Homeostasis Flashcards
What happens when blood sugar levels are too high/too low?
When beta cells in the pancreas detect an increase in blood glucose levels, they release insulin. Alternatively, if alpha cells detect a decrease in blood glucose levels then they release glucagon. Both of these hormones alter the amount of glycogen present in the liver.
What is the difference between glucagon and glycogen?
Glycogen is a stored form of glucose (sugar). Your body primarily stores glycogen in your liver and muscles. Glucagon is a hormone that triggers liver glycogen to convert back into glucose and to enter your bloodstream so that your body can use it for energy
What are the target cells for insulin?
Adipose (fat), skeletal muscle (muscle connected to skeleton), liver cells.
What is glucagon?
a hormone secreted by alpha cells of the pancreas when blood glucose levels are low
What is glycogen?
Another source of glucose.
Glycogen is essentially a long series of glucose molecules joined together, and in this form, glucose can be stored for prolonged periods of time in cells.
Can be broken down back into glucose via glycogenolysis
What is glycogenesis?
Glycogen is produced by the process known as glycogenesis that joins glucose absorbed by skeletal muscle and liver cells together into glycogen.
What is glycogenolysis?
When you don’t eat for a long period of time, or you exercise strenuously and use up all your available blood glucose, glycogen is broken down via a process called glycogenolysis back into glucose.
How is glucose transported?
Glucose is transported in blood plasma around the body. When we talk about the concentration of glucose in the body at any one time, we refer to this as the blood glucose level.
What does it mean if someone is hyperglycaemic?
the state of having blood glucose levels above the normal range (>7.8 mmol/L)
Can harm the body
What does it mean if someone is hypoglycaemic?
the state of having blood glucose levels below the normal range (<4.0 mmol/L)
may not be able to provide their cells with enough energy to function properly.
What is the receptor in the negative feedback loop model for blood glucose?
The receptor in the model is the pancreas, specifically, clusters of specialised cells called the islets of Langerhans. These islets are comprised of two types of cells – alpha cells and beta cells – and it is these cells that detect blood glucose levels
What is the modulator in the negative feedback loop model for blood glucose?
The modulator in the regulation of glucose is also the islets of Langerhans.
Insulin or glucagon is released depending on whether glucose levels are high or low
What is a beta cell?
cells that occupy the islets of Langerhans and secrete insulin
What is an alpha cell?
cells that occupy the islets of Langerhans and secrete glucagon
What are the islets of Langerhans?
regions of the pancreas that contain cells that secrete hormones
Where is glucose stored?
In the liver
Why is glucose needed?
To generate usable energy (ATP) via cellular respiration
What happens when blood glucose levels increase?
When above the normal level, beta cells release insulin that stimulate two different effectors. Skeletal muscle/fat cells and liver cells.
When cells absorb glucose, glucose levels in the blood are lowered. Once levels are around 5 mmol/L, insulin will stop being released by beta cells and these two effectors will no longer be stimulated.
How does insulin stimulate skeletal muscle and fat cells?
Skeletal muscle and fat cells absorb more glucose from the blood. When insulin binds to these cells, glucose transporters are inserted into the cells’ membrane, thus increasing the amount of glucose that can be absorbed by the cell via facilitated diffusion.
Once in the cell, this extra glucose can be used by mitochondria to create energy. Additionally, in skeletal muscle cells, some of the absorbed glucose gets turned into glycogen for storage. In fat cells, this extra glucose is converted into fatty acids for long term storage.
