Hormonal Regulation and Sensory Reception Vocabulary

Comprehensive set of vocabulary flashcards covering endocrine system regulation and sensory reception concepts.

Hormone

Chemical messenger produced by endocrine glands and transported via the bloodstream to regulate and control target cells or organs elsewhere in the body.

Endocrine System

System composed of glands, hormones, and the hypothalamus that works alongside the nervous system to regulate physiological processes and maintain homeostasis.

Tropic Hormone

A hormone whose target tissue is another endocrine gland, stimulating or inhibiting the secretion of other hormones.

Non-Tropic Hormone

A hormone that acts directly on non-endocrine body cells or organs rather than targeting another endocrine gland.

Hypothalamus

Region of the brain that integrates the nervous and endocrine systems; secretes releasing and inhibiting hormones to control the anterior pituitary and synthesizes ADH and oxytocin.

Posterior Pituitary

Lobe of the pituitary gland that stores and secretes antidiuretic hormone (ADH) and oxytocin produced by the hypothalamus, without synthesizing hormones itself.

Anterior Pituitary

Lobe of the pituitary gland regulated by hypothalamic releasing and inhibiting hormones via a portal system; synthesizes and secretes its own hormones including hGH, TSH, ACTH, FSH, LH, and PRL.

Thyroxine ($T_4$)

Metabolic hormone secreted by the thyroid gland that increases the rate of cellular metabolism of carbohydrates, fats, and proteins, and regulates growth.

Hypothyroidism

Condition caused by abnormally low production of thyroxine, resulting in cretinism in children and fatigue, low energy, low pulse rate, and weight gain in adults.

Hyperthyroidism

Condition caused by excessive production of thyroxine (such as in Graves' disease), leading to symptoms like anxiety, insomnia, heat intolerance, irregular heartbeat, and weight loss.

Calcitonin

Hormone produced by the thyroid gland that lowers blood calcium levels ($Ca^{2+}$) by inhibiting calcium release from bones and reducing renal reabsorption.

Parathyroid Hormone (PTH)

Hormone released by the parathyroid glands that increases blood calcium levels ($Ca^{2+}$) by stimulating bone cells to release calcium and kidneys/intestines to reabsorb it.

Antagonistic Hormones

Pairs of hormones that exert opposing physiological effects to maintain homeostatic balance (e.g., insulin and glucagon, calcitonin and PTH).

Insulin

Hormone produced by beta cells in the islets of Langerhans that lowers blood glucose levels by making target cells permeable to glucose and promoting glycogen storage in the liver.

Glucagon

Hormone produced by alpha cells in the islets of Langerhans that increases blood glucose levels by stimulating the liver to convert stored glycogen back into glucose.

Islets of Langerhans

Clusters of endocrine cells within the pancreas containing alpha cells (producing glucagon) and beta cells (producing insulin).

Diabetes Mellitus

Metabolic disorder marked by hyperglycemia, resulting either from an autoimmune destruction of beta cells (Type I) or reduced cell sensitivity to insulin (Type II).

Diabetes Insipidus

Disorder caused by insufficient production or release of antidiuretic hormone (ADH), characterized by the excretion of large volumes of dilute urine and ion loss.

Human Growth Hormone (hGH)

Protein hormone secreted by the anterior pituitary that promotes cellular division, protein synthesis, bone and muscle growth, and fat metabolism.

Gigantism

Condition caused by hypersecretion of human growth hormone (hGH) during childhood prior to bone plate closure, leading to excessive height and growth.

Acromegaly

Condition caused by overproduction of human growth hormone (hGH) in adulthood, characterized by abnormal widening of bones and soft tissues.

Dwarfism

Condition resulting from hyposecretion of human growth hormone (hGH) or skeletal dysplasia during childhood, producing an adult height under $4\text{ ft } 10\text{ in}$.

Adrenal Medulla

Inner layer of the adrenal gland that secretes epinephrine and norepinephrine to regulate short-term, fight-or-flight stress responses under sympathetic nervous system control.

Adrenal Cortex

Outer layer of the adrenal gland that secretes glucocorticoids, mineralocorticoids, and gonadocorticoids to mediate long-term stress responses.

Cortisol

Glucocorticoid steroid hormone released by the adrenal cortex during long-term stress that raises blood glucose levels by promoting the conversion of amino acids to glucose in the liver.

Aldosterone

Mineralocorticoid hormone secreted by the adrenal cortex that stimulates kidney nephrons to reabsorb sodium ($Na^+$) ions, promoting water retention and raising blood pressure.

Addison's Disease

Condition caused by inadequate production of glucocorticoids and mineralocorticoids by the adrenal cortex, resulting in hypoglycemia, sodium/potassium imbalance, weight loss, and low blood pressure.

Negative Feedback Loop

Primary homeostatic mechanism in which the output or response decreases or stops the initial stimulus that triggered the pathway.

Sensory Adaptation

Decrease in neural responsiveness and perception that occurs when sensory receptors are subjected to a constant, unchanging stimulus over time.

Photoreceptors

Sensory receptor cells located in the retina of the eye (rods and cones) that convert visible light energy into nerve impulses.

Chemoreceptors

Sensory receptors that respond to chemical molecules, including taste buds on the tongue, olfactory receptors in the nose, and internal blood pH or osmoreceptors.

Mechanoreceptors

Sensory receptors stimulated by mechanical pressure, stretching, or sound waves, located in skin, inner ear hair cells, and proprioceptors.

Thermoreceptors

Sensory receptors located in the skin that detect changes in temperature and radiant energy (heat and cold).

Proprioceptors

Mechanoreceptors located in muscles, tendons, and joints that detect muscle contraction, stretching, and movement to inform the brain of body position.

Nociceptors

Specialized nerve endings in the skin and tissues that sense pain and release chemical signals to the brain upon detecting injury or tissue damage.

Sclera

Outermost tough, fibrous white layer of the eye that protects and supports the internal structures of the eyeball.

Cornea

Transparent bulged structure at the front of the sclera that refracts light rays entering the eye as the primary stage of focusing.

Choroid

Middle vascular layer of the eye that absorbs scattered light rays and supplies blood and nutrients to eye tissues.

Retina

Innermost layer of the eye housing photoreceptor cells (rods and cones) that translate light patterns into neural signals.

Rods

Photoreceptors in the retina that operate in dim light to detect degrees of brightness and peripheral visual cues without color vision.

Cones

Photoreceptors in the retina that function in bright light and are sensitive to specific wavelengths to enable color vision.

Fovea Centralis

Central depression on the retina containing a high density of cones, providing the highest visual acuity and detailed color perception.

Aqueous Humor

Clear fluid produced daily in the anterior chamber of the eye that maintains corneal curvature and supplies oxygen and nutrients.

Vitreous Humor

Clear, gel-like substance filling the posterior cavity of the eye that maintains the structural shape of the eyeball.

Myopia

Visual condition (nearsightedness) in which distant light rays focus in front of the retina; corrected using concave lenses.

Hyperopia

Visual condition (farsightedness) in which close light rays focus behind the retina; corrected using convex lenses.

Astigmatism

Visual error caused by an irregular curvature of the cornea or lens that prevents uniform light focusing; corrected with cylindrical lenses.

Glaucoma

Eye condition caused by a blocked drainage canal, leading to aqueous humor buildup and increased intraocular pressure that damages optic nerve fibers.

Cataracts

Degenerative condition where proteins inside the lens break down, causing the lens to become cloudy or opaque and clouding vision.

Pinna

External cartilage structure of the outer ear that collects and funnels sound waves into the auditory canal.

Tympanum

Membrane (eardrum) at the end of the auditory canal that vibrates when struck by incoming sound pressure waves.

Ossicles

Trio of small bones in the middle ear—malleus (hammer), incus (anvil), and stapes (stirrup)—that mechanically amplify and conduct vibrations to the oval window.

Cochlea

Spiral, fluid-filled inner ear structure containing the Organ of Corti where fluid pressure waves are converted into auditory nerve impulses.

Organ of Corti

Primary organ of hearing situated on the basilar membrane in the cochlea, featuring specialized hair cells with stereocilia that bend against the tectorial membrane.

Eustachian Tube

Narrow duct linking the middle ear cavity to the throat that opens to equalize air pressure between the middle ear and external atmosphere.

Semicircular Canals

Three fluid-filled loops in the inner ear oriented in three spatial planes that house cilia sensors to detect rotational head movements and dynamic balance.

Utricle and Saccule

Fluid-filled sacs in the vestibule of the inner ear containing sensory receptors that detect gravitational pull and linear head movement.

Olfactory Cells

Chemoreceptor neurons in the nasal epithelium that bind specific volatile odorants and transmit impulses to the olfactory bulb and limbic system.

Pheromones

Chemical volatile substances secreted externally by animals that trigger specific behavioral or reproductive responses in members of the same species.