muscular system. facts about muscles… a skeleton cannot move by itself > 40% of the mass of the...
TRANSCRIPT
Muscular System
Facts about muscles…
• A skeleton cannot move by itself
• > 40% of the mass of the average human body is muscle
• Found everywhere in your body
• Power every movement from moving your lips to blinking your eyes
Types of Muscle Tissue:
• Skeletal• Smooth• Cardiac
3 Types of Muscle Tissue:
Type Voluntary/ Involuntary
Found Striations
(stripes)
Structure Nucleus
Skeletal
Smooth
Cardiac
Skeletal Muscles
• Voluntary
• Found attached to bones
• Yes, striations
• Cells are long and thin
• Many Nuclei
Smooth Muscles
• Usually involuntary• Found in hollow organs (i.e.
stomach, blood vessels, sm & lrg intestine)
• No striations• Spindle-shaped (draw a spindle)• One nucleus
Cardiac Muscle• Involuntary
• Cardio= –Greek word for Heart
• Found in the Heart
• Striations
• Intercalated Discs
• One to two nuclei
Type of muscle?
Type of muscle?
Type of muscle?
Type of muscle?
Type of muscle?
Type of muscle?
Skeletal Muscle Breakdown
• Muscle• Bundle• Fibers (cells)• Myofibril• Filaments
–Actin–Myosin
Closer look at the filaments:
• Actin:
• Myosin:
Closer look at the filaments:
• Actin: thin filaments on outside
• Myosin:
Closer look at the filaments:
• Actin: thin filaments on outside
• Myosin: thick filaments in the middle
Closer look at the filaments:
• Z lines:
Closer look at the filaments:
• Z lines: attach the actin together
ActinMyosinZ lines
Muscle contraction:
• Myosin heads grab and pull on actin
Muscle contraction
• Myosin heads grab and pull on actin
Muscle relaxed:
Muscle contracted:
Draw a picture of this in your notes
Muscles work in pairs
Superficial muscles of
the face
Anteriorsuperficial muscles
Posterior superficialmuscles
Superficial muscles of the thigh
Muscle Contraction
• Myofibrils are made of filaments• Striations are formed by a pattern of thick and thin
filaments made of protein• Thick filaments are made of the protein myosin• Thin filaments are made of the protein actin• Filaments are arranges in units called sarcomeres• Sarcomeres are separated by from eachother by regions
called Z discs
Actin and Myosin: Cause muscles to contract
• A muscle contracts when thin filaments slide over thick filaments
• Myosin forms a cross-bridge with actin• The cross bridge changes shape pulling
the actin filament toward the center of the sarcomere
• The distance between the Z discs decreases
• The cross-bridge then detaches
Control of Muscle Contraction• An enzyme produces an impulse causes the
release of Calcium ions (Ca+) allowing actin and myosin to interact
• The muscle remains contracted until the impulse ceases
• Calcium ions pumped back into storage and contraction ends
• Contraction of a single muscle fiber is an all-or-none process!
• Most skeletal muscles work in opposing pairs-when one contracts the other relaxes