Cell Communication and Feedback Loops: Hormones and Endocrine Signaling

What are hormones?

Chemical signals secreted into the circulatory system that communicate regulatory messages within the body.

How do hormones reach their target cells?

Hormones travel via the bloodstream and only target cells equipped to respond will react.

What is the role of endocrine signals?

Endocrine signals mediate responses to environmental stimuli and regulate growth, development, and reproduction.

What is the function of the thyroid gland?

The thyroid gland produces thyroid hormones (T3 and T4) that regulate metabolism.

What hormone is produced by the adrenal medulla?

Epinephrine and norepinephrine, which mediate the body's response to short-term stress.

What is the role of insulin?

Insulin helps lower blood glucose levels by facilitating the uptake of glucose into cells.

What is the function of glucagon?

Glucagon raises blood glucose levels by promoting the breakdown of glycogen in the liver.

What is negative feedback in hormonal signaling?

Negative feedback prevents excessive pathway activity to maintain homeostasis by shutting down processes once an ideal set-point is reached.

What is positive feedback in hormonal signaling?

Positive feedback amplifies a process until a stimulus is removed, such as during childbirth.

What is the relationship between insulin and glucagon?

Insulin and glucagon are antagonistic hormones that work together to maintain glucose homeostasis.

What triggers the release of glucagon?

A fall in blood glucose levels triggers alpha cells in the pancreas to release glucagon.

What triggers the release of insulin?

A rise in blood glucose levels triggers beta cells in the pancreas to release insulin.

What is the role of the hypothalamus in the endocrine system?

The hypothalamus regulates hormone release from the pituitary gland and coordinates the endocrine system.

What are the effects of epinephrine on liver cells?

Epinephrine binds to receptors on liver cells, promoting glycogen breakdown and glucose release into the bloodstream.

What is the function of the pituitary gland?

The pituitary gland secretes hormones that regulate various bodily functions, including growth and metabolism.

What is the role of the adrenal cortex?

The adrenal cortex produces glucocorticoids and mineralocorticoids that regulate metabolism and electrolyte balance.

What are the two populations of cells in the pancreatic islets?

Alpha cells produce glucagon, and beta cells produce insulin.

What is the significance of blood glucose homeostasis?

Maintaining blood glucose levels is crucial because glucose is a primary fuel for cell respiration and biosynthesis.

What is the function of melatonin?

Melatonin regulates sleep-wake cycles and is produced by the pineal gland.

How do hormones affect different target cells?

The same hormone can have different effects on different target cells depending on the receptors and signal transduction pathways.

What is the role of the parathyroid hormone (PTH)?

PTH regulates calcium levels in the blood by promoting the release of calcium from bones.

What is the role of follicle-stimulating hormone (FSH)?

FSH stimulates the growth of ovarian follicles in females and sperm production in males.

What is the function of luteinizing hormone (LH)?

LH triggers ovulation in females and stimulates testosterone production in males.

What is the role of growth hormone (GH)?

GH stimulates growth, cell reproduction, and regeneration in the body.

What is the function of prolactin?

Prolactin promotes milk production in mammals.

What is the role of insulin in blood glucose regulation?

Insulin reduces blood glucose levels by promoting cellular uptake of glucose, slowing glycogen breakdown in the liver, and increasing glycogen synthesis in the liver.

What effect does glucagon have on blood glucose levels?

Glucagon increases blood glucose levels by stimulating the breakdown of glycogen to glucose in the liver and the breakdown of fat and protein into glucose.

What is hyperglycemia?

Hyperglycemia is a condition characterized by frequent or ongoing high blood sugar levels that can cause damage to nerves, blood vessels, and organs.

What is diabetes mellitus?

Diabetes mellitus is an endocrine disorder caused by a deficiency of insulin or a decreased response to insulin in target tissues, marked by elevated blood glucose levels.

What distinguishes Type I diabetes mellitus?

Type I diabetes mellitus is an autoimmune disorder where the immune system destroys pancreatic beta cells that produce insulin, requiring treatment with insulin injections.

What is Type II diabetes mellitus?

Type II diabetes mellitus involves insulin deficiency or reduced response of target cells to insulin, often related to heredity, excess body weight, or lack of exercise, and accounts for 90% of all diabetics.

What are feedback mechanisms in biological systems?

Feedback mechanisms are processes that organisms use to maintain internal environments and respond to internal and external environmental changes.

Give an example of positive feedback in biological systems.

An example of positive feedback is lactation in mammals, where suckling stimulates the release of oxytocin, which promotes milk release.

What is the role of oxytocin in milk release?

Oxytocin regulates milk release during nursing by stimulating smooth muscle contraction in mammary glands.

What is an example of negative feedback in blood sugar regulation?

Blood sugar regulation by insulin and glucagon is an example of negative feedback, where insulin lowers blood sugar and glucagon raises it.

What is the function of antidiuretic hormone (ADH)?

ADH enhances water reabsorption in the kidneys, decreasing urine volume.

What hormones regulate calcium homeostasis in the blood?

Parathyroid hormone (PTH) increases blood calcium levels, while calcitonin decreases them.

What happens when blood calcium levels fall?

When blood calcium levels fall, it can lead to skeletal muscle contractions, known as tetany, which can be fatal.

How does PTH affect calcium levels?

PTH increases blood calcium levels by releasing calcium from bones and stimulating reabsorption in the kidneys.

What is the role of calcitonin in calcium regulation?

Calcitonin decreases blood calcium levels by promoting calcium deposition in bones and secretion by kidneys.

What is the ideal calcium blood level in mammals?

The ideal calcium blood level in mammals is about 10 mg/100 mL.

What can excessive calcium levels in the blood cause?

Excessive calcium levels can weaken bones, create kidney stones, and interfere with heart and brain function.

What is the relationship between insulin and glucose uptake?

Insulin promotes the uptake of glucose by all cells except brain cells, which always take up glucose.

What triggers the release of oxytocin during childbirth?

Suckling triggers sensory neurons that generate nerve impulses to the hypothalamus, stimulating the release of oxytocin.

What is the consequence of insulin deficiency?

Insulin deficiency leads to elevated blood glucose levels, characteristic of diabetes mellitus.

What is an example of a positive feedback loop in blood clotting?

In blood clotting, platelets attract more platelets to quickly form a plug at the site of injury.

How does the body respond to falling blood calcium levels?

The body responds to falling blood calcium levels by releasing PTH, which increases calcium levels through various mechanisms.

What is the primary function of glucagon?

The primary function of glucagon is to raise blood glucose levels by stimulating glycogen breakdown and gluconeogenesis.

What is the effect of insulin on glycogen synthesis?

Insulin increases glycogen synthesis in the liver, promoting storage of glucose.