Chapter 10 Study Guide

Name and identify the major muscles of the human body. State the origin, insertion, and action of each muscle.

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Names the three types of lever systems and indicate the arrangement of effort, fulcrum, and load in each. Also note the advantages of each type of lever system.

First-class lever: (scissors) Load Effort Fulcrum Mechanical advantage (strength) or mechanical disadvantage (speed and distance) Second-class lever: (wheelbarrow) Load Fulcrum Effort Strength Third-class lever: (tweezers) Load Effort Fulcrum Speed

Explain how a muscle's position relative to a joint affects its action.

A muscle that crosses on the anterior side of a joint produces flexion. A muscle that crosses on the posterior side of a joint produces extension. A muscle that crosses on the lateral side of a joint produces abduction. A muscle that crosses on the medial side of a joint produces adduction.

List the criteria used in naming muscles. Provide an example to illustrate the use of each criterion.

Muscle location: ex. temporalis overlies the temporal bone Muscle shape: ex. deltoid is roughly triangular Muscle size: ex. gluteus maximus vs. gluteus minimus Direction of muscle fibers: ex. transversus abdominis runs transverse in the abdomen Number of origins: ex. biceps brachii has two origins Location of the attachments: ex. sternocleidomastoid has a dual origin on the sternum and clavicle and inserts on the mastoid process Muscle action: ex. adductor longus

Describe the functions of prime movers, antagonists, synergists, and fixators.

Prime mover: a muscle that has the major responsibility for producing a specific movement. Antagonist: muscles that oppose, or reverse, a particular movement. Synergist: helps prime movers by adding a little extra force to the same movement or by reducing undesirable or unnecessary movements. Fixator: when a synergist immobilizes a bone or a muscle's origin so that the prime mover has a stable base on which to act.

Define lever.

a rigid bar that moves on a fixed point called a fulcrum when a force is applied to it.