This is a draft cheat sheet. It is a work in progress and is not finished yet.
Types of Muscle Tissue
Skeletal |
Cardiac |
Smooth |
multinucleate striated |
one nucleus striated |
one nucleus nonstriated |
voluntary |
involuntary |
involuntary |
attached to bones to cause movement |
heart (myocardium) |
GI, Uterus, Blood vessels |
Skeletal Muscle Cells
long cells (fibers) that contain repeating striations called bands |
bands composed of filaments of actin and myosin |
voluntarily controlled by motor neurons: |
1. descending motor tracts |
2. ventral root |
3. spinal nerve |
4. neuromuscular junction synapses with muscle fiber |
Innervation of Muscle Celll
motor neurons |
stimulate muscle cells |
excitable cells |
can change membrane potential |
acetylcholine |
released from neuron and tells muscles to contract |
Neuromuscular junction(synapse) |
axon terminal of motor neuron interacts with muscle |
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Smooth Muscle Cells
contain filaments of actin and myosin |
gap junctions allow movement between neighboring cells |
displays rhythmicity (peristalsis and segmentation) |
tetanic contraction |
multi-unit: more varicosities |
single unit: more gap junctions |
Gross Anatomy of Skeletal Muscle
A muscle is a bundle of fascicles |
Fascicles are bundles are muscle fibers(cells) |
muscle fiber(cell) serves as the unit of contraction |
Epimysium covers entire muscle |
Perimysium wrap around fascicle |
Endomysium encloses a single muscle fiber (cell) |
one nerve and one artery generally serve each muscle |
Sliding Filament Theory
Action potential in neuron |
motor neuron is activated an AP passes down axon |
AP arrives at axon terminal |
Calcium channels in neuron |
voltage change induces opening of Ca channles |
calcium induces docking of neurotransmitter-filled vesicles at plasma membrane |
Acetylcholine released |
ach diffuses across cleft |
Ach binds to its receptors |
Muscle cell response |
GP induces depolarization and MANY Ca channles open |
T-tubules carry impulse deep into muscle fiber |
power stroke and contraction |
Calcium binds to troponin-myosin binds to actin and uses ATP to generate a powerstroke |
Muscle fibers shift at each sarcomere |
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Cardiac Muscle Cells
connected by desmosomes and gap junctions |
contain filaments of actin and myosin that shorten to contract |
functional syncytium: all-or-none |
does not undergo tetanic contraction |
Microscopic Anatomy of Skeletal Muscle
Sarcoplasm: cytoplasm of muscle cell |
contains glycosomes and myoglobin |
Sarcolemma: specialized plasma membrane |
deep to endomysium |
T-tubules |
extensions of plasma membrane(sarcolemma), permut action potentials to penetrate, |
Sarcoplasmic reticulum(modified ER) |
calcium storage and release site |
Myofibrils |
Fibers that aid in muscle contraction they are made of lots of sarcomeres(contractile units) |
sarcomere |
contain thick(myosin) and thin(actin) filaments. the reason skeletal muscles are striated. slide along one another |
Troponin and Tropomyosin |
proteins that prevent actin from binding myosin by blocking myosin binding sites |
Myofibril structure
Dark A band |
actin and myosin filaments |
Light I band |
actin filaments |
H-zone |
area of A band with only myosin. shortens when muscle contraction occurs |
M-line |
attachment point for myosin |
Z-line |
attachment point for actin |
Sliding Filament Theory |
Filaments in sarcomere do not shorten, they slide past one another |
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