Chapter 11 and 19 :Endocrine Glands, Hormones, and Metabolism

Vocabulary practice flashcards covering endocrine gland anatomy, hormone classifications, pathology mechanisms, calcium regulation, and metabolic pathways based on lecture content.

Endocrine Glands

Ductless glands that secrete hormones directly into the bloodstream to be carried to target cells containing specific receptor proteins.

Neurohormones

Chemical messengers secreted directly into the blood by specialized neurons, such as releasing hormones produced in the hypothalamus.

Lipid-Soluble Hormones

Hormones that circulate bound to transport proteins and easily cross cell membranes and the intestinal lining; includes steroid hormones, thyroid hormones, and nitric oxide.

Water-Soluble Hormones

Hormones that circulate freely in plasma but are destroyed by digestive enzymes; includes amine, peptide, and protein hormones such as insulin.

Preprohormones

Inactive precursor proteins synthesized on ribosomes that are processed into prohormones in the rough endoplasmic reticulum and Golgi apparatus before being activated into peptide hormones.

Steroid Hormones

Lipophilic hormones derived from cholesterol that cross cell membranes to bind to cytoplasmic or nuclear receptors, activating DNA to synthesize new proteins.

Amine Hormones

Hormones synthesized from single amino acid precursors, specifically tryptophan or tyrosine, encompassing catecholamines and thyroid hormones.

Hypothalamic-Hypophyseal Portal System

A specialized blood vessel network that directly carries trophic hormones from the hypothalamus to the anterior pituitary, allowing minute hormone amounts to elicit a response.

Synergism

A hormone interaction where the combined effect of multiple hormones acting on a target cell is greater than the additive sum of their individual effects.

Permissiveness

A hormone interaction where a second hormone must be present to create an optimal environment for the first hormone to exert its full biological effect.

Antagonism

A hormone interaction where one hormone opposes or reverses the physiological action of another hormone, such as glucagon opposing insulin.

Primary Pathology

An endocrine defect originating in the final endocrine gland of a reflex pathway that directly secretes the primary effector hormone.

Secondary Pathology

An endocrine defect originating in upstream tissues that produce trophic hormones, such as the anterior pituitary or hypothalamus.

Zona Glomerulosa

The outermost region of the adrenal cortex that secretes mineralocorticoids, primarily aldosterone, to regulate mineral homeostasis.

Zona Fasciculata

The middle layer of the adrenal cortex that secretes glucocorticoids, primarily cortisol, to regulate glucose homeostasis.

Zona Reticularis

The innermost layer of the adrenal cortex that secretes weak androgens responsible for masculinizing effects.

Adrenal Medulla

The inner neuroendocrine region of the adrenal gland containing chromaffin cells that secrete epinephrine ($80\%$) and norepinephrine ($20\%$) during sympathetic stimulation.

Cortisol

A steroid glucocorticoid hormone regulated by the HPA axis that prevents hypoglycemia through muscle protein breakdown, lipolysis, gluconeogenesis, and immune suppression.

Cushing's Disease

A hypercortisolism disorder typically caused by an ACTH-secreting pituitary tumor, presenting with trunk obesity, thin extremities, moon face, and hypertension.

Addison's Disease

A primary hypocortisolism disorder caused by autoimmune destruction of the adrenal cortex, resulting in deficient secretion of all adrenal steroids.

Follicular Cells

Secretory cells of thyroid follicles that synthesize and release thyroid hormones triiodothyronine ($T_3$) and thyroxine ($T_4$) to regulate basal metabolic rate.

Parafollicular Cells (C Cells)

Cells located between thyroid follicles that secrete calcitonin in response to elevated blood calcium levels.

Calcitonin

A peptide hormone produced by thyroid C cells that decreases blood $Ca^{2+}$ levels by inhibiting osteoclasts and slowing bone matrix resorption.

Graves' Disease

An autoimmune cause of hyperthyroidism marked by overproduction of thyroid hormones, metabolic acceleration, and exophthalmos.

Acromegaly

An adult condition resulting from oversecretion of growth hormone, leading to jaw lengthening, facial feature coarsening, and enlargement of hands and feet.

Osteoclasts

Multinucleated bone-resorbing cells that secrete acids and proteases to dissolve calcified bone matrix and release $Ca^{2+}$ into the blood.

Osteoblasts

Bone-forming cells that deposit new collagen lattice and calcified extracellular matrix during bone growth and remodeling.

Parathyroid Hormone (PTH)

A hormone released by parathyroid chief cells in response to low blood calcium that raises plasma $Ca^{2+}$ via bone resorption, renal reabsorption, and activation of calcitriol.

Calcitriol

The active hormone form of vitamin $D_3$ that elevates blood $Ca^{2+}$ levels by increasing intestinal calcium absorption and renal reabsorption.

Glucostatic Theory

A theory proposing that glucose utilization by satiety and feeding centers in the hypothalamus regulates short-term food intake.

Lipostatic Theory

A theory proposing that chemical signals sent from body fat stores to the brain modulate long-term eating behavior and body weight.

Basal Metabolic Rate (BMR)

An individual's lowest rate of energy expenditure, influenced by age, gender, muscle mass, activity, diet, hormones, and genetics.

Anabolic Pathways

Metabolic reactions that synthesize complex molecules from smaller building blocks, characteristic of the fed (absorptive) state.

Catabolic Pathways

Metabolic reactions that break down large, complex molecules into smaller units to yield energy, characteristic of the fasted (post-absorptive) state.

Chylomicrons

Large lipoprotein complexes synthesized in intestinal cells that transport dietary triglycerides through lymphatic vessels and blood to adipose tissue.

Low-Density Lipoproteins (LDLs)

Lipoproteins that deliver cholesterol to peripheral tissues; elevated levels promote arterial plaque formation and coronary artery disease risk.

High-Density Lipoproteins (HDLs)

Lipoproteins that collect excess cholesterol from tissue cells and blood, delivering it to the liver for excretion in bile.

Islets of Langerhans

Endocrine cell clusters within the pancreas containing Alpha cells (secreting glucagon), Beta cells (secreting insulin and amylin), and D cells (secreting somatostatin).

Insulin

An anabolic peptide hormone secreted by pancreatic beta cells during the fed state that lowers blood glucose by accelerating cellular uptake, glycogenesis, lipogenesis, and protein synthesis.

Glucagon

A catabolic peptide hormone secreted by pancreatic alpha cells during the fasted state that elevates blood glucose through glycogenolysis, gluconeogenesis, and ketogenesis.

Glycogenolysis

The enzymatic pathway that breaks down stored glycogen into glucose-6-phosphate or free glucose.

Gluconeogenesis

The metabolic pathway that generates new glucose molecules from non-carbohydrate substrates like lactate, glycerol, and amino acids.

Ketogenesis

The hepatic conversion of free fatty acids into ketone bodies to supply alternative fuel during prolonged fasting or low glucose availability.

Type 1 Diabetes Mellitus

An autoimmune metabolic condition marked by severe insulin deficiency following destruction of pancreatic beta cells.

Type 2 Diabetes Mellitus

A metabolic disorder characterized by target cell insulin resistance and impaired glucose clearance, strongly linked to obesity and physical inactivity.

Metabolic Syndrome

A clinical diagnosis defined by meeting at least three of five criteria: central obesity, high blood pressure ($\ge 130/85\,\text{mm\,Hg}$), elevated fasting glucose ($\ge 110\,\text{mg/dL}$), high triglycerides, and low HDL-C.

Nonshivering Thermogenesis

Heat production generated through brown adipose tissue via mitochondrial uncoupling without muscle contraction.