Endocrine system

OVERVIEW OF THE ENDOCRINE SYSTEM

  • Endocrine system utilizes hormones as chemical messengers.

  • Hormones maintain homeostasis, regulate growth, and metabolic functions.

COMPARISON WITH NERVOUS SYSTEM

  • Nervous system communicates via neurotransmitters, effects are immediate but short-lived.

  • Endocrine system releases hormones into the bloodstream, effects may be slow or fast but longer-lasting.

TYPES OF CHEMICAL SIGNALS

  • Paracrine: affects nearby different cells.

  • Autocrine: affects the same cell or type.

  • Endocrine: hormones travel long distances through blood.

ENDOCRINE GLANDS

  • Primary organs: Only endocrine function (e.g., pituitary, thyroid).

  • Secondary organs: Mixed functions (e.g., pancreas, ovaries).

  • Neuroendocrine organs: Include hypothalamus and adrenal medulla; secrete neurohormones.

HORMONES

  • Hormones can be free or protein-bound in blood.

  • They have specific target cells with receptors.

  • Hydrophilic hormones bind to membrane receptors; hydrophobic hormones bind inside the cell.

REGULATION OF HORMONE SECRETION

  • Stimulated by hormonal, humoral, or neural signals.

  • Negative feedback loops help maintain balance in hormone levels.

HYPOTHALAMUS AND PITUITARY GLAND

  • Controls various body functions through releasing or inhibiting hormones.

  • Anterior pituitary hormones often have tropic effects on other endo. glands.

THYROID AND PARATHYROID GLANDS

  • Thyroid hormones (T3, T4): Control metabolism and development.

  • Parathyroid hormone (PTH): Regulates calcium levels, opposes calcitonin from thyroid.

ADRENAL GLANDS

  • Produce catecholamines and steroid hormones for stress response (e.g., cortisol, aldosterone).

  • Cortisol affects glucose metabolism and immune responses.

ENDOCRINE PANCREAS

  • Glucagon and insulin regulate blood glucose levels; they have opposing roles.

  • Imbalances lead to diabetes (Type I and II).

OTHER ENDOCRINE GLANDS

  • Pineal gland: Produces melatonin, regulates sleep-wake cycles.

  • Thymus: Produces thymosin, involved in T-cell maturation.

  • Adipose tissue: Produces leptin, regulates appetite.