Transcript Intro to Muscles

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
Skeletal
Smooth
Cardiac
Voluntary/
Involuntary
Found Striations Structure Nucleus
(stripes)
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
Z lines Myosin
Actin
Muscle contraction:
• Myosin heads grab and pull on actin
Muscle contraction
• Myosin heads grab and pull on actin
Draw a picture of this in your notes
Muscle relaxed:
Muscle contracted:
Muscles work in pairs
Superficial
muscles of
the face
Anterior
superficial
muscles
Posterior
superficial
muscles
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-ornone process!
• Most skeletal muscles work in opposing pairswhen one contracts the other relaxes