Endocrine Glands Lecture Review

Question-and-answer flashcards covering major concepts, mechanisms, and examples from the Endocrine Glands lecture to aid exam preparation.

Which two body systems are the major controllers of information flow between cells and tissues?

The endocrine and nervous systems.

What is the definition of an autocrine hormone action?

The hormone acts on receptors located on the same cell that produced it.

What distinguishes paracrine hormone action from endocrine action?

Paracrine hormones act on neighboring cells without entering the circulation, whereas endocrine hormones enter the bloodstream to reach distant targets.

Give an example of a hormone with intracrine action and describe it.

Insulin in pancreatic β-cells; it can inhibit its own release without being secreted.

Name the three broad chemical classes of hormones based on synthesis.

Protein/peptide hormones, steroid hormones, and thyroid hormones.

From what precursor are all steroid hormones synthesized?

Cholesterol.

What is the definition of an exocrine secretion?

Secretion released outside the circulation through ducts, e.g., sweat glands or GI tract ducts.

Define synergistic hormone interaction and give one example.

Two or more hormones work together to produce a result; example: epinephrine and norepinephrine increasing heart rate.

What is a permissive effect between hormones?

One hormone enhances the responsiveness or activity of a second hormone, e.g., cortisol enhances catecholamine action.

Which two hormones are classic antagonists in blood-glucose regulation?

Insulin and glucagon.

Where do peptide hormones such as insulin bind their receptors?

On the cell surface (membrane receptors).

Where do steroid and thyroid hormones exert their primary action?

Inside the cell on intracellular (nuclear) receptors.

How many transmembrane domains does a typical G-protein–coupled receptor (GPCR) have?

Seven transmembrane domains.

What subunit of a G-protein binds GTP to activate the protein?

The α subunit.

Differentiate Gs and Gi proteins by function.

Gs stimulates effector enzymes (e.g., adenylyl cyclase); Gi inhibits them.

Name three hormones that act through GPCRs.

Catecholamines, ACTH, parathyroid hormone (others possible).

Which receptor type possesses intrinsic tyrosine-kinase activity and is used by insulin?

Growth factor receptors (tyrosine-kinase receptors).

What intracellular enzyme is activated after insulin receptor dimerization?

The receptor’s own tyrosine-kinase domain, leading to autophosphorylation.

Which signaling molecule is central to cytokine receptors such as the growth hormone receptor?

JAK2 (Janus kinase 2).

Ligand-regulated guanylyl cyclase receptors increase what second messenger to promote vasorelaxation?

cGMP.

List the three domains of a nuclear receptor.

Amino-terminal transcriptional domain, DNA-binding domain, and carboxyl-terminal ligand-binding/dimerization domain.

Outline the first step of steroid/thyroid hormone action inside a cell.

Hormone diffuses across the membrane and binds to a cytosolic and then nuclear receptor, exposing the DNA-binding domain.

How is the hypothalamus connected to the posterior pituitary?

By nerve fibers from the supraoptic and paraventricular nuclei.

Name the six anterior pituitary hormones.

Growth hormone, ACTH, FSH, LH, TSH, and prolactin.

Which two hormones are secreted by the posterior pituitary?

Vasopressin (ADH) and oxytocin.

Identify the three zones of the adrenal cortex and the major product of each.

Zona glomerulosa – aldosterone; zona fasciculata – cortisol; zona reticulata – androgens (DHEA, androstenedione).

What primary system regulates aldosterone secretion apart from ACTH?

The renin–angiotensin–aldosterone system and plasma potassium levels.

State two renal actions of aldosterone.

Increases Na⁺ reabsorption and increases K⁺ secretion in the late distal tubule and collecting duct.

List two metabolic actions of cortisol that raise blood glucose.

Stimulates gluconeogenesis and increases lipolysis (also decreases glucose uptake in tissues).

What are the classic clinical syndromes of adrenal cortex pathology?

Addison’s disease (insufficiency), Cushing’s syndrome (excess cortisol), and Conn’s syndrome (hyperaldosteronism).

Which amino acid is the starting substrate for catecholamine synthesis in the adrenal medulla?

Tyrosine.

Which two iodinated thyroid hormones are produced by the thyroid gland?

Thyroxine (T4) and triiodothyronine (T3).

What enzyme catalyzes oxidation of iodide and coupling reactions in thyroid hormone synthesis?

Thyroid peroxidase.

Which pituitary hormone stimulates every step of thyroid hormone synthesis and release?

Thyroid-stimulating hormone (TSH).

What binding protein carries most circulating thyroid hormones?

Thyroxine-binding globulin (TBG).

Give one growth-related action of thyroid hormones.

They act synergistically with growth hormone to promote bone formation and maturation.

State one CNS effect of thyroid hormone deficiency in the perinatal period.

Irreversible mental retardation (cretinism).

How does thyroid hormone influence basal metabolic rate (BMR)?

It increases O₂ consumption and heat production in most tissues, elevating BMR.

How many parathyroid glands are typically present and what is their key hormone?

Four glands; they secrete parathyroid hormone (PTH).

What is the major stimulus for PTH secretion?

Decreased serum free Ca²⁺ concentration.

Describe two renal effects of PTH.

Inhibits phosphate reabsorption in proximal tubule (phosphaturia) and increases Ca²⁺ reabsorption in distal tubule.

Which pancreatic islet cell type secretes insulin?

β-cells located in the center of the islet.

What is the primary regulator of glucagon secretion?

Blood glucose concentration (low glucose stimulates glucagon release).

Name two hepatic actions of glucagon that raise blood glucose.

Stimulates glycogenolysis and gluconeogenesis.

How does insulin decrease blood glucose concentration in muscle and adipose tissue?

By increasing insertion of GLUT4 transporters into cell membranes, enhancing glucose uptake.

Mention one effect of insulin on lipid metabolism.

Stimulates fat deposition and inhibits lipolysis, lowering blood fatty acid levels.

What electrolyte does insulin drive into cells, and what clinical use does this have?

Potassium (K⁺); insulin is used to treat hyperkalemia.

State one local and one GI-mediated effect of somatostatin.

Locally inhibits insulin and glucagon release; decreases GI motility and secretions.

From which neurotransmitter is melatonin synthesized in the pineal gland?

Serotonin (derived from tryptophan).

How is light information transmitted from the retina to the pineal gland?

Via the suprachiasmatic nucleus → spinal cord → superior cervical ganglia → postganglionic sympathetic fibers to the pineal gland.

What chemical precursor gives rise to prostaglandins and leukotrienes?

Arachidonic acid.

Which enzyme pathway produces prostaglandins such as PGI₂, PGE₂, and TXA₂?

Cyclo-oxygenase (COX) pathway.

How do NSAIDs like ibuprofen reduce inflammation?

They inhibit cyclo-oxygenase, blocking prostaglandin synthesis.