Muscle and Nervous Tissue – Practice Flashcards

A set of 70 question-and-answer flashcards covering key facts about muscle and nervous tissue for exam review.

From which embryonic germ layer does all muscle tissue originate?

The mesoderm.

What is the cell membrane of a muscle fiber called?

The sarcolemma.

What is the muscle-cell equivalent of cytoplasm that contains many myofibrils, glycogen, and fats?

The sarcoplasm.

Which specialized smooth endoplasmic reticulum stores and releases Ca²⁺ in muscle cells?

The sarcoplasmic reticulum (SR).

What name is given to the large, specialized mitochondria in muscle fibers?

Sarcosomes.

Place these skeletal-muscle structural levels in correct macro-to-micro order.

Skeletal muscle → muscle fascicle → muscle fiber → myofibril → myofilament.

Where are the nuclei located in skeletal-muscle fibers?

Peripherally, just under the sarcolemma.

Which sarcomere band is dark, anisotropic, and contains thick filaments?

The A band.

Which sarcomere band is light, isotropic, and contains only thin filaments?

The I band.

Which muscle types are under voluntary (conscious) control?

Skeletal (striated) muscles.

Describe the contraction of skeletal muscle in three words.

Forceful, quick, discontinuous.

What connective-tissue layer envelops an entire muscle?

The epimysium.

Which connective-tissue layer surrounds a bundle (fascicle) of muscle fibers?

The perimysium.

Which delicate connective-tissue layer surrounds each individual muscle fiber?

The endomysium.

Define a myofibril.

The structural and functional subunit of a skeletal-muscle fiber composed of repeating sarcomeres.

Name the two main types of myofilaments.

Thick (myosin II) filaments and thin (actin) filaments.

List the three regulatory proteins of the thin filament.

F-actin, tropomyosin, and troponin.

Which troponin subunit binds calcium ions?

Troponin C.

What is the basic contractile unit of a myofibril?

The sarcomere.

Between which structures does a single sarcomere extend?

From one Z disk to the next Z disk.

Which line in the center of the A band bundles thick filaments together?

The M line.

During contraction, what happens to the width of the I band?

It becomes narrower.

During contraction, what happens to the width of the A band?

It remains unchanged.

Define a muscle triad.

Two terminal cisternae of SR plus one T-tubule.

What are the components of a triad?

1 T-tubule flanked by 2 terminal cisternae of SR.

State the primary function of T-tubules.

To propagate depolarization and regulate Ca²⁺ influx/efflux deep into the fiber.

What property of muscle tissue is its ability to respond to stimuli called?

Excitability.

Give one heat-related function of skeletal muscle.

Generation of body heat during contraction.

Which proprioceptor responds to excessive tension in tendons?

The Golgi tendon organ.

Which proprioceptor detects muscle stretch and rate of length change?

The neuromuscular (muscle) spindle.

What specific protein is absent in Duchenne muscular dystrophy?

Dystrophin.

What is the inheritance pattern of Duchenne muscular dystrophy?

X-linked recessive.

Myasthenia gravis is caused by antibodies against which structure?

Acetylcholine receptors at the motor end plate.

What specialized junction is unique to cardiac muscle cells?

The intercalated disc.

Name the three junctional specializations found in intercalated discs.

Fascia adherentes, desmosomes (maculae adherentes), and gap junctions.

What is a cardiac muscle diad composed of?

One SR cisterna plus one T-tubule.

Where in the heart wall are Purkinje fibers located?

The subendocardial layer.

Describe the shape and nuclear position of a smooth-muscle cell.

Spindle-shaped (fusiform) with a centrally located, cigar-shaped nucleus.

Which type of smooth muscle contains abundant gap junctions and functions syncytially?

Visceral (unitary) smooth muscle.

Compared with skeletal and cardiac muscle, what tubular system is absent in smooth muscle?

T-tubules are absent.

Which calcium-binding protein triggers smooth-muscle contraction?

Calmodulin.

What cytoplasmic structures in smooth muscle serve a role similar to Z discs?

Dense bodies.

How would you describe the regeneration capacity of skeletal muscle?

Limited regeneration via satellite cells.

What cells serve as the source for skeletal-muscle regeneration?

Satellite cells.

Which muscle type has virtually no regenerative capacity after childhood?

Cardiac muscle.

Which cells produce myelin in the central nervous system?

Oligodendrocytes.

Which peripheral-nerve connective-tissue layer is equivalent to epimysium?

The epineurium.

Of what are Nissl bodies composed?

Stacks of rough endoplasmic reticulum with free ribosomes.

Which basic dye commonly stains Nissl bodies blue?

Cresyl violet.

In myelination, the major dense line results from what membrane surfaces coming together?

The cytoplasmic surfaces of the Schwann-cell (or oligodendrocyte) membrane.

Give one location where bipolar neurons are found.

The retina (or inner ear or olfactory epithelium).

Name a typical example of a multipolar neuron.

A motor neuron in the ventral horn of the spinal cord (Purkinje cell, sympathetic-ganglion cell, etc.).

Where are pseudounipolar neurons located?

In dorsal root (spinal) ganglia.

What is unique about anaxonic neurons?

They lack a true axon and regulate electrical changes in nearby CNS neurons without generating action potentials.

Which neurons carry impulses toward the CNS?

Sensory (afferent) neurons.

What type of synapse connects an axon to a dendrite?

An axodendritic synapse.

Which cutaneous receptor detects light touch and object texture?

Merkel’s disk.

Which encapsulated receptor detects high-frequency vibration and transient pressure?

Pacinian (Vater-Pacinian) corpuscle.

Which receptor detects light touch and low-frequency vibration in the skin?

Meissner corpuscle.

Which receptor detects warmth and stretching of skin and ligaments?

Ruffini corpuscle.

Baroreceptors primarily monitor what physiologic variable?

Arterial blood pressure.

Which glial cell type helps form and maintain the blood–brain barrier?

Astrocytes (particularly protoplasmic astrocytes).

From which embryonic layer do microglia originate?

Mesoderm (they derive from bone-marrow precursors).

What is the primary function of oligodendrocytes?

Producing myelin sheaths and providing electrical insulation within the CNS.

State one major function of Schwann cells.

Forming myelin sheaths around PNS axons for electrical insulation.

CNS injury often results in what obstructive tissue response that impedes repair?

Formation of a glial scar.

Successful axonal regeneration in the PNS depends largely on which supportive cells?

Schwann cells, which form guiding cords (Büngner bands) for regrowing axons.

Summarize the SR/T-tubule relationships in the three muscle types.

Skeletal: triad (2 SR + 1 T-tubule); Cardiac: diad (1 SR + 1 T-tubule); Smooth: no T-tubules, rudimentary SR.

Which structural feature—branching fibers—is unique to cardiac muscle among striated types?

Branched (aligned) fibers connected by intercalated discs.

Which glial cell lines the brain’s ventricles and spinal-cord central canal?

Ependymal cells.