Chapter 16 - Homeostasis Flashcards
What is homeostasis?
Maintaining a constant internal environment
Why is homeostasis so important for enzymes?
Enzymes are sensitive to changes in pH and temperature
How are cells protected from changes in the external environment?
The conditions of the tissue fluid are carefully maintained
Why is homeostasis important in terms of water potential?
Water enters/leaves by osmosis, causing cells to swell/shrink
Why is it advantageous that an organism can regulate its internal environment?
It makes the organism more independent
What is the optimum point?
The point at which the system operates best
What is the function of the receptor?
Detects deviation from the optimum point
What is the coordinator?
Coordinates information from receptors to create the correct response
What is an effector?
Restores optimum conditions
What is negative feedback?
The stimulus detected by the receptor turns the system off
What is positive feedback?
Deviation from the optimum causes changes that result in greater deviation
What is the negative feedback system we study in detail?
The glucagon-insulin system
Describe the release of glucagon as a negative feedback system
Receptors detect a fall in glucose concentration. Glucagon is secreted, which causes the liver cells to convert glycogen to glucose and release it into the blood. The receptors then detect this rise in blood glucose concentration and stop releasing glucagon
Why is it advantageous to have two separate negative feedback systems controlling blood glucose concentration?
Gives the organism more control and independence
How do hormones reach the target cells?
Secreted from glands into the blood
Travels in blood plasma to target cells
What effectiveness do hormones have?
They are effective in low concentrations and have long-lasting and widespread effects
Describe the secondary messenger model
Adrenaline binds to a protein receptor on the cell membrane of a liver cell
This causes the protein to change shape inside the membrane
This activates the enzyme adenyl cyclase, which converts ATP to cAMP
The cAMP acts as the second messenger and binds to kinase, activating it
Kinase catalyses the breakdown of glycogen into glucose
What do the alpha cells secrete?
Glucagon
What do the beta cells secrete?
Insulin
What is glycogenesis?
Converting glucose - glycogen
What is glycogenolysis?
Breaking down glycogen to glucose
What is gluconeogenesis?
Producing glucose from sources other than carbohydrates
Why must the blood glucose concentration remain constant?
If it’s too low, there isn’t enough glucose for respiration
If it’s too high, it interferes with the water potential and water moves out of cells by osmosis
What are the three main sources of glucose?
Carbohydrates from the diet, glycogenolysis, gluconeogenesis