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INTRODUCTION

Objectives

  • To review the basic anatomy and function of the muscular and nervous systems

  • To review and understand the basic terminology used to describe muscular locations, arrangements, characteristics and roles, as well as tissue properties and neuromuscular functions

  • To learn and understand the different types of muscle contraction and the factors involved in each

  • To learn and understand basic neuromuscular concepts in relation to how muscles function in joint movement and work together in effecting motion

  • To develop a basic understanding of proprioception and kinesthesis

  • To develop a basic understanding of the neural control mechanisms for movement

Skeletal muscles are responsible for movement of the body and all its joints. Muscle contraction produces the force that causes joint movement in the human body but may also control and prevent movement. In addition to the function of movement, muscles also provide both dynamic stability of joints and protection, contribute to posture and support, and produce a major portion of total body heat. There are over 600 skeletal muscles, which constitute approximately 40% to 50% of body weight. Of these, there are 215 pairs of skeletal muscles. These pairs of muscles usually work in cooperation with each other to perform opposite actions at the joints they cross. In most cases, muscles work in groups rather than independently to achieve a given joint motion. This is known as aggregate muscle action.

MUSCLE NOMENCLATURE

In attempting to learn the skeletal muscles, it is helpful to have an understanding of how they are named. Muscles are usually named because of one or more distinctive characteristics, such as their visual appearance, anatomical location, or function. Examples of skeletal muscle naming are as follows:

  • Shape—deltoid, rhomboid

  • Size—gluteus maximus, teres minor

  • Number of divisions—triceps brachii

  • Direction of fibers—external abdominal oblique

  • Location—rectus femoris, palmaris longus

  • Points of attachment—coracobrachialis, sternocleidomastoid

  • Action—erector spinae, supinator, extensor digiti minimi

  • Action and shape—pronator quadratus

  • Action and size—adductor magnus

  • Shape and location—serratus anterior

  • Location and attachment—brachioradialis

  • Location and number of divisions—biceps femoris

In discussions regarding the muscles, they are often grouped together for brevity of conversation and clearer understanding. The naming of muscle groups follows a similar pattern. Here are just a few muscle groups assembled according to different naming rationales:

  • Shape—hamstrings

  • Number of divisions—quadriceps, triceps surae

  • Location—peroneals, abdominal, shoulder girdle

  • Action—hip flexors, rotator cuff

Figs. 2.1 and 2.2 depict the muscular system from both a superficial and a deep point of view.

FIG. 2.1

Superficial and deep muscles of the human body, anterior view.

FIG. 2.2

Superficial and deep muscles of the human body, posterior view.

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