muscle histology Flashcards
why do smooth muscles appear unstriated
because their myofibrils are not in a regular arrangment
describe the cell structure of a muscle cell
its a long unbranched cylindrical cell with peripheral nuclei - potentially multinucleated. striated appearance
why are the nuclei of skeletal muscle fibers peripheral
due to the myofibrils in the cell
are there organelles in a skeletal muscle cell
yes there are, they are just squished between the myofibrils
what is around the sarcolemma
a basal lamina and then the endomysium
what organelle is the sarcoplasmic reticulum
it is the smooth endoplasmic reticulum of the muscle cells
what makes up a T triad
a t triad is 2 of the terminal swellings of the sarcoplasmic reticulum - the terminal cisternae, and a t tubule
whats important about the terminal cisternae
this is where the excitation of the AP is coupled to the muscle contraction. as this is where the serca pumps are and stuff, so muscle contraction is initiated here.
in the myofibril geographies, where is the triad located
the A band
what is the space between the myosin heads and either side of the Z line
the I band- the blank space really
whats the H band
the parts where we only find the myosin filaments
what is the A band
the space where there is the myosin plus the overlap of the actin. so parts where its myosin plus actin, but also plus the rest of the myosin
during contraction, of the bands and all that jazz, what shortens what stays the same and shit
during contraction of the myofibril the Z disks get closer together. the A band stays the same thickness, the I band and the H band shortens.
what does the dystrophin protein do
it connects actin filaments to the basal lamina
what is muscular dystrophy
weakened contractions due to the defective dystrophin proteins.
where is the muscle spindle
this is in the inner of the muscle, the intrafusal.
what is the muscle spindle
specialised type of skeletal muscle within a connective tissue capsule - which itself is inside the muscle fascicle
the capsule of the muscle spindle is an extension from what
extension of connective tissue from the perimysium
what is the function of the muscle spindle and how do they do this
these are key in proprioception,
there will be stretch signal in the muscle spindle, this force is converted to the capsule then the nerve endings, this is sent to the spinal cord and back. the motor information back is to the extrafusal muscle to engage the muscles in some activity to prevent too greater tension on the connective tissues
where are the muscle sateillite cells and what do they do
these are found on the cell periphery and they are between the sarcolemma and the basal lamina. normally inactive but in acute muscle injury they act as a muscle stem cell, helping repair the damaged muscles
tell me about the type one muscle fibres
these are the slow twitch oxidative muscle fibers. these get their energy to contract from aerobic oxidation of fats. hence have many mitochondria and many capillaries to maintain blood supply. hence they are red in colour. these are used in long term activity - fatigue resistant - postural muscles for example
describe the type 2 muscle fibres
these are your white, fast twitch muscle fibres. these get their energy from anaerobic glycolysis. they have few mitochondria and capillaries. have granules of glycogen stores. they break down this glycogen quickly when activity us needed. but once this glycogen is used they need rest period to restore the glycogen and ph - as lactic acid was made
