Hormonal communication

Where are the adrenal glands located?

Just above the kidneys.

What are the two main parts of the adrenal glands?

The outer adrenal cortex and the inner adrenal medulla.

What hormone does the adrenal cortex produce?

Steroid hormones, including glucocorticoids and mineralocorticoids.

What is the role of cortisol?

Regulates blood pressure and cardiovascular function in response to stress and metabolism.

What does aldosterone do?

Controls blood pressure by acting on the distal tubule of the kidney to increase water potential.

How does aldosterone affect sodium and water levels?

Activates the Na+/K+ pump, leading to a net gain of Na+ outside the nephron tubule and water retention through osmosis.

What hormones does the adrenal medulla secrete?

Adrenaline and noradrenaline in response to stress.

What is the effect of adrenaline on the body?

Converts glycogen to glucose, increases heart rate, and delivers more glucose and oxygen to muscles and the brain.

What is the normal range for blood glucose levels?

4-6 mmol dm-3 (90 mg/100 cm^3).

What are the symptoms of hypoglycemia?

Mild symptoms include tiredness and irritability; severe symptoms can lead to death, unconsciousness, or seizures.

What happens when blood glucose levels are too high?

Alpha cells stop glucagon secretion, and beta cells secrete more insulin into the blood.

What is the action of insulin on target cells?

Increases cell permeability to glucose and activates enzymes that convert glucose to glycogen (glycogenesis).

What triggers the secretion of glucagon?

Low blood glucose levels detected by alpha cells.

What is glycogenolysis?

The breakdown of glycogen to glucose, activated by glucagon and adrenaline.

What is the role of ATP in beta cells during high blood glucose levels?

High ATP levels close potassium channels, leading to membrane potential changes and calcium influx, which triggers insulin secretion.

How does insulin increase glucose uptake in cells?

By binding to receptors and stimulating the addition of glucose transporter proteins to the cell membrane.

What is glycogenesis?

The synthesis of glycogen from glucose molecules.

What is the effect of adrenaline on glycogen stores during exercise?

Stimulates the breakdown of glycogen stores in muscle cells for respiration.

What is the function of the pancreas in the endocrine system?

Islets of Langerhans cells secrete hormones into the blood.

What are acinar cells in the pancreas responsible for?

Secreting digestive hormones into the pancreas duct.

What is the resting state of beta cells in terms of potassium channels?

ATP-sensitive potassium channels are open, allowing potassium ions to exit the cell.

What happens to the membrane potential of beta cells during hyperpolarization?

It becomes approximately -70 mV, keeping insulin secretion minimal.

What is the role of cyclic AMP in glucose regulation?

Acts as a second messenger that activates protein kinase enzymes involved in glycogen breakdown.

What process allows glucose uptake into cells?

Facilitated diffusion through glucose transporter proteins.

What limits the rate of glucose uptake in cells?

The number of glucose transporter proteins present.

How does insulin affect glucose transporter proteins?

Insulin stimulates the addition of more glucose transporter proteins to the cell surface, increasing permeability to glucose.

What is gluconeogenesis?

The synthesis of glucose from non-carbohydrate molecules, activated by glucagon.

What triggers insulin secretion from beta cells?

Increased blood glucose levels after a carbohydrate-rich meal.

What happens to ATP levels when glucose enters beta cells?

ATP production increases due to glucose metabolism in mitochondria.

What is the role of ATP-sensitive potassium channels in insulin secretion?

Closure of these channels prevents potassium from leaving the cell, leading to depolarization.

What occurs during membrane depolarization in beta cells?

Voltage-gated calcium channels open, allowing calcium influx.

What is the result of calcium influx in beta cells?

It triggers secretory vesicles containing insulin to fuse with the cell membrane, releasing insulin via exocytosis.

What are the two main functions of the pancreas?

Exocrine function (producing digestive enzymes) and endocrine function (regulating blood glucose through hormone secretion).

What is the exocrine function of the pancreas?

Producing digestive enzymes like amylase, proteases, and lipases, which are secreted into the small intestine.

What is the structure of pancreatic acini?

They appear as dark, small, berry-like clusters responsible for enzyme secretion.

What is the endocrine function of the pancreas?

Producing hormones like insulin and glucagon in the islets of Langerhans.

What are the key cell types in the islets of Langerhans?

Alpha cells (produce glucagon) and beta cells (produce insulin).

How do alpha and beta cells regulate blood glucose levels?

Alpha cells raise blood glucose via glucagon, while beta cells lower it via insulin.

What histological technique helps identify cell types in the pancreas?

Differential staining, which highlights insulin in beta cells and glucagon in alpha cells.

What is the appearance of islets of Langerhans?

They are large, lightly stained spherical clusters surrounded by connective tissue.

What is the significance of the vascularization in the islets of Langerhans?

Rich capillary networks allow hormones to enter the bloodstream efficiently.

What happens to blood glucose levels after insulin is released?

Insulin helps lower blood glucose levels back to normal.

What is the role of glucagon in blood glucose regulation?

It stimulates the liver to convert glycogen into glucose and promotes gluconeogenesis.

What is the function of secretory vesicles in beta cells?

They contain insulin and are ready to be released into the bloodstream.

How does the pancreas contribute to digestion?

By releasing digestive enzymes into the pancreatic duct leading to the small intestine.

What is the role of the pancreatic duct?

It transports digestive enzymes from the acini to the small intestine.

What happens to potassium channels during increased ATP levels in beta cells?

They close, leading to depolarization and subsequent calcium influx.

What is the overall process of insulin secretion in response to high blood glucose?

Increased glucose uptake → ATP production → Potassium channel closure → Depolarization → Calcium influx → Insulin release.