PHIS 206 Lecture Notes - Lecture 9: Micrograph, Multinucleate, Motor Protein
2 May 2018
School
Department
Course
Professor
Lecture 9: Muscle Physiology
Muscle Types
• Skeletal Muscle
o Classification: Striated (striped) muscle, voluntary muscle
o Description: Bundles of long, thick, cylindrical, striated, contractile,
multinucleate cells that extend the length of the muscle
o Typical location: Attached to bones of skeleton
o Function: Movement of body in relation to external environment
• Cardiac Muscle
o Classification: Striated muscle, voluntary muscle
o Description: Interlinked network of short, slender, cylindrical, striated, branched,
contractile cells connected cell to cell by intercalated discs
o Location: Wall of heart
o Function: Pumping of blood out of heart
• Smooth Muscle
o Classification: Unstriated muscle, involuntary muscle
o Description: Loose network of short, slender, spindle-shaped, striated, contractile
cells that are arranged in sheets
o Typical location: walls of hollow organs and tubes, such as stomach and blood
vessels
o Function: movement of contents within hollow organs
• Differences in:
o Appearance
o Control
o Organization
Striations
• Filaments
o Overlap of thin and thick filaments causes banding (striations)
• We see thick filaments as dark in the micrograph?
• A band is where the thick filament is, I band is where the thick filament isn’t
• Sarcomere is one a band and one I band
Thick Filament
• Myosin (splits ATP)
o “Motor” protein
o Tail & Head
o Tails line up
o Heads face out
o Binds Actin
o Splits ATP
• Does its job by moving, as it splits ATP, head swings back and forth
• The heads swing back and forth
• Heads attached to actin, when heads move it moves actin
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Interdigitation: sliding filament hypothesis, thin filaments slide over thick filaments, shortening the sarcomere. Interdigitate means they slide past each other (like your fingers slipping in between each other) Regulation of cross-bridge cycling: calcium, ca2+ ions play key role in allowing actin and myosin to interact. If there"s not enough calcium in the cell, then the tropomyosin is in the way: when there is enough calcium, the tropomyosin shifts out of the way. Slightly more cross-bridge cycling: atp involvement, splitting of atp cocks the myosin head, binding of atp allows for cycle to repeat, rigor mortis muscles are stiff after death. Whole story: players, ap travels down t-tubule, receptors activated on t-tubule and sarcoplasmic reticulum (sr) (inside another room inside the cell, where all the calcium is/like a bag of calcium, ca2+ released from sr. Time scale: delay, note delay between ap and twitch, note relative lengths of ap and twitch, a twitch must be an up and down.
