205 L5

Question 1

What is the function of the kidney?

Answer 1

Maintains homeostasis of hydration. blood volume and pressure

Question 2

If you drink more water than you need the excess volume is excreted as ——.

If you drink less water than you need, you try and —– the fluid ingested to maintain ——.

Answer 2

If you drink more water than you need the excess volume is excreted as urine.

If you drink less water than you need, you try and reabsorb the fluid ingested to maintain homeostasis.

Question 3

What is the normal intake and out take of the kidney?

Answer 3

2300ml/day

Question 4

What is the outer part of the kidney called?

Answer 4

Cortex

Question 5

What is the inside of the kidney called?

Answer 5

Medulla

Question 6

What is the functional unit of the kidney?

Answer 6

Nephrons

Question 7

The afferent arteriole goes —– the bowman’s capsule.

The efferent arteriole goes —- the bowman’s capsule.

Answer 7

The afferent arteriole goes into the bowman’s capsule.

The efferent arteriole goes out the bowman’s capsule.

Question 8

What are the two types of nephrons?

Whats the difference between them?

Answer 8

Cortical - have small loop of henle’s

Juxtamedullary - long loop of henle’s

Question 9

What is glomerular filtration rate (GFR)?

Answer 9

The rate at which fluid which is virtually free of protein is filtered from the glomerular capillaries into Bowman’s capsule.

Question 10

What is the normal average GFR?

Answer 10

125 ml/min or 144-180L/day

Question 11

Most substances in the plasma are freely filtered so the concentration of the glomerular filtrate in the bowman’s capsule is almost the ——- as the plasma.

As the filtrate passes through the ———, it is modified by both the ———– of water and certain solutes back into the blood as well as by the ——— of substances from the peritubular capillaries into the tubules thereby forming urine

Answer 11

Most substances in the plasma are freely filtered so the concentration of the glomerular filtrate in the bowman’s capsule is almost the same as the plasma.

As the filtrate passes through the nephron, it is modified by both the reabosption of water and certain solutes back into the blood as well as by the secretion of substances from the peritubular capillaries into the tubules thereby forming urine.

Question 12

Subtle changes in —– can lead to relatively —– changes in renal excretion if the tubular ——- remained constant.

Answer 12

Subtle changes in GFR can lead to relatively large changes in renal excretion if the tubular reabsorption remained constant.

Question 13

Subtle changes in —– can lead to relatively —– changes in renal excretion if the tubular ——- remained constant.

Answer 13

Subtle changes in GFR can lead to relatively large changes in renal excretion if the tubular reabsorption remained constant.

Question 14

If the pressure in the ——- is greater than the pressure in the —— you get filtration

Answer 14

If the pressure in the capillaries is greater than the pressure in the capsule you get filtration

Question 15

What pressures make up the GFR?

Answer 15

Hydrostatic pressue

Osmotic pressure

glomerular capillary filtration coefficient

Question 16

When the efferent arteriole constricts there is an increase ——- in the glomerulus resulting in the GFR ——-.

When the afferent arteriole constricts —– fluid will be filtered

Answer 16

When the efferent arteriole constricts there is an increased pressure in the glomerulus resulting in the GFR increasing.

When the afferent arteriole constricts less fluid will be filtered

Question 17

What mechanism of GFR control is described below?

The concentration of —— and —— in the ——- tubule is sensed by the —– —— cells.

If the GFR is high the concentration of — and —- would be —– causing the —- ——- cells to ——. This is sensed by the ——– arteriole and as a result it ———- to ——- the GFR.

If the GFR is low the concentration of — and —-would be —– causing the — —– cells to ——-. This is sensed by the —— arteriole and as a result it ———- to ——- the GFR.

This is a —— feedback system

This is an ——- mechanism and is called ————- Feedback

Answer 17

The concentration of Na and Cl in the distal tubule is sensed by the macula densa cells.

If the GFR is high the concentration of Na and Cl would be high causing the macula densa cells to swell. This is sensed by the afferent arteriole and as a result it vasoconstricts to decrease the GFR.

If the GFR is low the concentration of Na and Cl would be low causing the Macula densa cells to shrink. This is sensed by the afferent arteriole and as a result it vasodilates to increase the GFR.

This is a negative feedback system

This is an intrinsic mechanism and is called tubuloglomerular Feedback

Question 18

Is the afferent or efferent arteriole more innervated by the sympathetic nerves?

Answer 18

Afferent arteriole

Question 19

Sympathetic nerve innervation and GFR.

There are —- types of sympathetic fibres that innervate the kidney.

Type 1 fibres innervate just the —— arteriole, while type 2 innervates —– and ——– arterioles. As a result the —— arteriole is more innervated than the ——- and therefore will ———– more than the ——–, so more blood passes through and doesn’t get ——.

When you want to retain fluid the sympathetic nerve activity ——— and GFR —–.

If you want to get rid of fluid sympathetic nerve activity —— and GFR ——-.

If you lose blood volume there is an ——– in sympathetic nerve activity causing ————, of the ——- arteriole, ——— GFR, increasing —– —-, therefore not allowing a lot of fluid to be ——–.

Increase in fluid consumption causes a ——— in renal sympathetic nerve activity, causing ———- of the ——– arteriole (efferent doesn’t open up much), ——– GFR and all the fluid is filtered into bowman’s capsule

Answer 19

Sympathetic nerve innervation and GFR.

There are 2 types of sympathetic fibres that innervate the kidney.

Type 1 fibres innervate just the afferent arteriole, while type 2 innervates afferent and efferent arterioles. As a result the afferent arteriole is more innervated than the efferent and therefore will vasoconstrict more than the efferent, so more blood passes through and doesn’t get filtered.

When you want to retain fluid the sympathetic nerve activity increases and GFR decreases.

If you want to get rid of fluid sympathetic nerve activity decreases and GFR increases.

If you lose blood volume there is an increase in sympathetic nerve activity causing vasocontriction, of the afferent arteriole, decreaseing GFR, increasing blood pressure, therefore not allowing a lot of fluid to be filtered.

Increase in fluid consumption causes a decrease in renal sympathetic nerve activity, causing vasodilation of the afferent arteriole (efferent doesn’t open up much), increase GFR and all the fluid is filtered into bowman’s capsule

Question 20

Tubular reabsorption

The —- passes along a tube that has ——– that are impermeable to urea.

——- moves into the cell or intercellular space and gets reabsorbed by the ——– capillary.

——- passes through via osmosis because of the higher —- pressure in the —– than in the —— fluid.

The cell has —- Na and —-K due to the ——– ——- in the basolateral membrane.

The cell has a ——— potential of ——.

Answer 20

The filtrate passes along a tube that has aquaporens that are impermeable to urea.

Na+ moves into the cell or intercellular space and gets reabsorbed by the peritubular capillary.

water passes through via osmosis because of the higher osmotic pressure in the lumen than in the interstitual fluid.

The cell has low Na and high K due to the Na/K ATPase in the basolateral membrane.

The cell has a negative potential of -70mV.

Question 21

Secondary active reabsorption

The —— gradient is maintained by the —- ——–.

The ——- ———– cotransporter, ——–, brings ——- and —– into the cell. The ——- then leaves the cell via ——- and gets absorbed into the capillaries.

Answer 21

The sodium gradient is maintained by the Na/K ATPase.

The sodium glucose cotransporter, SGLT, brings sodium and glucose into the cell. The glucose then leaves the cell via GLUT and gets absorbed into the capillaries.

Question 22

In the first 1/4 of the proximal convoluted tubule most of the —– and ——- acids are reabsorbed.

A lot of —— is reabsorbed but the concentration remains the same because —— is being dragged along with it.

Answer 22

In the first 1/4 of the proximal convoluted tubule most of the glucose and amino acids are reabsorbed.

A lot of sodium is reabsorbed but the concentration remains the same because water is being dragged along with it.

Question 23

Glucose filtration

All the glucose gets ——-.

You are trying to ——– the glucose using the —– —— co transporter, but it can only go so fast.

At some point it cannot ——- at a faster rate so it starts ——– down

Once it starts slowing down glucose starts to show in the ——–, dragging ——with it, ——– urine output

At some point your glucose transporter becomes ———, your plasma glucose levels still ———, so you start —— glucose.

Answer 23

All the glucose gets filtered.

You are trying to reabsorb the glucose using the sodium glucose co transporter, but it can only go so fast.

At some point it cannot reabsorb at a faster rate so it starts slowing down

Once it starts slowing down glucose starts to show in the urine, dragging water with it, increasing urine output

At some point your glucose transporter becomes saturated, your plasma glucose levels still increase, so you start excreting glucose.

Question 24

At the end of the proximal tubule

Around –% of the tubular fluid from the glomerulus has been ———-.

This means a decrease from —L/hr to around — L/hr.

There has been no change in ——- concentration because —– passively follows the —–.

All of the ——– and —— acids have been reabsorbed

The tubular fluid is also ——- with the initial filtrate - missing osmoles (sodium) is replaced by ——

Urea concentration is ~ 2-4x higher than it was in the original glomerular filtrate (and ECF of course) because the proximal convoluted tubule is impermeable to urea

Answer 24

Around 80% of the tubular fluid from the glomerulus has been reabsorbed.

This means a decrease from 6L/hr to around 1.2 L/hr.

There has been no change in sodium concentration because water passively follows the sodium.

All of the glucose and amino acids have been reabsorbed

The tubular fluid is also isoosmoitic with the initial filtrate - missing osmoles (sodium) is replaced by urea.

Iso-osmotic; the missing osmoles are made up by urea (the number of osmoles per unit solution is the same at the end of the proximal convoluted tubule as at the beginning even though the total volume is less by about 80%

Urea concentration is ~ 2-4x higher than it was in the original glomerular filtrate (and ECF of course) because the proximal convoluted tubule is impermeable to urea