Zusammenfassung der Ressource
Muscle Cells
- Characteristics of
muscles
- responsiveness/excitability
- Conductivity
- Contractility
- Extensibility
- elasticity
- returns to original resting length after being
stretched.
- can be stretched between contractions
- shortens when stimulated
- local electrical change triggers a wave
of excitation, travels along muscle
fiber.
- responds to chemical signals, stretch and
electrical changes across plasma membrane
- Connective Tissue Elements
- Tendons
- Endomysium
- Perimysium
- epimysium
- con tissue
surrounds
entire
muscle.
- continuous
with
collagen
fibers of
tendon
- connec
tissue
around
muscle
fascicles
- connec
tissue
AROUND
muscle cells
- tendons are
attachments
between muscle
and bone matrix
- The Muscle Fiber
- Sarcolemma
- Sarcoplasm
- Myofibrils
- Multiple nuclei
- mitochondria
- SR sarcoplasmic reticulum
- tubules
- triad
- a T tubule and two terminal cisterns
- tubular infoldings of
sarcolemma penetrates
through the cell and exists
other side
- release
of Ca2+
into cell
- smooth ER
forms
network
around each
myofibril
- calcium
reservoir
needed to
contract
- packed in
between myofibrils
to produce ATP
- flat nuclei
pressed
against
inside of
sarcolemma
- long protein bundles occupies the main portion of sarcoplam
- Glycogen
- stored in abudance, long
chain of glucsoe, provides
energy with heightened
exercise.
- myoglobin
- red pigment,
stores oxygen
to produce
ATP
- cytoplasm of m. fiber
- plasma membrane of m. fiber.
- Myofiliments
- each myofibril is a bundle of parallel
protein microfilaments called myofilaments
- 3 kinds of Myofilaments
- Thick filament= Myosin
- hundreds of myosin molecules
- shaped like a golf club 2 chains intertwined
forms a shaft like tail, double globular head
- myosin heads are cross bridges attaches to actin and pulls it with regular movement.
- Thin filament= Actin
- Fibrous (F) actin; two intertwined strands.
string of globular (G) actin submunits
- string of globular (G) actin subunits each with
an active site, binds to head of myosin
molecule.
- like a double strand
of pearls.
- Tropomyosin molecules each
blocking 6-7 active sites on G actin
subunits
- Troponin molecule- small, calcium-binding
protein , a calcium receptor on each tropomyosin molecule
- needs calcium or it
wont bind.
- Elastic Myofilaments
- Titin
- made of protien (connectin)
- Huge springy protein
- helps stabilize thick filament=myosin
- prevents over stretchin
- contractile proteins
- myosin and
actin are called
contractile
proteins they
shorten the
muscle fiber.
- Regulatory Proteins
- troponin and topomyosin act like
a switch to determine when fiber
can contract and when it can't
- contraction activated
by rels of calcium into
sarcoplasm and its
binding to troponin
- troponin changes shape and move
topomyosin off the active sites on
actin
- Striations
- myosin and actin are proteins that occur in all cells
- function in cellular motility, mitosis, transport of intracellular material
- organized in a precise way in skeletal and cardiac muscles.
- A band= anisotropic.
protein is myosin
- part of A band where
thick and thin filaments
overlap
- H band in the middle of A band, these are
thick filaments
- M line is in the middle of the H band
- I band= isotropic.
protein is actin.
- alternating lighter band the
way the bands reflect
polarized light
- Z Disc
- provides anchorage
for thin filaments and
elastic filaments
- Sarcomere
- the segment of the
myofibril one z disc to
the next is one
sarcomere