Endocrine System and Feedback Mechanisms

Study Notes

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 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 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.

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.

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).

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

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 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 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.

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 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

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