Endocrine Physiology & Hormonal Control Flashcards

Vocabulary flashcards covering basic endocrine signaling types, main regulatory feedback loops, major endocrine axes (HPA, HPG, GH/IGF-1), pancreatic regulation, and target receptor dynamics.

Endocrine Signaling

A form of cell-to-cell communication where a hormone travels through circulation to act on a distant target.

Paracrine Signaling

A form of cell-to-cell communication where a signaling molecule acts on nearby cells.

Autocrine Signaling

A form of cell-to-cell communication where a signal acts on the same cell that released it.

Juxtacrine Signaling

A form of cell-to-cell communication that requires direct cell-to-cell contact.

Hormone

A signaling molecule that can act at distant targets through the blood circulation.

Negative Feedback Loop

The primary mechanism of endocrine system regulation where a response opposes the initial change to stabilize the system once a variable returns to normal.

Normal Blood Glucose Range

The standard physiological concentration range for blood glucose in the body, typically $\text{70--110 mg/dL}$.

HPA Axis

The Hypothalamic Pituitary Adrenal axis, a systemic endocrine pathway triggered by stress or diurnal rhythms where CRH and ACTH stimulate cortisol release.

CRH

Corticotropin-releasing hormone; released by the hypothalamus to stimulate the pituitary gland in the HPA axis.

ACTH

Adrenocorticotropic hormone; released by the pituitary gland to stimulate the adrenal gland to secrete cortisol.

Cortisol

A hormonally active steroid hormone released by the adrenal gland in response to ACTH, which exerts negative feedback on the hypothalamus and pituitary.

HPG Axis

The Hypothalamic Pituitary Gonadal axis, wherein the hypothalamus releases GnRH to stimulate anterior pituitary secretion of LH and FSH, leading to gonadal production of steroid hormones and gametes.

GnRH

Gonadotropin-releasing hormone; secreted by the hypothalamus to stimulate the anterior pituitary to release LH and FSH.

LH and FSH

Luteinizing hormone and follicle-stimulating hormone; pituitary hormones that prompt the gonads to produce gametes and steroid hormones.

Androgens

Gonadal steroid hormones (e.g., testosterone, androstenedione) that support muscle and bone health, influence libido, and contribute to secondary sex characteristics.

Estrogens

Gonadal steroid hormones (e.g., estradiol, estrone, estriol) that support bone health, regulate reproductive function, and influence cardiovascular and brain health.

Progesterone

A gonadal steroid hormone that prepares and maintains the endometrium, supports pregnancy, and influences mood and behavior.

Somatotropic Axis

The GH/IGF-1 axis where hypothalamic GHRH and Somatostatin regulate anterior pituitary release of Growth Hormone, mediating direct cellular effects or indirect effects via IGF-1.

Somatostatin (SS/SST)

A hypothalamic hormone that exerts short-loop negative feedback to inhibit Growth Hormone secretion from the anterior pituitary.

IGF-1

Insulin-like Growth Factor-1; a factor released primarily by the liver in response to GH that mediates indirect effects such as linear growth, increased muscle mass, and lipolysis.

Pancreatic ̢ cells

Pancreatic cells that act as both sensor and control center in detecting high blood glucose and releasing insulin.

Pancreatic ̑ cells

Pancreatic cells that release glucagon during hypoglycemia to stimulate liver glycogenolysis and gluconeogenesis.

Upregulation

An increase in receptor number by a target tissue following prolonged exposure to low hormone levels.

Downregulation / Desensitization

A decrease in tissue responsiveness or receptor density following extended exposure to high concentrations of a hormone.