Chapters 10-12 – Muscle Tissue, Mechanics & Nervous System

Vocabulary flashcards covering muscle tissue structure, contraction mechanics, movement principles, nervous system organization, neurophysiology, and related disorders.

Skeletal muscle

Long, striated, multinucleate fibers attached to bones; produces voluntary body movement.

Cardiac muscle

Branched, striated cells with a single nucleus and intercalated discs; forms heart wall and pumps blood involuntarily.

Smooth muscle

Spindle-shaped, non-striated cells with a single nucleus; lines hollow organs and drives involuntary movements like peristalsis.

T-tubules

Sarcolemma invaginations that conduct action potentials deep into a muscle fiber.

Sarcoplasmic reticulum (SR)

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

Terminal cisterns

Enlarged SR regions adjacent to T-tubules; release Ca²⁺ during excitation-contraction coupling.

Sarcoplasm

Cytoplasm of a muscle fiber containing glycogen, myoglobin, and organelles.

Myofibrils

Cylindrical protein bundles composed of repeating sarcomeres, the contractile units of muscle.

Sarcomere

The basic contractile unit of striated muscle extending from Z-line to Z-line.

Actin

Thin filament protein with myosin-binding sites; pulled toward the M-line during contraction.

Myosin

Thick filament motor protein with ATPase activity; forms cross-bridges with actin.

Troponin

Regulatory protein that binds Ca²⁺ and shifts tropomyosin off actin’s binding sites.

Tropomyosin

Regulatory protein blocking myosin-binding sites on actin when muscle is at rest.

Titin

Giant elastic protein that stabilizes thick filaments and provides passive elasticity to sarcomeres.

Nebulin

Structural protein that helps align thin filaments within a sarcomere.

Dystrophin

Protein linking sarcomere to sarcolemma; defects cause muscular dystrophy.

Neuromuscular junction (NMJ)

Synapse between a motor neuron and a skeletal muscle fiber.

Synaptic end bulb

Swollen axon terminal containing vesicles of acetylcholine (ACh).

Synaptic cleft

Microscopic gap between neuron and muscle fiber at the NMJ.

Motor end plate

Region of muscle sarcolemma rich in ACh receptors opposite the synaptic end bulb.

Excitation-contraction coupling

Sequence linking muscle fiber action potential to Ca²⁺ release and sarcomere contraction.

Sliding filament theory

Model stating that myosin heads pull actin filaments toward the M-line, shortening the sarcomere.

ATP hydrolysis (cocking)

Splitting of ATP energizes and repositions the myosin head for cross-bridge formation.

Motor unit

A motor neuron and all the skeletal muscle fibers it innervates.

Isotonic contraction

Muscle generates constant tension while changing length.

Concentric contraction

Type of isotonic contraction where muscle shortens while producing force.

Eccentric contraction

Type of isotonic contraction where muscle lengthens while maintaining tension.

Isometric contraction

Muscle develops tension without changing length.

Origin (muscle)

Fixed, typically proximal attachment point of a muscle.

Insertion (muscle)

Movable, typically distal attachment point pulled toward the origin during contraction.

First-class lever

Lever with fulcrum between effort and load; example: atlanto-occipital joint (nodding).

Second-class lever

Lever with load between fulcrum and effort; example: standing on tiptoe.

Third-class lever

Lever with effort between fulcrum and load; example: biceps flexing forearm.

Prime mover (agonist)

Primary muscle responsible for a specific movement.

Antagonist

Muscle that opposes the action of the prime mover.

Synergist

Muscle that assists the agonist by adding extra force or reducing undesirable movements.

Fixator

Muscle that stabilizes the origin of the agonist for efficient action.

Muscular dystrophy

Genetic disorder marked by progressive muscle fiber degeneration due to faulty dystrophin.

Myasthenia gravis

Autoimmune disease where antibodies block ACh receptors, causing muscle weakness.

Fibromyalgia

Chronic condition characterized by widespread musculoskeletal pain and fatigue.

Central nervous system (CNS)

Brain and spinal cord; integrates and processes information.

Peripheral nervous system (PNS)

All neural tissue outside CNS; includes sensory and motor nerves, ganglia.

Unipolar neuron

Neuron with one process that splits into peripheral and central branches; mainly sensory.

Bipolar neuron

Neuron with one axon and one dendrite; found in special sense organs (e.g., retina).

Multipolar neuron

Neuron with one axon and many dendrites; includes motor neurons and interneurons.

Astrocyte

CNS glial cell that forms blood-brain barrier and supports neurons.

Oligodendrocyte

CNS glial cell that produces myelin sheaths around multiple axons.

Microglia

Small CNS glial cells acting as phagocytic immune defenders.

Ependymal cell

CNS glial cell lining ventricles and producing cerebrospinal fluid (CSF).

Schwann cell

PNS glial cell that forms myelin sheath around a single axon segment.

Satellite cell

PNS glial cell that surrounds neuron cell bodies in ganglia, providing support.

Nerve

Bundle of axons in the peripheral nervous system.

Ganglia

Clusters of neuron cell bodies in the PNS.

Tract

Bundle of axons located within the CNS.

Nuclei (CNS)

Clusters of neuron cell bodies within the central nervous system.

Resting membrane potential (RMP)

Baseline electrical charge of ‑70 mV across neuronal membrane due to ion distribution and Na⁺/K⁺ pump.

Gated ion channel

Membrane protein that opens in response to specific stimuli (ligand, voltage, mechanical).

Leak channel

Non-gated ion channel that is always open, allowing passive ion movement.

Graded potential

Small, localized change in membrane potential that decreases with distance.

Temporal summation

Addition of graded potentials from the same synapse in rapid succession.

Spatial summation

Addition of simultaneous graded potentials from multiple synapses.

Action potential

All-or-none electrical impulse that propagates along an axon once threshold is reached.

Threshold

Membrane potential (~-55 mV) that must be reached to trigger an action potential.

Depolarization

Phase of an action potential where Na⁺ influx makes the inside of the cell more positive.

Repolarization

Phase of an action potential where K⁺ efflux returns membrane potential toward resting values.

Hyperpolarization

Membrane potential becomes more negative than RMP due to continued K⁺ efflux or Cl⁻ influx.

Synaptic transmission

Process where an action potential triggers neurotransmitter release and communication across a synapse.

Excitatory postsynaptic potential (EPSP)

Depolarizing graded potential that moves the postsynaptic neuron closer to threshold.

Inhibitory postsynaptic potential (IPSP)

Hyperpolarizing graded potential that moves the postsynaptic neuron farther from threshold.

Metabotropic receptor

Neurotransmitter receptor that activates a second-messenger cascade for slow, prolonged effects.

Creatine phosphate

High-energy compound that rapidly regenerates ATP in muscle fibers for short bursts of activity.

Anaerobic glycolysis

ATP production from glucose without oxygen; yields lactic acid and supports short, intense exercise.

Aerobic respiration

ATP production in mitochondria using oxygen; fuels prolonged, moderate-intensity activity.