Introduction

The skeletal and muscular systems of the body work together to produce motions and locomotion of the body. All of these actions are mechanical in nature. They utilize the various mechanics as studied in physics.

a. Vectors. The various forces produced by contracting muscles have specific direction and magnitude. As such, these vectors or forces when plotted are represented by arrows whose length corresponds to the magnitude of the force and whose direction corresponds to the direction of the force.

b. Lever Systems. The majority of the motions are of the rotary type and occur around an axis or fulcrum. These motions follow the physics of lever systems. The third class of lever (Figure 5-2) is the most common.

FIRST CLASS SECOND CLASS THIRD CLASS

FIRST CLASS SECOND CLASS THIRD CLASS

Human Body Levers

Figure 5-2. Types of lever systems.

Figure 5-2. Types of lever systems.

c. Simple Pulley Systems. Another common mechanism of the human body is the simple pulley system. Here, the direction of force can be at an angle to the muscle. This is achieved by having the muscle's tendon go around a bony eminence in the same way as a rope goes around a single pulley.

d. Pendulums. During locomotion, the body uses several pendulums in the swinging of the upper and lower limbs.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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