6C homeostasis

Created by

Heather ward

Cards (56)

What is homeostasis?
Homeostasis involves physiological control systems that maintain the internal environment within restricted limits.
what does homeostasis control?
a stable core temperature
stable blood pH in relation to enzyme activity.
how does homeostasis work?
Negative feedback is involved and this is when any deviation from the normal values are restored to their original level. This involves the nervous system and often hormones too.
What increases BGC?
ingestion of food or drink containing carbohydrates
what decreases BGC?
Following exercise or if you have not eaten.
what is the pancreases role in BGC?
detects changes in the blood glucose levels. Islets of Langerhans cells release insulin & glucagon to bring blood glucose levels back to normal.
what is insulins role in BGC?
Released when blood glucose levels are too high. Causes a decrease in blood glucose levels.
what is glucagons role in BGC?
Released when blood glucose levels are too low. Causes an increase in blood glucose levels.
what is adrenalines role in BGC?
Released by adrenal glands when your body anticipates danger & this results in more glucose being released from hydrolysis of glycogen in the liver.
what is the pathway for increased BGC?
Blood glucose levels increases
detected by the beta cells in the slets of Langerhans (pancreas)
Beta cells release insulin
Liver cells become more permeable to glucose and enzymes are activated to convert glucose to glycogen
Glucose is removed from the blood and stored as glycogen in cells
Normal blood glucose levels
what is the pathway when BGC is low?
Blood glucose levels decrease
detected by the alpha cells in the islets of Langerhans (pancreas)
Alpha cells release glucagon
Adrenal gland release adrenaline
Second messenger model occurs to activate enzymes to hydrolyse glycogen
Glycogen is hydrolysed to glucose and more glucose is release back into the blood.
normal blood glucose levels
how does insulin decrease BGC?
does this in 3 ways
Attaching to receptors on the surfaces of target cells. This changes the tertiary structure of the channel proteins resulting in more glucose being absorbed by facilitated diffusion.
More protein carriers are incorporated into cell membranes so that more glucose is absorbed from the blood into cells.
Activating enzymes involved in the conversion of glucose to glycogen. This results in glycogenesis in the liver.
How does glucose increase BGC?
does this in 3 ways
Attaching to receptors on the surfaces of target cells (liver cells).
When glucagon binds it causes a protein to be activated into adenylate cyclase and to convert ATP in a molecule called cyclic AMP (CAMP). CAMP activates an enzyme, protein kinase, that can hydrolyse glycogen into glucose
Activating enzymes involved in the conversion of glycerol and amino acids into glucose.
how does adrenaline increase BGC
Adrenaline attaches to receptors on the surfaces of target cells. This causes a protein (G protein) to be activated and to convert ATP into CAMP.
CAMP activates an enzyme that can hydrolyse glycogen into glucose
This is known as the second messenger model of adrenaline and glucagon action, because the process results in the formation of cAMP, which acts as a second messenger.
what is the role of the liver in controlling BGC?
the site of glycogenesis, glycogenolysis, and gluconeogenesis
what is glycogenesis?
Converting glucose into glycogen. This occurs in the liver and is catalysed by enzymes there.
what is Glycogenolysis
Hydrolysis of glycogen to glucose. This occurs in the liver due the second messenger model.
what is Gluconeogenesis
Creating of glucose from other molecules, such as amino acids and glycerol in the liver.
outline type 1 diabetes?
Unable to produce insulin.
Usually starts in childhood & could be the result of an autoimmune disease where the beta cells are attacked. Treatment involves injections of insulin.
outline type 2 diabetes?
Receptors on the target cells lose their responsiveness to insulin. Usually develops in adults because of obesity & poor diet. It is controlled by regulating intake of carbohydrates, increasing exercise and sometimes instin injections.
what is osmoregulation?
the control of water potential in the blood.
what happens if blood water potential is too low?
Too much water will leave the cells and move into the blood by osmosis. Cells will shrivel (crenation)
what happens if blood water potential is too high?
Too much water will move from the blood into the cells by osmosis. Cells will burst (lysis)
What causes blood water potential to be too low?
Too much sweating
Not drinking enough water
Lots of ions in diet (lots of salt)
how do we correct a high blood water potential?
More water is reabsorbed by osmosis into the blood from the tubules of the nephrons.
This means the urine is more concentrated as less water is lost in the urine.
what causes a low blood water potential?
Drinking too much water
Not enough salt in diet
how do we correct a too low blood water potential?
Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons. This means the urine is more dilute and more water is lost in the urine.
where does osmoregulation occur?
nephrons in the kidneys
what are nephrons?
Nephrons are long tubules surrounded by capillaries and there are around 1 million per kidney.
what occurs in the nephrons?
osmoregulation, The blood is filtered here to remove waste and selectively reabsorb useful substances back into the blood.
describe the process of filtration and reabsorbtion?
Ultrafiltration occurs due to the high hydrostatic pressure. Water & small molecules are forced out of the glomerulus capillaries into the renal capsule.
Selective reabsorption occurs in the proximal convoluted tubule
The loop of Henle maintains a sodium ion gradient so water can be reabsorbed into the blood.
Water moves out of the distal convoluted tubule & collecting duct to return back to the blood.
The collecting duct carries the remaining liquid (urine) to the ureter.
what is the hypothalamouses role in osmoregulation?
osmoreceptors in the hypothalamus detect changes in the blood water potential
how does the hypothalamous detect low blood water potential?
If the water potential of the blood is too low water leaves the osmoreceptors by osmosis and they shrivel. This stimulates the hypothalamus to produce more of the hormone ADH.
how does the hypothalamus detect high blood water potential?
If the water potential of the blood is too high water enters the osmoreceptors by osmosis. This stimulates the hypothalamus to produce less ADH
where is ADH produced?
hypothalamus
how does ADH enter the kidney?
The hypothalamus is where ADH is produced. ADH then moves to the posterior pituitary and from here it is released into capillaries and into the blood.
ADH travels through the blood to its target organ, the kidney.
describe the pathway when blood water potential is too high?
Water potential of blood increases (too much water)
detected by osmoreceptors in hypothalamus.
Hypothalamus releases less ADH
DCT and collecting duct walls become less permeable to water
Less water is reabsorbed into the blood and more is lost in the urine (dilute urine)
Normal water potential of blood
describe the pathway if blood water potential is too low?
Water potential of blood decreases ( not enough water)
detected by osmoreceptors in hypothalamus.
Hypothalamus releases more ADH which is released into the blood by the posterior pituitary gland
DCT and collecting duct walls become more permeable to water
More water is reabsorbed into the blood and less is lost in the urine (concentrated urine)
Normal water potential of blood
describe how ADH increases blood water potential?
Causes an increase in the permeability of the walls of the collecting duct & distal convoluted tubule to water.
This causes more water to leave the nephron and be reabsorbed into the blood, so urine is more concentrated.
what is ADH
Antidiuretic hormone