Muscle & Nervous Tissue – Vocabulary Flashcards

A comprehensive set of vocabulary flashcards covering key terms from the lecture on muscle and nervous tissue, including structural components, functional concepts, clinical conditions, and important cell types.

Sarcolemma

The plasma membrane of a muscle fiber.

Sarcoplasm

The cytoplasm of a muscle cell; contains few rough ER cisternae and many myofibrils.

Sarcoplasmic Reticulum (SR)

A specialized smooth endoplasmic reticulum that stores and releases Ca²⁺ in muscle fibers.

Sarcosome

Large, specialized mitochondrion within muscle cells.

Muscle Fiber

A single, elongated muscle cell; also called a myocyte.

Fascicle

A bundle of muscle fibers surrounded by perimysium.

Striated Muscle

Muscle with alternating light and dark bands (skeletal and cardiac).

Smooth (Non-striated) Muscle

Muscle lacking cross-striations; controlled involuntarily by ANS/PNS.

Voluntary Muscle

Muscle whose contraction is under conscious control (e.g., skeletal).

Involuntary Muscle

Muscle that contracts without conscious control (cardiac, smooth).

Excitability

Ability of muscle tissue to receive and respond to stimuli.

Contractility

Ability of muscle to shorten when stimulated.

Extensibility

Capacity of muscle to be stretched.

Elasticity

Muscle’s ability to recoil to resting length after stretching.

Epimysium

Dense connective tissue covering the entire muscle; houses larger blood vessels.

Perimysium

Fibrous connective tissue that surrounds and groups muscle fibers into fascicles.

Endomysium

Delicate connective tissue surrounding each individual muscle fiber; rich in reticular fibers.

Myofibril

Cylindrical bundle of myofilaments; structural and functional subunit of a muscle fiber.

Myofilament

Individual contractile filament (actin or myosin) within a myofibril.

Sarcomere

Smallest functional (contractile) unit of striated muscle; region between two Z discs.

A Band

Dark band containing thick filaments; remains unchanged during contraction.

I Band

Light band containing thin filaments; narrows during contraction.

H Zone

Lighter central region of the A band lacking actin-myosin overlap; disappears on contraction.

M Line

Protein line in center of A band that binds thick filaments together.

Z Disc (Z Line)

Dark line bisecting the I band; anchors thin filaments and defines sarcomere boundaries.

Actin

Thin filament protein composed of F-actin strands with myosin binding sites.

Myosin II

Thick filament protein with two heavy chains and four light chains; heads possess ATPase activity.

Tropomyosin

Double-helix protein that lies in the groove of F-actin, blocking myosin-binding sites at rest.

Troponin

Ca²⁺-regulated protein complex (C, T, I subunits) controlling actin-myosin interaction.

T-Tubule

Transverse sarcolemmal invagination that transmits action potentials into the muscle fiber.

Triad (Skeletal)

Complex of one T-tubule flanked by two SR terminal cisternae; coordinates Ca²⁺ release.

Diad/Dyad (Cardiac)

Association of one T-tubule with one SR cisterna in cardiac muscle.

Neuromuscular Junction (Motor End Plate)

Synapse between a motor neuron and a skeletal muscle fiber where ACh is released.

Sliding Filament Model

Theory describing muscle contraction by sliding of thin past thick filaments, shortening sarcomeres.

Muscle Spindle

Encapsulated proprioceptor that detects muscle stretch via intrafusal fibers.

Golgi Tendon Organ

Encapsulated proprioceptor in tendons that senses tension to modulate contraction force.

Duchenne Muscular Dystrophy (DMD)

X-linked disorder due to dystrophin mutation causing progressive skeletal muscle degeneration.

Myasthenia Gravis

Autoimmune disease with antibodies blocking ACh receptors, leading to fluctuating skeletal muscle weakness.

Rigor Mortis

Post-mortem stiffening caused by lack of ATP preventing actin-myosin detachment.

Intercalated Disc

Specialized junctional complex connecting cardiac muscle cells; contains fascia adherens, desmosomes, and gap junctions.

Fascia Adherens

Anchoring component of intercalated discs that secures actin filaments of terminal sarcomeres.

Macula Adherens (Desmosome)

Spot junction in intercalated discs providing strong cell-to-cell adhesion.

Gap Junction

Communicating junction allowing ionic continuity and synchronized contraction in cardiac/smooth muscle.

Purkinje Fiber

Large, glycogen-rich conducting cardiac cell in subendocardium that rapidly transmits impulses.

Dense Body

Structure in smooth muscle where thin and intermediate filaments anchor, analogous to Z discs.

Calmodulin

Ca²⁺-binding protein crucial for activating myosin light-chain kinase in smooth muscle contraction.

Visceral (Unitary) Smooth Muscle

Smooth muscle with abundant gap junctions acting as a functional syncytium (e.g., intestines, uterus).

Multiunit Smooth Muscle

Smooth muscle with few gap junctions allowing precise, graded contractions (e.g., iris).

Satellite Cell (Muscle)

Skeletal muscle stem cell responsible for limited muscle fiber regeneration.

Neuron

Excitable cell that receives, integrates, and transmits electrical impulses in nervous tissue.

Nissl Bodies

Clumps of rough ER and ribosomes in neuronal soma; sites of protein synthesis.

Myelin

Lipid-rich sheath surrounding axons, produced by oligodendrocytes (CNS) and Schwann cells (PNS).

Oligodendrocyte

Glial cell of CNS that forms myelin sheaths around multiple axons.

Schwann Cell

Glial cell of PNS that myelinates a single axon segment or encloses unmyelinated fibers.

Astrocyte

Most abundant CNS glial cell; provides metabolic support, forms part of the blood-brain barrier.

Microglia

Mesoderm-derived phagocytic glial cell providing immune defense within CNS.

Ependymal Cell

Ciliated cuboidal cells lining brain ventricles and spinal cord canal; aid CSF movement.

Synapse

Specialized junction where a neuron communicates with another cell via neurotransmitter release.

Axodendritic Synapse

Synaptic contact between an axon terminal and a dendrite.

Axosomatic Synapse

Synaptic contact between an axon terminal and a neuronal cell body.

Axoaxonic Synapse

Synaptic contact between two axon terminals.

Afferent (Sensory) Neuron

Neuron conveying impulses toward the CNS.

Efferent (Motor) Neuron

Neuron transmitting impulses from CNS to effector organs.

Bipolar Neuron

Neuron with one axon and one dendrite; found in retina, olfactory epithelium, inner ear.

Multipolar Neuron

Neuron with one axon and multiple dendrites; most common form in CNS.

Pseudounipolar Neuron

Neuron with a single process that bifurcates into peripheral and central branches; located in dorsal root ganglia.

Endoneurium

Loose connective tissue surrounding individual peripheral nerve fibers (axons plus Schwann cells).

Perineurium

Specialized connective tissue sheath enclosing a fascicle of nerve fibers; forms blood-nerve barrier.

Epineurium

Dense irregular connective tissue forming the outermost covering of a peripheral nerve.