Homeostasis Flashcards
definition of homeostasis
maintainence of constant internal environment in the body
what happens with low concentration of glucose
slow respiration
what happens with high concentration of glucose
water moves out by osmosis
definition of negative feedback
change in factor away from set point detected by receptor hormone is released/impulse sent reaches target organ performs corrective action returns to set point
thermoregulation when it is too hot
central thermoreceptor detect increase in blood temperature
thermoreceptors in skin detect in surrounding temperature
vasodilation - arterioles in skin dilate
sweat glands secrete sweat
for heat loss
thermoregulation when it is too cold
central thermoreceptors/thermorecpetors vasoconstruction shivering hair erector muscles contract decreasing production of sweat increase in adrenaline = in respiration increase heat generation
definition of positive feedback
amplify changes
definition of excretion
removal of unwanted producted of metabolic reactions such as urea and carbon dioxide
definition of deamination
removal of amino groups to produce urea
describe process and location of deamination
(liver cells) amino group + H form ammonia + keto acid keto acid used in krebs cycle/respired/convert to glucose form urea by NH3 + CO2
why is ammonia converted to urea
less toxic and less soluble
where does urea diffuse into
blood plasma
what are the three nitrogenous excretory products
urea
creatinine - creatine made in liver and used in muscles and some converted to creatinine
uric acid - breakdown of purines and nucleotides
what is the overall route of ultrafiltration and reabsorption
glomerulus
proximal convoluted tubule
loop of henle
distal convoluted tubule
describe structure of kidney
cortex medulla renal pelvis renal vein (out) renal artery (in) - afferent arteriole larger diameter than efferent arteriole ureter
describe structure of bowman’s capsule
surrounded by tight network of capillaries (glomerulus)
describe three layers of bowman’s capsule
endothelium (cell layer) fenestration filters large cells basement membrane molecular filter 68000 molecular mass epithelial cells (bcapsule) podocytes stable structure and provide less resistance to fluid
factors affecting glomerulus filtration rate
blood pressure
water potential
kidney disease
cancer
what needs to removed from PCT into capillaries
glucose
amino acids
ions
describe adaptations of cuboidal epithelial cells in PCT (6)
many microvilli tight junctions many mitochondria many cotransporter proteins folded basal membrane aquaporins
describe how glucose diffuses from PCT into capillaries
active transport of Na+ into blood
sodium pumps in basal membrane
Na+ conc decreases in cell
Na+ enter into cell
facilitated diffusion with glucose cotransporting into cell
secondary active transport
diffusion of glucose into blood by GLUT proteins
what occurs in loop of henle
water reabsorption
describe descending limb of loop of henle
permeable to water
aquaporins - osmosis
Na+ and Cl- diffuse in
describe ascending limb of loop of henle
impermeable to water
active transport Na+/Cl-
decrease water potential in tissue fluid
describe counter current multiplies in loop of henle
fluid in two different directions allow max conc. of solutes to be built inside and outside the bottom of loop
describe reabsorption in distal convoluted tubule and collecting duct
Na+ actively pumped into tissue fluid
K+ pumped into tubule
regulate concentration of ions in blood
where does glucose reabsorption occur
PCT
what should not be present in urine
glucose and proteins
cause of protein in urine
kidney infection/heart disease
describe how glucose dip stick works
glucose oxidase
peroxidase
G.O + glucose makes hydrogen peroxide
Peroxidase + hydrogen peroxide → brown compound
darker brown = more conc. glucose
advantage/disadvantage of dipsticks
painless/don’t give current measure of glucose
describe how biosensors work
pad impregnated with glucose oxidase used sample of blood glucose oxidase catalyse reaction tiny electric current supplied detected by electrode produce reading
advantage of biosensors
rapid/quantitative/re-usable data
how is water content controlled
osmoreceptors detect decrease in water potential
in hypothalamus
ADH released
by posterior pituitary gland
increase in aquaporins in collecting duct
more water reabsorbed
water potential returns to set point
which cells secrete glucagon
a
which cells secrete insulin
b
describe process when glucose concentration is high
b cells insulin bind to receptor on liver cells increase permeability of cells to glucose more GLUT4 proteins added by vesicles fusing with cell surface membrane stimulates glycogenesis increase in respiration more diffusion of glucose into cells decrease blood glucose conc.
describe process when glucose concentration is low
glucagon binds to receptor on cell surface membrane receptor change shape activate G proteins adenlylyl cyclase activated cyclic AMP second messenger activates kinase enzyme cascade glycogen broken to glucose diffuse out of cells increase in blood conc.
describe closure of stomata
At low water potential (water stress) Abscisic acid binds to receptors On cell membrane of guard cells Proton pumps inhibited from pumping potassium ions Stimulates Ca2+ to diffuse into cytoplasm Acts as secondary messenger High concentration of H+ in cell Volume of guard cell decreases Cell is flaccid Fast response
describe opening of stomata
H+ pumped out of guard cells by active transport
Negative potential triggers voltage gated potassium ion channels to open
Potassium ions diffuse into lower water potential inside
Water moves in cell by osmosis
Turgor increases and stomatal pore opens as guard cells change shape
