Muscle Microanatomy Flashcards
Myoblast are derived from mesenchymal cells (embryonic ct) what do they form
myoblast fuse to form a myotube and some myoblast become satellite cells.
What do satellite cells do?
they are able to proliferate after injury
Muscle fibers are surrounded by what?
endomysium
what are fascicles surrounded by ?
Perimysium
The muscle organ is surrounded by a tough fibrous ct called ?
epimysium
What are the featuresof type 1 muscle fiber?
lots of myoglobin and mitochondria , used for extended periods of slow contraction. example : muscles on the back for posture
features of type IIa muscle fiber?
intermediate fibers rich in myoglobin and glycogen .
use for extended periods of slow contractions with high peak tension , example limb muscles
type IIb fiber?
large fibers rich in glycogen few mitochonria and myoglobin
use for rapid contraction, high peak tension and fatigue quickly
How do you know there is high oxidative enzyme activity ?
dark staining indicates high oxidative enzyme activity
Myofilaments are organized in contractile units called?
Sarcomeres
How is the sarcomere defined?
from z disk to z disk
How does the A zone look?
dark portion of the sarcomere represented by the location of myosin , some overlap with actin/thin filaments.
M line?
standing for middle of sarcomere a region for anchor protein for myosin
I band
only thin filaments no region of overlap
what links actin to basal lamina ? what disease is associated with this?
dystrophin, in muscular dysttrophy this is targeted
what attaches z lines to other z lines and sarcolemma
desmin
what protein anchor thick filament to adjacent z lines
titin
What happens when Ca2+ is sequestered back to the SR?
it stops contraction because the binding site of Troponin C on actin will be blocked so the muscle will relax
what happens if atp is not available to bind the sarcomere
if no atp, then myosin stays attached because atp binding is what happens in order for myosin to be released which this leads to rigor mortis
in a contracted sarcomere what is not visible?
the I band or H band.
In skeletal muscle a triad formation is formed, what is this?
one t tubule and two terminal cisternae of SR at junction of a band and i band.
What happens in the autoimmune disease Myasthenia gravis?
antibodies bind acetylcholine receptors in the junctional folds of the motor endplate and therefore no innervation . symptoms weak movement of muscles (hypotonia)
how can you increase muscle mass?
by hypertrophy, on the contrary if you don’t work out like most of us med students we get atrophy of muscles
/=
What are some characteristics of cardiac muscle?
fibers have 1-2 centrally located nuclei, striations are present, sarcoplasm contains elongated mitochondria, and glycogen granules.
What are some characteristics of cardiac muscle?
fibers have 1-2 centrally located nuclei, striations are present, sarcoplasm contains elongated mitochondria, and glycogen granules.
adjacent cells connected by specialized juncions
for the conducting system for cardiac muscle how does it differ from skeletal?
SR is similar to skeletal muscle, gap junctions, and a diad instead of the triad formation.
Also intercalated discs available
why does cardiac tissue if it dies does not repair and become fibrous scar?
because in cardiac cells there is not satellite cell. if tissue die there will be scarring.
What are some characteristics of smooth muscle tissue?
found in visceral (involuntary) organs and blood vessels, with a centrally located nucleus oval shape and long. No striations!!
What are some examples of molecules that affect Smooth Muscle?
atrial natriuretic factor a vasodilator , oxytocin in labor
