Chapter 16: Endocrine System Review

Vocabulary flashcards covering fundamental concepts, mechanisms, chemical classes, and interactions of the endocrine system from Chapter 16 notes.

Gap Junctions

Pores in cell membranes that allow signaling molecules, nutrients, and electrolytes to move directly from cell to cell.

Neurotransmitters

Chemical messengers released from neurons that travel across a synaptic cleft to a second cell.

Paracrine Signals

Chemical secretions released into tissue fluids to affect nearby local cells.

Hormones

Chemical messengers secreted by specialized cells into the bloodstream that travel to other tissues and organs to alter target cell activity.

Neuroendocrine Cells

Neurons that release their secretions, such as oxytocin and catecholamines, directly into the bloodstream.

Target Cells

Organs or cells that possess functional, specific protein receptors for a given hormone and can respond to it.

Homeostasis

A dynamic process that enables the body to maintain balanced conditions in the face of internal or external change.

Receptor (Homeostatic System)

A type of sensor that monitors the environment and responds to changes (stimuli) by sending input to a control center.

Control Center

The homeostatic component that determines the set point, analyzes incoming input, and determines the appropriate response.

Effector

The homeostatic component that provides the means for the control center's response (output) to a stimulus.

Negative Feedback

A regulatory system in which an increase or decrease in a variable brings about responses that tend to move the variable in the direction opposite to the original change.

Positive Feedback

A system that leads to acceleration of a process, resulting in an explosive system to produce rapid physiological changes.

Endocrinology

The study of the endocrine system and the diagnosis and treatment of its disorders.

Exocrine Glands

Glands with ducts that carry external secretions to an epithelial surface or the mucosa of the digestive tract, producing extracellular effects.

Endocrine Glands

Ductless glands containing dense, fenestrated capillary networks that secrete internal secretions directly into the bloodstream for intracellular effects.

Steroids

Lipid-soluble hormones derived from cholesterol and secreted by the gonads and adrenal glands, such as cortisol and testosterone.

Peptides and Glycoproteins

Amino acid-derived hormones created from chains of amino acids and secreted by the pituitary and hypothalamus.

Monoamines

Biogenic amines derived from amino acids and secreted by the adrenal, pineal, and thyroid glands, such as epinephrine and melatonin.

Eicosanoids

Biologically active lipids, including leukotrienes and prostaglandins, that primarily exert autocrine or paracrine effects.

Second Messengers

Intracellular chemical pathways activated by water-soluble hormones binding to plasma membrane receptors coupled via regulatory G proteins.

Direct Gene Activation

A mechanism used by lipid-soluble hormones that pass into target cells and bind intracellular receptors to directly turn on specific genes.

Humoral Stimuli

The synthesis and release of hormones in direct response to changing blood levels of critical ions and nutrients.

Neural Stimuli

The stimulation of hormone release caused directly by nerve fibers from the autonomic nervous system.

Hormonal Stimuli

The release of hormones in response to hormones produced by other endocrine organs.

Up-Regulation

An increase in the number of a hormone's receptors resulting from prolonged exposure to low hormone concentrations, increasing target cell responsiveness.

Down-Regulation

A decrease in target cell receptor number caused by exposure to high levels of a hormone, decreasing responsiveness to prevent overstimulation.

Permissiveness

A hormone interaction where one hormone cannot exert its effects without another hormone being present.

Synergism

A hormone interaction where more than one hormone produces the same effect on a target cell and their combined effects are amplified, such as a $150\%$ glucose release response.

Antagonism

A hormone interaction where one or more hormones opposes the action of another hormone.

Metabolic Clearance Rate (MCR)

The rate at which hormones are removed and degraded by the body, where a faster MCR results in a shorter hormone half-life.