4.1 Homeostasis & Kidney

Question 1

What is Homeostasis

Answer 1

The maintenance of a internal environment e.g interstitial fluid.

Question 2

Example of things in the blood that need to be kept within a narrow limit

Answer 2

• pH
  -Temperature
• water potential
• conc. of sodium, potassium and Calcium ions
• oxygen levels

Question 3

What are the kidneys roles?

Answer 3

Excretion & osmoregulation

Question 4

Excretion ?

Answer 4

Removal of toxic waste products of metabolism. Main one being urea which is produced during the deamination in the liver. As nuclei acids and proteins cause they can’t be stored in the body. Another toxic product is creating which is the product of the break down of creating phosphate in muscles

Question 5

Osmoregulation

Answer 5

Control of water potential of body fluids. As a result the vol. and conc. of urine produced will vary

Question 6

The kidneys fact

Answer 6

• receive blood blood through the renal artery ( this contains blood with high conc. of urea )
• drained by the renal vein
• require a blood supply at high pressures to function if not high enough they will fail.

Question 7

Urine journey

Answer 7

Flows through the kidney int o the ureter and is pushed via peristalsis to the bladder where it is stored, when full, the sphincter muscle at the base relax allowing urine to pass into the urethra.

Question 8

Kidney consists of …

Answer 8

• thin outer covering layer called - renal capsule
• outer cortex
• inner medulla or medulla pyramids
  -millions of nephrons which transverse both the cortex and medulla
  -a central pelvis that the pyramids drain into

Question 9

6 regions of the nephron

Answer 9

• renal corpuscle ( the glomerulus and bowman’s capsule )
  -proximal convoluted tubule
• descending limb of the loop of Henle
• ascending limb of the loop of henle
• collecting duct

Question 10

Glomerulus

Answer 10

Dense net work of capillaries, held in the bowman’s capsule , blood enter via the afferent arteriole and exit via the narrower efferent arteriole to maintain a high hydrostatic pressure.- this helps the filtration via the pores in the golmerulus

Question 11

Bow mans capsule

Answer 11

Cup shaped structure contain the glomerulus,between which there is a capsular space. Inner layer contains cells called PODOCYTES ( that look like a star fish on stilts ). The small slit like holes allow blood plasma through the golmerular pores into the capsular space .

Question 12

Ultrafiltration

Answer 12

Happens on the renal corpuscle, the fluid removed is called the glomerular filtrate, the major differences between glomerular filtrate and blood plasma are that the filtrate DOSE NOT contain blood cells and plasma proteins

Question 13

Glomerular filtrate contains

Answer 13

Glucose , hormones, water , ions ,amino, vitamins , urea, creatinine

Question 14

Hydrostatic pressure and it’s problem one

Answer 14

There is pressure created by remaining plasma proteins in the blood - this pulls fluids back into the blood by osmosis - COLLODIAL OSMOTIC PRESSURE

Question 15

Problem two

Answer 15

Pressure in the capsular space - forces blood back into the glomerulus ( glomerular filtrate pressure)

Question 16

Proximal convoluted tubule

Answer 16

Is reabsorbed in the P.C.T into the blood to ensure that dehydration doesn’t occur

Question 17

Adaptations of the P.C.T

Answer 17

Lining of the tube is covered by epithelial cells which have numerous microvilli. The S.A of the base of the epithelium is increased due to in foldings of plasma membrane . Numerous mitochondria lie between the infolding - these provide the energy required for the Active Uptake of salts and glucose

Question 18

How are Amino Acids and Glucose move

Answer 18

Facilitated diffusion into the cells and are then actively transported into intercellular spaces from where they diffuse into the surrounding capillaries.

Question 19

Solutes uptake -

Answer 19

Make water potential in the blood more negative so 70% of water in the filtrate follows by osmosis

Question 20

Small plasma proteins

Answer 20

Pass through basement membrane via pinocytosis

Question 21

Urea reabsorbed ?

Answer 21

NO, but fluid flows along the tubule and water is removed , urea conc. in the P.C.T increases

Question 22

After PCT there should be no

Answer 22

glucose , amino acids and should be isotonic with blood plasma

Question 23

Descending and Ascending limbs of the Loop of Henle helps

Answer 23

To produce hypertonic urine . Enduring that the filtrate is always coming in contact with more conc. surroundings as it travels into the medulla

Question 24

The ascending limb is

Answer 24

• wider
  -the walls are => lined with cuboidal epithelium cells
  numerous mitochondria
  impermeable to water

Question 25

What does the ascending loop of henle do

Answer 25

Spectres Na+ and Cl- ions into the medulla via Active Transport

Question 26

Why does the A. Loop of Henle secret ions

Answer 26

The NaCl builds up in the interstitial fluid of the medulla and creates a very negative solute potential.

Question 27

What happens when ions are secreted

Answer 27

The filtrate becomes progressively dilute as it ascends , so it is hypotonic by the time it reaches the top of the limb

Question 28

The descending limb is

Answer 28

Narrow

Question 29

The descending limbs wall

Answer 29

Is highly permeable to water

Question 30

What happends to the fluid in this limb

Answer 30

Due to the very negative solute potential in the interstitial fluid surrounding the limb , water is osmotically removed from the limb into the fluid and enters the network of capillaries called the vasa recta removing it from the medulla , there for it has little effect on the solute potential in the interstitial fluid

Question 31

What happens to the filtrate during this process

Answer 31

The filtrate becomes more conc. as it’s moves down the loop, until at the apex of the loop it is hypertonic in the blood

Question 32

What does the vasa recta do

Answer 32

Returns the water to the general circulation of the body , they are highly permeable and slow flowing blood

Question 33

The tissues surrounding the descending limb the water drawn out of this loop via

Answer 33

Osmosis

Question 34

The counter current system in the loop of Henle ensures that filtrate is always coming into contact with more conc. surrounding as it travels deeper into the medulla

Question 35

Countercurrent multiplier effects

Answer 35

Osmotic differences between the descending and ascending. The cumulative effect over the length of limbs and depth of medulla is significant. This together with filtrate moving in opposite directions.

Question 36

Distal convoluted Tubule

Answer 36

pH and the ionic composition of the blood in the capillaries surrounding the tubule are adjusted and some toxic substances eg creating are secreted from the blood into the filtrate for disposal.

Question 37

Collecting duct and osmoregulation

Answer 37

Can be controlled by a hormone called ADH (anti diuretic hormone ) which controls the degree of permeability of the collecting duct walls

Question 38

Negative feedback

Answer 38

Is a response to ensure homeostasis

Question 39

Homeostasis

Answer 39

Makes organisms independent of changing external conditions .

Question 40

Osmoreceptors cells in

Answer 40

The hypothalamus

Question 41

Adh is released into the

Answer 41

Lobe of the pituitary gland

Question 42

Adh increases

Answer 42

The permeability of the distal tubule and water is reabsorbed into blood vessels , small volume of hypertonic urine

Question 43

Less ADH

Answer 43

Distal tubule and collecting ducts remain impermeable , large volume of dilute urine