lecture 5 glucose homeostasis Flashcards
Describe the mechanisms that maintain blood sugar in the fed state (after eating) Describe the mechanisms that maintain the blood sugar during fasting (time before eating) (18 cards)
what are the key forms of diabetes
type 1 diabetes: cannot secrete inulin. its an autoimmune disease.
type 2 diabetes: lifestyle, can still secrete insulin but slowly degrades.
why is it important to regulate glucose levels
the brain is dependant on it. its the main source of energy for the brain. the brain does not have the ability to store glucose. the brain can use ketones and fatty acids as fuels but are poor. he normal set point of glucose is 5 millimolar. anything below three, we are at risk of a coma.
what is the principle of feedback loops
stimulus enters the body (variable)
the change get detected by usually a receptor
this triggers a response relevant to the change in the set point.
initiation event or stimulus, variable, receptor notices the change in variable, control centre compares it to the set point, effectors make adjustment to the variable.
what happens when glucose enters the body
glucose moves from the gut, to the blood, to the target tissue. this happens through diffusion. eg. when you eat a donut, the glucose is higher in your gut than in your blood. it will then move to your blood and then diffuse (facilitated) to that target tissue.
why is diffusion itself not enough of a mechanism to regulate our blood glucose.
diffusion by itself will mean there will be a spike and a come down, this means that the more we keep eating, the more our blood sugar spikes and is not regulated.
how exactly does diffusion work for glucose to enter the cell membrane.
we use transporters to allow facilitated diffusion. we have SGLT (sodium glucose transporter) and GLUT (glucose transporter)
what are the tissues that glucose diffuses into
skeletal muscle: as majority of our body is made up of skeletal muscle, this provides a massive sink for glucose to move out of the blood into the tissue.
fat: we also have a lot of fat so it absorbs a lot of glucose
liver: not only does it take up glucose and stores it, it can also make glucose, regulating glucose levels.
SGLT (sodium glucose transporter)
allows sodium and glucose to enter the cell. facilities diffusion. because of this, it can take out glucose and take it in when the gradient of glucose changes. they are important for the movement of glucose but they are not required for the control of glucose. they are seen in the small intestine- move glucose from gut to the blood. and kidney - takes glucose in the urine in the nephron so we can keep it and not take it out. they both just try to take as much glucose as we can.
SLGT 2 inhibitors what are they and its impact
they block the SLGT transporters so instead of keeping t in in the kidney, we pee it out, helpful for those with type 2 diabetes as they struggle with high levels of glucose.
GLUT transporters types and function
GLUT 4 transporters: found in fat and muscle
GLUT 2: found in liver
how do we regulate glucose using GLUT transporters
the glucose is converted into glycogen in the target tissues during the fed state. in the fasted state, the pancreas releases glucagon to the liver to release stored glycogen as glucose
muscles and glucose relationship
GLUT 4 take sup glucose in to the muscle cell. it will get converted through the pyruvate to glycogen to allow us to take up more glucose and not saturate the muscle or prevent reaching equilibrium. during the fasting state or exercise (aerobic or anaerobic) we use glycogen stores as energy and turn it into lactate (glycolysis). when we go into extreme fasting state, we will then break down muscles into amino acids to be used as energy.
fat cells and glucose
works the same way as muscles but uses different molecules. instead of glycogen, it stores glucose as triglycerides using fatty acids. during the fasting state, we will use triglycerides which turns into glycerol and free fatty acids as energy.
liver and glucose levels
glucose enters the liver and gets stored using glycogenesis. it can also generate glucose during the fasting state and move out to the blood. additionally, it can utilise glycerol (fatty acids into energy-ketones), amino acids, lactate or amino acids to generate more glucose.
how do we regulate glucose
two control mechanisms:
insulin (beta cells) during fed state and glucagon Alpha cells) during fasting state.
muscles, regulation of glucose
insulin is secreted from the pancreas using beta cells, going into the muscles through GLUT 4 transporters. unlike normal regulation processes where it causes phosphorylation, GLUT 4 is present in the membrane of vesicles. when the insulin bind to the insulin receptors, these vesicles fuse with the membrane and inserts GLUT 4 transporters to the membrane. they get attached and removed from the membrane all the time. the insulin makes this process quicker.
fat and glucose regulation
works the same way as skeletal muscle
