Unit 3: Endocrine and Digestive Systems

Flashcards covering key vocabulary and concepts from the lecture on the endocrine and digestive systems.

Endocrine system

A system of organs and glands that produce chemical messengers (hormones) to regulate physiological processes.

Hormone

A chemical messenger produced in small quantities that has long-lasting effects on distant target tissues.

Endocrine glands

Glands that secrete hormones directly into the circulatory system.

Exocrine glands

Glands that secrete substances through ducts to external surfaces or into cavities.

Nervous system vs. Endocrine system

The nervous system operates through fast, short-term signals, while the endocrine system functions with slower, long-lasting chemical messages.

Autocrine messengers

Chemical signals that act on the same cell that secretes them.

Paracrine messengers

Chemical signals that affect neighboring cells in the extracellular fluid.

Neurotransmitters

Chemicals released by neurons that transmit signals across synapses.

Epinephrine

A hormone released by the adrenal gland during stress that increases heart rate and breathing.

Chronic hormone secretion

Relatively constant levels of hormone in the blood over long periods.

Acute hormone secretion

Sudden, irregular changes in hormone concentration in response to stimuli.

Episodic hormone secretion

Hormone release with a predictable pattern over time.

Lipid-soluble hormones

Hormones that are nonpolar and can pass through the plasma membrane to bind intracellular receptors.

Water-soluble hormones

Hormones that are polar and bind to receptors on the cell surface, unable to pass through the plasma membrane.

Bound hormones

Hormones that are reversibly bonded to a specific carrier protein, allowing them to circulate in the blood.

Free hormones

Hormones that are not bound to carrier proteins and can fluctuate in concentration.

Negative feedback

A regulatory mechanism where the presence of a hormone inhibits its own further production.

Positive feedback

A regulatory mechanism where the presence of a hormone stimulates further production.

Half-life

The time it takes for half of a circulating hormone to be removed or excreted from the body.

Down-regulation

A decrease in the total number of receptors on the cell surface in response to long-term exposure to a hormone.

Up-regulation

An increase in the total number of receptors on the cell surface in response to low hormone levels.