Muscular System Flashcards
Skeletal Muscle
Causes voluntary body movements
Attached to bones
Striated
Multinucleated
T-tubule system
Smooth Muscle
Lines wall of blood vessels
Lines digestive tract
Mono nucleated
Tapered shape
Not striated
No T-tubule system (contraction is slow and highly regulated)
Cardiac Muscle
Involved in rhythmic contractions of the heart
Involuntary
Striated, branched. cross linked to each other
mono or bi nucleated
Cells connected by gap junctions
Generates its own AP, which spreads rapidly throughout muscle tissues by electrical synapses across gap junctions
Muscle Fiber
Cell in a muscle
Multinucleated
Nuclei lie along periphery of cell
Sarcolemma
PM of muscle cell
Invaginated by T-tubules
Sarcoplasm
Cytoplasm of muscle cell
Contains sarcoplasmic reticulum (ER of muscle cell) which stores Ca
Myofibrils
Fill nearly entire volume of muscle cells
Contains microfilaments
Actin
Thin filaments
2 strands of globular actin protein arranged in a double helix
Troponin and tropomysoin (sit on actin proteins, covering binding sites)
Myosin
Thick filaments
Filamentous protein with protruding head on one end
Filaments laid together so that there are numerous protruding heads on both ends
Sarcomere
In a myofibril, actin and myosin run paralle to each other
Filament overlap, creating striated appearance in skeletal muscle
Each repeating unit is a sarcomere
Z line
Separates sarcomeres
Where actin is attached (no myosin at z line
Sliding Filament Model- Attachement
Myosin head attached to actin filament when nothing is bound to head
Sliding Filament Model-Release
ATP binds to myosin, causing it to release from actin
Sliding Filament Model-Cocked
ATP hydrolyze to ADP
Pushes myosin head into “cocked” position
ADP still attached to myosin head
Sliding Filament Model- Binding Sites Exposure
Ca binds to troponin, causing tropomyosin to expose positions on actin filament for myosin heads to attach to
Sliding Filament Model- Cross Bridges
Formed between myosin and actin filaments
Sliding Filament Model- ADP Release
ADP and PI are released
Sliding motion of actin results
Myosin released like a spring, generating a sliding movement of actin towards center of sarcomere
2 Z lines pulled together, contracting muscle fiber
ATP binds to myosin, releasing it from actin, cycle starts over
Rigor Mortis
IF no more ATP generated in body (after death), there is nothing to bind myosin and cause it to release from actin
Causes stiffness of corpses
Eventual degradation of the ATP causes rigor mortis
NMJ
Neurons synapse with muscle cells
AP generates ACH release
AP generated on sarcolemma and throughout T-tubules (receptors on sarcolemma bind ACH and open Na channels)
Sarcoplasmic reticulum releases Ca in response to AP
Ca binds to troponin
Cross bridges form
Power stroke occurs if ATP is available
Myogenesis of Skeletal muscles
myoblasts fuse together to form large multinucleated cell
Unique to skeletal muscles
Myoblast
Progenitor cells (can differentiate, but more specialized than stem cells