Chapter 16

Question 1

Homeostasis definition

Answer 1

maintenance and control of a constant internal environment

Question 2

3 processes in the liver to control blood glucose concentration

Answer 2

glycogenesis, glycogenolysis, gluconeogenesis

Question 3

glycogenesis

Answer 3

the conversion of glucose to glycogen

Question 4

glycogenolysis

Answer 4

the conversion of glycogen to glucose

Question 5

gluconeogenesis

Answer 5

the conversion of non-carbohydrates into glucose

Question 6

Target organ for glucagon and insulin

Answer 6

liver

Question 7

Second messenger model

Answer 7

the first messenger (adrenaline) binds to specific receptors on target cell surface membranes to form a hormone-receptor complex, the complex activates an enzyme (adenylate cyclase) inside the membrane, the adenylate cyclase enzyme converts ATP into cyclic AMP, cAMP acts as the second messenger and activates another enzyme in the cytoplasm which causes the conversion of glycogen to glucose

Question 8

2 ways adrenaline can raise blood glucose concentration

Answer 8

attaching to receptors on target cells, activating enzymes involved in glycogenolysis

Question 9

4 factors affecting blood glucose concentration

Answer 9

the breakdown of carbohydrates during digestion, the breakdown of glycogen stored in the liver, gluconeogenesis, level of mental and physical activity

Question 10

where is insulin secreted from

Answer 10

Beta cells in the islets of langerhans

Question 11

where is glucagon secreted from

Answer 11

alpha cells in the islets of langerhans

Question 12

what do beta cells in the islets of Langerhans detect

Answer 12

raised blood glucose levels

Question 13

what do alpha cells in the islets of Langerhans detect

Answer 13

below normal - reduced blood glucose levels

Question 14

How does insulin reduce blood glucose concentration

Answer 14

causing more glucose channels to be inserted into the cell membrane increasing the uptake of glucose, increasing the rate of respiration, activating enzymes involved in glycogenesis (glucose to glycogen), causing excess glucose to be converted into fat

Question 15

how does glucagon increase blood glucose concentration

Answer 15

attaching to receptors on the surface of target cells like liver and muscle cells, activating enzymes involved in glycogenolysis (glycogen to glucose), activating enzymes involved in gluconeogenesis, causing the body to use more fatty acids in respiration

Question 16

cause of type 1 diabetes

Answer 16

pancreas stops producing insulin

Question 17

cause of type 2 diabetes

Answer 17

glycoprotein receptors lose their sensitivity to insulin

Question 18

treatment of type 1 diabetes

Answer 18

injecting insulin 2-4 times a day

Question 19

treatment of type 2 diabetes

Answer 19

regulate dietary requirements, may require insulin or drugs to stimulate insulin production

Question 20

Osmoregulation

Answer 20

control of water potential

Question 21

3 ways osmoregulation is controlled

Answer 21

ADH, hypothalamus and posterior pituitary gland

Question 22

How does ADH aid osmoregulation

Answer 22

acts in the collecting ducts in the kidney to increase water reabsorbtion

Question 23

How does the hypothalamus aid osmoregulation

Answer 23

contains osmoregulatory receptors and produces ADH

Question 24

How does the pituitary gland aid osmoregulation

Answer 24

secretes ADH

Question 25

what are nephrons

Answer 25

tiny tubules that make up the kidney

Question 26

what do nephrons do

Answer 26

remove wate products and produce urine

Question 27

how do nephrons produce urine

Answer 27

formation of glomerular filtrate, reabsorption of glucose and water by the proximal convoluted tubule, maintaining a concentration gradient of sodium ions across the medulla by the loop of Henle, reabsorption of water by the distal convoluted tubule and collecting ducts

Question 28

Where does ultrafiltration occur

Answer 28

bowman’s capsule

Question 29

what is the knot of capillaries in the bowman’s capsule called

Answer 29

glomerulus

Question 30

Steps of ultrafiltration

Answer 30

the glomerulus is supplied with blood by the afferent arteriole (wider) and drained by the efferent arteriole (narrower) creating pressure in the glomerulus. The pressure forces fluid from the glomerulus into the the lumen of the Bowman’s capsule through a filter made up of of capillary endothelium and podocytes. The filter prevents the passing of large molecules. The fluid in the lumen of the Bowman’s capsule is called the glomerular filtrate

Question 31

substances in the glomerular filtrate

Answer 31

water, glucose, amino acids, urea, mineral ions

Question 32

Process after ultrafiltration

Answer 32

selective reabsorption

Question 33

Selective reabsorption

Answer 33

the glomerular filtrate flows from the Bowman’s capsule to the proximal convoluted tubule where all the glucose and amino acids are reabsorbed, some inorganic salts and most of the water.

Question 34

site of selective reabsorption

Answer 34

proximal convoluted tubule

Question 35

ways the cells lining the proximal convoluted tubule are specialised to maximise reabsorption

Answer 35

highly folded with microvilli, co-transport proteins that allow the diffusion of sodium ions accompanied by glucose or amino acids

Question 36

how does the loop of Henle achieve water reabsorbtion

Answer 36

creates a very negative water potential in the surrounding tissue

Question 37

Steps of water reabsorption in the loop of Henle

Answer 37

as the fluid moves up the ascending limb, sodium ions are actively transported out of the fluid but water is unable to leave. The sodium ions lower the water potential of the surrounding tissue and the after potential becomes more negative at the base of the loop of Henle. Therefore water moves out of the descending limb by osmosis into the surrounding tissue and is taken away by the blood capillary

Question 38

What is the loop of henle said to be

Answer 38

hairpin counter-current multiplier

Question 39

what controls the permeability of the distal convoluted tubule and the collecting duct

Answer 39

ADH

Question 40

steps of ADH

Answer 40

the change in water potential in the blood is detected by the hypothalamus, if water potential is too low the hypothalamus stimulates the secretion of ADH. ADH makes the cell surface membrane more permeable so more water is reabsorbed into the blood stream. This causes a smaller amount of higher concentrated urine to be produced