Exam 4 Study Guide – Muscle & Nervous System Vocabulary

Vocabulary flashcards covering key terms in skeletal muscle physiology, energy metabolism, neural pathways, and muscular anatomy for Exam 4 preparation.

Voluntary (muscle)

Muscle that is consciously controlled; skeletal muscle contracts when the brain sends signals via somatic motor neurons.

Multinucleated Fiber

A skeletal muscle cell formed from fused myoblasts, containing many nuclei for increased protein synthesis and rapid repair.

Actin (Thin Filament)

Protein anchored to Z-discs in a sarcomere; contains binding sites for myosin heads.

Myosin (Thick Filament)

Central filament in a sarcomere whose heads attach to actin to produce contraction.

Tropomyosin

Regulatory protein that blocks actin’s binding sites at rest, preventing cross-bridge formation.

Troponin

Calcium-binding protein that moves tropomyosin away from actin’s binding sites to initiate contraction.

Sarcoplasmic Reticulum (SR)

Specialized endoplasmic reticulum in muscle fibers that stores and releases Ca²⁺ needed for contraction.

T Tubule

Deep invagination of the sarcolemma that conducts action potentials into the muscle fiber to trigger Ca²⁺ release from the SR.

Sliding Filament Theory

Concept that thin filaments slide past thick filaments, increasing overlap and shortening the sarcomere during contraction.

Cross Bridge

Temporary attachment formed when a myosin head binds to an exposed actin site, powered by ATP and Ca²⁺.

Motor Cortex

Brain region where a voluntary movement action potential originates before traveling down a motor neuron.

Acetylcholine (ACh)

Neurotransmitter released at the neuromuscular junction to propagate the action potential to the muscle fiber.

Neuromuscular Junction (NMJ)

Chemical synapse where a motor neuron communicates with a skeletal muscle fiber.

Depolarization

Phase of an action potential when Na⁺ ions rush into the cell, making the inside more positive.

Repolarization

Phase of an action potential when K⁺ ions exit the cell, restoring the negative interior.

Polarized Membrane

Resting state of the sarcolemma with negative interior and positive exterior voltage difference.

Wave Summation

Increased muscle tension produced when two stimuli arrive in rapid succession.

Unfused Tetanus

Sustained yet wavering muscle contraction with partial relaxation between stimuli.

Fused Tetanus

Smooth, sustained muscle contraction with no relaxation between rapid stimuli.

ATP (Adenosine Triphosphate)

Primary energy currency of muscle cells, fueling cross-bridge cycling and ion pumps.

Direct Phosphorylation

Fast, oxygen-independent ATP regeneration using creatine phosphate; lasts ~15 seconds.

Anaerobic Glycolysis

Oxygen-independent pathway that converts glucose to lactic acid, supplying ATP for 30-60 seconds.

Aerobic Respiration

Oxygen-requiring pathway producing about 32 ATP per glucose for prolonged activity.

Lactic Acid Fermentation

Anaerobic process that converts pyruvate to lactic acid when oxygen is unavailable in muscle.

Reactants of Cellular Respiration

Glucose (C₆H₁₂O₆) and oxygen (O₂) used to produce ATP, CO₂, and H₂O.

Carbon Dioxide Removal

CO₂ diffuses into blood, is transported to the lungs, and exhaled from the body.

Tendon

Dense connective tissue that anchors muscle to bone.

Ligament

Dense connective tissue that connects bone to bone.

Meissner’s Corpuscle

Dermal receptor specialized for detecting light touch.

Pacinian Corpuscle

Dermal receptor that senses deep pressure and vibration.

Free Nerve Ending

Unencapsulated receptor detecting pain and temperature.

Sensory Neuron (Afferent)

Neuron that carries information from the body toward the CNS.

Motor Neuron (Efferent)

Neuron that transmits signals from the CNS to effectors such as muscles.

Interneuron

CNS neuron that connects sensory and motor pathways, facilitating integration.

Reflex Arc

Pathway: stimulus → receptor → sensory neuron → interneuron → motor neuron → effector.

Circular Fascicle Arrangement

Muscle fibers arranged in concentric rings; e.g., orbicularis oris.

Convergent Fascicle Arrangement

Fibers converge toward a single tendon; e.g., pectoralis major.

Parallel Fascicle Arrangement

Fibers run parallel to the long axis; e.g., sartorius.

Fusiform Fascicle Arrangement

Spindle-shaped muscle with expanded belly; e.g., biceps brachii.

Pennate Fascicle Arrangement

Short fibers attach obliquely to a tendon; e.g., rectus femoris.

Rectus Fibers

Muscle fibers running straight to the midline.

Transverse Fibers

Muscle fibers running at right angles to the midline.

Oblique Fibers

Muscle fibers running at angles other than 90° to the midline.

Mechanical Advantage Lever

Lever system requiring less effort to move a load; sacrifices speed for force.

Mechanical Disadvantage Lever

Lever system allowing greater speed and range of motion but requiring more effort.

Muscle Naming Criteria

Basis include shape, size, location, action, and number of origins.

Trapezius & Deltoid Names

Muscles named after their geometric shapes (trapezoid, triangle).

Cross-Bridge Formation

Step 1 of cycle: myosin head attaches to actin.

Power Stroke

Step 2: myosin pulls actin toward the M-line.

Cross-Bridge Detachment

Step 3: ATP binding causes myosin to release actin.

Myosin Cocking

Step 4: ATP hydrolysis re-energizes the myosin head for the next cycle.