Endocrine System & Hormonal Control Flashcards

Vocabulary practice flashcards covering endocrine mechanisms, hormone transport, hypothalamic-pituitary pathways, and specific pituitary hormones based on the lecture transcript.

Water-Soluble Hormones

Hormones made from amino acid building blocks (except thyroid hormone) that are easily transported in blood but cannot cross the lipid plasma membrane of target cells, requiring a second messenger system.

Lipid-Soluble Hormones

Steroid-based hormones that are soluble in lipids and can freely cross the plasma membrane of a cell to act via direct gene activation.

Thyroid Hormone Mechanism Exception

An exception among amino acid-based hormones ($T_3$ and $T_4$) that behaves like a lipid-soluble steroid hormone by crossing the plasma membrane to act via direct gene activation.

First Messenger

The hormone itself when it binds to a specific receptor on the outer plasma membrane of a target cell because it cannot cross the membrane.

Second Messenger System

An intracellular cascade of relay events (such as cyclic AMP or PIP2-calcium) activated when a water-soluble hormone binds its cell membrane receptor.

Direct Gene Activation

The mechanism used by steroid and thyroid hormones, where the hormone enters the cell and nucleus, binds directly to DNA, and activates transcription to produce messenger RNA for protein synthesis.

Receptor-Hormone Complex

The structural complex formed inside a target cell when a lipid-soluble hormone enters the cell and binds to an intracellular receptor protein.

Upregulation

The process in which a target cell produces and displays more receptors on its surface, often in response to low hormone levels or low binding affinity.

Downregulation

The process in which a target cell decreases the total number of its receptors for a specific hormone.

Humoral Stimuli

Hormone release triggered by direct monitoring of blood levels of specific ions or solutes, such as glucose or calcium.

Neural Stimuli

Hormone release directly stimulated by nerve fibers from the nervous system.

Hormonal Stimuli

A mechanism of endocrine control where one hormone causes the release or inhibition of another hormone.

Infundibulum

The stalk of neural tissue that physically connects the hypothalamus to the pituitary gland.

Neurohypophysis

The posterior lobe of the pituitary gland, made of neural tissue, which stores and releases oxytocin and antidiuretic hormone (ADH) produced by the hypothalamus.

Adenohypophysis

The anterior lobe of the pituitary gland, composed of true glandular epithelial tissue, which manufactures and secretes six main hormones.

Hypothalamic-Hypophyseal Tract

The neural pathway running through the infundibulum that transports oxytocin and antidiuretic hormone (ADH) from the hypothalamus to the posterior pituitary.

Oxytocin

A posterior pituitary hormone synthesized in the hypothalamus that stimulates uterine contractions during childbirth, the milk letdown reflex, and bonding behaviors via positive feedback.

Antidiuretic Hormone (ADH)

Also known as vasopressin, a posterior pituitary hormone produced in the hypothalamus that targets kidney tubules to reabsorb water and prevent urine formation.

Diabetes Insipidus

A homeostatic imbalance resulting from hyposecretion of antidiuretic hormone (ADH), leading to excessive urine output and chronic dehydration.

Syndrome of Inappropriate ADH Secretion (SIADH)

A condition caused by hypersecretion of ADH, resulting in fluid retention, elevated blood volume and pressure, headache, and potential brain swelling.

Hypophyseal Portal System

A vascular network consisting of a primary capillary plexus, portal veins, and a secondary capillary plexus that carries releasing and inhibiting hormones from the hypothalamus to the anterior pituitary.

Tropic Hormones

Hormones that target other endocrine glands to regulate their secretion, specifically including TSH, ACTH, FSH, and LH from the anterior pituitary.

Growth Hormone (GH)

Also known as somatotropin, an anterior pituitary hormone that directly alters metabolism (mobilizing fats and increasing blood glucose) and indirectly stimulates bone and muscle growth via insulin-like growth factors (IGFs).

Gigantism

A condition caused by hypersecretion of growth hormone during childhood or adolescence while epiphyseal growth plates remain open.

Acromegaly

A condition caused by hypersecretion of growth hormone in adults after epiphyseal growth plates have closed, leading to enlargement of facial features, hands, and feet.

Pituitary Dwarfism

A condition caused by hyposecretion of growth hormone during childhood, resulting in severely restricted bone growth and short stature.

Thyroid Stimulating Hormone (TSH)

An anterior pituitary tropic hormone, also called thyrotropin, that stimulates the thyroid gland to synthesize and release thyroid hormones.

Adrenocorticotropic Hormone (ACTH)

An anterior pituitary tropic hormone that stimulates the adrenal cortex to release corticosteroid hormones, primarily cortisol.

Follicle Stimulating Hormone (FSH)

A gonadotropin produced by the anterior pituitary that stimulates gamete (egg and sperm) production in the gonads.

Luteinizing Hormone (LH)

A gonadotropin produced by the anterior pituitary that triggers ovulation and sex hormone production in the gonads.

Prolactin (PRL)

An anterior pituitary hormone that directly stimulates milk production in the mammary glands.

Hyperprolactinaemia

The most frequent pituitary tumor abnormality, marked by hypersecretion of prolactin, causing inappropriate lactation, lack of menses, female infertility, and male impotence.