28 flashcard

What is the cytoplasm of a muscle cell called?

Sarcoplasm

What is the plasma membrane of a muscle cell called?

Sarcolemma

What is the smooth endoplasmic reticulum of a muscle cell called?

Sarcoplasmic reticulum

Name the three types of muscle tissue.

keletal, Cardiac, and Smooth

Which type of muscle is voluntary and multinucleated?

Skeletal muscle

Which type of muscle is involuntary and branched with intercalated discs?

Cardiac muscle

Which muscle type is involuntary, non-striated, and fusiform?

Smooth muscle

What are the three connective tissue layers in skeletal muscle?

Endomysium, Perimysium, Epimysium

What does the endomysium surround?

Individual muscle fibers

What does the perimysium surround?

Fascicles (bundles of muscle fibers)

What does the epimysium surround?

The entire muscle

What is the junction where the muscle connects to tendon called?

Myotendinous junction

What is a myofibril composed of?

Thick and thin myofilaments

What are the dark and light bands of skeletal muscle called?

A bands (dark) and I bands (light)

What is the functional contractile unit of skeletal muscle?

Sarcomere

Between which structures is a sarcomere defined?

From one Z-disc to the next

What is found in the H zone?

Only thick filaments (myosin)

What is the role of the sarcoplasmic reticulum in muscle contraction?

Releases calcium ions (Ca²⁺) during depolarization to trigger contraction

What are T-tubules?

Invaginations of the sarcolemma that conduct depolarization deep into the fiber

What is a triad?

A T-tubule flanked by two terminal cisternae of the SR

Where are triads located in skeletal muscle?

At the junction of the A and I bands

What are muscle spindles?

Sensory proprioceptors that detect muscle stretch within fascicles

What do muscle spindles contain?

Intrafusal fibers and sensory axons

What are Golgi tendon organs?

Proprioceptors that detect tension at the myotendinous junction

What is the function of the neuromuscular junction?

Motor innervation—where a neuron stimulates muscle contraction

What are the three major skeletal muscle fiber types?

1. Type I – Slow oxidative

2. Type IIa – Fast oxidative-glycolytic

3. Type IIb – Fast glycolytic

Which type is fatigue-resistant and red?

Type I (slow oxidative)

Which type is white and fatigues rapidly?

Type IIb (fast glycolytic)

Which type is intermediate in fatigue and color?

Type IIa (fast oxidative-glycolytic)

What unique structural features are present in cardiac muscle?

Intercalated discs with desmosomes, fascia adherens, and gap junctions

How are cardiac muscle cells arranged

Branched fibers with central nuclei

What percentage of the cardiac cell volume is mitochondria?

About 40%

What type of junction is formed by a T-tubule and one terminal cisterna in cardiac muscle?

Dyad

What do atrial secretory granules release?

Atrial natriuretic factor (ANF)

Where is smooth muscle found?

Walls of blood vessels and hollow organs (digestive, respiratory, urinary, reproductive tracts)

What shape are smooth muscle cells?

Spindle-shaped (fusiform) with central nuclei

Do smooth muscle cells have striations or sarcomeres?

No

What replaces troponin and tropomyosin in smooth muscle?

Calmodulin and Myosin light chain kinase (MLCK)

What are dense bodies

Structures anchoring actin filaments, analogous to Z-discs

What is the role of caveolae in smooth muscle?

Invaginations of the sarcolemma containing ion channels for Ca²⁺ regulation

Is smooth muscle under voluntary control?

No, it is involuntary and regulated by the autonomic nervous system and hormones (e.g., oxytocin)

What additional function do smooth muscle cells perform besides contraction?

They synthesize collagen, elastin, and proteoglycans

Which muscle type has the best regenerative capacity?

Smooth muscle

Which muscle type regenerates poorly but has satellite cells?

Skeletal muscle

: Which muscle type has virtually no regenerative capacity?

cardiac muscle

What replaces dead cardiac muscle after infarction?

Fibroblasts and scar tissue

What protein is deficient in Duchenne Muscular Dystrophy?

Dystrophin

What is the function of dystrophin?

Links cytoskeleton to the ECM and stabilizes sarcolemma during contraction

What happens when dystrophin is absent?

Sarcolemma ruptures, calcium enters, leading to necrosis of muscle fibers

What is Myasthenia Gravis?

Autoimmune disorder where antibodies block acetylcholine receptors at neuromuscular junctions

What is the main symptom of Myasthenia Gravis?

Progressive muscle weakness, especially of facial and ocular muscles

What is Botulism?

: Food poisoning that inhibits acetylcholine release, causing paralysis

What is a leiomyoma?

benign tumor of smooth muscle cells

Describe skeletal muscle in longitudinal section

Multinucleated, striated, non-branching fibers with peripheral nuclei

Describe skeletal muscle in cross-section.

Large, round fibers with peripherally located nuclei and uniform diameter

Describe cardiac muscle in longitudinal section.

Branched, striated fibers with intercalated discs and central nuclei

Describe smooth muscle in longitudinal section.

Spindle-shaped cells with elongated, wavy nuclei

: Describe smooth muscle in cross-section.

Round to oval fibers; some show central nuclei, others lack visible nuclei