homeostasis

Question 1

what is homeostasis?

Answer 1

maintaining a stable internal environment by regulating different processes

Question 2

what is negative feedback?

Answer 2

• a series of changes that result in a system being restored to its original state
• when the stimulus causes the corrective measures to be turned off, returning the system to its original level

Question 3

what is positive feedback?

Answer 3

• occurs when the feedback causes the corrective measures to remain on
• in doing so it causes the system to deviate even further from the norm

Question 4

methods of gaining heat:

Answer 4

• production of heat - metabolism of food

* gain heat from environment - conduction, convection, radiation

Question 5

methods of lowering heat:

Answer 5

• evaporation of water - during sweating

* loss of heat to environment - conduction, convection & radiation

Question 6

go through the process of negative feedback

Answer 6

stimulus -> receptors -> control center -> effectors -> response

Question 7

type of message sent

Answer 7

chemical

Question 8

speed of transmission

Answer 8

slow

Question 9

method of transmission

Answer 9

in the blood

Question 10

how long does a response last

Answer 10

long term

Question 11

what is glycogenolysis

Answer 11

breakdown of glycogen by glucagon

Question 12

what is glycogensis

Answer 12

creation of glycogen by insulin

Question 13

what is gluconeogenesis

Answer 13

creation of new glucose from non-carbohydrate substrates e.g amino acids & lipids

Question 14

what do hormones do

Answer 14

carry information from one part of a mammals body to another part

Question 15

what produces hormones

Answer 15

endocrine glands

Question 16

how do endocrine glands produce hormones?

Answer 16

contain secretory cells which secrete hormones directly into the blood e.g pituitary, adrenal, pancreas

Question 17

what are exocrine glands?

Answer 17

• exocrine = secreting to the outside

* they secrete substances which are not hormones into a tube or duct along which the secretions show

Question 18

what is the pancreas

Answer 18

an organ that has both endocrine and exocrine functions

Question 19

how do hormones work?

Answer 19

• small molecules
• can be polypeptides (insulin) or steroids (oestrogen)
• concentrations in the blood are always very small
• broken down by enzymes or lost in urine
• effects particular cells called target cells which contain receptors that are complementary to the hormone

Question 20

what is the pancreas’ endocrine function

Answer 20

secretes insulin and glucagon

Question 21

what does the pancreas do

Answer 21

• control blood glucose levels, produced by group of cells called islets of langerhans
• 2 types of cell:
- alpha cells are larger and secrete glucagon
- beta cells are smaller and secrete insulin

Question 22

what do alpha cells do

Answer 22

secrete glucagon

Question 23

what do beta cells do

Answer 23

secrete insulin

Question 24

the effect of insulin in body cells

Answer 24

• insulin binds to glycoprotein receptors complementary to the hormone insulin found on the plasma membrane of most cells
• this causes the tertiary structure of the glucose transport protein channel to change shape and open, allowing more glucose into the cell by facilitated diffusion

Question 25

the effect of insulin on the muscles

Answer 25

* insulin causes additional carrier proteins to join the membrane * insulin bids to receptors, this releases a chemical signal which causes vesicles inside the cell to move and fuse with the plasma membrane * this adds more carrier proteins to the plasma membrane for glucose to be transported through

Question 26

the effect of insulin on liver cells

Answer 26

* after glucose has entered by facilitated diffusion, insulin activates an enzyme that rapidly converts glucose to glucose phosphate * this maintains a steep concentration gradient between the blood and the liver cells * ensures glucose still enters the cells and equilibrium isn’t reached * glycogenesis eventually becomes glycogen

Question 27

what do alpha cells do

Answer 27

detect a fall in the blood glucose concentration and respond by secreting glucagon into the blood plasma

Question 28

what does glucagon do (full process)

Answer 28

* glucagon binds w receptor on liver cell membrane * causes protein on the inside of the plasma membrane to change shape * this activates enzyme adenyl cyclase * this breaks two phosphate groups away from ATP to form CAMP * CAMP binds w enzyme protein kinase which changes the shape of the enzyme and activates it * protein kinase then catalyses the reaction to break glycogen into glucose * glucose leaves the cell via facilitated diffusion

Question 29

how does gluconeogenesis work

Answer 29

* breakdown of non carbohydrate substrates * glucagon will bind to receptors on target cells and will activate enzymes * the enzymes will convert glycerol, amino acids and fatty acids into glucose * glucose will leave the target cells by facilitated diffusion and will raise the blood glucose level

Question 30

what causes type 1 diabetes

Answer 30

* when the immune system attacks and destroys the insulin-producing beta cells of the pancreas * insulin isn’t produced so glycogenesis cant happen to promote the uptake of glucose * blood glucose levels stay high

Question 31

how is type 1 diabetes treated

Answer 31

insulin injections into the body

Question 32

what causes type 2 diabetes

Answer 32

* when the body becomes resistant to insulin/pancreas is unable to produce enough insulin * can be caused by poor diet/obesity * body breaks down carbs into glucose but glucose levels keep rising as insulin doesn’t work properly * therefore more insulin is released = tires out pancreas & makes less insulin

Question 33

how is type 2 diabetes treated

Answer 33

* lifestyle changes = losing weight * blood glucose monitoring & medication * insulin injections