Hormonal Control During Exercise

Comprehensive vocabulary flashcards covering the neuroendocrine system, hormone classifications, mechanism of action, gland secretions, glucose homeostasis, fluid regulation, and endocrine responses to exercise.

Neuroendocrine System

The integrated physiological network wherein the nervous system and endocrine system work cooperatively to regulate body functions.

Hormone

A chemical substance secreted by specialized endocrine glands that travels through the bloodstream to act on distant target cells by binding to specific receptors.

Steroid Hormones

Lipid-soluble hormones synthesized from cholesterol (such as testosterone, cortisol, and estradiol) that diffuse across cell membranes and bind intracellular receptors.

Peptide and Protein Hormones

Hormones formed by chains ranging from 2 to 3 up to thousands of amino acids (such as insulin and glucagon) that bind surface receptors on the cell membrane.

Amine Hormones

Small signaling molecules synthesized through the degradation or modification of amino acids, including epinephrine, norepinephrine, thyroxine ($\text{T}_4$), and triiodothyronine ($\text{T}_3$).

Steroid Hormone Mechanism of Action

The pathway where a steroid hormone enters a cell, binds a specific receptor in the cytoplasm or nucleus, and forms a complex that activates cellular DNA to synthesize mRNA, which subsequently directs protein synthesis in the cytoplasm.

Non-Steroid Hormone Mechanism of Action

The second messenger pathway where a non-steroid hormone binds a specific cell-surface receptor, activating membrane-bound adenylate cyclase to convert ATP to cAMP, which then activates protein kinases that alter cellular processes.

Antidiuretic Hormone (ADH)

A posterior pituitary hormone secreted when increased blood osmolality stimulates hypothalamic osmoreceptors during sweating; it increases water reabsorption in renal tubules and collecting ducts to reduce urine volume.

Adrenocorticotropic Hormone (ACTH)

An anterior pituitary hormone released in response to hypothalamic CRH that triggers the adrenal cortex to synthesize and secrete corticosteroids.

Growth Hormone (GH)

An anterior pituitary hormone that stimulates bone and muscle growth, enhances lipase synthesis and lipolysis, and induces hepatic IGF-1 release.

Thyroid-Stimulating Hormone (TSH)

An anterior pituitary tropic hormone (thyrotropin) that stimulates the thyroid gland to produce and secrete thyroid hormones.

Follicle-Stimulating Hormone (FSH)

An anterior pituitary gonadotropin that promotes follicle maturation and estrogen production in females and stimulates spermatogenesis in males.

Luteinizing Hormone (LH)

An anterior pituitary gonadotropin that stimulates sex steroid hormone production in the gonads and induces ovulation in females.

Prolactin (PRL)

An anterior pituitary hormone responsible for promoting lactation and milk production.

Triiodothyronine ($\text{T}_3$) and Thyroxine ($\text{T}_4$)

Thyroid hormones that regulate the basal metabolic rate; increased circulating concentrations directly increase overall metabolic rate.

Calcitonin

A thyroid hormone that lowers blood calcium levels by inhibiting osteoclasts and promoting renal calcium excretion.

Parathyroid Hormone (PTH)

The primary hormone regulating plasma calcium concentration, secreted in response to hypocalcemia to stimulate bone resorption and intestinal calcium absorption.

Catecholamines

Adrenal medulla hormones (epinephrine and norepinephrine) that increase heart rate, contractile force, blood pressure, respiration, metabolic rate, glycogenolysis, and redistribute blood flow to active skeletal muscles.

Renin-Angiotensin-Aldosterone System (RAAS)

A fluid-regulating pathway activated by reduced renal blood pressure where kidneys secrete renin to convert angiotensinogen to angiotensin I, ACE converts it to angiotensin II, and angiotensin II triggers vasoconstriction and adrenal aldosterone secretion.

Aldosterone

A mineralocorticoid released from the adrenal cortex that acts on the kidneys to increase sodium ($\text{Na}^+$) reabsorption, indirectly conserving water and maintaining blood pressure.

Cortisol

A glucocorticoid secreted by the adrenal cortex that increases gluconeogenesis, free fatty acid mobilization, and amino acid catabolism, while reducing glucose utilization and immune/inflammatory responses.

Insulin

An anabolic peptide hormone secreted by pancreatic $\beta$ cells that facilitates GLUT-4-mediated cellular glucose uptake, increases glycogenesis, protein synthesis, and lipogenesis, and inhibits lipolysis and gluconeogenesis.

Glucagon

A catabolic peptide hormone secreted by pancreatic $\alpha$ cells in response to low blood glucose that stimulates hepatic glycogenolysis and gluconeogenesis to elevate blood glucose.

Normal Fasting Blood Glucose

A fasting blood glucose range between $4.0\text{--}6.0\,\text{mmol/L}$ ($80\text{--}100\,\text{mg/dL}$), with the WHO defining clinical normal fasting as $< 6.1\,\text{mmol/L}$ ($< 110\,\text{mg/dL}$).

Impaired Fasting Glycemia

A clinical state defined by the World Health Organization as a fasting blood glucose concentration between $\ge 6.1\,\text{mmol/L}$ and $< 7.0\,\text{mmol/L}$ ($\ge 110\,\text{mg/dL}$ to $< 126\,\text{mg/dL}$).

Diabetes Mellitus Fasting Threshold

A diagnostic threshold defined by the World Health Organization as a fasting blood glucose concentration of $\ge 7.0\,\text{mmol/L}$ ($\ge 126\,\text{mg/dL}$).

Hypoglycemia

A condition of abnormally low blood glucose (defined clinically in non-diabetics as $< 2.8\,\text{mmol/L}$ or $< 50\,\text{mg/dL}$ and in diabetics as $< 3.9\,\text{mmol/L}$ or $< 70\,\text{mg/dL}$) characterized by shakiness, sweating, pallor, hunger, and irritability.

Hyperglycemia

A condition of elevated blood glucose ($\ge 6.1\,\text{mmol/L}$ fasting) with symptoms typically evident around $11\,\text{mmol/L}$, including polyuria, polydipsia, dry mouth, blurred vision, and weakness.

Erythropoietin (EPO)

A glycoprotein hormone produced and released by the kidneys that stimulates red blood cell production (erythropoiesis) in bone marrow.

Testosterone

The primary male androgenic-anabolic steroid hormone secreted by the testes that stimulates muscle hypertrophy, linear bone growth, epiphyseal plate closure, and spermatogenesis.

Insulin-Like Growth Factor 1 (IGF-1)

A liver-produced polypeptide hormone structurally similar to insulin that is stimulated by growth hormone to promote systemic growth and protein synthesis across tissues.

Hormonal Response to Graded Exercise

An exercise-induced endocrine shift wherein plasma insulin declines while counter-regulatory hormones (epinephrine, norepinephrine, GH, cortisol, and glucagon) progressively rise relative to percent $\dot{V}O_2\text{max}$.