What You'll Learn
After you finish this lesson, you will be able to:
- Describe the functions of the muscular system.
- Explain the common traits of all muscles.
- Identify the types of muscles.
- Define types of body movements.
The muscular system contains over 600 muscles. About 40% of a person's body weight comes from muscles. The muscular system performs these functions:
- Helps with body movement
- Supports body posture
- Produces heat and energy
- Protects internal organs
- Helps move blood, food, and waste products through the body
- Opens and closes body openings
Muscles usually act in groups to create movement, although each muscle is a distinct part. All muscles have four common traits.
Excitability or Irritability: The ability to respond to a stimulus, such as anerve orhormone. Muscles can be stimulated electrically, mechanically, or chemically.
- Contractibility: The ability to shorten and produce movement when stimulated.
- Extensibility: The ability to be stretched and lengthened.
- Elasticity: The ability to return to its original shape after contracting or stretching.
Muscle tone refers to the ability of muscles to be slightly contracted at all times, even when not in use. It allows a person to be in a state of readiness to act.
The ability of muscles to be slightly contracted at all times to be ready to act is known as muscle _______.
Ability to be stretched and lengthened
Ability to shorten and produce movement when stimulated
Ability to respond to a stimulus, such as a nerve or hormone
Ability to return to its original shape after contracting or stretching
Types of Muscles
The three types of muscle tissue are cardiac, visceral, and skeletal.
Cardiac muscle forms the walls of the heart. When it contracts, this type of muscle causes the heart to beat to circulate blood.
- Visceral, or smooth, muscle is found in hollow organs, in the walls of blood vessels, and in the eyes. It contracts to produce movement in these organs.
- Skeletal muscle is attached to the bones. It helps produce body movement.
Cardiac and visceral muscles are involuntary, which means that they are not controlled by a person's conscious thought, or will. Most skeletal muscles are voluntary, which means that a person can control their actions.
A person can control the actions of involuntary muscles.
Which types of muscle are generally voluntary?
- All of the above
Attached to the bones to help produce body movement
Forms the walls of the heart and causes the heart to beat
Found in hollow organs, in the walls of blood vessels, and in the eyes
Attachment of Skeletal Muscles
While ligaments attach bone to bone, muscles are attached to bones by bands of fibrous tissue called tendons.
The end of the muscle that is connected to the bone that does not move is called the origin.
The end connected to the bone that moves when the muscle contracts is called the insertion.
Fascia is a sheet of tough fibrous tissue that wraps around an individual muscle.
Attaches muscle to bone
End of the muscle connected to the bone that moves
Sheet of tough fibrous tissue that wraps around an individual muscle
End of the muscle connected to the bone that does NOT move
Types of Body Movements
Types of body movements made by skeletal muscles include:
Flexion: Bending a body part, which decreases the angle of thejoint.
- Extension: Straightening a body part, which increases the angle of the joint.
- Abduction: Moving a body part away from the midline.
- Adduction: Moving a body part toward the midline.
- Rotation: Turning a body part around on its own axis to produce a circular or semi-circular motion.
What type of body movement occurs in the leg when a person kicks a soccer ball forward?
What type of body movement occurs in the neck when a person turns the head from side-to-side to signal "No?"
In this lesson, you learned that:
- The main function of the muscular system is to supply body movement.
- All muscles share four common traits: excitability or irritability, contractibility, extensibility, and elasticity.
- The three types of muscle tissue are cardiac, visceral, and skeletal.
- Types of body movements made by skeletal muscles include: flexion, extension, adduction, abduction, and rotation.