endocrine system

The endocrine system is slower acting but allows for more sustained effects.

How does the endocrine system compare to the nervous system in terms of speed and duration?

Released into the blood by a ductless glandular tissue, 2) travels some distance in the blood, 3) elicits a biological response by binding to a receptor in target tissue.

What are the three classic criteria that define a hormone?

Paracrine = acts on adjacent cells. Autocrine = acts on the same cell that produced it.

What is the difference between paracrine and autocrine hormone functions?

A hormone produced by neurons (rather than glands) that is released into the blood and affects target tissue via receptor binding.

What is a neurohormone?

Tyrosine: thyroxine, epinephrine/norepinephrine. Tryptophan: serotonin, melatonin.

What are the two tyrosine-derived hormones and the two tryptophan-derived hormones?

Small: thyroid releasing hormone (TSH). Large: insulin. Large glycoprotein: FSH and LH.

Give examples of a small, large, and large glycoprotein peptide hormone.

Derived from cholesterol. They are lipid soluble and carried by carrier proteins in the blood. Examples: testosterone, estrogen, cortisol, aldosterone.

What are steroid hormones derived from, and what makes them unique in transport?

They bind to surface receptors on the cell membrane → activate G proteins → regulate enzymes (like adenylate cyclase) → produce second messengers (cAMP, cGMP, PI metabolites) → induce protein phosphorylation → alter cellular physiology.

How do peptide/glycoprotein hormones exert their effects?

They dissociate from carrier proteins, pass directly through the cell membrane, bind to an intracellular receptor, and the hormone-receptor complex binds to DNA — altering transcription by turning genes on or off.

How do steroid hormones exert their effects?

The hypothalamus (via releasing hormones) and feedback from hormones in the blood.

What controls the release of pituitary hormones?

Posterior lobe = outgrowth of brain (neural tissue). Anterior lobe = originates from the top of the mouth cavity (non-neural tissue).

What are the two lobes of the pituitary and what tissue does each originate from?

Neurosecretory neurons have cell bodies in the hypothalamus; their axons extend down the pituitary stalk and release neurohormones directly into the blood.

How does the posterior pituitary release hormones?

Vasopressin (ADH) — stimulates water retention by kidneys. Oxytocin — stimulates uterine contractions during birth and milk ejection during breastfeeding.

What are the two posterior pituitary hormones and their functions?

They are released into blood vessels that travel down the pituitary stalk and bind to specific receptors on anterior pituitary cells.

How do hypothalamic releasing hormones reach the anterior pituitary?

CRH, TRH, GnRH, GHRH, somatostatin (SST), prolactin-inhibiting factor (PIF), prolactin-releasing factor (PRF). (Any five count.)

Name five hypothalamic releasing/inhibiting factors.

Produced in both males and females. They stimulate the gonads for gamete development and steroid production.

What do LH and FSH do, and in which sexes are they produced?

TSH stimulates the thyroid to release thyroxine, which promotes growth, development, and increased metabolic rate. Overstimulation causes goiter (thyroid enlargement).

What does TSH do, and what happens if the thyroid is overstimulated?

Also called somatotropin. It stimulates cell growth and anabolic processes, and has been linked to increased cognitive function. Regulated by GHRH.

What is growth hormone (GH) also called, and what does it do?

Gigantism = GH overproduction during childhood/adolescence → overgrowth of long bones. Acromegaly = GH overproduction in adults → enlargement of flat bones, hands, and feet.

What is the difference between gigantism and acromegaly?

Released in response to stress; stimulates the adrenal cortex to release glucocorticoids.

What does ACTH do?

Important in mammary gland development and milk production.

What is prolactin's function?

Stimulates reabsorption of Na⁺ from the distal tubules and collecting ducts of the kidneys. Release is regulated by angiotensin II.

What does aldosterone do and what regulates its release?

Released in response to stress (stimulated by ACTH). Affects carbohydrate, lipid, and protein metabolism — overall increasing blood glucose. Also suppresses the immune system.

What does cortisol do and when is it released?

Exocrine: secretes digestive enzymes (amylase, lipase, etc.) into the GI tract. Endocrine: secretes insulin, glucagon, and somatostatin into the bloodstream.

What is the difference between the exocrine and endocrine functions of the pancreas?

1) Increases cellular glucose uptake, 2) increases glycogenesis, 3) decreases glycogenolysis, 4) decreases gluconeogenesis. (Released when blood glucose is high.)

What are the four functions of insulin?

1) Decreases cellular glucose uptake, 2) decreases glycogenesis, 3) increases glycogenolysis, 4) increases gluconeogenesis. (Released when blood glucose is low.)

What are the four functions of glucagon?

Insulin → beta cells. Glucagon → alpha cells. Both are found in the islets of Langerhans.

What cells produce insulin and glucagon in the pancreas?