Chapters 16 & 17 Exam Study Guide - Sensory & Endocrine Systems

Vocabulary flashcards covering key sensory and endocrine system concepts, pathways, receptors, and hormones from Chapters 16 & 17.

General senses

Senses whose receptors are generally the receptive ends of sensory neurons, with signals traveling through cranial and spinal nerves (e.g., touch, pressure, temperature, pain, stretch, and proprioception).

Special senses

Head-based senses (olfaction, gustation, vision, hearing, vestibular sensation) that use specialized receptor cells/organs and travel through cranial nerves.

Free nerve endings

Cutaneous receptors responsible for pain, temperature, itch, and joint movement/proprioception; display slow/tonic adaptation for pain.

Merkel disks

Also known as tactile disks; cutaneous receptors responsible for light touch and superficial pressure with slow/tonic adaptation.

Hair follicle receptors

Also known as root hair plexus; cutaneous receptors responsible for light touch and slight hair bending with fast/phasic adaptation.

Tactile corpuscles

Also known as Meissner corpuscles; cutaneous receptors responsible for touch and two-point discrimination.

Ruffini end organs

Also known as bulbous corpuscles; cutaneous receptors responsible for continuous touch/pressure and skin stretch/depression with slow/tonic adaptation.

Lamellar corpuscles

Also known as Pacinian corpuscles; cutaneous receptors responsible for deep pressure, vibration, and proprioception with fast/phasic adaptation.

Fast/phasic adaptation

Sensory receptor adaptation that responds strongly when a stimulus begins, then decreases during a constant stimulus.

Slow/tonic adaptation

Sensory receptor adaptation that continues signaling throughout the duration of a constant stimulus.

Spinothalamic tract

Ascending pathway carrying pain, temperature, and nondiscriminative touch that decussates in the spinal cord before ascending to the thalamus and primary somatosensory cortex.

Type C fibers

Small, unmyelinated, slow-conducting nerve fibers that carry pain, temperature, and certain pressure sensations.

Endogenous opioids

Natural analgesic chemicals including enkephalins, endorphins, and dynorphins that inhibit ascending pain signals.

Gustatory cranial nerves

CN VII (Facial), CN IX (Glossopharyngeal), and CN X (Vagus) for taste sensations; CN V (Trigeminal) for tongue texture and temperature.

Endolymph

Fluid inside the membranous labyrinth of the inner ear characterized by a higher concentration of $K^+$ ions.

Perilymph

Fluid located between the bony and membranous labyrinths of the inner ear characterized by a higher concentration of $Na^+$ ions.

Utricle and saccule

Structures containing maculae responsible for sensing static equilibrium and linear acceleration.

Semicircular canals

Structures in the inner ear responsible for dynamic equilibrium and rotational or angular movements.

Ganglion cells

Retinal cells whose axons form the optic nerve (CN II) and are the sole retinal cells that generate action potentials leaving the eye.

Near response

Triad mechanism required for near vision focus, consisting of convergence, pupillary constriction, and lens accommodation.

Rods

Photoreceptor cells responsible for dim/night vision and peripheral vision without color, utilizing the photopigment rhodopsin.

Cones

Photoreceptor cells responsible for bright-light and high-sharpness color vision, concentrated mainly in the fovea, utilizing iodopsin.

Photoreceptor dark reaction

State where cGMP keeps $Na^+$ channels open, causing photoreceptor depolarization and continuous release of glutamate.

Photoreceptor light reaction

State where transducin and PDE activate to close $Na^+$ channels, causing photoreceptor hyperpolarization and decreased glutamate release.

Neuroendocrine organs

Organs containing neural tissue and control that secrete hormones: the hypothalamus, posterior pituitary, pineal gland, and adrenal medulla.

Melatonin

Hormone secreted by the pineal gland that regulates 24-hour circadian rhythms.

Thymopoietin and thymosin

Hormones secreted by the thymus gland that stimulate T-lymphocyte maturation.

Thyroid hormones (T3 and T4)

Hydrophobic hormones (triiodothyronine and thyroxine) derived from tyrosine and iodine secreted by follicular cells to regulate cellular metabolism.

Calcitonin

Hormone secreted by parafollicular (C) cells of the thyroid that lowers blood $Ca^{2+}$ by inhibiting osteoclasts and favoring osteoblast activity.

Parathyroid hormone (PTH)

Hormone that raises blood $Ca^{2+}$ by stimulating osteoclasts, increasing kidney $Ca^{2+}$ reabsorption, and activating vitamin D.

Tropic hormone

A hormone whose main function is to stimulate or control hormone secretion from another endocrine gland.

Trophic hormone

A hormone that directly induces growth in its target cells.

Zona glomerulosa

The outer region of the adrenal cortex that produces mineralocorticoids, primarily aldosterone.

Chromaffin cells

Specialized cells of the adrenal medulla that synthesize and secrete catecholamines (epinephrine, norepinephrine, and dopamine).

Aldosterone

A mineralocorticoid that regulates $Na^+/K^+$ balance, maintains fluid volume and blood pressure via RAAS, and assists acid-base balance.

Cortisol

The primary stress glucocorticoid that increases gluconeogenesis, breaks down skeletal muscle proteins and adipose fats, and reduces inflammation.

Pancreatic alpha cells

Islet cells that secrete glucagon to raise blood glucose by stimulating glycogenolysis, gluconeogenesis, and ketone production.

Pancreatic beta cells

Islet cells that secrete insulin to lower blood glucose by stimulating cellular glucose uptake and storage.

Leptin

An amino acid-derived hormone produced primarily by white adipose tissue that acts on the hypothalamus to suppress appetite.

Hydrophilic hormones

Water-soluble messengers (peptides and catecholamines) that travel unbound in blood, bind to plasma membrane receptors, and use second messenger pathways.

Hydrophobic hormones

Lipid-soluble messengers (steroids and thyroid hormones) that require transport proteins in blood, cross plasma membranes, and bind intracellular receptors.

Autocrine signaling

Chemical communication where a secreted signaling molecule acts on the same cell or cell type that produced it.

Paracrine signaling

Chemical communication where a secreted signaling molecule affects neighboring, distinct target cells.

Up-regulation

Increase in target cell receptor density in response to elevated hormone levels, leading to increased sensitivity.

Down-regulation

Decrease in target cell receptor density due to prolonged high hormone exposure, resulting in diminished sensitivity.

Type II diabetes

Metabolic disorder defined by insulin resistance where target tissues become insensitive to available insulin, causing hyperglycemia.

Graves disease

Autoimmune hyperthyroid condition where autoantibodies mimic TSH, overstimulating the thyroid gland to produce excess thyroid hormones.