Histology Flashcards

Which feature distinguishes cardiac muscle from both skeletal and smooth muscle on light microscopy?

Answer: Intercalated discs

Intercalated discs are unique to cardiac muscle and contain gap junctions and desmosomes that electrically and mechanically couple cardiomyocytes.

Nissl bodies, seen in the neuronal soma, represent which ultrastructural organelle?

Answer: Rough endoplasmic reticulum with ribosomes

Nissl bodies are stacks of rough ER studded with ribosomes, reflecting the neuron's high protein synthesis demands.

In the peripheral nervous system, which glial cell forms the myelin sheath around a single axon segment?

Answer: Schwann cell

Each Schwann cell myelinates one segment of a single PNS axon, whereas one oligodendrocyte myelinates multiple CNS axons.

Nodes of Ranvier are gaps in the myelin sheath where the axonal membrane is exposed. What is their primary functional significance?

Answer: Allow saltatory conduction to increase impulse speed

Action potentials jump between nodes (saltatory conduction), dramatically accelerating nerve impulse propagation in myelinated fibers.

Satellite cells surrounding neuronal cell bodies in dorsal root ganglia are analogous to which CNS glial cell type?

Answer: Astrocytes

Satellite cells in peripheral ganglia support and regulate the microenvironment of neuronal somas, analogous to astrocyte function in the CNS.

A biopsy of skeletal muscle shows central nuclei in many fibers. This finding is most consistent with which condition?

Answer: Muscle regeneration after injury

Centrally located nuclei in skeletal muscle fibers indicate regenerating myofibers, as mature fibers have peripherally located nuclei.

Which structural feature of smooth muscle cells allows for coordinated contraction of the bladder wall?

Answer: Gap junctions between cells

Gap junctions electrically couple smooth muscle cells in visceral (unitary) smooth muscle, enabling coordinated wave-like contractions.