Chapter 10: The Muscular System
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1. Simple explanations of the main concepts
The muscular system produces movement, helps maintain posture, and contributes to body temperature regulation.
The three muscle types
Skeletal muscle: Usually attaches to bones and produces voluntary movement. It also helps maintain posture and generate heat.
Cardiac muscle: Found in the heart. It contracts involuntarily to pump blood.
Smooth muscle: Found in the walls of organs and blood vessels. It moves substances through organs and adjusts the diameter of blood vessels.
Major skeletal muscles to recognize
Deltoid: Moves the arm at the shoulder.
Pectoralis major: Helps move the arm forward and toward the body.
Biceps brachii: Flexes the elbow.
Triceps brachii: Extends the elbow.
Rectus abdominis: Flexes the trunk.
Gluteus maximus: Extends the hip.
Quadriceps femoris: Extends the knee.
Hamstrings: Primarily flex the knee and help extend the hip.
Gastrocnemius: Helps point the foot downward at the ankle.
Tibialis anterior: Lifts the foot upward at the ankle.
How muscles work together
Muscles generally pull rather than push. Many movements involve opposing muscle groups. For example, the biceps brachii flexes the elbow, while the triceps brachii extends it.
A muscle's origin is generally its more stationary attachment, and its insertion is generally the attachment that moves more during contraction.
2. Important vocabulary and definitions
Term | Simple definition |
|---|---|
Origin | Usually the less movable attachment of a muscle |
Insertion | Usually the more movable attachment |
Agonist | Muscle primarily responsible for a movement |
Antagonist | Muscle that opposes or reverses a movement |
Synergist | Muscle that assists the main muscle |
Fixator | Muscle that stabilizes a body part |
Flexor | Muscle that produces flexion |
Extensor | Muscle that produces extension |
Abductor | Muscle that moves a part away from the midline |
Adductor | Muscle that moves a part toward the midline |
Tendon | Connective tissue attaching muscle to bone |
Muscle tone | Continuous, low-level muscle activity that supports readiness and posture |
3. Key facts to memorize
Skeletal muscle is generally voluntary and striated.
Cardiac muscle is involuntary and striated.
Smooth muscle is involuntary and nonstriated.
Biceps brachii flexes the elbow; triceps brachii extends it.
Quadriceps extend the knee; hamstrings flex the knee.
Gastrocnemius helps with plantar flexion; tibialis anterior helps with dorsiflexion.
Muscles create movement by contracting and pulling on their attachments.
Muscles need energy in the form of ATP to contract.
Regular resistance exercise can increase muscle fiber size, a process called hypertrophy.