The Kidney And Osmoregulation NF

Question 1

what role do the kidneys have?

Answer 1

1. excretion function - removes urea from the body.
2. homeostatic function - main organ of osmoregulation.

Question 2

what is urea?

Answer 2

the nitrogenous waste product from metabolism.

Question 3

what is osmoregulation?

Answer 3

controlling the water potential of the blood within narrow boundaries, regardless of the activities of the body.

Question 4

what are examples of activities that can put osmotic pressure on the body?

Answer 4

• eating a salty meal
• drinking large volumes of liquid.
• exercising hard
• running a fever
• visiting a hot climate.

Question 5

why is it important to keep the water potential of tissue fluid stable?

Answer 5

if water moves into and out of cells by osmosis, it can cause damage and even death.

Question 6

how is water and mineral ions lost?

Answer 6

• sweating
• defaecation
• urine

Question 7

what hormone controls the amount of water lost in urine?

Answer 7

ADH (antidiuretic hormone)

Question 8

what type of feedback system is water lost in the urine?

Answer 8

negative feedback system

Question 9

where is ADH produced?

Answer 9

by the hypothalamus

Question 10

where is ADH stored?

Answer 10

posterior pituitary gland

Question 11

what is the role of ADH?

Answer 11

ADH increases the permeability of the distal convoluted tubule and the collecting duct to water.

Question 12

where does ADH have its effect?

Answer 12

collecting duct.

Question 13

does the hormone cross the membrane of the tubule cells?

Answer 13

no

Question 14

what triggers the formation of cyclic AMP?

Answer 14

when ADH binds to receptors on the cell membrane

Question 15

what is a second messenger?

Answer 15

a molecule which relays signals recieved at cell surface receptors to molecules inside the cell.

Question 16

what is the cascade of events caused by cAMP?

Answer 16

• vesicles in the cells lining the collecting duct fuse with the cell surface membranes on the side of the cell in contact with the tissue fluid of the medulla.
• the membranes of these vesicles contain protein-based water channels (aquaporins) and when they are inserted into the cell surface membrane, they make it permeable to water.
• this provides a route for waer to move out of the tubule cells into the tissue fluid of the medulla and the blood capillaries by osmosis.

Question 17

what are aquaporins?

Answer 17

protein based water channels found in vesicles in the cells lining the collecting dust.

Question 18

what happens when more ADH is released?

Answer 18

more water channels are inserted into membranes of the tubule cells.