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Muscular system
Anatomy & Physiology
Functions
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Movement, pumping/transport
Breathing
Posture
Produce heat, regulate body temperature
Protection,(of organs, stabilize joints, etc.)
Muscle Types
• Skeletal- voluntary (bones, face), over 400, long cells, many
nuclei, striated
• Cardiac- involuntary (heart and blood vessels), strongest, 1 nuclei
per cell, some striations with gap junctions
• Smooth- involuntary (intestines, internal organs), slow and
smooth, 1 nuclei per cell, no striations
Muscle Contraction
• All or None!
• Opposites contract! Muscles work in pairs
• Bicep bends at the elbow (relaxed) → tricep straightens the arm
(contracted)
• muscle contraction animation video
Sarcomere = contractile unit
Muscle contraction
• Actin (thin) filaments, with myosin, are responsible for cell
movements
• Myosin (thick) “molecular motor”—a protein that converts
chemical energy (ATP) to mechanical energy, (force and
movement)
• Need Ca++ ions AND ATP to contract
• Acetylcholine
Types of Muscles
• Slow Twitch- red fibers, oxygen storage, can build over time, used
for aerobic exercise, long distance running
• Fast Twitch- white fibers, used for short burst of energy, born with
a certain amount, sprinters
• Intermediate- most common, mixture of red and white
Naming Muscles
• Location
• Shape
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Size
Direction of fibers
Number of origins
Location of attachments
Action
Vastus lateralis/medialis
Deltoid
Gluteus maximus
Oblique, rectus abdominus or femoris
Triceps, biceps
Sternocleidomastoid
Adductors/abductors
• 600+ muscles in the body
• Approx. 640
• Muscles comprise approx. 45% of our body weight
• Smallest muscle = stapedius in ear
• Largest muscle = gluteus maximus
• Most active muscles are in the eye
• Over 100,000 movements per day