6.4 Homeostasis is the Maintenance of a Stable Internal Environment Flashcards
What is homeostasis?
Internal environment is maintained within set limits around an optimum
Why is it important that core temperature remains stable?
- Maintain stable rate of enzyme controlled reactions and prevent damage to membranes
- Temp too low = enzyme and substrate molecules have insufficient kinetic energy
- Temp to high = enzymes denature
Why is it important that blood ph remains stable?
- Maintain stable rate of enzyme controlled reactions and optimum conditions for other proteins
- Acidic pH = H+ ions interact with H bonds and ionic bonds in tertiary structure of enzymes - shape of active site changes so no ES complexes form
Why is it important that blood glucose concentration remains stable?
- Maintain constant blood water potential: prevent osmotic lysis
- Maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions
Define negative feedback
Self-regulatory mechanisms return internal environment to optimum when there is fluctuation
Define positive feedback
A fluctuation triggers changes that result in an even greater deviation from the normal level
Outline the general stages involved in negative feedback
- Receptors detect deviation
- Coordinator
- Corrective mechanism by effector
- Receptors detect that conditions have returned to normal
Suggest why separate negative feedback mechanisms control fluctuations in different directions
Provides more control, especially in case 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 effector
Why is there a time lag between hormone production and response by effector?
It takes time to:
- produce hormone
- transport hormone in the blood
- cause required change to target protein
Name the factors that affect blood glucose concentration
- Amount of carbohydrate digested from diet
- Rate of glycogenolysis
- Rate of gluconeogenesis
Define glycogenesis
Liver converts glucose into glycogen
Define glycogenolysis
Liver hydrolyses glycogen into glucose which can diffuse into blood
Define gluconeogenesis
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 pancreas detect decrease and secrete glucagon into bloodstream
- Glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
- Glucose diffuses from liver into bloodstream
Outline the role of adrenaline when blood glucose concentration decreases
- Adrenal glands produce adrenaline. Binds to surface receptors on liver cells and activate enzymes for glycogenolysis
- Glucose diffuses from liver into bloodstream
Outline what happens when blood glucose concentration increases
- Beta cells in Islets of Langerhans in pancreas detect increase and secrete insulin into bloodstream
- Insulin binds to surface receptors on target cells to:
a) increase cellular glucose uptake
b) activate enzymes for glycogenesis
c) stimulate adipose tissue to synthesise fat