Regulation of plasma glucose Flashcards
What is the normal range of plasma glucose?
100 mg/dL
5.5 mmol/L
What is hypoglycemia?
A drop in blood glucose
What happens to the body during hypoglycemia?
Different organs have different dependencies on glucose
Brain - requires continuous glucose supply, very sensitive to changes - main source of energy for neural cells
Heart - can produce energy from fatty acids
Liver - hepatocytes have glycogen storage and can catalise metabolites to make ATP - not sensitive to glucose changes
Muscle - glycogen is primary fuel - large storage of glycogen
What happens to the brain during hypoglycemia?
A limited amount of glucose can be derived from the glycogen stored in astrocytes - consumed within minutes
cognitive dysfunction -> seizure -> coma
What is hyperglycemia?
High blood glucose
Normal if transcient
If prolonged - complications
What are the short term complications from hyperglycemia?
Increased urine output
Thirst
Ketoacidosis
What are the long term complications from hyperglycemis?
Atherosclerosis
Kidney failure
Eye complications
Diabetic foot ulcer
How is glucose in the plasma maintained?
Exchanged between the cytoplasm and the extracellular fluid
Can glucose pass through the membrane by diffusion?
NO
What facilitates trasfer of glucose into cells?
Carrier proteins
What are the different types of carrier proteins found in cells?
GLUT - 1
GLUT - 2
GLUT - 3
GLUT - 4
Where is the carrier protein GLUT-1 found?
Brain and RBC
Where is the carrier protein GLUT-2 found?
Liver, pancreas and intestine
Where is the carrier protein GLUT-3 found?
Brain and kidney
Where is the carrier protein GLUT-4 found?
Muscle and adipose tissue
What glucose protein carrier is insulin dependent?
GLUT - 4
Which hormones enhance the catabolic pathways of glucose metabolism?
Glucagon
Epinephrine
Which hormone enhances the anabolic pathways of glucose metabolism?
Insulin
What is the cells response to low blood glucose?
- Activates catabolic pathways at the cell metabolic level
- Glycogen -> glucose = glycogenolysis
- Amino acids -> glucose = gluconeogenesis
- Lipids -> Acetyl CoA = beta oxidation
Which amino acids can undergo gluconeogenesis?
Glucogenic amino acids
All but leucine and lysine
From essential proteins
What happens to Acetyl-CoA formed by beta oxidation of lipids?
Enters the Krebs cycle to form ATP
Form ketone bodies - byproducts of Acetyl-CoA formation
Can be used as a source of energy
What is the cells response to high blood glucose?
- Activation of anabolic pathways in cells
- Excess glucose is stored as:
glycogen -> glycogenesis
makes lipids using Acetyl-CoA -> lipogenesis
Make amino acids - assembled to make proteins -> non-essential amino acidss
Which sensors detect hypoglycaemia?
Endocrine pancreas
Autonomic nervous system
What does the endocrine pancreas release in response to hypoglycaemia?
Makes glucagon
Receptors for glucagon afre found in the liver
Glucagon activates catabolic pathways in hepatocytes to make glucose
What does the ANS do in response to hypoglycemia?
Vasoconstriction and activation of sweat glands
Leads to manifestation of hypoglycemia - pale facre and cold sweat
Stimulates the medulla of the adrenal gland to release catecholamines - have receptors on hepatocytes to activate catabolic pathways
Catecholamines also cause tachycardia
What sensors detect hyperglycemia?
Endocrine pancreas
What does the endocrine pancreas release in response to hyperglycemia?
Insulin
What does insulin do in response to hyperglycemia?
- Increases expression of GLUT-4 receptors on CSM of muscle and adipose tissue
Blood glucose goes down since there are more glucose transporters to transport glucose into the cells
- Regulates anabolic metabolism in liver, muscle and adipose tissue
