homeostasis Flashcards
(23 cards)
what is homeostasis
internal environment is maintained within set limits around an optimum
why is it important that core temperature remains stable
maintain stable rate of enzyme-controlled reactions and prevent damage to membranes
temperature too low = enzyme and substrate molecules have insufficient kinetic energy
too high = enzymes denature
why is it important that blood pH remains stable
maintain stable rate of enzyme-controlled reactions
acidic pH - H+ ions interact with H-bonds and ionic bonds in tertiary structure of enzymes
why is it important that blood glucose concentration remains stable
maintain constant blood water potential: prevent osmotic lysis / crenation of cells
maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions
define positive and negative feedback
positive feedback - a fluctuation triggers changes that result in an even greater deviation from the normal level
negative feedback - self-regulatory mechanisms return internal environment to optimum when there is a fluctuation
outline the general stages involved in negative feedback
receptors detect deviation, coordinator, corrective mechanism by effector, receptors detect that conditions have returned to normal
suggest why separate negative feedback mechanisms control fluctuations in different directions
provides more control, especially in case of overcorrection, which would lead to a deviation in the opposite direction from the original one
suggest why coordinators analyse inputs from several receptors before sending an impulse to signal
receptors may send conflicting information
optimum response may require multiple types of effector
why is there a time lag between hormone production and response by an effector
it takes time to:
produce hormone
transport hormone in blood
cause required change to target protein
factor that affect blood glucose concentration
amount of carbohydrate digested from diet
rate of glycogenolysis
rate of gluconeogenesis
define glycogenesis
define glycogenolysis
define gluconeogenesis
glycogenesis - liver converts glucose into the storage polymer glycogen
glycogenolysis - liver hydrolyses glycogen into glucose which can diffuse into blood
gluconeogenesis - liver converts glycerol and amino acids into glucose
explain type 1 diabetes
body cannot produce insulin eg due to autoimmune response that attacked beta cells
treat by injecting insulin
explain type 2 diabetes
glycoprotein receptors are damaged or become less responsive to insulin
strong positive correlation with poor diet / obesity
treat by controlling diet and exercise regime
outline how colorimetry could be used to identify the glucose concentration in a sample
benedict’s test on solutions of known glucose concentration
use colorimeter to record absorbance
plot calibration curve
y - absorbance
x - glucose concentration
benedict’s test on unknown sample - use calibration curve to read glucose concentration at its absorbance value
define osmoregulation
control of blood water potential via homeostatic mechanisms
how are cells for bowman’s capsule adapted for ultrafiltration
fenestrations between epithelial cells of capillaries
fluid can pass between and under folded membrane of podocytes
state what happens during selective reabsorption
useful molecules from glomerular filtrate eg glucose are reabsorbed into the blood
occurs in proximal convoluted tubule
how are cells in the proximal convoluted tubule adapted for selective reabsorption
microvilli - large surface area for co-transporter proteins
many mitochondria - ATP for active transport of glucose into intercellular spaces
folded basal membrane - large surface area
explain the role of the collecting duct
reabsorption of water from filtrate into interstitial fluid via osmosis through aquaporins
why is it important to maintain a sodium gradient
countercurrent principle - filtrate in collecting ducts is always beside an area of interstitial fluid that has a lower water potential
maintains water potential gradient for maximum reabsorption of water
what might cause blood water potential to change
level of water intake
level of ion intake in diet
level of ions used in metabolic processes or excreted
sweating
explain the role of the hypothalamus in osmoregulation
osmosis of water out of osmoreceptors in hypothalamus causes them to shrink
triggers hypothalamus to produce more antidiuretic hormone
explain the role of the posterior pituitary gland in osmoregulation
stores and secretes the ADH produced by the hypothalamus
