Introduction to Physiology: Endocrine System

Introduction to Physiology

• Physiology is the study of the functions of living organisms and their parts
• The endocrine system is a complex network of glands and organs that produce and release hormones
• Hormones regulate important body functions such as metabolism, growth, reproduction, and stress responses
• Unlike the nervous system which uses electrical signals, the endocrine system uses chemical messengers carried by the bloodstream.

The Endocrine System

• The endocrine system is a network of glands and organs
• These organs produce hormones which regulate various bodily functions
• Examples of endocrine organs include the pineal gland, pituitary gland, parathyroid gland, thyroid gland, adrenal glands, pancreas, ovaries, testes, thymus

Pituitary Gland

• The pituitary gland is a small gland located at the base of the brain
• It is divided into two lobes: anterior and posterior lobes, each producing hormones with various functions
• The pituitary gland is often referred to as the "master gland"
• It plays a crucial role in regulating growth, development, metabolism, and other vital bodily functions.

Thyroid Gland

• The thyroid gland is located in the lower neck
• It produces hormones, thyroxine (T4) and triiodothyronine (T3), regulating metabolism, energy production, and growth
• Calcitonin helps regulate calcium levels by lowering blood calcium

Parathyroid Glands

• The parathyroid glands are located on the posterior surface of the thyroid gland
• Parathyroid hormone (PTH) increases calcium levels in the blood by stimulating bone resorption and enhancing calcium absorption.

Adrenal Glands

• Adrenal Glands which are located on top of the kidneys, have two components: cortex and medulla
• The adrenal cortex produces hormones like cortisol, regulating metabolism and stress response
• Aldosterone, produced by the adrenal cortex, regulates sodium and potassium levels in the blood, affecting blood pressure
• The adrenal medulla produces adrenaline and noradrenaline, which prepare the body for the fight-or-flight response

Pancreas

• The pancreas is an organ responsible for both endocrine and exocrine functions
• Insulin lowers blood sugar by facilitating glucose uptake
• Glucagon raises blood sugar by promoting glucose release from the liver
• Somatostatin regulates the secretion of other pancreatic hormones

Pineal Gland

• The pineal gland is a small endocrine gland located in the brain
• Melatonin regulates sleep-wake cycles and circadian rhythms

Ovaries (Female Reproductive System)

• Ovaries are the female reproductive glands
• Estrogen regulates the menstrual cycle and development of female secondary characteristics
• Progesterone prepares the uterus for pregnancy and maintains pregnancy
• Inhibin inhibits FSH production

Testes (Male Reproductive System)

• Testes are the male reproductive glands
• Testosterone regulates sperm production, libido, and male secondary sexual characteristics
• Inhibin inhibits FSH production.

Thymus

• The thymus is an organ important in the development of the immune system
• Thymosin promotes the development of T-cells essential for the immune system