Human Physiology - Endocrine System

Flashcards about the endocrine system, hormone action and release, and related diseases.

Endocrine System

Second most important messenger system of the body using chemical messages (hormones) released by specialist cells.

Hormones

Chemical messages released by specialist cells that target cells with corresponding receptors; effects depend on programmed response of target cells.

Major Endocrine Glands

System of ductless glands scattered throughout the body with longer-lasting effects controlling reproduction, growth, body defenses, homeostasis, and metabolism.

Hormone Effects

Include changes in PM permeability, protein synthesis, enzyme activation/inactivation, mitosis, and secretory activation.

Chemistry of Hormones

Includes amino acid-based hormones (peptides, amines, thyroxine), steroids (gonadal and adrenocortical), and eicosanoids (leukotrienes, prostaglandins).

Endocrine Signaling

Signaling where molecules travel through the bloodstream to target cells.

Paracrine Signaling

Signaling between a signaling cell and a target cell within close proximity.

Autocrine Signaling

Signaling where a cell targets itself.

Hormone Action Mechanisms

Hormones alter target cell activity either through second messengers (regulatory G proteins, amino acid-based hormones) or direct gene activation (steroid hormones).

Nonsteroid Hormone Mechanism

Involves a second messenger system to activate a change in the cell.

Steroid Hormone Mechanism

Involves direct gene activation where the hormone-receptor complex affects DNA and mRNA.

Hormonal Hormone Release

The hypothalamus secretes hormones which stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones.

Humoral Hormone Release

Capillary blood contains low concentration of Ca2+, which stimulates secretion of parathyroid hormone (PTH) by parathyroid glands.

Neural Hormone Release

Preganglionic SNS fiber stimulates adrenal medulla cells to secrete catecholamines.

Homeostatic Control Mechanism

Involves a stimulus, receptor, control center, effector, and feedback.

Calcium Homeostasis

Regulated by calcitonin (thyroid) and PTH (parathyroid) based on calcium levels in the blood.

ADH (Antidiuretic Hormone)

Increases water reabsorption in the kidneys, triggered by osmoreceptors in the hypothalamus detecting increased blood osmolarity.

Multiple Effects of Hormones

The same hormone can have different effects based on different receptors, signal transduction pathways, and proteins in target cells.

Acromegaly

A disease of the endocrine system. Too much growth hormone in adulthood.

Diabetes Insipidus

A disease of the endocrine system. Too much anti-diuretic hormone (ADH) being produced.

HPA Axis

Hypothalamic-pituitary-adrenal axis involving CRH, ACTH, and cortisol.

Hypothalamus functions

Regulates bodily processes: thirst, hunger, autonomic nervous system, circadian rhythms, body temperature, blood pressure, breast feeding, learning, sexual drive, emotional expression. Also produces hormones.

Adrenal Gland Hormones

The adrenal cortex produces Glucocorticoids (Cortisol & Cortisone), Mineralocorticoids (Aldosterone & Corticosterone), Androgens (Estrogens & Testosterone). The adrenal medulla produces Catecholamines (Epinephrine & Norepinephrine).

Stress Response

Involves adrenal medulla (short-term, epinephrine) and adrenal cortex (long-term, mineralocorticoids and glucocorticoids).