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Smooth and Cardiac Muscle: Characteristics and Types

Learn about the characteristics and types of smooth and cardiac muscle, including their contraction mechanisms and differences from skeletal muscle.

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Smooth and Cardiac Muscle: Characteristics and Types

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  1. Ch. 9a Part 4 Notes Smooth and Cardiac Muscle Interactive Notes pages 308-310

  2. Smooth Muscle Compared to skeletal muscle fibers, smooth muscle fibers are: Shorter. Single, centrally located nucleus. Elongated with tapering ends. Myofilaments randomly organized. Lack striations. Lack transverse tubules. Sarcoplasmic reticulum (SR) not well developed.

  3. Types of Smooth Muscle 2 types of smooth muscle: Multi-unit Smooth Muscle: • Cells are less organized. • Function as separate units. • Fibers function independently. • Iris of eye, walls of blood vessels. • Stimulated by neurons, hormones. Visceral Smooth Muscle: • Single-unit smooth muscle; cells respond as a unit. • Sheets of spindle-shaped muscle fibers. • Fibers held together by gap junctions. • Exhibit rhythmicity. • Conduct peristalsis. • Walls of most hollow organs. • More common type of smooth muscle.

  4. Smooth Muscle Contraction Resembles skeletal muscle contraction in these ways: • Interaction between actin and myosin. • Both use calcium and ATP. • Both are triggered by membrane impulses. Different from skeletal muscle contraction in these ways: • Smooth muscle lacks troponin; uses calmodulin instead. • Two neurotransmitters affect smooth muscle: Acetylcholine (Ach) and norepinephrine (NE). • Hormones can stimulate or inhibit smooth muscle. • Stretching can trigger smooth muscle contraction. • Smooth muscle slower to contract and relax. • Smooth muscle more resistant to fatigue. • Smooth muscle can change length without changing tautness.

  5. Cardiac Muscle Cardiac Muscle: Located only in the heart. Striated muscle cells. Muscle fibers joined together by intercalated discs. Fibers branch, contain a single nucleus. Network of fibers contracts as a unit (syncytium). Self-exciting and rhythmic. Longer refractory period than skeletal muscle. No sustained or tetanic contractions.

  6. Table 9.3 Characteristics of Muscle Tissues

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