Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

Chapter 15
Skeletal Muscle Function
Stephanie J. Valberg
Department of Veterinary Population Medicine
College of Veterinary Medicine
University of Minnesota
St. Paul, Minnesota
I. INTRODUCTION
II. SPECIALIZATION OF THE SARCOLEMMA
AND SARCOPLASM FOR MUSCULAR
CONTRACTION
A. Neuromuscular Transmission: Excitation-
Conduction
B. Coupling Excitation to Contraction
C. Muscular Contraction
D. Muscular Energetics
III. HETEROGENEITY OF SKELETAL MUSCLE
A. Gross Muscle Coloration
B. Physiological Properties
C. Motor Units
D. Histology and Histochemistry
E. Quantitative Biochemistry
F. Muscle Fiber Composition
G. Muscle Fiber Recruitment
IV. ORIGINS OF FIBER DIVERSITY
V. EXERCISE AND ADAPTATIONS TO TRAINING
A. Exercise Intensity and Sources of Energy
B. Adaptations to Exercise Training
VI. DIAGNOSTIC LABORATORY METHODS
FOR THE EVALUATION OF NEUROMUSCULAR
DISORDERS
A. Muscle-Specific Serum Enzyme
Determinations Used in the Diagnosis of
Neuromuscular Disorders
B. Muscle-Specific Serum Proteins and Antibodies
VII. MUSCLE BIOPSY AND HISTOCHEMISTRY
IN THE DIAGNOSIS OF NEUROMUSCULAR
DISORDERS
VIII. MOLECULAR DIAGNOSTIC TESTING
IX. SELECTED NEUROMUSCULAR DISORDERS OF
DOMESTIC ANIMALS
A. Ion Channelopathies
B. Cytoskeletal Dystrophin Deficiency and Muscular
Dystrophy
C. Immune-Mediated Canine Masticatory Muscle
Myositis
D. Disorders of Glyco(geno)lysis Affecting Skeletal
Muscle
E. Mitochondrial Myopathies
F. Endocrine Myopathies
REFERENCES
I . INTRODUCTION
This chapter outlines skeletal muscle form and function,
reviews mechanisms of assessment, and introduces selected
neuromuscular diseases that highlight the close relationship
between muscle form and function. Skeletal muscle comprises
approximately 50% of the body’s mass. It is largely composed
of long multinucleated spindle shaped skeletal muscle
cells (myofibers) that are highly specialized by virtue of a
structured array of muscle-specific contractile proteins and
conductile membranes containing ion channels and pumps.
Muscles in the body differ in their constituent myofiber populations
and vascular and nerve supply, which affects the speed
and force developed during muscle contraction as well as the
neuromuscular disorders with which they are afflicted.
II . SPECIALIZATION OF THE SARCOLEMMA
AND SARCOPLASM FOR MUSCULAR
CONTRACTION
A . Neuromuscular Transmission: Excitation-
Conduction
The plasmalemma (sarcolemma) of the skeletal myofiber
is an electrically excitable membrane that can activate
the contractile machinery in response to signals received
from the motor nerve. The properties of excitation and
conduction largely result from the presence of membranespanning
ion conducting pathways and channel gaits that
regulate the selective and nonselective conductance of
sodium, potassium, calcium, and chloride across the sarcolemma.
They activate (open) in response to ligands,
Clinical Biochemistry of Domestic Animals, 6th Edition 459
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