Homeostasis Flashcards
What is homeostasis?
Homeostasis is the regulation of internal conditions in cells or organisms to maintain optimal function despite internal and external changes.
It ensures optimal conditions for enzyme action and cellular processes within specific limits.
What are feedback mechanisms?
By which a receptor responds to a stimulus created by the change by the effector this is important as receptor stops stimulating the effector and over correction is avoided.
What is negative feedback?
Creates a more to counteract a decrease however if decrease is too much may not be able to counteract
What is positive feedback?
amplifies the change however not part of homeostasis as doesn’t regulate.
What is an example of negative feedback?
- Blood glucose levels are detected by α cells in the pancreas
- Glucagon is produced by these cells in response to low levels
- Liver hydrolyses glycogen
- Increased blood glucose level reduces the stimulus of α cells, glucagon production reduced.
What is an example of positive feedback?
For example Na+ channel permeability during action potential.
What is the difference between positive and negative feedback?
Negative regulates however positive deviates from optimal range.
What’s the effects of adrenaline?
- Glycogen break-down
- Increase heart and breathing rate
- Pupils dilate
- Blood diverted to muscles
What is the Second Messenger Model?
- Adrenaline binds to its receptor on the target liver cell
- Receptor changes shape activating adenyl cyclase
- Activated adenyl cyclase converts ATP to cAMP
- cAMP binds to protein kinase, changes its shape, and therefore activates PK, which will convert glycogen into glucose. Glucose leave cells by facilitated diffusion
Role of pancreas in homeostasis
The pancreas is a large gland behind the stomach that plays a dual role in digestion and blood sugar regulation. It produces:
- Digestive enzymes: protease, amylase, and lipase
- Hormones: insulin and glucagon, which regulate blood glucose levels
The pancreas consists mainly of enzyme-producing cells, with hormone-producing cells (islets of Langerhans) scattered throughout. These islets contain:
- α cells: Larger cells that produce glucagon
- β cells: Smaller cells that produce insulin
Role of the Liver in homeostasis
The liver, a large organ below the diaphragm, plays a crucial role in regulating blood glucose. It performs three key processes:
- Glycogenesis: Converts glucose to glycogen for storage
- Glycogenolysis: Breaks down glycogen into glucose when needed
- Gluconeogenesis: Produces glucose from non-carbohydrate sources
Regulation of blood glucose concentration
Glucose is vital for cellular respiration in most organisms. In mammals, maintaining stable blood glucose levels is crucial. Too low levels can cause cell death, while too high levels can lead to osmotic imbalances, dehydration, and potentially death. Therefore, blood glucose concentration must be tightly regulated.
Where are Insulin and the β cells located
β cells in the islets of Langerhans detect a rise in blood glucose concentration and secrete insulin directly into the blood plasma.
How does insulin work
The number of GLUTs increase on the cell surface
Glucose transport carrier proteins are stored in vesicles
Vesicles move to cell surface where they fuse with the membrane
More GLUTs available for glucose transport
Enzymes which convert glucose to glycogen and fat are activated
How does Glucagon and the α cells work
α cells in the islets of Langerhans detect a fall in blood glucose concentration and secrete glucagon directly into the blood plasma
Glucagon binds to receptors on liver cells and activate enzymes which convert glycogen into glucose.
Glucagon also activates enzymes involved in gluconeogenesis.
As the blood glucose concentration increases, production of glucagon also decreases -negative feedback.
