homeostasis Flashcards
what is homeostasis
homeostasis in mammals involves a physiological control systems that maintain a constant internal environment
why is it important that core temperature remains stable?
- maintain a stable rate of enzyme-controlled reactions and prevent damage to membranes
- temperature too low = enzyme and substrate molecules have insufficient kinetic energy
- temperature too high = enzymes denature
why is it important that blood pH remains stable?
- maintains a stable rate of enzyme-controlled reactions and optimum conditions for other protein
- if too acidic pH = H+ ions interact with hydrogen bonds and ionic bonds in the tertiary structure of enzymes, the shape of the active site changes so no substrate-enzyme complexes form
why is it important that blood glucose concentration remains stable?
- maintain constant blood water potential to prevent osmotic damage
- maintain a constant concentration of respiratory substrate, organism maintains a constant level of respiration regardless of environmental conditions
define negative and positive feedback
- negative feedback - self-regulatory mechanisms return the internal environment to optimum when there is a fluctuation
- positive feedback - a fluctuation triggers changes that result in an even greater deviation from that normal level
outline the general stages involved in negative feedback
- receptors detect a deviation
- effectors activate mechanisms to return body to optimum
suggest why separate negative feedback mechanisms control fluctuations in different directions
provides more control in cases of overcorrection which would lead to a deviation in the opposite direction from the original one
suggest why coordinators analyse inputs from several receptors before sending an impulse to effectors
- receptors may send conflicting information
- optimum response may require multiple types of effectors
why is there a time lag between hormone production and response by an effector?
it takes time to:
- produce hormone
- transport hormone in the blood
- cause required change to the target protein
name the factors that affect blood glucose concentration
- amount of carbohydrate digested from diet
- rate of glycogenolysis
- rate of gluconeogensis
define glycogenesis, glycogenolysis and gluconeogenesis
- glycogenesis - liver converts glucose into glycogen
- glycogenolysis - liver hydrolyses glycogen into glucose
- glyconeogenesis - liver converts glycerol and amino acids into glucose
outline the role of glucagon when blood glucose concentration decreases
- alpha cells in islets of Langerhans in the pancreas detect decrease and secrete glucagon into the bloodstream
- glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
- glucose diffuses from the liver into the bloodstream
outline the role of adrenaline when blood glucose concentration decreases
- adrenal glands produce adrenaline, it binds to surface receptors on liver cells and activates enzymes for glycogenolysis
- glucose diffuses from liver into bloodstream
outline what happens when blood glucose concentration increases
- receptors in the pancreas detect an increase in blood glucose
- beta cells in the islets of Langerhans secrete insulin into bloodstream
- insulin binds to surface receptors on target cells in the liver and muscle, increasing their permeability to glucose
- absorption of glucose by facilitated diffusion increases, and glycogenesis occurs
- rate of respiration increases, glucose used up as respiratory substrate
describe how insulin leads to a decrease in blood glucose concentration
- increases the permeability of cells to glucose
- increases glucose concentration gradient
- triggers inhibition of enzymes for glycogenolysis
