Anatomical Terminology & Introduction to Homeostasis

Vocabulary practice flashcards covering anatomical terminology, directional terms, body planes, cavities, and key concepts of homeostatic regulation via the autonomic nervous system and endocrine system.

Principle of Complementarity of Structure and Function

The anatomical concept that function always reflects structure; for example, sharp incisors are structured to cut like scissors while flat molars grind food.

Atom

The smallest particle of an element that retains all of the chemical properties of that element.

Molecule

The smallest unit of a chemical compound that can exist independently, formed by a combination of two or more atoms.

Organelle

A specialized component within a cell formed by associated molecules that performs a specific cellular function.

Cell

The fundamental structural and functional unit of living organisms, which varies in size and shape to suit specific functions and can arise only from pre-existing cells.

Tissue

A group of similar cells working together to perform a common function.

Organ

A discrete structure composed of at least two (and usually four) tissue types that performs a specific functional role in the body.

Organ System

A group of organs that work closely with one another to accomplish a common physiological purpose.

Standard Anatomical Position

The standard reference posture for anatomical description: body erect, feet slightly apart, and palms facing forward with thumbs pointing away from the body.

Superior (Cranial)

Directional term meaning toward the head end or upper part of a structure or the body; above.

Inferior (Caudal)

Directional term meaning away from the head end or toward the lower part of a structure or the body; below.

Anterior (Ventral)

Directional term meaning toward or at the front end of the body; in front of.

Posterior (Dorsal)

Directional term meaning toward or at the back of the body; behind.

Medial

Directional term meaning toward or at the midline of the body; on the inner side of.

Lateral

Directional term meaning away from the midline of the body; on the outer side of.

Intermediate

Directional term meaning located between a more medial and a more lateral structure.

Proximal

Directional term meaning closer to the origin of a body part or point of attachment of a limb to the body trunk.

Distal

Directional term meaning farther from the origin of a body part or point of attachment of a limb to the body trunk.

Superficial

Directional term meaning toward or at the body surface.

Deep

Directional term meaning away from the body surface; more internal.

Axial Part

The central main axis division of the body, which includes the head, neck, and trunk.

Appendicular Part

The division of the body consisting of the limbs or appendages attached to the central axis.

Sagittal Plane

A vertical plane that divides the body or an organ into right and left portions.

Frontal (Coronal) Plane

A vertical plane that divides the body or an organ into anterior (front) and posterior (back) parts.

Transverse Plane

A horizontal plane running from right to left that divides the body or an organ into superior (top) and inferior (bottom) parts.

Dorsal Body Cavity

Body cavity located near the posterior surface that encloses the cranial cavity (housing the brain) and the vertebral cavity (housing the spinal cord).

Ventral Body Cavity

The larger, anterior body cavity housing internal organs (viscera), subdivided into the thoracic cavity and the abdominopelvic cavity.

Abdominopelvic Quadrants

Four divisions (RUQ, LUQ, RLQ, LLQ) of the abdominal area delineated by perpendicular transverse and median planes intersecting at the umbilicus.

Homeostasis

The ability of the body to maintain relatively stable internal conditions despite continuous changes in the external environment, described by Walter Cannon as a dynamic state of equilibrium.

Receptor (Homeostasis)

A sensor that monitors the environment, detects a stimulus (change), and sends information along the afferent pathway to the control center.

Control Centre

The component in a homeostatic control system that determines the set point, analyzes incoming information from receptors, and determines appropriate responses.

Effector

The component of a homeostatic system that receives output from the control center along the efferent pathway and carries out the response to adjust the variable.

Negative Feedback Mechanism

A primary regulatory mechanism where output reduces or shuts off the original stimulus to prevent sudden, severe changes and return the variable to a normal range.

Positive Feedback Mechanism

A homeostatic mechanism where the response enhances or accelerates the original stimulus, pushing the variable further in the same direction until a specific goal (such as blood clotting) is attained.

Homeostatic Imbalance

A disturbance in homeostasis that underlies most diseases and increases in frequency with aging.

Autonomic Nervous System (ANS)

A system of motor neurons supplying smooth muscle, cardiac muscle, and glands that regulates internal organ functions automatically without conscious awareness.

Hypothalamus

The main integration center of the autonomic nervous system ("the boss") that coordinates heart rate, blood pressure, body temperature, water balance, and endocrine activities.

Hormone

A chemical messenger secreted directly into extracellular fluid (ECF) that travels to regulate the functions of target cells in the body.

Humoral Stimulus

Hormone release triggered directly by changing blood levels of specific critical ions or nutrients, such as low $\text{Ca}^{2+}$ levels stimulating parathyroid hormone secretion.

Neural Stimulus

Hormone secretion caused by direct neural input, such as preganglionic sympathetic fibers stimulating the adrenal medulla to secrete epinephrine and norepinephrine.

Hormonal Stimulus

Hormone release stimulated in response to other hormones, such as hypothalamic release factors prompting anterior pituitary hormone secretion.