion rate

So filtration - reabsprtion

it makes intuitive sense

Question 10

WHat is the normal glomerular filtration rate in a day?

What is the normal urine production rate in a day?

Answer 10

180 L/day

1-2 L/day

SO MUCH GETS REABSORBED!

Question 11

What does urinary excretion of a substance depend on?

Answer 11

It depends on its filtraiton, reabsorption and secretion

Amount of solute excrete = amount filtered - amount reabsorped + amount secreted

Question 12

How is glucose handled by the nephron?

Answer 12

Glucose is small enough to pass trhough into the filtrate. The more glucose there is int he blood being filtered, the more glucose there will be in the initial filtrate.

In the tubules, reabsoprtion occurs via active transport (remember that the body wants to hand onto its glucose)

However, this reabsorption can be maxed out. The upper limit is 300 mg glucose/100 ml. At that level the transporters are swamped and whatever glucose is in excess of that will not be reabsorbed

This results in glucose leaving the body in the urine.

This is what occurs in diabetes

Question 13

How does the kidney exert renal control over blood volume and blood pressure?

Answer 13

The kidney cntrols sodium and water excretion, thus affecting blood volume and pressure.

Question 14

WHat is the kidney’s response/body’s response to salt intake?

Answer 14

After ingesting salt, the osmolarity of the plasma increases.

1. This results in thirst, which results in water intake
2. It also results in secretion of vasopressin which increases renal water absoprtion
3. These two things serve to increase the water content in the body as a way of maintaining osmolarity in the event of increased salt intake.
4. However, this increase in ECF volume increases blood pressure which isn’t a good thing.
5. THe body has two ways to deal with this: a fast way and a slow way.
6. In the fast way, the cardiovascular refleses lower blood pressure
7. In the slow way, the kidneys excrete more salt and water
8. These two responses serve to normalize the blood pressure (and keep the osmolarity normal)

Question 15

When is vasopressin/antidiuretic hormone secreted?

WHat does it do?

Answer 15

ANtidiruetic hormone is secreted by the posterior pituitary gland when osmolarity of the blood increases.

THis promotes water retention in the kidneys, which will normalize osmolarity but increase blood pressure.