Homeostasis Flashcards
Outline the action insulin in lowering blood glucose levels
1) Beta cells in the islets of Langerhans in the pancreas detect the increase of blood glucose
2) beta Cells start secreting insulin and alpha cells stop secreting glucagon
3) Insulin binds on its receptors on the cell surface membrane
4) vesicles of GLUT4 proteins facilitate movement of glucose into the cell
5) Enzyme glucokinase phosphorylates glucose which traps the glucose inside the cell because phosphorylated glucose cannot pass through the transporters in the cell surface membrane
6) enzymes phosphofructokinase and glycogen synthase add glucose mol to glycogen
7) decreases gluconeogenesis
8) Increase his rate of aerobic respiration
Outline the action of glucagon in raising the blood glucose
1) Alpha cells in the isles of Langerhans detect the decrease in blood glucose and start secreting glucagon
2) Beta cells stop secreting insulin
3) Glucagon binds to its receptor on the cell surface membrane
4) This activates a G Protein which in turn catalyses conversion of ATP to cyclic AMP
5) Cyclic AMP binds to kinase enzymes within the cytoplasm and activate other enzymes by phosphorylation
6) Glycogen phosphorylase is the end enzyme and catalyzes the breakdown of glycogen to glucose
7) decreases rate of aerobic respiration
8) increases gluconeogensis
Outline how dipsticks are used for urine analysis
1) Pad is immersed in urine and if it contains glucose glucose oxidase catalyzes a chemical reaction in which glucose is oxidized into a substance called gluconolatone and hydrogen peroxide is produced
2) Peroxidase catalyze a reaction between hydrogen peroxide and a color just chemical in the bra in the pad to form a brown compound
3) The resulting color of the pad is matched against the color chart
What are some of the physiological factors controlled by homeostasis
Core body temp Metabolic wastes Blood ph Blood glucose conc Water potential of blood Conc in blood of respiratory gases
What are the 3 features of tissue fluid that influence cell activities
Temp:low slow down metabolic reactions High denatures proteins and enzymes Water potential:if water potential dec water may move out of cells by osmosis causing metabolic reactions to slow or stop If water potential inc cell may burst Conc of glucose:fuel for respiration
Describe the changes which happen in the body when a drop in body temp occurs
▪️Hypothalamus detects decrease in temperature
▪️vasoconstriction,muscles in walls of arterioles that supply blood to capillaries near the skin surface contract,which reduces heat loss from blood
▪️shivering,involuntary contraction of skeletal muscles generates heat which is absorbed by the blood and carried around the rest of the body
▪️raising body hairs,muscles at the base of hairs in the skin contract to inc depth of fur to trap air
▪️decreasing production of swear,reduces heat lost by evaporation
▪️increasing secretion of adrenaline,inc rate of heat production in liver
▪️hypothalamus releases a hr which activates the pituitary gland to release TSH
▪️TSH stimulates thyroid to secrete thyroxin
▪️thyroxine inc BMR which inc heat production especially in liver
Describe the changes that occur in the body when a rise in temperature is detceted
▪️Rise in temp detected by hypothalamus
▪️vasodilation,muscles in arterioles in the skin relax allowing more blood to flow through the capillaries so that heat is lost to the surroundings
▪️lowering of body hairs,muscles attached to the hairs relax so they lie flat,reducing the depth of fur
▪️inc in sweat production,sweat glands inc production of sweat which evaporates on surface of skin removing heat from body
Outline the process of deamination
In liver cells,(-NH2) the amino group is removed from an amino acid with an extra hydrogen
Combine to produce ammonia(NH3)
Keto acid that remains may enter krebs cycle and be respired or it may be converted glucose or converted to glycogen or fat for storage
ammonia is converted to urea
Describe the structure of a kidney nephron
.bowman’s capsule where ultra filtration occurs
.podocytes in epitelial cells which make the inner lining of the BC
.PCT DCT in cortex where selective reabsorption occurs
.loop of henle in medulla selective re absorption
.distal convluted tubule
.afferent arteriole
.glomerulus
.efferent arteriole
.capillary network around PCT DCT and loop
.Collecting duct where osmoregulation occurs
What is the glomerular filtration rate
Rate at which fluid filters the blood in glomerular capillaries in to the bowmans capsule
How is the proximal convoluted tubule adapted for re absorption
Microvilli to inc surface area of inner lining facing lumen
Tight junctions that hold adjacent cells together so that fluid cannot pass between cells
Many mitochondria to provide energy for the Na-K pump
Co transporter proteins
Describe the process of selective reabsorption the PCT
Na+ and Cl- are actively pumped using ATP from mitochondria
This lowers the the concentration of ions in the cell
Na+ and Cl- diffuse back through co transporter proteins taking glucose with them by secondary active uptake
No glucose is left in filtrate(nor amino acids,vit,ions)
Creatinine secreted in to lumen
Some water and urea reabsorbed
Outline re absorption in the loop of henle
In ascending limb:Na and Cl ions are actively transported out of the ascending limb
This raises the conc of Na and Cl ions in the tissue fluid
So water moves out by osmosis from the descending limb
Loss of water concentrates Cl and Na ions in descending limb
Na and Cl ions diffuse out of this conc sol in the lower part of the ascending limb
Outline the role of homeostasis in osmoregulation
▪️Osmoreceptors in hypothalamus detect decrease in water potential of blood
▪️Impulses are sent to posterior pituitary glands which stimulates the release of ADH
▪️ADH target cells of collecting duct
▪️Binds to receptors in cell surface membrane
▪️Activates a series of enzyme controlled reactions ending with active phosphorylase enzyme
▪️Phosphorylase causes vesicles surrounded by membrane containing water permeable channels to move towards cell surface membrane
▪️Vesicles fuse with cell surface membrane
▪️Cell membrane becomes more permeable to water and water moves by osmosis
▪️Concentrated urine
