Muscles and Muscle Tissue – Chapter 09 Study Notes

Muscles and Muscle Tissue

Introduction

This chapter provides an overview of the muscular system, focusing on the structure, function, and types of muscle tissue. It covers the characteristics of muscle cells, the differences between skeletal, cardiac, and smooth muscle, and the physiological processes underlying muscle contraction.

Objectives

• Identify the functions and organs of the muscular system.

• Compare and contrast the three types of muscle tissue.

• Describe the macroscopic and microscopic structure of skeletal muscle, including muscle fibers, myofibrils, and sarcomeres.

• Explain the events of skeletal and smooth muscle cell contraction.

• Discuss the pathways by which skeletal muscle cells generate ATP.

• Define EPOC (Excess Postexercise Oxygen Consumption) and muscle fatigue, listing possible causes.

• Define motor unit and muscle twitch, and describe the phases of a muscle twitch.

• Explain how smooth, graded contractions of skeletal muscle are produced.

• Differentiation between isometric and isotonic contractions.

• Describe the three types of skeletal muscle fibers.

• Compare and contrast skeletal muscle and smooth muscle contraction.

Muscle Tissue

Terminology and Cell Types

• Prefixes: myo-, mys-, and sarco- are used for muscle-related terms. Example: sarcoplasm refers to the cytoplasm of a muscle cell.

• Muscle fibers: Elongated muscle cells found in skeletal and smooth muscle, but not in cardiac muscle.

• Myoblasts: Embryonic cells that fuse to form multinucleate skeletal muscle fibers.

Characteristics of Muscle Tissue

• Excitability (Responsiveness): Ability to receive and respond to stimuli.

• Contractility: Ability to shorten forcibly when stimulated.

• Extensibility: Ability to be stretched.

• Elasticity: Ability to recoil to resting length after being stretched.

Functions of Muscle Tissue

• Produce movement: Responsible for locomotion and manipulation.

• Maintain posture and body position

• Stabilize joints

• Generate heat: Muscles contract to produce heat, helping maintain body temperature.

Comparison of Muscle Types

Structural and Functional Differences

The three types of muscle tissue—skeletal, cardiac, and smooth—differ in location, structure, and function.

Characteristic	Skeletal	Cardiac	Smooth
Location	Attached to bones (or skin for some facial muscles)	Walls of the heart	Walls of hollow organs (except heart); intrinsic eye muscles, airways, large arteries
Cell Shape & Appearance	Single, very long, cylindrical, multinucleate cells with obvious striations	Branching chains of cells; uni- or binucleate; striations	Single, spindle-shaped, uninucleate; no striations

Additional info:

• Skeletal muscle: Voluntary control, rapid contractions, tires easily.

• Cardiac muscle: Involuntary control, rhythmic contractions, does not tire easily.

• Smooth muscle: Involuntary control, slow contractions, resistant to fatigue.

Summary Table: Key Features of Muscle Tissue

Feature	Skeletal Muscle	Cardiac Muscle	Smooth Muscle
Control	Voluntary	Involuntary	Involuntary
Striations	Present	Present	Absent
Number of Nuclei	Multinucleate	Uni- or binucleate	Uninucleate
Location	Bones/skin	Heart	Walls of hollow organs

Example

• Skeletal muscle: Biceps brachii, responsible for arm movement.

• Cardiac muscle: Myocardium, responsible for heart contractions.

• Smooth muscle: Muscular layer of the intestine, responsible for peristalsis.