3.7 Homeostasis and the kidney

Question 1

What is the definition of homeostasis?

Answer 1

Mechanisms by which a constant internal environment is achieved

Question 2

What are 3 factors controlled by homeostasis?

Answer 2

Temperature, blood glucose and water levels

Question 3

What is negative feedback?

Answer 3

Increase causes a decrease in production and vis versa

Question 4

What are the 3 stages in the negative feedback loop?

Answer 4

Detector, Controller and effector

Question 5

What detects low water levels?

Answer 5

Osmoreceptors in the hypothalamus

Question 6

What controls Water levels and how?

Answer 6

Posterior lobe of the pituitary gland release ADH

Question 7

What effects the water levels of the blood?

Answer 7

The permeability of the walls of the collecting ducts

Question 8

What are the 2 functions of the kidney?

Answer 8

excrete urea and control and regulate water and ion levels

Question 9

What processes occur in the nephron?

Answer 9

Ultrafiltration, selective reabsorption, secretion

Question 10

What structures are present in the nephron?

Answer 10

Bowman’s capsule, loop of Henle, distal convoluted tubes, collecting duct

Question 11

What is urea?

Answer 11

Toxic waste product formed from deaminated amino acids

Question 12

Where does ultra filtration occur?

Answer 12

The bowman’s capsule

Question 13

What is the function of the Ureter?

Answer 13

Transport urine from the kidneys to the bladder

Question 14

What is the medulla?

Answer 14

inner part of the kidney, contains loop of Henle

Question 15

What is the cortex?

Answer 15

Outer part of the kidney, contains glomeruli and bowmans capsules

Question 16

What are the adaptations for ultra filtration? (3)

Answer 16

Hydrostatic pressure (created by the narrowing from the afferent to efferent capillaries) Basement membrane of capillaries acts as a selective barrier, inner layer of podocytes allow movement of small molecules

Question 17

What is ultrafiltration?

Answer 17

non selective filtering of small soluble molecules from the blood plasma

Question 18

Where does selective reabsorption occur?

Answer 18

Proximal convoluted tubule

Question 19

How is the PCT adapted for selective reabsorption?

Answer 19

Microvilli, tight junction (preventing seepage), capillaries maintain conc gradient, short diffusion pathway, abundant mitochondria (good ATP supply)

Question 20

How are glucose and amino acids reabsorbed?

Answer 20

Secondary active transport using co-transport with sodium

Question 21

How are mineral ions reabsorbed?

Answer 21

Active transport

Question 22

How is water reabsorbed?

Answer 22

Osmosis

Question 23

How are proteins reabsorbed?

Answer 23

diffusion

Question 24

What is the glucose threshold?

Answer 24

reabsorption is limited by the number of proteins available for facilitated diffusion

Question 25

What are the functions of the descending limb in the loop of Henle?

Answer 25

highly permeable to water
Na+ and Cl- ions enter via facilitated diffusion

Question 26

What are the functions of the accending limb in the loop of Henle?

Answer 26

Impermeable to water
Pumps out Na+ and Cl- ions (first by facilitated diffusion then by active transport)

Question 27

What is the function of the loop of Henle?

Answer 27

To create a low water potential in the medulla

Question 28

What is secondary active transport?

Answer 28

Coupling of diffusion down a conc gradient providing energy for active transport

Question 29

How is a sodium gradient created in the sodium potassium pump?

Answer 29

Na+ actively transported out of epithelial cells to intercellular space
Na+ concentration is reduced creating a gradient between the lumen of the nephron and the epithelial cytoplasm

Question 30

How does Sodium enter the blood?

Answer 30

1 glucose molecules and 2 sodium ions bind to a transport protein in cuboidal epithelium
They are carried into the cell by facilitated diffusion
Na+ diffuses into the capillary

Question 31

How does Glucose enter the blood?

Answer 31

Energy provided by sodium diffusion allows glucose to enter the blood by active transport

Question 32

How do aquaporins work?

Answer 32

Bind to collecting duct osmoreceptors and incorporate via vesicles into the membrane
this creates pores allowing water molecules to pass thorough the membrane in single file down a gradient

Question 33

What do aquatic animals excrete?

Answer 33

Ammonia

Question 34

How do aquatic animals excrete waste?

Answer 34

ammonia dissolves and is dilulted and quickly diffuses across the gills

Question 35

What do birds and insects excrete?

Answer 35

Uric acid

Question 36

Why do birds and insects excrete uric acid?

Answer 36

low toxicity for infants in eggs
lightweight to aid flight
low water requirements to excrete (large energy cost)

Question 37

What do mammals excrete?

Answer 37

Urea

Question 38

Why do mammals excrete Urea?

Answer 38

Less toxic than ammonia
can be tolerated for short periods

Question 39

What causes kidney failure? (5)

Answer 39

Diabetes
high blood pressure
auto immune disease
infection
crushing injuries

Question 40

How does diabetes cause kidney failure?

Answer 40

high glucose levels scars the glomerulli

Question 41

How does high blood pressure cause kidney failure?

Answer 41

damages the capillaries preventing ultra filtration

Question 42

What are 5 treatments for kidney failure?

Answer 42

Dietary restrictions on salt and protines
Blood pressure drugs
Potassium and calcium level drugs
Dialysis
transplants