Topic 6- Kidney

Question 1

What is selective reabsorption?

Answer 1

-Only certain substances (mostly small molecules are reabsorbed

Question 2

How does selective reabsorption occur? What is the result of this?

Answer 2

-The basal membrane (at the capillary end) actively transports sodium ions out of the cells on the wall of the proximal convoluted tube
-Lowers the sodium concentration inside the cell so they diffuse in from the PCT down their concentration gradient

Question 3

Which molecules in the filtrate are transported out of the PCT into the blood?

Answer 3

-Glucose
-Amino acids

Question 4

What is caused by a decrease in water potential?

Answer 4

-Water transported by osmosis

Question 5

What causes a decrease in the volume of filtrate?

Answer 5

Reabsorption of water and solutes from the filtrate

Question 6

Where does reabsorption occur?

Answer 6

-Distal convulted tubule
-Collecting duct

Question 7

In the DCT and collecting duct 1. __ ions are activley pumped from the filtrate into the 2.____ ___ whereas potassium ions are activley pumped into the 3.____

Answer 7

1.NA
2.Tissue fluid
3.Filtrate

Question 8

What helps to regulate the concentration of NA and K ions in the blood?

Answer 8

-The rate at which they are moved out of the filtrate is varied

Question 9

What is the first step in the counter-current multiplierloop? What is the result of this?

Answer 9

-NA + CL are activley transported out of the ascending limb
-Raises the concentration of NA and CL in the tissue fluid

Question 10

What is the 2nd step in the counter current multiplier loop?

Answer 10

-Raised concentration causes the loss of water from the descending loop which concentrates the NA and CL (in the descending limb)

Question 11

What is the 3rd step in the counter current multiplier loop?

Answer 11

-NA and CL ions diffuse out of the concentrated solution

Question 12

Which process leads to the formation of urine?

Answer 12

Ultrafiltration

Question 13

1s step in ultrafiltration

Answer 13

-Increased hydrostatic pressure in the glomerous in the afferent aerteriole (as it is wider) than the efferent

Question 14

2nd step in ultrafiltration

Answer 14

-Blood in the glomerous separates from the lumen of the renal capsule by the cell layers + basement membrane
-Stops large molecules from passing through

Question 15

3rd step in ultrafiltration

Answer 15

-Endothelium of capillary wall has many gaps between cells (in comparison to other capillaries in the body) to allow substanes through (as they are to large)

Question 16

What is the renal capsule wall made up of?

Answer 16

-Epithelial cells with projections on them called podocytes

Question 17

What is the basement membranes made up of?

Answer 17

-A network of collagen + glycoproteins and acts as a filter

Question 18

What is the aim of ultrafiltration?

Answer 18

-All small molcules (water,ureas,glucose,ions,amino acids) are filtered out of the blood into the renal capsule

Question 19

Give some examples of substances that are too large to pass through the barrier?

Answer 19

Red + white blood cells

Question 20

Explain why protein in the urine is often a symptom of chronic high blood pressure?

Answer 20

-Glomerular blood pressure is higher
-Proteins are forced through which causes damage to the capillaries and basement membrane

Question 21

Which hormone is is produced the by the hypothalamus?

Answer 21

Antidirecetic hrmone? (ADH)

Question 22

Where is ADH stored and released from?

Answer 22

The proserior pituatary galnd

Question 23

What is the function of ADH?

Answer 23

Helps to regulate water balance in the body

Question 24

Where is osmorgulation acrried out and by what?

Answer 24

-Osmoreceptors in the hypothalamus

Question 25

Why is ADH secreted?

Answer 25

As a response to the change of water potential in the blood

Question 26

What are the 3 roles of the hypothalamus?

Answer 26

-Controls and regulates thirst -ADH secretion -Osmoregulatory centre

Question 27

Osmoreceptors send 1.___ ___ to the pituatary galnd (effector) which impacts 2.____ secretion

Answer 27

1.Action potenials 2.ADH

Question 28

When does a person become dehydrated?

Answer 28

When water potential in the blood is too low

Question 29

What is the response to dehydration?

Answer 29

Increased ADH secretion

Question 30

When does a person become overhydrated?

Answer 30

When water potential of the blood is too high

Question 31

What is the response to overhydration?

Answer 31

Decreased ADH secretion

Question 32

Explain the response to dehydration?

Answer 32

-ADH secreted into the bloodstream -Travels to the kidneys via the bloodstream -ADH binds to reptors in plasma membranes making up the wall of the collecting duct -Triggers vesicles containing aqauporins to fuse with the cell membrane -Incraesed aqauporin = increased permeability of wall of cllecting duct which increases the reabsorption of water -Water moves from filtrate/urine collecting duct into the tissue fluid/ blood plasma via osmosis

Question 33

What happens as a result of low ADH in urine formation?

Answer 33

-Increasing concentrtion of NACL and urea in tissue fluid -large volumes of dilute urine

Question 34

What happens as a result of high ADH in urine formation?

Answer 34

-Collecting duct wall is permeable to water -allows for osmotic absorption of water by the concentrated tissue fluid in the medulla -Small volumes of concentrated urine produced