Homeostasis 5.2 Flashcards
What happens if blood glucose is too high?
The water potential of blood is reduced to a point where water molecules diffuse out of cells into the blood by osmosis, this can cause cells to shrivel and die.
What happens if a level becomes too high or too low?
Receptors detect a change and the information is passed on to the effectors via the CNS or hormonal system. The effectors respond to counteract the change. The mechanism that restores the level to normal is called a negative feedback mechanism.
What do positive feedbacks do?
Some changes trigger a positive feedback mechanism, which amplifies change. The effectors respond to further increase the level away from the normal level. It is useful to rapidly activate something. E.g. A blood clot after an injury.
What are Ectotherms and how do they control body temperature?
Reptiles, fish
They can’t Control their own body temperature internally, their internal temperature depends on the external temperature. Their activity level depends on the external temperature they’re more active at higher temperatures.
What are endotherms and how do they control their body temperature?
Mammals, birds
Control their body temperature internally by homeostasis
Three ways in which mammals can bring down body temperature….
Heat loss
Hairs lie flat
Vasodilation
How do mammals raise their internal body temperature?
Shivering
Hormones
What is Homeostasis?
The maintenance of a constant internal Environment
How do mammals increase body temperature?
Less sweat
Hairs stand up
Vasoconstriction
Which cluster of cells in the pancreas secretes insulin and which secretes glucagon?
Beta cells secrete insulin
Alpha cells secrete glucagon
Together these clusters of cells are called islets of langerhans
How does insulin lower blood glucose?
Insulin binds to specific receptors on cell membranes of liver cells and muscle cells. It increases the permeability of cell membranes to glucose, so the cells take up more glucose. Insulin also activates enzymes that convert glucose into glycogen, cells are able to store glycogen in their cytoplasm as an energy source. This process of glucose to glycogen is glycogenesis.
How does glucagon raise blood glucose?
Glucagon binds to specific receptors on the cell membranes of liver cells. It activates enzymes that break down glycogen into glucose this process is called glycogenolysis.
How does adrenaline raise glucose levels in the body (same for glucagon)?
Bind to specific receptors and activate an enzyme called adnylate cyclase. His activated enzyme converts ATP into a second messenger called cyclic AMP (cAMP). cAMP activates a cascade that break down glycogen into glucose.
What does the hormone FSH do?
Stimulates the release of an egg from the ovary and the ovaries to oestrogen
What does LH do?
Stimulates ovulation and the corpus luteum to develop
