d3.3 homeostasis Flashcards
homeostasis
maintenance of internal environment of the organisms
- variable are kept within preset limits despite fluctuations in the external environment
endocrine system mechanism [6]
- a stimulus is received (eg. high blood glucose level)
- use of hormones (eg. insulin)
- secreted into the blood
- transported to target tissues (eg. liver cells)
- hormone changes the conditions of the tissue (eg. take in glucose and convert to glycogen)
- the change is monitored through feedback (mostly negative feedback)
what secretes insulin and glucagon
Islets of Langerhans in the pancreases
what cells synthesise and secrete glucagon
alpha cells
what cells synthesise and secrete insulin
beta cells
type 1 diabetes
- cant produce the sufficient amount of insulin
- beta cells are destroyed by their own immune system
why problem when blood glucose stays at a high level
- only can use simple diffusion bc glucose is polar
- too slow
- not enough insulin- channels wont open
type 2 diabetes
lack of insulin receptors or glucose channels on cell membranes
what is body temp detected by
thermoreceptors
where are thermoreceptors found
- peripheral thermoceptors can be found in the skin
- central thermoreceptors are found in the care of the body, including the hypothalamus
heat generation
– hypothalamus secretes thyrotropin releasing hormone (TRH)
- pituitary gland receives this chemical signal and releases thyroid stimulating hormone (TSH)
thyroxin
secreted by the thyroid gland when it receives thyroid stimulating hormone
thyroxin increase temp
cooling- trigger more thyroxin to be secreted
- increases metabolic rate of cells and increases body temperature
consequence of lack of thyroxin
hypothyroidism
- goiter (thyroid enlarges to try and capture iodine)
muscles when cold
- muscles contract → movement → generates heat
brown fat contains
a lot of mitochondria
- all energy is transformed into heat rather than producing atp
when body is overheated
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
vasoconstriction
- 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
arterioles
branches of arteries that supply blood to part of an organ
what are walls of arterioles
ring of muscle
sweating
- 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
hair erection
- 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
hormone in kidney + function
ADH
osmoregulation
excretion
removal from the body of waste production of metabolism
why is defacation not excretion
not waste of metabolism
what does urine contain
water
salt
urea
renal capsule function
ultrafiltration
renal artery function
blood pressure so blood goes in
what cant go through in ultrafiltration (from blood to urea)
red blood cells
platelets
proteins
what can go thru (from blood to urea) [6]
water
urea
glucose
sodium ions
chloride ions
amino acids
where can u find the substances that go from blood to urea
glomerular filtrate
microvilli function
increase surface area for diffusion
why is the movement slow around the convoluted tubule
more time to reabsorb nutrients
why proximal convoluted tubule cell has lots of mitochondria
active transport to reabsorb all wanted nutrients
= ATP production
proximal convoluted tubule function
selective reabsorption in the kidney
why diabetes occur
not enough glucose channels open to reabsorb to urine would have glucose
what does it mean when there is protein in urine
something wrong with the glomerulus
why doesnt burst of high pressure
basement membrane that restricts the passage of blood cells and proteins
afferent arteriole function
brings blood to the nephron to be filtered
efferent arteriole
removes blood from nephron (except for filtered components)
glomerulus function
capillary tuft where filtration occurs
bowman’s capsule function
first part of nephron where filtrate is collected
proximal convoluted tubule function
where selective reabsorption occurs
loop of henle function
important for establishing a salt gradient in the medulla
distal convoluted tubule function
final site of selective reabsorption
collecting duct function
feeds into ureter and where osmoregulation occurs
vasa recta function
blood network that reabsorbs components from the filtrate
what happens when ur dehydrated
high adh
high reabsorption of water back into the blood
hypothalamus function
detects how hydrated blood is then signals to pituitary gland
how collecting duct reabsorbs
affects aquaporin so water go through plasma membrane faster
what are aquaporin
protein channels for water
aquaporin function
allows water pass through the plasma membrane faster
movement through aquaporins
facilitated diffusion so no energy involved
why cant water go thru the aquaporins fast
polar
what happens when adh increases
gene expression of aquaporin on the collecting duct → more water is reabsorbed → urine becomes more concentrated
what happens to aquaporins when there is too much water
aquaporins will break down
why is a countercurrent needed
because diffusion will cause it to reach an equilibrium to maintain a concentration gradient
water movement in collecting duct (to where + using what)
from collecting duct to capillaries by osmosis
how does blood supply changes
- 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
shunt vessels function
direct blood directly from arterioles to venules
vasodilation
relaxation of circular muscle in arterioles (widening of the lumen)
