Chapter 9: The Muscular System

*in all forms, muscle makes up nearly 1/2 of the body’s mass; distinguished by their ability to transform ATP (chemical energy) into mechanical

A. There are 3 types: skeletal, cardiac and smooth

  1. ==Skeletal-==

  • packaged into skeletal muscles, organs the attach to and cover the skeleton

    • fibers are the longest muscle cell

  • striated; voluntary (usually activated by reflexes)

  • responsible for mobility; contracts rapidly

  1. ^^Cardiac Muscle-^^
  • occurs only in heart; bulk of heart walls
  • striated; involuntary (contracts without stimulation from nervous system)
  1. %%Smooth Muscle-%%
  • found in walls of hollow visceral organs (stomach, urinary bladder, respiratory system)
  • role is to force fluids + substances through internal body channels
  • elongated cells, but involuntary

B. Characteristics of Muscle Tissue

  1. Excitability- Responsiveness; Ability to receive and respond to a stimulus by changing its membrane potential

   

  1. stimulus is usually a chemical
    1. Contractility- ability to shorten forcibly when adequately stimulated
    2. Extensibility- ability to extend or stretch

   

  1. shorten when contracting, stretched when relaxed
    1. Elasticity- ability of a muscle cell to recoil and resume its resting length after stretching

C. Muscle Functions

  1. Produce Movement-

   

  1. Skeletal Muscles are responsible for all locomotion and manipulation
  2. Blood courses through your body because of Cardiac Muscle
  3. Smooth Muscles in certain tracts propel substances (foodstuffs, urine, semen) through the organs and along the tract
    1. Maintain Posture and Body Position
    2. Stabilize Joints
    3. Generate Heat

D. A Skeletal Muscle is Made Up of Muscle Fibers, Nerves, Blood Vessels, and CT

  • Each skeletal muscle is a discrete organ made up of several kinds of tissues
    • Nerve and Blood Supply:
    • 1 nerve, 1 artery and 1 or more veins serve each muscle (all enter or exit through central part of muscle and branch through its CT Sheaths)
    • ever skeletal muscle fiber is supplied with nerve ending to control activity
    • Rich blood supply (contracting muscles requires a lot of oxygen and nutrients via arteries)
    • Muscle cells release a lot of metabolic waste that needs to be removed by veins
    • Capillaries take a long path through muscles and have cross-links (accommodate changes in muscle length)
      • straighten when muscle stretches and contorts when muscle contracts