Homeostasis Flashcards
What happens at high glucose levels?
Insuliin secreted
Increase in glucose carriers/channels resulting in increased glucose uptake
glucose is converted to glycogen
What happens at low glucose levels?
Glycogenolysis
Gluconeogenesis
What is glycogensis?
Glucose to glycogen
What is gluconeogenesis?
Amino acids and fats into glucose
What is glycogenolysis?
Glycogen into glucose
How does adrenaline change blood glucose concentration?
Binds to receptors on the surface of liver cells which activates the enzyme adenyl cyclase which converts ATP into cAMP to activate protein kinase, stimulating glycogenolysis
What are the causes of type 1 and type 2 diabetes?
Type 1:
- Genetic origin where B cells are destroyed by the immune system
Type 2:
- Cells become insensitive to insulin due to lifestyle factors
How are type 1 and type 2 diabetes controlled?
Type 1:
Insulin injections to regulate blood glucose levels
Type 2:
Oral medication. Strict diet management and increased exercise
What is the difference between positive and negative feedback?
Negative feedback is when the body opposes the change to bring it back to normal but positive feedback is the response to the change is to continue the change
What is the composition of the filtrate?
Water, glucose, urea and mineral ions can pass through the Bowman’s capsule.
Where does ultrafiltration occur?
Bowman’s/renal capsule
What features allow ultrafiltration to happen?
- Afferent arteriole is wider than the efferent arteriole building hydrostatic pressure
- Small substances get filtered out and can fit between haps between podocytes to enter the Bowmans capsule
How is the proximal convoluted tubule adapted for efficient absorption?
Microvilli increase surface area
High number of mitochondria for ATP for active transport
Foldings near blood capillaries to increase the surface area
How does selective reabsorption of glucose and amino acids occur in the proximal convoluted tubule?
Form of co-transport
Sodium ions are moved from the epithelia ccells of PCT into the blood so more sodium ions diffuse into the PCT pulling glucose and amino acids with them
How does selective reabsorption of water occur?
Sodium ions are actively transported from the PCT into the blood lowering the water potential so water travels into the blood via osmosis
What happens in the descending limb of the loop of Henle?
Walls are permeable to water so it leaves by osmosis
What happens in the ascending limb of the loop of Henle?
Sodium and chloride ions diffuse out of the fluid at the base and actively transported at the top. impermeable to water
What is the counter current multiplier?
The lower water potential is at the hair pin of the loop of Henle, so there is a counter current flow as the water flows down both the descending loop and collecting duct.
Where are the osmoreceptors found?
Hypothalamus
What happens to the osmoreceptors at low water levels?
Shrink
What happens when blood water levels are too low?
Osmoreceptors in hypothalamus shrink triggering increased released of ADH from pituitary gland. ADH stims the increase in number of aquaporins so the collecting duct is more permeable to water allowing water to return to the blood.
What is homeostasis?
The maintenance of a constant internal environment
Why must body temp remain constant?
As temp increases, so does kinetic energy. As temperature moves past the optimum, molecules vibrate more and hydrogen bonds within the enzyme break changing the shape of the active site
Why must blood glucose concentration remain constant?
If blood glucose is too high, it lowers the water potential of the blood causing water to move from cells into the blood causing the cells to die
How does negative feedback work?
Receptors detect change
Communicated by the nervous or hormonal system
Change is brought about by effectors
What is the name of the cells that make up the epithelium of the Bowmans capsule?
Podocytes
What is the purpose of the microvilli in the proximal convoluted tubule?
Increases the surface area for selective reabsorption
Why do some organisms have longer loops of Henle?
Allows organisms that live in dry habitats to reabsorb more water from the glomerular filtrate