Module 6 Intro

Module 6—The Motor System and Homeostasis

The Purpose of Muscles

Muscles contract—it’s that simple! Whatever the type and function, all muscle tissues are specialized so that they are capable of shortening and producing a motion. In addition, because of the sizable energy requirement for muscle contraction, a significant amount of heat is released during this process. As a result of these two characteristics—the ability to contract and generate heat as a by-product of their metabolism—muscles serve a number of functions. These functions include

• support and movement
• the propulsion of blood through vessels
• the movement of food or body secretions through tracts
• thermoregulation, or the ability to regulate body temperature

Muscle cells possess other attributes besides contractility.

• All muscles are excitable—they are able to respond to stimuli. This important capability is also common to nervous tissues.
  
  
• Muscles are extensible in that they can be stretched and still maintain contractile ability. As you will see, some muscles are better at this than are others.
  
  
• Finally, muscle cells are associated with elastic connective tissues. These connective-tissue elements enable muscles to contract or stretch and then return to their original length. This attribute is called elasticity.