Homeostasis

Question 1

Define homeostasis

Answer 1

Maintenance of constant internal environment within restricted limits

Question 2

Describe the importance of homeostasis

Answer 2

Maintaining pH of blood = prevent denaturing of enzymes

Constant water potential= reliable source of Respiratory substrate prevent Osmotic damage

Allow organisms to live in larger range of environments

Question 3

What features do all control mechanisms posses

Answer 3

Optimum point

Receptor

CO ordinator

Effector

Feedback mechanism

Question 4

Define feedback mechanism

Answer 4

Receptor responds to stimulus brought about by Effector

Question 5

Define negetive feedback

Answer 5

Restores system to original level

Question 6

Define positive feedback

Answer 6

Deviation from optimum causes further deviation from optimum

Question 7

Where are hormones produced

Answer 7

Endocrine Glands

Question 8

How do hormones reach target cells

Answer 8

Blood plasma

Question 9

By what action do hormones act

Answer 9

Second messenger model

Question 10

What hormones act vía second messenger model

Answer 10

Glucagon

Adrenaline

Question 11

Describe the second messenger model

Answer 11

Hormones bind to como receptor on liver cell

Activates adenylate cyclase

Converts ATP to cAMP

cAMP activates protein kinase

Catalyses glycogenolysis

Question 12

Describe the role of the pancreas

Answer 12

Exocrine - secrete digestive enzymes into ileum

Endocrine– secrete hormones into blood

Detect change in blood glucose conc and secrete hormones

Question 13

What cells secrete insulin and glucagon and where are they found

Answer 13

Islet of langerhans

Alpha= glucagon

Beta = insulin

Question 14

What is the role of the liver

Answer 14

Where hormones have effect

Glycogenolysis gluconeognesis and glycogenolysis gave effect

Question 15

What are liver cells called

Answer 15

Hepatocytes

Question 16

Define glycogenolysis

Answer 16

Hydrolysis of glycogen to glucose

Question 17

Define gluconeognesis

Answer 17

Glucose production from non carbohydrate sources

Question 18

Define gluconeognesis

Answer 18

Glucose production from non carbohydrate sources

Question 19

Define glycogeneiss

Answer 19

Production of glycogen from glucose

Question 20

Sources of blood glucose

Answer 20

Diet

Glycogenolysis

Gluconeognesis

Question 21

Describe the action of insulin

Answer 21

Change structure of gcp to allow more glucose in

Cause vesicles with gcp to fuse with cell membrane increasing number of gcp and permeability to glucose

Activate enzymes involved in glycogenesis

Question 22

Describe the action of glucagon

Answer 22

Activate enzymes involved in glycogenolysis and gluconeognesis via second messenger model

Question 23

Describe action of Adrenaline

Answer 23

Acts via second messenger model

Activating enzymes involved in glycogenolysis and gluconeognesis

Question 24

What is diabetes

Answer 24

Metabolic diabetes causing inability to control BGC

Question 25

Describe type 1 diabetes

Answer 25

Produce little to no insulin. Insulin dependent Rapid and early development Can be due to autoimmunity Treated with insulin injections

Question 26

Describe type 2 diabetes

Answer 26

Insulin independent Loss of insulin receptors/ sensitivity May also be due to inadequate insulin supply Poor diet and excersie Treat with diet and exercise

Question 27

What steps are involved in osmoregulation?

Answer 27

Ultrafiltration Reabsorption of glucose and water on PCT Maintenance of water potential gradient Reabsorption of water and sodium ions

Question 28

Describe ultrafiltration

Answer 28

Small molecules such as glucose and Amino acids are forced out of the blood into glomerular filtrate. Due to higher HPa of blood

Question 29

What resists ultrafiltration

Answer 29

HPa of glomerular filtrate Osmotic Pa of filtrate Basmenet membrane cells (endo podocyte)

Question 30

Why are small molecules forces out of glomerular capillaries

Answer 30

Diameter of effernet artiriole is smaller than afferent causing increase in blood pressure.

Question 31

Where does ultrafiltration occur

Answer 31

Renal bowman's capsule

Question 32

How is the capsule adapted for ultrafiltration

Answer 32

Podocyte have foot like processes allowing molecules to pass between Endothelium of glomerular capillaries are fenestrated so have gaps

Question 33

What adaptions does the proximal convoluted tubule have?

Answer 33

Epithelial cells have microvilli and I folding to increase surface area Many mitochondria for na/k pump Good blood supply to maintain conc gradient

Question 34

Name the parts for the system a small molecule passes when producing urine

Answer 34

Glomerular Renal bowman's capsule Proximal convoluted tubule Loop of henle Distal convoluted tubule Collecting duct

Question 35

Describe how substances are reabsorbed in the PCT

Answer 35

3 Na+ are pumped out and 2k+ are pumped in Na+ conc gradient set up Glucose Amino acids mineral ion and vitamins enter via FD until equilibrium and then Co Transported with Na+ Glucose e.t.c then FD into tissue fluid and then cappilaries Solutes into epithelial cells and blood decrease water potential so water reabsorbed vía Osmosis Lipid soluble substances reabsorbed via simple diffusion Ions move via SD through tight junction

Question 36

Where is the loop of henle found

Answer 36

In nephron in medulla

Question 37

Describe the descending limb

Answer 37

Permeable to water impermeable to ions Narrow with thin walls

Question 38

Describe the ascending limb

Answer 38

Wide with thick walls Impermeable to water Permeable to ions

Question 39

How is the gradient in the loop of henle maintained

Answer 39

Counter current multiplier

Question 40

How and why does the length of the loop of henle affect the amount of water absorbed

Answer 40

Longer loop = more water absorbed so more conc urine

Question 41

What is the function of the DCT

Answer 41

Make final adjustments to water potential and ion conc

Question 42

What occurs in the DCT and how is it adapted for this

Answer 42

Water and ions are reabsorbed into blood Many microvilli and mitochondria Permeability affects by hormones

Question 43

Where is the collecting duct found

Answer 43

Medulla

Question 44

What occurs in the collecting duct

Answer 44

Water leaves via Osmosis Nephron is connected to Ureter

Question 45

What is the WP of the blood affected by

Answer 45

Sweating Water consumed Intake of ions

Question 46

Describe the response to a decrease in blood wp

Answer 46

Osmoreceptors in the hypothalamus decent change in wp Impulses sent to hypothalamus to produce more ADH Impulses to posterior pituitary gland so more ADH released into blood Increased absorption of water in DCT and collecting duct Prevent further lower of wp (impulses also sent to theist centre)

Question 47

Describe response to increase in wp

Answer 47

Detected by osmoreceptors in hypothalamus Less impulses to hypothalamus so less ADH Produced Less ADH released from posterior pituitary gland Less water reabsorbed in DCT and collecting duct Larger volume of Dilute urine decreases wp