Anatomy and Physiology: Skeletal System, Joints, and Nervous System

Comprehensive practice flashcards covering bone biology, skeletal tissue, joint classifications, synovial joint anatomy, the central nervous system, and neurophysiology based on lecture slides.

Hematopoiesis

The biological process of blood cell formation, producing red blood cells, white blood cells, and platelets within red bone marrow.

Osteocalcin

A bone-derived hormone that regulates insulin release, glucose homeostasis, and energy expenditure by stimulating the pancreas to produce and release more insulin.

Perichondrium

A sheath of dense fibrous connective tissue surrounding external cartilage surfaces that resists outward expansion, contains blood vessels, and provides nutrients to maintain chondrocyte viability.

Hyaline Cartilage

The most abundant cartilage type in the human body; contains collagen fibers and is found in movable arm joints, the respiratory bronchial tree, and attaching ribs to the sternum.

Elastic Cartilage

A flexible cartilage containing a high proportion of elastic fibers alongside collagen, located in the external ear (pinna) and epiglottis.

Fibrocartilage

A highly compressible cartilage containing rows of chondrocytes alternating with thick collagen bands, specialized to withstand heavy mechanical loading in intervertebral discs, the pubic symphysis, and menisci.

Appositional Growth

Cartilage or bone growth in width or thickness resulting from the deposition of new matrix onto the existing surface beneath the perichondrium or periosteum.

Interstitial Growth

Cartilage growth from within, wherein chondrocytes divide and secrete new matrix inside pre-existing lacunae, expanding and lengthening the tissue from the inside out.

Axial Skeleton

The central structural skeletal division aligned along the long axis of the body, comprising the skull, vertebral column, and rib cage to provide protection and support for vital organs.

Appendicular Skeleton

The skeletal division consisting of the upper and lower limbs and the pectoral and pelvic girdles, adapted primarily for locomotion and manipulation of the environment.

Trabeculae

Needle-like or honeycomb-shaped struts of bone tissue found in spongy bone, precisely aligned along lines of mechanical stress to resist bone fracturing.

Diaphysis

The tubular shaft that constitutes the elongated main axis of a long bone, formed of a thick outer collar of compact bone enclosing a central medullary cavity.

Epiphysis

The expanded proximal and distal ends of a long bone, consisting of an outer shell of compact bone, an internal network of spongy bone, and an exterior cushion of articular cartilage.

Periosteum

A tough, double-layered, vascularized, and innervated fibrous membrane that covers all external bone surfaces except at joint-forming articular ends.

Endosteum

A delicate internal connective tissue membrane covering internal bone surfaces, lining medullary cavities, trabeculae of spongy bone, and internal canals of compact bone.

Osteoid

The unmineralized organic component of the bone extracellular matrix secreted by osteoblasts, composed of ground substance and collagen fibers before calcification.

Osteoprogenitor Cells

Mitotically active bone stem cells that can reproduce as stem cells or differentiate into bone-forming osteoblasts.

Osteoblasts

Bone-forming cells that synthesize and secrete unmineralized osteoid until they become completely surrounded by matrix and mature into osteocytes.

Osteocytes

Mature bone cells situated within lacunae that monitor and maintain the bone matrix, communicating through dendritic projections in response to mechanical loading and chemical signals.

Osteoclasts

Large, multinucleated bone-resorbing cells that secrete collagenase and acid to degrade bone matrix, critical for skeletal remodeling and elevating blood $\text{Ca}^{2+}$ levels.

Osteon

The fundamental structural and functional unit of mature compact bone, consisting of concentric lamellae arranged around a central neurovascular canal.

Lamellae

Concentric rings of mineralized extracellular matrix within an osteon, in which collagen fibers run in alternating oblique directions in adjacent rings to resist torsional (twisting) stress.

Endochondral Ossification

The embryonic bone formation process in which a pre-existing hyaline cartilage model is calcified, broken down, and replaced by ossified bone tissue in almost all bones inferior to the skull.

Epiphyseal Plate

A band of hyaline cartilage located between the diaphysis and epiphysis of growing long bones that undergoes interstitial growth to elongate the bone until adulthood.

Wolff's Law

The physiological principle stating that bone tissue grows, remodels, and adapts structurally in direct response to the mechanical forces and physical stresses placed upon it.

Bone Repair Stages

The four-step sequence of bone fracture healing consisting of: $1)$ hematoma formation, $2)$ fibrocartilaginous (soft) callus formation, $3)$ bony callus formation, and $4)$ bone remodeling.

Synarthroses

A functional classification of joints that permit no movement, prioritizing stability over mobility (e.g., skull sutures).

Amphiarthroses

A functional classification of joints that permit slight, limited movement (e.g., intervertebral discs and the pubic symphysis).

Diarthroses

A functional classification describing freely movable joints, characteristic of all synovial joints predominantly found in the appendicular skeleton.

Syndesmoses

Fibrous joints where articulating bones are joined solely by bands of ligaments; mobility depends on the length of connecting collagen fibers.

Gomphoses

Peg-in-socket fibrous joints that anchor teeth into alveolar sockets of the mandible and maxilla via the short fibrous periodontal ligament.

Synchondroses

Cartilaginous joints where bones are united by rigid plates of hyaline cartilage, functionally serving as synarthroses (e.g., epiphyseal plates and the first sternocostal joint).

Symphyses

Cartilaginous joints where articulating bones are fused by a compressible pad of fibrocartilage, acting as amphiarthroses designed for shock absorption and weight-bearing.

Synovial Joints

Articulations defined by a fluid-filled joint cavity enclosed within an articular capsule, providing free diarthrotic movement across the appendicular skeleton.

Synovial Fluid

A slippery, viscous egg-white-like fluid within the joint cavity and articular cartilages that lubricates surfaces, reduces friction, and thins during physical activity.

Bursae

Flattened, fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid, positioned between adjacent tissues to alleviate friction during movement.

Tendon Sheath

An elongated, cylindrical bursa that wraps completely around a tendon subjected to friction, common in tight anatomical spaces such as the wrists and ankles.

Rotator Cuff

A stabilizing muscular arrangement composed of four muscles and their associated tendons encircling the glenohumeral joint to brace the humeral head in the glenoid cavity.

Osteoarthritis

The most common form of chronic non-inflammatory arthritis, caused by the progressive degradation of articular cartilage exceeding replacement, leading to exposed bone friction and osteophyte (bone spur) formation.

Rheumatoid Arthritis

A chronic autoimmune inflammatory disease characterized by bilateral joint inflammation, in which immune cells attack the synovial membrane, producing an erosive pannus and possible joint ankylosis.

Pannus

An abnormal, destructive thickening of inflamed synovial membrane in rheumatoid arthritis that releases enzymes to break down underlying articular cartilage.

Cerebral Cortex

The superficial outer gray matter layer of the cerebrum responsible for conscious thought, self-awareness, sensory perception, voluntary motor initiation, and memory.

Primary Motor Cortex

A region in the precentral gyrus containing large pyramidal cells that generate motor signals executing skilled, precise voluntary contractions of skeletal muscles.

Motor Homunculus

A topographical neural map on the primary motor cortex where the size of each represented body region corresponds directly to the number of motor neurons controlling it and the precision of its movements.

Premotor Cortex

A cortical motor association region anterior to the primary motor cortex that coordinates and sequences basic motor movements into complex learned tasks based on sensory feedback.

Broca's Area

A specialized motor speech region, typically located in the left cerebral hemisphere, that coordinates the muscular movements required for speech articulation.

Primary Somatosensory Cortex

A sensory area in the postcentral gyrus that receives somatic sensory information regarding touch, pain, temperature, and proprioception from peripheral receptors.

Hypothalamus

The chief visceral control center of the diencephalon, regulating autonomic activities, body temperature, hunger, thirst, sleep-wake cycles, and pituitary hormonal secretion.

Basal Nuclei

Subcortical gray matter masses deep within the cerebral white matter that filter out inappropriate muscle movements, unnecessary motor activities, and excessive emotional responses.

Limbic System

A functional neural network spanning multiple brain structures, including the amygdala and cingulate gyrus, that governs emotion, memory, and emotional responses to smell.

Reticular Activating System

A brainstem functional network that continuously sends alerting signals to the cerebral cortex to preserve wakefulness and filters out repetitive, weak, or familiar sensory signals.

Blood-Brain Barrier

A specialized protective physiological barrier formed by capillary endothelial tight junctions, thick basement membranes, and astrocyte processes that protects brain neural tissue from bloodborne toxins and fluctuations.

Conus Medullaris

The tapered, cone-shaped inferior termination of the spinal cord located approximately at the level of the $L_1\text{--}L_2$ vertebrae.

Cauda Equina

A collection of nerve roots extending inferiorly from the conus medullaris through the lower vertebral canal, named for its resemblance to a horse's tail.

Astrocytes

The most abundant CNS neuroglia, possessing numerous radiating processes that anchor neurons to nutrient capillaries, maintain extracellular ion concentrations, and clean up released neurotransmitters.

Microglial Cells

Small, defensive CNS neuroglia that monitor neuronal integrity and transform into active phagocytic macrophages to engulf cellular debris and damaged neurons.

Ependymal Cells

Ciliated CNS neuroglial cells lining the ventricles of the brain and central canal of the spinal cord to produce, cushion, and circulate cerebrospinal fluid.

Oligodendrocytes

CNS neuroglial cells whose cytoplasmic processes wrap repeatedly around thick nerve fibers to construct insulating lipid-rich myelin sheaths.

Schwann Cells

Neuroglia of the peripheral nervous system that wrap individually around peripheral axons to build segmented insulating myelin coverings.

Neuron

An excitable structural cell of the nervous system specialized to generate, conduct, and transmit electrical nerve impulses across the body.

Dendrites

Short, tapering, highly branched neuronal extensions that act as receptive input zones, collecting incoming electrical signals and conveying graded potentials toward the soma.

Axon

The singular conducting process of a neuron that generates nerve impulses at the axon hillock and transmits action potentials away from the cell body toward synaptic terminals.

Myelin Sheath Gaps

Unmyelinated spaces along an axon located between adjacent Schwann cells or oligodendrocyte wraps, where voltage-gated ion channels are concentrated.

Depolarization

A reduction in membrane potential characterized by the interior of the cell membrane becoming more positive relative to resting membrane potential due to $\text{Na}^+$ influx.

Hyperpolarization

An increase in membrane potential where the cytoplasmic side becomes more negative than resting membrane potential (falling below $-70\,\text{mV}$), decreasing the probability of action potential firing.

Graded Potential

A local, short-distance electrical fluctuation across a plasma membrane whose magnitude varies in direct proportion to stimulus intensity.

Action Potential

A self-propagating, all-or-none reversal of membrane voltage from $-70\,\text{mV}$ to $+30\,\text{mV}$ conducted along an axon without loss of amplitude.

Absolute Refractory Period

The time period following action potential initiation during which voltage-gated $\text{Na}^+$ channel inactivation gates are shut, completely preventing generation of another impulse regardless of stimulus strength.

Relative Refractory Period

The interval following the absolute refractory period where $\text{Na}^+$ channels have reset to resting state while $\text{K}^+$ channels remain open, permitting an action potential only under an exceptionally strong stimulus.

Saltatory Conduction

The rapid electrical transmission mechanism in myelinated axons where the electrical depolarization jumps from one myelin sheath gap (node of Ranvier) to the next.

Excitatory Postsynaptic Potential

A local depolarizing graded potential at the postsynaptic membrane driven by neurotransmitter binding that shifts the membrane potential toward the firing threshold.

Inhibitory Postsynaptic Potential

A local hyperpolarizing graded potential at the postsynaptic membrane caused by opening of $\text{K}^+$ or $\text{Cl}^-$ channels, moving membrane potential farther from threshold.

Acetylcholine

A common neurotransmitter synthesized in somatic motor neurons and autonomic pathways that depolarizes postsynaptic membranes to trigger skeletal muscle contraction.

Gamma-Aminobutyric Acid

The primary inhibitory neurotransmitter of the central nervous system that induces hyperpolarization, dampening neuronal excitability to promote sensory processing and prevent overstimulation.

Endorphins

Natural endogenous opiate neuropeptides released during stress or exercise that inhibit pain transmission pathways and enhance mood.