Anatomy: Muscle and Nervous Tissue

Vocabulary flashcards covering the morphology, structure, function, and clinical correlates of skeletal, cardiac, and smooth muscle, along with the organization of the nervous system and neuroglial cells.

Sarcolemma

The cell membrane of the muscle tissue.

Sarcoplasm

The equivalent of cytoplasm in muscle cells, containing glycogen, fats, and many myofibrils.

Sarcosome

Large, specialized mitochondria found in muscle cells.

A bands

Dark bands in striated muscle that are anisotropic and birefringent in polarized light.

I bands

Light bands in striated muscle that are isotropic and do not alter polarized light.

Sarcomere

The structural and functional subunit of striated muscles, extending from one Z-disk to another Z-disk.

Epimysium

The outermost covering of entire muscle made of dense connective tissue where larger blood vessels are located.

Perimysium

Fibrous connective tissue sheath that groups muscle fibers into bundles called fascicles.

Endomysium

Fine areolar connective tissue covering each individual muscle fiber, composed mostly of reticular fibers.

Tropomyosin

A double helix of two polypeptide chains that runs in the groove between F-actin molecules.

Troponin C

The subunit of the troponin complex that binds to Calcium ($Ca^{2+}$).

Triad

A structure found in skeletal muscle composed of one T-tubule and two lateral portions of the sarcoplasmic reticulum.

Diad

A structure characteristic of cardiac muscle composed of one T-tubule and one terminal cistern of the sarcoplasmic reticulum.

Golgi Tendon Organ

Encapsulated sensory receptors found in muscle tendons that respond to tension and inhibit motor nerve activity if force becomes excessive.

Muscle Spindle

A sensory receptor encapsulated by perimysium that detects when a muscle is stretched or lengthened.

Dystrophin

A large actin-binding protein inside the sarcolemma; its absence leads to Duchenne Muscular Dystrophy (DMD).

Myasthenia Gravis

A chronic autoimmune neuromuscular disease caused by antibodies blocking Acetylcholine (ACh) receptors in the motor end plate.

Intercalated Disk

The unique interface between adjacent cardiac muscle cells containing fascia adherentes, desmosomes, and gap junctions.

Purkinje Fibers

Pale-staining cardiac cells rich in glycogen located in the sub-endocardial layer that rapidly transmit contractile impulses.

Dense Bodies

Structures in smooth muscle where thin and intermediate filaments insert, serving to transmit contractile forces to adjacent cells.

Satellite cells

The source of limited regeneration in skeletal muscle tissue.

Oligodendrocytes

Glial cells of the CNS that produce myelin sheaths for electrical insulation of axons.

Schwann Cells

Also known as neurolemmocytes, these cells produce myelin sheaths around axons in the Peripheral Nervous System (PNS).

Nissl Bodies

Basophilic clumps in the neuronal perikaryon made of rough endoplasmic reticulum (RER) and free ribosomes, representing sites of protein synthesis.

Bipolar Neurons

Neurons with one axon and one dendrite, found in the retina, inner ear, and olfactory epithelium.

Pseudounipolar Neurons

Neurons with a single process that divides into two branches, typically found in the dorsal root ganglion.

Protoplasmic Astrocyte

A type of astrocyte with many branching processes and few Glial Fibrillary Acid Protein (GFAP) filaments, primarily located in the grey matter.

Microglia

Small, phagocytic glial cells of mesodermal origin that serve as the immune defense of the Central Nervous System.

Ependymal Cell

Simple cuboidal cells that line the ventricles of the brain and the central canal of the spinal cord.

Pacinian corpuscle

Encapsulated nerve endings resembling large onion-like concentric lamellae that detect transient pressure and high-frequency vibrations.