Homeostasis Flashcards
Homeostasis
Maintains stable internal envi within restricted limits by physiological control systems
Importance of maintaining stable core temp
Temp too high do hydrogen bonds in tertiary structure of enzymes break so enzymes denature and active site change shape and substrates can’t bind so fewer e-s complexes
Importance in maintaining stable blood ph
Above or optimum ph ionic and hydrogen bonds break In tertiary break
Enzyme denature active site change shape and substrates can’t bind
So fewer E-S complex
BGC conc too low
Hypoglycaemia
Not enough glucose for respiration so less atp produced and active transport can’t happen
BGC. Too high
Hyperglycaemia
Wp of blood decreased
Water lost from tissues to blood via osmosis
Kidneys can’t absorb all glucose so more water lost in urine causing dehydration
Negative feedback
Receptors detect change from optimum and effectors respond to counteract change returning levels back to optimum
Conditions controlled by sep mechanisms in negative feedback
Departures In different directions from original state can all be controlled
Giving greater degree of control
Positive feedback
Receptors detect change from normal
Effectors respond to amplify change
Producing greater deviation from normal
Glycogenesis
Glucose 2 glycogen
Glycogenolysis
Glycogen to glucose
Gluconeogenesis
AA or glycerol to glucose
Insulin’s role In decr BGC
Beta cells in IOL in pancreas detect BGC too high so secrete insulin
Attach to specific receptors on CSM of target cells like liver
Causing more glucose channel protiens to join CSM
increasing permeability to glucose so more glucose enter cell by FD
Also activates enzymes for glycogenesis
Lowering glucose conc in cells creating a conc gradient so glucose enters cells via FD
Glucagon in incr BGC
Alpha cells In IOL in pancreas detect BGC too low so they secrete glucagon
Attach to specific receptors on target cells eg liver activating enzymes for glycogenolysis and gluconegensis establishing a conc gradient so glucose enters blood via FD
Adrenaline role in increasing BGC
Adrenal glands secrete adrenaline
Attach to specific receptors on CSM of target cells eg liver
Activating exhumed for glycogenolysis
Establishing a conc gradient so glucose enters blood via FD
2nd messenger model of adrenaline and glucagon action
Adrenaline and glucagon attach to specific receptors on cell memb which
Activate enzyme adenyl Cyclade which changes shape
Which convert many ATP to many cyclic AMP
cAMP acts as 2nd msngr activating protein kinase enzymes
Protein kinases activate enzymes to break down glycogen to glucose
Adv of 2nd msngr model
Amplify signal from hormone
As each hormone can stimulate production of many molecules of cAMP which can in turn activate many enzymes for rapid increase in glucose
Type 1 diabetes
B cells in IOL. In pancreas produce insufficient insulin
Normally develop in childhood due to auto immune response destroying B cells of IOL
controlled by injections of insulin
Bgc monitored with biosensors and dose of insulin matched to glucose intake
Eat regularly and control carbs
Type 2 diabetes
Receptors lose responsiveness to insulin so fewer glucose transport protein less uptake of glucose and less conversion of glucose to glycogen
Reduce sugar and fat intake
More exercise and lose weight
Why can’t insulin be taken as tablet
Insulin is a protein
Would be hydrolysed by endo and exopeptidases
Formation of glomerular filtrate
High hydrostatic pressure in glomerulus as diameter of afferent arteriole > efferent arteriole
Small substances like water glucose forced into glomerular filtrate filtered by
Pores podocytes and capillary basement memb
Large protiens remain in blood
Reabsorp of glucose by PCT
Na AT out epithelial cells to capillary
na moves by FD into epithelial cells down a conc gradient bringing glucose against its conc gradient
Glucose moves into capillary by FD down its conc gradient
Reabsorp of water by PCT
Glucose in capillary lowers wp
Water moves by osmosis down a WPG
Features of cells in PCT allowing rapid Reabsorp of glucose into blood
Microvilli provide LSA
many channel and carrier protiens for FD and co transport
Many Mitochondria produce ATP FOR AT
many ribosomes produce carrier and channel protiens
Why is glucose found in urine of untreated diabetic
BGC is too high so not all glucose re absorbed at the PCT
As glucose carrier and co transporter protiens are saturated and working at max rate
