Hormonal control

Question 1

homeostasis

Answer 1

the maintenance of a stable equilibrium in the conditions inside the body within a narrow limit

Question 2

three key homeostatic mechanisms

Answer 2

• thermoregulation
• osmoregulation
• control of blood glucose concentration

Question 3

hormone

Answer 3

a chemical messenger produced by an endocrine gland that travels around the body in the bloodstream

Question 4

endocrine gland

Answer 4

a group of cells that secrete hormones directly into the bloodstream

Question 5

endocrine vs nervous system (3)

Answer 5

endocrine - slower, long-term, widespread
nervous - immediate, short-term, localised

Question 6

what stimulates hormones to be produced? (3)

Answer 6

• other hormones
• nerve impulse
• change in concentration of a specific substance

Question 7

how do hormones reach target organs?

Answer 7

• hormones are secreted directly into the blood plasma
• hormones diffuse out of blood plasma and bind to specific complementary receptors in the plasma membranes of target cells (binding site)

Question 8

steroid hormones

Answer 8

• lipid soluble, pass through the phospholipid bilayer
• hormone binds to receptors in the cytoplasm or the nucleus
• hormone-receptor complexes act as transcription factors
• example: oestrogen

Question 9

non-steroid hormones

Answer 9

• hydrophilic, cannot pass through the phospholipid bilayer
• hormone binds to receptors in the plasma membrane
• triggers a cascade reaction executed by second messengers
• example: adrenaline

Question 10

first messenger

Answer 10

the hormone secreted by an endocrine gland that signals the target cells

Question 11

second messenger

Answer 11

the molecule that triggers the effect by causing a cascade reaction (cAMP in the response to adrenaline)

Question 12

adrenal glands location

Answer 12

above the kidneys

Question 13

adrenal gland structure and hormones

Answer 13

adrenal cortex - cortisol, corticosterone aldosterone and small amounts of oestrogen and testosterone (hormones are vital to life)
medulla - adrenaline, noradrenaline (non-essential hormones)

Question 14

cortisol function (1)

Answer 14

primary stress hormone regulates metabolism of glucose, proteins and fats to release usable energy

Question 15

corticosterone function (2)

Answer 15

• regulate the immune response
• suppress inflammatory reactions

Question 16

aldosterone function (1)

Answer 16

regulates levels of Na and K salts and the water balance in the blood (to maintain blood volume and pressure)

Question 17

adrenaline function (2)

Answer 17

• increases heart rate to transport more blood to the brain and muscles
• increase blood glucose concentrations by converting glycogen to glucose in the liver

Question 18

noradrenaline function (4)

Answer 18

• increases heart rate
• widens pupils
• widens air passages in lungs
• vasoconstriction of blood vessels in non-essential organs (increases blood pressure)

Question 19

exocrine function of the pancreas

Answer 19

• produce pancreatic juice containing digestive enzymes
• delivered to small intestine

Question 20

endocrine function of the pancreas

Answer 20

Islets of Langerhan:
- alpha cells secrete glucagon
- beta cells secrete insulin

Question 21

ABBA pneumonic

Answer 21

ABBA

Alpha
Below (low [glucose], secrete glucagon)
Beta
Above (high [glucose], secrete insulin)

Question 22

Three ways in which glucose can enter the bloodstream:

Answer 22

• absorption in gut (from carb digestion)
• glycogenolysis (hydrolysis of glycogen)
• gluconeogenesis (convert lipids/lactate/amino acids into glucose)

Question 23

consequences of low blood glucose concentration

Answer 23

cells don’t have enough glucose for respiration so don’t function properly

Question 24

consequences of high blood glucose concentration

Answer 24

high blood pressure
(glucose lowers water potential in blood, water moves out of cells and into bloodstream)

Question 25

what features might you see in a micrograph of pancreatic tissue?

Answer 25

- Islets of Langerhans (stained lighter) - exocrine tissue (surrounding tissue stained darker) - connective tissue - pancreatic ducts (empty) - blood vessels

Question 26

sequence of responses if blood glucose concentration is too low

Answer 26

- detected by α cells - α cells secrete more glucagon, β cells secrete less insulin - glucagon binds to receptors of target cells in the liver causing a confirmational change in the receptors protein - activates a G protein which activates adenylyl cyclase - adenylyl cyclase catalyses conversion of ATP --> cAMP - cAMP acts a secondary messenger by causing an enzyme cascade - stimulates glycogenolysis and gluconeogenesis

Question 27

how do the β cells detect and secrete insulin?

Answer 27

- glucose molecules enter β cells by facilitated diffusion - β cells respire glucose and produce ATP - high [ATP] closes K+ channels in the β cells to close changing membrane potential - voltage gated Ca2+ channels open which stimulate insulin containing vesicles to move towards plasma membrane - insulin releases into capillaries via exocytosis

Question 28

outline the enzyme cascade in response to glucagon

Answer 28

- cAMP binds to protein kinase A enzymes - PKA activates phosphorylase kinase enzymes (by phosphorylating them) - phosphorylase kinase enzymes activate glycogen phosphorylase enzymes which catalyse glycogenolysis - gluconeogenesis also stimulated (glycerol/amino acids --> glucose etc)

Question 29

sequence of responses when blood glucose concentration is too high

Answer 29

- detected by β cells - α cells secrete less glucagon, β cells secrete more insulin - insulin binds to specific receptors on target cells in liver - more glucose channels incorporated into plasma membranes which increases the permeability to glucose - more glucose diffuses into target cells - glucose used in respiration and glycogenesis

Question 30

three examples of target cells of insulin

Answer 30

- skeletal muscle cells (increase rate of respiration) - fat storage cells (increase glycogenesis) - liver cells (increase glycogenesis)

Question 31

reason for type 1 diabetes

Answer 31

- pancreas produces insufficient insulin - autoimmune response damaging β cells - lack of insulin affects glycogen stores (leading to fatigue)

Question 32

type 1 diabetes treatments

Answer 32

- regular blood tests - insulin injections - appropriate diet - increase physical activity

Question 33

what would be an appropriate diet for diabetic patients?

Answer 33

- five a day - minimal processed food - more polysaccharides than di/monosaccharides (slow release energy)

Question 34

reasons for type 2 diabetes

Answer 34

receptors have reduced sensitivity to insulin (in liver and fat storage tissues) OR receptors have reduced in numbers

Question 35

consequences of type 2 diabetes

Answer 35

- reduced glucose uptake --> high blood glucose concentration --> β cells produce a large amount of insulin which damages them

Question 36

six risk factors of type 2 diabetes

Answer 36

- obesity - physical inactivity - high blood pressure - high blood cholesterol - genetics - specific ethnic groups

Question 37

type 2 diabetes treatment

Answer 37

- appropriate diet (can be reversed if treated early) - increasing physical activity - drugs (stimulate insulin production or slow down rate of glucose absorptions from intestine or insulin injections depending on the cause)

Question 38

why do diabetic patients have high blood pressure?

Answer 38

- high blood [glucose] - water diffuses into blood via osmosis - increases volume of blood - increases blood pressure

Question 39

advantages of stem cell treatments for diabetes

Answer 39

- availability is less limited than pancreas donors - reduced likelihood of rejection - people no longer have to inject themselves

Question 40

limitations of stem cell treatment in diabetes

Answer 40

- immunosuppressants must still be used for type 1 diabetes as it is an autoimmune disease - ethical concerns with the termination of embryos - tumours

Question 41

gluconeogenesis

Answer 41

conversion of non-glucose sources into glucose

Question 42

glycogenesis

Answer 42

conversion of glucose to glycogen

Question 43

glycogenolysis

Answer 43

conversion of glycogen to glucose (in liver and muscle cells)