6: Homeostasis Flashcards
(37 cards)
Homeostasis definition?
Maintaining a stable internal environment, by using negative feedback mechanisms, in response to changes to the external and internal environment
What happens if blood glucose concentration is too high?
Water potential of blood is reduced - water molecules diffuse out of cells into the blood by osmosis - cells shrivel up and die
Normal blood glucose concentration?
90mg per 100cm3
What cells in the pancreas control blood glucose concentration?
the islets of Langerhans
Which cells in the pancreas secrete insulin?
Beta cells
Which cells in the pancreas secrete glucagon?
Alpha cells
Where does insulin bind?
to specific receptors on the cell membranes of liver cells and muscle cells
What is the process of forming glycogen from glucose know as?
Glycogenesis
What does insulin do once bound?
Increases the permeability of muscle cell membranes to glucose, involves increasing the number of channel proteins
Activates enzymes in the liver and muscle cells that convert glucose to glycogen - able to be stored in cells cytoplasm
Increases the rate of respiration of glucose
Where do glucagon bind?
Receptors on cell membranes of liver cells
What does glucagon lead to once bound?
Activates enzymes in liver cells that break down glycogen into glucose
Activates enzymes that are involved in the formation of glucose from glycerol and amino acids
Decreases the rate of respiration
What is the process of breaking down glycogen known as?
Glycogenolysis
What is the process of forming glucose from non-carbohydrates called?
Glyconeogenesis
2 features of hormonal communication?
Slower than nervous - travel in blood
Effects last longer - not broken down as quickly as neurotransmitters
What glucose transporter do skeletal and cardiac cells contain?
GLUT4 - channel protein
Where is GLUT4 stored?
vesicles in the cytoplasm of cells
What happens to GLUT4 when insulin binds to receptors?
Movement of GLUT4 to the membrane triggered, glucose transported by facilitated diffusion
Where is adrenaline secreted from?
Adrenal glands
When is adrenaline secreted?
Low blood glucose concentration, stressed, exercising
Where does adrenaline bind?
Receptors on the liver cell membrane
What does adrenaline activate?
Glycogenolysis, glucagon secretion
What does adrenaline inhibit?
Glycogenesis, insulin secretion
Which hormones activate glycogenolysis inside a cell?
Adrenaline, glucagon
What enzyme do adrenaline and glucagon activate once bound to a receptor?
Adenylate cyclase
