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NSCI 1413 (15)
Lecture 11

NSCI 1413 Lecture 11: MuscularSystem

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Natural Science
NSCI 1413
Guy Robinson

Muscular Anatomy ● Three types of muscle: 1. Smooth Muscle:​ Involuntary; no striations due to the arrangement of actin and myosin filaments; controlled by the autonomic nervous system ● Walls of blood vessels and the digestive tract (peristalsis) 2. Cardiac Muscle:​ Involuntary; striated; generates its own action potential ● The heart 3. Skeletal Muscle:​ Voluntary; very large and multinucleate; work in antagonistic pairs ● Biceps and triceps (antagonistic pair) ● Each muscle contains bundles of long, cylindrical, and multinucleate muscle cells ● Various modified structures that allow muscles to contract: ○ Sarcolemma:​ The modified plasma membrane of a muscle cell that surrounds each muscle cell; can propagate an action potential 2+​ ○ Sarcoplasmic Reticulum:​ Modified ER that contains sacks of Ca​ necessary for normal muscle contraction ○ T System:​ A system of tubules that runs perpendicular to the SR and connects the SR to the extracellular fluid ○ Sarcomere:​ The functional unit of the muscle cell; boundaries marked by ​z-lines​; gives skeletal muscle its striated appearance Muscular Physiology ● Sliding Filament Theory ● Muscle cells contain thousands of ​myofibrils​ running parallel to the length of the cell; consists of thick (two long chains of myosin w/ a globular head at one end) and thin filaments (two strands of actin) ■ Actin:​ The protein from which microfilaments are composed; forms the contractile filaments of sarcomeres ■ Myosin:​ A fibrous protein that forms some of the contractile filaments of muscle cells; contains head ● Contraction of a sarcomeres depends on: ■ Troponin:​ A globular protein complex involved in muscle contraction; part of the thin filaments of muscle tissue ■ Tropomyosin: A thin filament protein involved in muscle contraction; controls the access of myosin to the myosin binding site of actin ● Process of Muscle Contraction: 1. Neuromuscular Control: ​The axons of the nerve cells of the spinal cord branch and attach to each muscle fiber forming a ​neuromuscular junction i. An action potential passes down the nerve ii. The nerve rel
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