d3.3 homeostasis

Question 1

homeostasis

Answer 1

maintenance of internal environment of the organisms
- variable are kept within preset limits despite fluctuations in the external environment

Question 2

endocrine system mechanism [6]

Answer 2

1. a stimulus is received (eg. high blood glucose level)
2. use of hormones (eg. insulin)
3. secreted into the blood
4. transported to target tissues (eg. liver cells)
5. hormone changes the conditions of the tissue (eg. take in glucose and convert to glycogen)
6. the change is monitored through feedback (mostly negative feedback)

Question 3

what secretes insulin and glucagon

Answer 3

Islets of Langerhans in the pancreases

Question 4

what cells synthesise and secrete glucagon

Answer 4

alpha cells

Question 5

what cells synthesise and secrete insulin

Answer 5

beta cells

Question 6

type 1 diabetes

Answer 6

• beta cells are destroyed by their own immune system
• cant produce the sufficient amount of insulin

Question 7

why problem when blood glucose stays at a high level

Answer 7

• only can use simple diffusion bc glucose is polar
  
  • too slow
• not enough insulin- channels wont open

Question 8

type 2 diabetes

Answer 8

lack of insulin receptors or glucose channels on cell membranes

Question 9

what is body temp detected by

Answer 9

thermoreceptors

Question 10

where are thermoreceptors found

Answer 10

• peripheral thermoceptors can be found in the skin
• central thermoreceptors are found in the care of the body, including the hypothalamus

Question 11

heat generation

Answer 11

• hypothalamus secretes thyrotropin releasing hormone (TRH)
• pituitary gland receives this chemical signal and releases thyroid stimulating hormone (TSH)
• increased thryroxin = increase metabolic rate and heat generation

Question 12

thyroxin

Answer 12

secreted by the thyroid gland when it receives thyroid stimulating hormone

Question 13

thyroxin increase temp

Answer 13

cooling- trigger more thyroxin to be secreted
- increases metabolic rate of cells and increases body temperature

Question 14

consequence of lack of thyroxin

Answer 14

hypothyroidism
- goiter (thyroid enlarges to try and capture iodine)

Question 15

muscles when cold

Answer 15

• muscles contract → movement → generates heat

Question 16

brown fat contains

Answer 16

a lot of mitochondria
- all energy is transformed into heat rather than producing atp

Question 17

when body is overheated

Answer 17

vasodilatation- arterioles supplying the skin relax → arterioles widen
- more blood flows to the skin → warms up to core temperature
- increased temp difference between skin and external environment causes more heat to be lost from the body
- only the amount of blood flowing through capillaries in the skin can be varied

Question 18

vasoconstriction

Answer 18

• when circular muscle contracts- circumference of arteriole is reduced and lumen along the blood flows is narrowed
• less blood flows to the region supplied by the arteriole
• reduce heat loss- vasoconstriction of arterioles supplying the skin
• less blood flows to capillaries in the skin and cools below core body temperature
• with reduced temperature difference between the skin and external environment- less heat is lost from the body

Question 19

arterioles

Answer 19

branches of arteries that supply blood to part of an organ

Question 20

what are walls of arterioles

Answer 20

ring of muscle

Question 21

sweating

Answer 21

• secreted by glands in the skin and passes through narrow ducts to the skin surface, where water in the sweat evaporates
• solutes in the sweat (ions: sodium) left on the skin surface
• water has a high latent heat of vaporisation so its evaporation causes significant cooling
• blood flowing through the skin loses heat and can then cool other parts of the body

Question 22

hair erection

Answer 22

• air between the hairs acts as a thermal insulator
• erector muscles can move the hairs to make the coat thicker and the insulating effect greater
• human- only a few short hairs so erector muscles can still make the hairs stand up but they dont trap air well enough to insulate the body
• goose-bumps: ineffectual response to cold

Question 23

hormone in kidney + function

Answer 23

ADH
osmoregulation

Question 24

excretion

Answer 24

removal from the body of waste production of metabolism

Question 25

why is defacation not excretion

Answer 25

not waste of metabolism

Question 26

what does urine contain

Answer 26

water salt urea

Question 27

renal capsule function

Answer 27

ultrafiltration

Question 28

renal artery function

Answer 28

blood pressure so blood goes in

Question 29

what cant go through in ultrafiltration (from blood to urea)

Answer 29

red blood cells platelets proteins

Question 30

what can go thru (from blood to urea) [6]

Answer 30

water urea glucose sodium ions chloride ions amino acids

Question 31

where can u find the substances that go from blood to urea

Answer 31

glomerular filtrate

Question 32

microvilli function

Answer 32

increase surface area for diffusion

Question 33

why is the movement slow around the convoluted tubule

Answer 33

more time to reabsorb nutrients

Question 34

why proximal convoluted tubule cell has lots of mitochondria

Answer 34

active transport to reabsorb all wanted nutrients = ATP production

Question 35

proximal convoluted tubule function

Answer 35

selective reabsorption in the kidney

Question 36

why diabetes occur

Answer 36

not enough glucose channels open to reabsorb to urine would have glucose

Question 37

what does it mean when there is protein in urine

Answer 37

something wrong with the glomerulus

Question 38

why doesnt burst of high pressure

Answer 38

basement membrane restricts the passage of blood cells and proteins

Question 39

afferent arteriole function

Answer 39

brings blood to the nephron to be filtered

Question 40

efferent arteriole

Answer 40

removes blood from nephron (except for filtered components)

Question 41

glomerulus function

Answer 41

capillary tuft where filtration occurs

Question 42

bowman's capsule function

Answer 42

first part of nephron where filtrate is collected

Question 43

proximal convoluted tubule function

Answer 43

where selective reabsorption occurs

Question 44

loop of Henle function

Answer 44

important for establishing a salt gradient in the medulla

Question 45

distal convoluted tubule function

Answer 45

final site of selective reabsorption

Question 46

collecting duct function

Answer 46

feeds into ureter and where osmoregulation occurs

Question 47

vasa recta function

Answer 47

blood network that reabsorbs components from the filtrate

Question 48

what happens when ur dehydrated

Answer 48

high adh high reabsorption of water back into the blood

Question 49

hypothalamus function

Answer 49

detects how hydrated blood is then signals to pituitary gland

Question 50

how collecting duct reabsorbs

Answer 50

affects aquaporin so water go through plasma membrane faster

Question 51

what are aquaporin

Answer 51

protein channels for water

Question 52

aquaporin function

Answer 52

allows water pass through the plasma membrane faster

Question 53

movement through aquaporins

Answer 53

facilitated diffusion so no energy involved

Question 54

why cant water go thru the aquaporins fast

Answer 54

polar

Question 55

what happens when adh increases

Answer 55

gene expression of aquaporin on the collecting duct → more water is reabsorbed → urine becomes more concentrated

Question 56

what happens to aquaporins when there is too much water

Answer 56

aquaporins will break down

Question 57

why is a countercurrent needed

Answer 57

because diffusion will cause it to reach an equilibrium to maintain a concentration gradient

Question 58

water movement in collecting duct (to where + using what)

Answer 58

from collecting duct to capillaries by osmosis

Question 59

how blood supply changes

Answer 59

- adjusted using rings of circular muscle in the walls of the arterioles serving the organ - contraction of the rings of muscle causes vasoconstriction (narrowing of the lumen) and restricts blood flow

Question 60

shunt vessels function

Answer 60

direct blood directly from arterioles to venules

Question 61

vasodilation

Answer 61

relaxation of circular muscle in arterioles (widening of the lumen)