Essential Nervous System, Occupation-Based Anatomy, and Spine Functional Anatomy

Comprehensive vocabulary flashcards covering the nervous system organization, peripheral nerve plexuses, neuromuscular control, biomechanics, muscle types/contractions, lever systems, and spinal functional anatomy from the provided lecture sources.

Neuron

A specialized nerve cell that acts as the body's building block for sending electrical messages, made of a main cell body, receiving branches, and one long sending cable.

Axon

The long cable extension of a nerve cell that carries electrical signals away from the cell body toward other cells or muscles.

Dendrite

The branch-like parts of a nerve cell that receive incoming messages from other cells and carry them toward the main cell body.

Endoneurium

The delicate innermost layer of tissue that wraps directly around each individual nerve fiber.

Perineurium

The middle protective tissue layer that wraps around a bundle (fascicle) of multiple nerve fibers.

Epineurium

The tough outermost tissue layer that wraps around multiple fiber bundles to form a complete peripheral nerve.

Afferent Neurons

Sensory nerve cells that carry incoming signals from body receptors back up to the brain and spinal cord.

Efferent Neurons

Motor nerve cells that carry outgoing commands from the brain and spinal cord down to muscles and glands.

Sympathetic Nervous System

The branch of the automatic nervous system that triggers 'fight or flight' responses, speeding up heart rate and spending body energy.

Parasympathetic Nervous System

The branch of the automatic nervous system that controls 'rest and digest' mode, slowing heart rate and conserving body energy.

Neuropraxia

The mildest nerve injury where the wire structure stays intact but signals are temporarily blocked (like a temporary freeze), usually healing in days to weeks.

Axonotmesis

A middle-severity nerve injury where the inner signal wire breaks but the outer tissue framework stays intact, allowing slow regrowth over months.

Neurotmesis

The most severe nerve injury where both the inner wire and outer tissue casing are completely cut through, requiring surgery to heal.

Dermatome

A specific strip of skin connected to sensory signals from one single spinal nerve, tested clinically to check for spinal cord damage.

Brachial Plexus

A major network of nerves coming from the neck (C5–T1) that splits and recombines to control all movement and feeling in the arm and hand.

Axillary Nerve

A branch from the neck nerve network (C5, C6) that powers shoulder muscles (deltoid and teres minor) to lift and rotate the arm for reaching.

Radial Nerve

A major nerve running down the back of the arm (C5–T1) that powers muscles that straighten the elbow, wrist, fingers, and thumb.

Ulnar Nerve

A nerve running down the inner arm (C8, T1) that controls forearm flexors and key hand muscles used for gripping and pinching (often called the 'funny bone' nerve).

Median Nerve

A main nerve in the arm (C5–T1) that lets you turn your palm down, bend your fingers, move your thumb, and feel things on the palm side of your hand.

Femoral Nerve

A large nerve in the lower back and front thigh (L2–L4) that powers muscles like the quadriceps to flex the hip and straighten the knee.

Obturator Nerve

A nerve from the lower back (L2–L4) that powers inner thigh muscles to pull the legs together; tightness here can cause legs to cross while walking.

Sciatic Nerve

The longest and thickest nerve in the body (L4–S3) running down the back of the leg, powering hamstrings before splitting near the knee.

Tibial Nerve

A branch of the main back-leg nerve running down the calf to control muscles that point the foot downward and curl the toes.

Common Fibular Nerve

A branch of the main back-leg nerve wrapping around the side of the knee to the front leg, powering muscles that lift the foot up and straighten the toes.

Stereognosis

The ability to recognize what an object is using only your sense of touch without looking at it (like reaching into a pocket and finding a key).

Open Kinetic Chain

A movement where the end of the arm or leg moves freely in the air, working a single joint in isolation (like lifting a dumbbell or kicking a ball).

Closed Kinetic Chain

A movement where the hands or feet are pressed against a fixed surface, forcing multiple joints and muscles to work together (like doing a push-up or squat).

First-Class Lever

A lever setup where the balance point (fulcrum) sits in the middle between the muscle force and the load, like a see-saw or tilting the head back.

Second-Class Lever

A lever setup where the heavy load sits in the middle between the balance point and the muscle force, like a wheelbarrow or standing up on tiptoes.

Third-Class Lever

The most common body lever setup where muscle effort pulls in the middle between the balance point and the load, like bending the elbow to lift a weight.

Ligament

A tough, flexible band of tissue that holds bone to bone to keep joints stable.

Tendon

A strong cord of tissue that attaches muscle to bone to transfer force and create joint movement.

Joint Capsule

A protective sleeve of tissue that completely surrounds a moving joint to hold it together and keep lubricating fluid inside.

Aponeurosis

A wide, flat sheet of strong tissue that acts like a broad ribbon to anchor muscles to bones or to other muscles.

Motor Unit

A single motor nerve cell and all the specific muscle fibers it turns on to contract together.

Sarcomere

The basic tiny contracting unit inside a muscle fiber, where thin and thick protein threads slide past each other to create muscle force.

Muscle Spindle

A tiny stretch sensor inside muscle tissue that detects how long a muscle is and how fast it stretches to prevent tearing.

Slow-Twitch Fibers

Endurance-focused muscle fibers (Type I) that produce gentle force for a long time without getting tired easily.

Fast-Twitch Fibers

Power-focused muscle fibers (Type II) that give quick, explosive bursts of force but burn out quickly.

Agonist

The main muscle ('prime mover') doing most of the work to create a specific movement.

Antagonist

The muscle that acts opposite to the prime mover and must relax or stretch to let movement happen smoothly.

Fixator

A stabilizing muscle that holds the base bone steady so the main working muscle can pull effectively without slipping.

Synergist

A helper muscle that works alongside the prime mover to add extra force or steady the joint.

Force Couple

A team of muscles pulling in different directions around a joint to create a smooth rotating movement (like two hands turning a steering wheel).

Isometric Contraction

A muscle squeeze where tension builds up but the muscle length does not change and the joint stays still (like pushing against a wall).

Concentric Contraction

A muscle squeeze where the muscle actively shortens as it overcomes weight (like lifting a dumbbell during a bicep curl).

Eccentric Contraction

A muscle squeeze where the muscle slowly lengthens under tension to resist gravity or control a load (like lowering a dumbbell steadily).

Active Insufficiency

A problem occurring in multi-joint muscles where the muscle is fully shortened and crumpled up, so it cannot squeeze any harder to produce force.

Passive Insufficiency

A problem occurring in multi-joint muscles where the muscle is stretched out as far as it can go, stopping the joints from moving any further.

Close-Pack Position

The joint position where bone surfaces fit together most tightly and supporting straps are stretched firm, offering maximum stability.

Loose-Pack Position

The joint position where bone contact is minimal and supporting straps are relaxed, giving the joint its greatest freedom to move.

Lordosis

The natural inward curve of the spine found in the neck (cervical) and lower back (lumbar) areas.

Kyphosis

The natural outward, rounded curve of the spine found in the upper back (thoracic) and tailbone areas.

Atlas

The very first cervical vertebra (C1) at the top of the neck that holds up the skull and lets you nod your head 'yes'.

Axis

The second cervical vertebra (C2) featuring a vertical bony peg (dens) that allows the skull to swivel side-to-side when shaking your head 'no'.

Nucleus Pulposus

The soft, jelly-like center of a spinal disc that squishes and shifts to absorb shocks between spinal bones.

Annulus Fibrosus

The tough, rubbery outer ring of a spinal disc that wraps around the jelly center to keep it contained.

Herniated Disc

A condition where the jelly core of a spinal disc tears through the outer rubber ring and presses against nearby spinal nerves.

Bulging Disc

A condition where a spinal disc swells outward past its normal space, but the outer ring stays completely unbroken.

Ankylosing Spondylitis

An inflammatory disease that causes spinal bones to fuse together over time, turning the spine into a rigid, non-bending pole ('bamboo spine').

Spondylosis

General age-related wear and tear (osteoarthritis) of the spine, leading to stiff joints, worn discs, and bone spurs.

Radiculopathy

A pinched nerve root where it exits the spine, causing sharp pain, numbness, or weakness traveling down an arm or leg.

Erector Spinae Group

The large superficial muscle group along the back of the spine (iliocostalis, longissimus, spinalis) responsible for standing up straight and arching the back.

Transversospinalis Group

A set of deep back muscles (multifidi, rotatores, semispinalis) connecting individual vertebrae to stabilize the spine and help with twisting.

Quadratus Lumborum

A deep lower-back muscle that anchors the lumbar spine, bends the waist to the side, and lifts the hip.

Transverse Abdominis

The deepest layer of core muscles that wraps around the abdomen like a natural corset to protect the spine and brace the core during heavy lifting.

Thoracolumbar Fascia

A thick sheet of tough connective tissue in the lower back that anchors core muscles and protects the spine from twisting strain.