chapter 14 Homeostasis

Question 1

homeostasis

Answer 1

maintenance of constant internal environment

Question 2

negative feedback

Answer 2

.response counteracts the original stimulus

.to maintain homeostasis

Question 3

deamination

Answer 3

.remove the amine group and a H atom from amino
acid
.produce ammonia

Question 4

urea cycle

Answer 4

NH3 + CO2 -> urea -> excreted via kidney

Question 5

renal vein

Answer 5

going out

Question 6

renal artery

Answer 6

going in

Question 7

ureter

Answer 7

urine out from kidney to urinary bladder

Question 8

urethra

Answer 8

urine out from urinary bladder

Question 9

afferent arteriole

Answer 9

going in

Question 10

efferent arteriole

Answer 10

going out

Question 11

structure of glomerular wall and bowman’s capsule wall

Answer 11

1. endothelium of the blood capillaries of the
   glomerulus -> with many more gaps
2. basement membrane -> a mesh of collagen and
   glycoprotein fibres which is the main selective barrier
3. epithelial cells of the bowman’s capsule -> inner
   lining of the bowman’s capsule which wraps around
   the capillary of glomerulus and have finger-like
   projections (podocytes) which form gaps

Question 12

how the structure adapts for ultrafiltration

Answer 12

1. the endothelium and filtration slits between the foot
   processes of podocytes provides a large amount of
   filtrate which allows the movement of substance from
   the blood plasma to the bowman’s capsule lumen
2. the diameter of lumen of afferent arteriole is wider
   than the efferent arteriole this results in a high blood
   pressure in the glomerulus than bowman’s capsule
   which forces fluid out of the glomerulus into the
   lumen of bowman’s capsule
3. basement membrane acts as a filtrate which
   prevents large plasma proteins, red blood cells and
   white blood cells to pass through

Question 13

where does selective absorption happens?

Answer 13

. proximal convoluted tube
. loop of henle
. distal convoluted tube
. collecting duct

Question 14

selective reabsorption @ PCT

Answer 14

1. active transport of NA+ ions from the PCT cells into
   the capillary via the Na+/K+ ion pump. Concentration
   of the Na+ ions in the PCT cells decreases which
   builds up a concentration
2. Na+ ions in PCT lumen diffuses into the cells lining
   the PCT down the gradient by facilitated diffusion via
   the co-transporter carrier protein. Na+ ions are co-
   transported with glucose, amino acid and vitamins
3. Glucose and amino acid diffuses into the
   bloodstream down the concentration gradient via
   facilitated diffusion.

Question 15

adaptations of PCT cells

Answer 15

1. Numerous microvilli which increases the surface area
   of absorption
2. high density of mitochondria which provides energy
   in the form of ATP for processes such as active
   transport
3. high infoldings of basal membrane
4. presence of different transport proteins in the
   membrane
5. tight junctions holding adjacent cells together which
   separate proteins of front and basal membrane, so
   fluid cannot pass between cells and must pass
   through the cells

Question 16

selective reabsorption @ loop of henle (ascending limbs)

Answer 16

1. Na+ and Cl- moves out of the tube by active
   transport into the tissue fluids in the medulla spaces
2. high concentrations of Na+ and Cl- ions in the
   medulla space causes renal fluid o become more
   dilute and enters the distal convoluted tube. The
   longer the tube the more concentrated the urine and
   more water reabsorbed

Question 17

selective reabsorption @ loop of henle (descending limbs)

Answer 17

1. due to the high concentrations of solutes in the
   medulla space, water moves out the tube into the
   medulla tissue fluid by osmosis and water is reabsorb
2. urea, Na+ and Cl- ions and medulla space diffuse
   into descending limbs this causes the fluid in
   descending limbs to become very concentratedas it
   moves down the loop

Question 18

selective reabsorption @ distal convoluted tube

Answer 18

1. Na+ and Cl- ions are transported actively back into
   the blood
2. Water is reabsorbed by osmosis back into the blood

Question 19

selective reabsorption @ collecting duct

Answer 19

.the tissue fluid has a high concentration of solutes so water moves out of the collecting duct by osmosis back into the blood
.formation of urine occurs
.rate of water reabsorption determine by ADH (antidiuretic hormone)

Question 20

glucagon

Answer 20

.secreted by alpha cells

.increase blood sugar

Question 21

insulin

Answer 21

.secreted by beta cells

.decrease blood sugar

Question 22

when blood glucose level increases

Answer 22

1. beta cells secretes more insulin into the blood
2. insulin binds to receptors on the cell surface
   membrane of liver cells
3. increases permeability of membrane to glucose in
   liver cells which triggers the vesicles carrying glucose
   transport proteins(GLUT protein) to fuse with the
   plasma membrane increasing the facilitated diffusion
   of glucose into cells
4. increase glucose uptake, activates the enzyme
   glucokinase which phosphorylates glucose and
   glucose are trapped in cells
5. increase rate of respiration of glucose
6. increase conversion of glucose to glycogen by
   activating the enzymes phosphofructokinase and
   glycogen synthetase which will be stores in the liver
   and muscles
7. increase protein and lipid synthesis
8. inhibit the secretion of glucagon by alpha cells and
   inhibit the breakdown of glycogen to glucose
9. inhibit the production of glucose form proteins and
   fats

Question 23

when blood glucose decreases

Answer 23

1. alpha cells secrete glucagon into blood
2. glucagon binds to receptor on cell surface
   membrane, the receptor changes shape activating G
   protein which then activates adenyl cyclase
3. adenyl cyclase produces cyclic AMP (cAMP) from
   ATP which acts as the second messenger activating
   protein kinase which triggers an enzyme cascade and
   the signal amplifies
4. cAMP activates the enzyme glycogen phosphorylase
   which increases the breakdown of glycogen into
   glucose.
5. use fatty acids and proteins as respiratory substance
   instead of glusoce
6. increase the production of glucose from proteins
   and fats
7. glucose diffuse through GLUT proteins fro liver into
   blood