Grade 12 Biology - First Semester Vocabulary

Vocabulary practice flashcards generated from Grade 12 Biology course materials covering skeletal, muscular, circulatory, respiratory, defense, and nervous systems.

Tissue

A collection of cells that are similar in structure and work together to perform a particular function.

Periosteum

A tough membrane covering the surface of a bone, containing a network of blood vessels that supply nutrients and nerves that signal pain.

Compact bone

A hard layer of bone beneath the periosteum composed of cylinders of mineral crystals and protein fibers called lamellae.

Haversian canal

A narrow channel in the center of each cylinder of compact bone through which blood vessels run to carry nourishment to living bone tissue.

Ossification

The process by which cartilage is slowly replaced by bone as a result of the deposition of minerals such as calcium and phosphate.

Epiphyseal plate

An area located near the ends of long bones composed of cartilage cells that divide and elongate the bone until full height is reached.

Sarcomere

The functional unit of muscle contraction, defined as the region from one Z line to the next within a myofibril.

Oxygen debt

A temporary lack of oxygen availability following heavy exertion, leading to an accumulation of lactic acid in muscle fibers.

Sinoatrial node

A group of specialized heart-muscle cells located in the right atrium that acts as the pacemaker regulating the contraction rate of the heart.

Atherosclerosis

A disease characterized by the buildup of fatty materials on the interior walls of coronary arteries.

Plasma

The sticky, straw-colored liquid portion of blood that makes up about $55\%$ of total blood volume and is composed of about $90\%$ water.

Hemoglobin

An iron-containing protein in red blood cells that transports oxygen and, to a lesser degree, carbon dioxide.

Alveoli

Clusters of tiny air sacs surrounded by capillaries at the ends of bronchioles, serving as the functional units for gas exchange in the lungs.

Koch's postulates

A four-step experimental procedure established by Robert Koch to identify the specific pathogen responsible for an infectious disease.

Histamine

A chemical messenger released by damaged cells that increases capillary permeability and blood flow, triggering an inflammatory response.

Interferon

A protein released by virus-infected cells that stimulates neighboring cells to produce proteins that help them resist viral infection.

Memory cells

Long-lived lymphocytes that remain in the body after an initial infection to provide rapid protection upon subsequent exposure to the same pathogen.

Dendrite

A membrane-covered extension from a neuron's cell body that receives information from other neurons or cells and carries it toward the cell body.

Resting potential

The electrical charge difference across a neuron membrane at rest, typically about $-70\,\text{mV}$, with the interior negatively charged relative to the exterior.

Cerebral cortex

The folded outer layer of grey matter covering the cerebrum, containing cell bodies and unmyelinated axons that process sensory information and motor responses.