Muscle
What is the troponin complex?
-troponin I inhibits binding of myosin -troponin T binds to tropomyosin -troponin C binds to calcium
What are the 2 muscle types based on appearance of cells?
1. striated 2. smooth
What is the function of alpha-actinin?
anchors actin at the Z line and crosslinks titan
What protein helps to store calcium?
calsequestrin
Describe the H band of a sarcomere.
central region of A band, contains only thick filaments (myosin)
Describe type IIb fibers
fast glycolytic, appear pink in fresh specimens, fast-twitch, fatigue-prone fastest myosin ATPase velocity, fatigue rapidly (lactic acid) think extraocular muscles/muscles controlling digits, lots in short distance sprinters, weightlifters
Describe type IIa fibers
fast oxidative, intermediate color in fresh speciments, fast twitch, fatigue resistant motor units high myosin ATPase velocity generate high peak muscle tension (think sprinters, swimmers, hockey players)
What is the function of desmin?
forms a lattice surrounding the sarcomere at the Z lines. It uses the protein ankyrin to attach Z lines to eachother
Why does skeletal muscle stain eosinophilic?
high concentration of actin filaments
Where would you find smooth muscle?
in viscera, blood vessels, arrector pili muscles of skin and intrinsic muscles of the eye
What is the purpose of the triad?
it allows coupling of nerve stimulation with calcium release and muscle contraction
Why is connective tissue surrounding skeletal muscle cells important?
it is essential for force transduction
What is the function of dystrophin?
links laminin (part of ECM) to actin filaments
Describe the I-band of a sarcomere.
located on either side of the Z line and extends into the A band. Only composed of actin filaments
What is the structural subunit of muscle cells
myofibrils
What does the encapsulated sensory receptor detect?
proprioception degree of stretching/tension in muscle
What happens when there is a conformational change of voltage-sensor proteins?
ryanodine receptors get activated which allows release of calcium
What is the functional unit of muscle fibers?
sarcomere (fascicle)
What is the storage site of calcium in muscle?
sarcoplasmic reticulum (rER)
What attaches to the Z line of a sarcomere? What mediates this?
site of attachment for actin filaments; mediated by alpha-actinin
What are the 3 types of muscles?
skeletal, smooth, cardiac
What are examples of striated muscle?
skeletal, visceral, and cardiac
Describe type I skeletal muscle fibers
slow oxidative, appear red in fresh specimens, slow-twitch, fatigue-resistant motor units. Slowest myosin ATPase reaction velocity strong succinic dehydrogenase and NADH-TR staining
Which muscles type is primarily responsible for changes in size/shape of internal organs?
smooth muscle
What is the function of titan in the sarcomere?
spands 1/2 of sarcomere, extending from Z-Z, helps space thick filaments correctly
What regulates the length of f-actin?
tropomodulin (caps the (-) end
What neurotransmitter gets released with depolarization of nerve terminal?
Acetylcholine
Which neurotransmitter is responsible for depolarizing the muscle membrane?
Acetylcholine
What is epimysium?
Dense connective tissue that bundles fascicles into a muscle and contains major vascular/nerve supply
What is a clinical manifestation of a dystrophin defect?
Duchenne and Becker muscular dystrophy
Which components allows the (+) end of the f-actin to bind the Z line?
alpha-actinin
What are terminal cisternae?
Sarcoplasmic reticulum expansion that serves as a calcium reservoir with ryanodine receptors.
Which muscle type contains multinucleated syncytium with nuclei on periphery?
Skeletal muscle
What component of the muscle cell contains voltage-sensor proteins that are sensitive to membrane depolarization?
T tubules
What happens to the I and H band as a muscle contracts and sarcomere shortens?
They both decrease
What is the function of myofibrils?
They help extend the length of muscle fibers
What are the 3 types of skeletal muscle fibers?
Type I, Type IIa, Type IIb
What is endomysium?
delicate layer of reticular fibers around each muscle cell. They contain small blood vessels and fine neuronal branches
What is used as a clinical marker for muscle cells?
desmin
What is the intermediate filament of muscle?
desmin (IF)
What do the terminal cisternae of sarcoplasmic reticulum and T tubule form?
the triad
What is perimysium?
thick layer of dense, irregular connective tissue that groups individual muscle cells into a bundle or fascicle.
Describe the A-band of a sarcomere.
thin and thick filaments overlap here "dark" portion of the sarcomere
