Unit 6 Homeostasis & Maintaining Stable Internal environment Flashcards
Describe Homeostasis
- Involves physiological control systems that maintain the internal environment within restricted limits.
Describe what homeostais is important in maintaining
Stable core temperature
- If temp low insufficient kinetic energy for enzyme-controlled reactions, and if body temperature is too high then enzymes will denature
Stable blood pH in relation to enzyme activity
- Alterations in blood pH will also result in enzymes denaturing as changes tertiary structure as canges ionic/hydrogen bonds
Outline the control of blood glucose
- Controlled by the Pancreas
- Contains the Islets of Langerhans
- Made of alpha and beta cells which bring glucose levels back to normal
- Alpha cells produce glucagon
- Beta cells produce insulin
Outline the importance of maintaining a stable blood glucose
concentration
IF HIGH
- Lower the water potential of the blood and water will leave surrounding cells by osmosis and prevent normal cell function.
- IF LOW
- Highers the water potential of blood, water will move into cells by osmosis and can cause them to burst (lyse).
- Glucose is needed for respiration so a lack of glucose in the blood could result in cell death.
Outline postive feedback and give an example
Negative feedback restores systems to their original level
WHEN BLOOD GLUCOSE INCREASES
- Detected by beta cells on islets of Langerhans
- Beta cells release insulin
- Liver cells become more permeable to glucose and enzymes activated to convert glucose to glycogen(Glycogenesis) in liver
- Glucose removed from blood and stores as glycogen in cells
Outline the other example of negative feedback
WHEN BLOOD GLUCOSE DECREASE
- Detected by alpha cells in islets of Langerhands
- Alpha cells release glucagon and adrenal gland releases adrenaline
- Second messenger model occurs to activate enzymes to hydrolyse glycogen
- Glycogen is hydrolysed to glucose(Glycogenolysis) in liver and more glucose realeased back into blood
Define the 3 nesises
Glycogenesis - When excess glucose is converted to glycogen when blood glucose is higher than normal, which occurs in the liver
Glycogenolysis - This is the breakdown of glycogen back into glucose in the liver. This occurs when blood glucose is lower than normal.
Gluconeogenesis (amino acids to glucose) -Process of creating glucose from non- carbohydrate stores in the liver. This will occur if all glycogen has already been hydrolysed back into glucose and your body still needs more glucose.
Describe the action of insulin
- Attaching to receptors on the surfaces of target cells which changes the tertiary structure of the channel proteins resulting in more glucose being absorbed by facilitated diffusion
- More channel proteins fuse into cell membranes so that more glucose is absorbed from the blood into cells via facilitated diffusion
- Activating enzymes involved in the conversion of glucose to glycogen (Glycogenesis)
Describe the action of glucagon
- Attaching to receptors on the surfaces of target cells (liver cells).
- Causes a protein to be activated into adenylate cyclase which
catalyses the conversion of ATP into cyclic AMP. - 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.
- (GLYCOGENOLYSIS AND GLUCONEOGENESIS)
Describe the role of adrenaline
- Adrenaline attaches to receptors on the surfaces of target cells.
- Causes a protein to be activated into adenylate cyclase which
catalyses the conversion of ATP into cyclic AMP. - cAMP activates an
enzyme, protein kinase, that can hydrolyse glycogen into glucose. - cAMP, which acts as a second messenger.
Describe the cause and solutions of diabetes
- Type I diabetes is due to the body being unable to produce
insulin, it starts in childhood and could be the result of an autoimmune disease where the beta cells are attacked. - Treatment involves an injection of insulin and control of diet
- Type II diabetes is due to receptors on the target cells losing their responsiveness to insulin, which usually develops in adults because of obesity and poor diet.
- Controlled by regulating the intake of carbohydrates, increasing exercise and insulin injections.
Define osmoregulation
Osmoregulation as control of the water potential of the blood.
Describe the formation of glomerular filtrate in the nephron
- Decrease in diamater causes high hydrostatic pressure in glomerulus capillaries which forces small molecules (urea, water, glucose, mineral ions)
- Through small gaps in capillary endothelium and through capillary basement membrane into Bowmans capsule however proteins too big forming glomerular filtrate
Describe the reabsorption of glucose and water by the proximal convoluted tubule
- Selective reabsorption where salts (sodium ions) are actively transported from PCT cell into the blood
- Lowers sodium ion concentration in PCT cells, so sodium ions diffuse from the
lumen of the PCT into the PCT cells via facilitated diffusion pull in glucose with them via co-
transport - Glucose and amino acids build up in the cell which then diffuse into the blood/capillary
- Movement of salt/glucose into the blood, lowers its water potential,
so water follows into blood by osmosis
Desrcribe the maintaining a gradient of sodium ions in the medulla by the loop of Henle in the nephron
( LONGER LOOP OF HENLE MEANS MORE SODIUM IONS ACTIVELY TRANSPORTED OUT INTO MEDULLA)
- Sodium and chloride ions are actively transported out of the ascending limb of the into the surrounding medulla of kidney
- Lowers water potential of medulla and ascending limb impermeable to waters so water remains
- Water moves out of the descending limb of loop of henle by
osmosis into intersistial limb and Na+ in - Water then moves into the blood
- Some Na+ ions diffuse out at bottom of ascending limb
- Lowest water potential at bottom and highest at top of ascending limb
