Endocrine System and Feedback Mechanisms

Endocrine System and Feedback Mechanisms

• Hormones are chemical messengers regulating bodily processes.
• Hormones are secreted by glands, specialized for hormone production, or organs that also secrete hormones as part of their primary function.
• Glands and organs working together in hormone secretion are called the endocrine system.
• Hormones are categorized into protein hormones (e.g., insulin) and steroid hormones (e.g., cortisol).
• Hormones exert their effects through distinct mechanisms, steroid hormones affecting cells via intracellular receptors, while non-steroid hormones utilize membrane-bound receptors and secondary messengers.

Glucose Regulation

• Glucose is crucial for cellular function in all animals.
• Glycogen, stored in liver and muscles, is broken down when blood glucose levels are low.
• Blood glucose levels must be maintained within a specific range for optimal cellular function, and exceeding this range can have severe consequences.
• Hyperglycemia (above 130 mg/dL) and hypoglycemia (below 60 mg/dL) both present symptoms requiring medical attention.
• The pancreas plays a crucial role in regulating blood glucose, and disruptions in pancreatic function can lead to diabetes.

Diabetes

• Diabetes is a chronic condition stemming from insufficient insulin production or effectiveness.
• Diabetic symptoms include frequent urination, increased thirst, and increased appetite.
• There are different types of diabetes with varying causes and symptoms, including Type 1, Type 2, and gestational diabetes.

Metabolic Control

• Metabolism encompasses all chemical reactions within an organism necessary for sustenance.
• Basal metabolic rate (BMR) is the energy expenditure of an organism at rest.
• The thyroid is a critical gland in metabolic regulation, along with the parathyroid gland, which controls calcium levels in the blood.

The Endocrine System Axes

• Key endocrine axes include hypothalamic-pituitary-adrenal (HPA), hypothalamic-pituitary-thyroid (HPT), and hypothalamic-pituitary-gonadal (HPG) axes.
• The hypothalamic-pituitary-adrenal (HPA) axis is a crucial part of the endocrine system's response to stress.
• The hypothalamic-pituitary-thyroid (HPT) axis controls metabolic rate.
• The hypothalamus and pituitary gland regulate the HPT and HPG axes (in both males and females).

Growth Hormone

• Human growth hormone (HGH) plays an essential role in growth in children and adolescents.
• Growth hormone influences metabolic processes and stimulates cell proliferation in various tissues. 

The Stress Response

• The body's stress response triggers hormonal changes to mobilize resources.
• The "fight-or-flight" response activates the adrenal gland, releasing hormones like adrenaline (epinephrine) and noradrenaline (norepinephrine), which rapidly prepare the body to deal with imminent or perceived threats.

The Reproductive System

• The reproductive system involves the gonads (ovaries in females and testes in males).
• Gonads secrete hormones impacting sexual development and reproduction.

FSH and LH overview

• Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) both affect the gonads in males and females.
• In males, FSH stimulates spermatogenesis (sperm production), and LH stimulates testosterone production.
• In females, FSH stimulates follicle development, and LH triggers ovulation.

The Male Reproductive System

• The male reproductive system involves the testes, epididymis, and various accessory ducts and glands.
• Testerone production and sperm maturation are key processes within this system, regulated by FSH and LH.

The Female Reproductive System

• The female reproductive system comprises the ovaries, uterus, and associated structures.
• The menstrual cycle plays a crucial role in female reproductive function involving different hormonal stages like follicular phase, ovulation, and luteal phase..
• Hormones such as estrogen and progesterone regulate the menstrual cycle and prepare the body for potential pregnancy.

Thyroid Hormones

• The thyroid gland produces T3 and T4, affecting metabolic rate.
• Imbalances can lead to conditions like hyperthyroidism (high metabolic rate) and hypothyroidism (low metabolic rate).

Calcium Homeostasis

• Calcium is essential for various bodily functions, and the parathyroid gland and thyroid gland play key roles in maintaining calcium homeostasis.
• Parathyroid hormone (PTH) and calcitonin regulate calcium levels in blood, muscle contractions, and maintaining bones’ health

Adrenal Glands

• The adrenal glands play crucial roles in the stress response secreting hormones like epinephrine, norepinephrine, mineralocorticoids and glucocorticoids.

Other hormones are covered in the document