Regulating blood glucose level

People obtain glucose from the food that they eat, predominantly starch-rich foods such as potatoes, rice, bread, and pasta.

Glucose is the key metabolic substrate for tissue energy production. Glucose is one of the body’s principal fuels. It is an energy-rich monosaccharide sugar that is broken down in body cells to produce adenosine triphosphate.

Regulating the blood glucose level is a challenging control problem for the human body.

Prolonged irregularities in the blood glucose level can result in major health problems such as diabetes, an incurable disease caused when the pancreas no longer makes insulin (type 1 diabetes), or when the pancreas cannot make enough insulin and the body develops insulin resistance (type 2 diabetes).

The key hormones which regulate glucose homoeostasis include insulin, glucagon, epinephrine, norepinephrine, cortisol and growth hormone.

After meals, the body is said to be in an absorptive state as it absorbs nutrients from the gut. Blood-glucose levels rise although this is buffered by glucose storage in the liver.

*Rising blood glucose levels after a meal stimulates insulin release which disposes of this load. Falling blood glucose levels stimulates glucagon, which maintains a basic minimum level of glucose in the blood. Glucagon works primarily on the hepatocytes in the liver to:
● Convert stored glycogen into glucose and release it into the blood;
● Promote gluconeogenesis

*Norepinephrine and epinephrine help maintain normal blood glucose levels by stimulating glucagon release, glycogenolysis, and food consumption, and by inhibiting insulin release.

*Cortisol, a steroid hormone, is synthesized from cholesterol. Cortisol increases the availability of blood glucose to the brain. Cortisol acts on the liver, muscle, adipose tissue, and pancreas. In the liver, high cortisol levels increase gluconeogenesis and decrease glycogen synthesis.

*Growth hormone therapy antagonizes insulin's action on peripheral tissues, such as the skeletal muscle, liver, and adipose tissue, thereby increases glucose production from the skeletal muscle and liver and decreases glucose uptake from adipose tissue.
Regulating blood glucose level

Calcium homeostasis

Homeostasis is a condition of a cell which describe a steady state of flow of material and energy. Calcium homeostasis can be defined as a state of optimum calcium balance in the body.

Approximately 99% of body calcium is in bone, most of the remaining 1% is in extracellular fluid. Calcium is an important regulator of many cellular functions in the body, including neuromuscular activity, blood coagulation, intercellular signal transmission, exocrine-endocrine functions and the control of cell membrane potentials.

Calcium balance is regulated by parathyroid hormone and calcitriol.

The cell- surface-calcium-sensing receptor (CASR) is expressed abundantly in the parathyroid hormone or PTH producing chief cells of the parathyroid gland, the calcitonin-producing C-cells of the thyroid and the cells lining the kidney tubule. It increases serum calcium by stimulating bone resorption, increasing reclamation in the kidney and promoting renal conversion of vitamin D to calcitriol.

Calcitriol is the active form of vitamin D and it stimulates intestinal absorption of calcium and is one of many factors that provide feedback to the parathyroid gland.

Calcium is absorbed in the proximal tubules though a solvent gradient but active transport occurs in the distal portions by a sodium calcium exchange pump. Some calcium absorption also takes place in the loop of Henle via an electrochemical gradient.

Calcium homeostasis is important in critically ill patients to prevent blood pressure and cardiac instabilities.
Calcium homeostasis