Muscle Flashcards
sarcoplasmic reticulum AKA
Smooth ER
skeletal muscle is derived from
mesenchyme
myofibril
aligned protein structures made of thick and thin myofilaments
thick filaments are made of
myosin, heavy and light
thin myofilaments are made of
actin (filamentous or globular), troponin, tropomyosin
A-band and I-band stand for
anisotropic and isotropic, referring to how they refract polarized light. A-bands are dark because they refract different planes of polarized light differently.
the sarcomere is bounded by
two z-lines
the z-line bisects the ___ and is attachment point of ___ filaments
i-band, thin (actin)
M-line
cross-links centers of thick filaments
h-zone
lightest area within the A-band, where thick and thin filaments don’t overlap
during muscle contraction, the ____ filaments are pulled to the ___ band, causing the width of the ____, ___, and ___ to decrease
thing, I, H and sarcomere
sarcolemma
plasmalemma, outer membrane of skeletal muscle fiber, with invaginations called T (transverse) tubules)
T tubules
tranverse tubules. contain extracellular fluid and bring AP into muscle fiber.
SR
sarcoplasmic reticulum, smooth ER, sleeve around myofibril.
terminal cisternae
flank T tubules at A-I junctions in skeletal muscle
triad
t-tubule, terminal cisternae,
t-tubules are located at the ___
z-line
how many triads are found in cardiac and skeletal muscle?
2 in skeletal
1 in cardiac
how many nuclei do skeletal and smooth muscle have?
skeletal - multinucleated
smooth - uninucleated
what are two other cytoplasmic components found in myofibrils
glycogen granules and mitochondria
three fiber types
red, white, intermediate
three characteristics of red fibers
slow contracting
darker in color (more mitochondria)
fatigue resistant
myosatellite cells
?
hyperplasia vs. hypertrophy
fusion of cells (dividing)
hypertrophy is increased size, not cell #
motor unit
motor neuron + all of it’s muscle fibers (fewer fibers = more precise control)
motor end plate AKA
neuromuscular junction
motor end plate definition
wher neurons synapse with muscle fibers.
junctional folds
at NMJ, sarcolemma is more foled, increasing area of synaptic cleft
each muscle fiber is innervated by how many motor neurons?
1
what are two components of muscle cells that make them specialized for integrated motion?
contractility and conductivity
muscle cells stain ____. why?
acidophilically, due to abundance of actin/myosin proteins
what is a muscle spindle? how are they arranged?
receptors that sense the length and degree of stretch in a muscle.
arranged in parallel with muscle fibers
what is the composition of a muscle spindle?
intrafusal muscle fiers, fluid space, and capsule
what are intrafusal fibers? what are the two types? what do these names refer to?
small muscle fibers in muscle spindles?
nuclear bag (larger) nuclear chain (smaller) the names refer to the arrangement of nuclei, clustered or distributed along fiber
what is the smallest muscle type?
smooth. 20-500um in length, 10-50umn in diameter
what is the nucleus of a smooth muscle cell like?
leptochromatic, fusiform, centrally located.
the cytoplasm of smooth muscle cells stain ____
acidophilically
what is endomysium?
CT around (smooth?) muscle cells
can you regenerate smooth muscle?
no, replaced with scar tissue except uterus.
the sarcolemma of smooth muscles have special vesicles called ____. what do they do?
caveolae release Ca2+ and initiate contraction by activating myosin light chain kinase that phosphorylates myosin, activating it. these show up as studs on EM
dense bodies
in smooth muscle cytoplams (sarcoplasm) and along plasmolemma, these are dark patches which intermediate and myosin filaments attach.
