Lecture 4 Skeletal Muscle and Nerve tissue Flashcards
Muscle cell
Made up of myofibrils
Myofiber/Myocyte/Muscle fiber
Fascicle
group of myofibers
Muscle
group of fascicles
nebulin
“ruler” for determining
length of actin filament
M-line:
attachment site for myosin
Z-disk:
separates sarcomeres; attachment site for actin and titin
H band:
space on either side of M-line where there is no actin
A band:
distance from the end of one myosin head to the head of the opposite myosin (overlap of actin + myosin and H band)
I band:
space on either side of the Z-disk where there is no myosin
Sliding Filament Mechanism
Thin filaments slide past thick filaments • This brings Z-disk’s closer together • All myofibrils in a muscle contract at the same time making the entire muscle shorten • *Actin and myosin DO NOT change in length, they simply overlap each other
Sarcolemma:
membrane around
each muscle cell
Transverse (T) tubules:
membrane
system penetrating the muscle cell
to convey electrical impulses from
sarcolemma into cell
Sarcoplasm:
cytoplasm of muscle
cell
Sarcoplasmic Reticulum:
tubular
system acting like the smooth-ER
Terminal Cisternae =
flattened sac of
SR on either side of a Transverse T
Tubule
-store Ca2+
Triad
T tubule + 2 Terminal
cisternae (1 on either side)
End Feet:
connect T tubules with
SR to allow Ca release
Neuromuscular Junction (NMJ)
Skeletal muscle innervated by peripheral a-motor neurons from the anterior horn of the spinal cord
Neuromuscular Spindle Apparatus Action
reflexive response to
prevent overstretching of a
muscle
Extrafusal muscle fibers:
contract
the muscle
Intrafusal muscle fibers:
sense length
and rate of change of the muscle
Type Ia sensory nerve fibers:
afferent innervation of intrafusal fibers
sense stretch and rate of change of intrafusal fibers
a-motor nerve fibers:
efferent
innervation of extrafusal muscle fibers
-receive signal from type Ia fibers
g-motor nerve fibers:
efferent
innervation of intrafusal muscle fibers
-receive signal from type Ia fibers
soma/body
contains all organelles of neuron
nissle substance
abundant RER w/in the cytoplasm of soma
dendrite
receives signals from other neurons
axon hillock
connection between soma and axon
axon
conveys electrical impulse to synapse
synapse
transfers electrical impulse from neuron to target tissue
Multipolar:
multiple
dendrites and one axon
Bipolar:
single dendrite
(multiple extensions) and
one axon
Pseudounipolar:
one
cell process with a single
dendrite branch and axon
branch
Schwann cell:
surround axon and create myelin sheath in PNS
– Wrap around one part of one axon
Oligodendrocyte:
surround axon and create myelin sheath in CNS
– Wrap around a part of many axons
Myelin Sheath:
circumferential layers of myelin allowing for faster
signal conduction velocity
