IndietroPhysiology of Muscle: Structure, Function, and Comparison of Muscle Types
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Topic 2.3 - Physiology of Muscle
Overview
This section covers the microscopic structure and physiology of muscle tissue, including skeletal, cardiac, and smooth muscle. Key topics include muscle cell anatomy, mechanisms of contraction, neuromuscular junctions, contractile properties, muscle metabolism, and comparative features of muscle types.
General Features of Muscle Cells
Muscle Cell Terminology and Structure
Muscle fibers are elongated cells specialized for contraction.
Common prefixes: myo- and sarco- refer to muscle and flesh, respectively.
Muscle contraction depends on the interaction of actin and myosin myofilaments.
Comparison of Muscle Types
The three main muscle types differ in location, structure, and function. The table below summarizes their key features:
Feature | Cardiac Muscle | Skeletal Muscle | Smooth Muscle |
|---|---|---|---|
Location | Only in heart | Attach to & cover bony skeleton | Walls of hollow, visceral organs |
Striations | Striated | Striated | Nonstriated |
Control | Involuntary | Voluntary | Involuntary |
Special Features | Pacemaker sets rate; neural input can increase rate | Longest muscle fibers; can contract rapidly; tires easily & must rest; strong, adaptable | Slow, sustained contractions |
Muscle Functions and Functional Characteristics
Major Functions of Muscle
Generate movement: Responsible for locomotion, manipulation, blood pressure control, respiration, propulsion of food and urine.
Maintain posture: Muscles constantly work against gravity to keep the body upright.
Joint stabilization: Muscles stabilize joints, especially during movement (e.g., shoulders, knees).
Generation of heat: Muscle activity produces heat, helping maintain body temperature (skeletal muscle accounts for at least 40% of body mass).
Functional Characteristics of Muscle
Excitability (Irritability): Ability to receive and respond to a stimulus, usually a chemical (neurotransmitter, hormone, pH change). The response is an action potential along the sarcolemma, leading to contraction.
Contractility: Ability to shorten forcibly when adequately stimulated.
Extensibility: Ability to be stretched or extended.
Elasticity: Ability to resume resting length after being stretched.
Example
During exercise, skeletal muscles contract to move limbs, stabilize joints, and generate heat, demonstrating all four functional characteristics.
*Additional info: The above notes are expanded from the provided slides and images, with definitions and examples added for clarity and completeness.*
