MUSCLE TISSUE Flashcards
Composed of cell that optimize the universal cell property of CONTRACTILITY
Muscle tisse
muscle tissue is also known as
myocytes
Actin microfilaments and associated proteins generate the
forces necessary for the muscle contraction, which drives movement within the organ system, of blood, and body as a whole.
bone serves as liever allowing
body movement
muscle cells are of ___ origin
mesodermal
muscle cell differentiate by
a gradual process of cell lengthening with abundant synthesis of the myofibrillar proteins such as actin and myosin.
two filaments that makes muscle contract
actin and myosin
3 types of muscle tissue
Skeletal
cardiac
smooth
Skeletal muscle contains
bundles of very long multinucleated cells with cross striation.
Skeletal muscle contraction is
quick, forceful, and usually under voluntary control.
striated muscle
skeletal muscle
muscle fiber is also known as
muscle cell
why is skeletal muscle multi-nucleated?
because individual cells fused
Cardiac muscle
Also has cross striations and is composed with elongated, often brached cell bound to another at structures called intercalated discs that
structures that are unique to cardiac muscle
intercalated discs
contraction is vigorous, involuntary and rhythmic
cardiac muscle
has boundaries
cardiac muscle
consist of a collection of fusiform cells wich lack striations
smooth muscle
smooth muscle movement
slow involuntary contraction
like a football
fusiform cells
in all types of muscle, contraction is caused by
sliding interaction of thick myofilaments along thin actin filaments
cytoplasm of muscle cells is called
sacroplasm
the smooth ER is the
Sarcoplasmic reticulum
the muscle cell membrane and its external lamina
sarcolemma
increased cell volume
hypertrophy
tissue growth by an increase of the number of cells
hyperplasia
during exercise, muscle, especially skeletal
hypertrophy
location of nucleus of skeletal muscle
on top, on sarcolemma
alternating light and dark bands are
striations
in between muscle fibers, there are
connective tissues
elongated nuclei of skeletal muscle are found in
periphery, just under the sarcolemma, a characteristic nuclear location unique to skeletal muscle fiber/cells.
thin layers of connective tissue surround and organize the contractile fibers in
all types of muscle (seen specially in skeletal muscle)
epimysium
external sheath of dense connective tissue, surrounds the entire muscle, carying the larger nerves blood vessels and lymphatic of the muscle.
perimysium
thin connective tissue layer that immediately surrounds each bundle of muscle fiber that is termed as FASCICLE.
endomysium
a very thin delicate layer of reticular fiber and scattered fibroblast
sorrounds the external lamina of individual muscle fiber
endomysium
sorrounds muscle cells
endomysium
some skeletal muscles taper and their ends, where the epimysium is continuous with the dense connective tissue of a tendon at
myotendinous junction
how skeletal muscle form?
myoblasts—> fuse—-> forms one long muscle fiber
myoblasts
immature muscle cells
some myoblasts become
satellite cells for support
dark bands are called
A bands
because they are anisotropic or birefringent in polarized light microscopy.
light bands are called
I bands
isotropic, do not alter the polarized light
refraction into two fragments
bifringent
each I band is bisected by a dark transverse line called
Z disc
The repetitive functional subunits of the contractile apparatus
sarcomere
extends from Z disc to Z disc
bisects A band/ thick myosin filaments
M line
where can u see the thick myosin filaments
A band
where can u see the thin actin filaments
half on I banda half on A band when relax
spaces between actin filaments
H zone
The A and I banding pattern in sarcomere is due to
mainly the regular arrangement of thick and thin myofilaments composed of myosin and F-actin respectively.
occupy the A band and middle region of the sarcomere
thick myosin filaments
Myosin has
two identical heavy chains and two pair of light chains. GLOBULAR PROJECTION containing 4 myosin light chain from a head at one end of each heavy chain.
myosin head binds
both actin forming transient cross bridges bet. the thick and thin filaments and ATP (catalyze energy release)
the thin helical actin filaments run between the
thick filaments
each G actin monomer contains
a binding site for myosin
Actin filaments are anchored perpendicularly to
Z disc by the actin-binding protein alpha-actinin.
globular heads also known as
myosin head
Covers the myosin binding site
Tropomyosin
contraction of a muscle takes place by sliding of thin filaments over the thick filaments
sliding filament theory
the junction between the motor neuron and the sarcolemma is called
neuromuscular junction
it is a synapse
neurotransmitter in muscle
acetyl choline
conformational shape
change in shape of the molecule
the same length during contraction and relax
A band
change shape
I band
no more ATP to break the bind
rigor mortis
thin filaments are tightly associated with two regulatory protein
tropomyosin
troponin
troponin subunits
TnT- Attaches to the tropomyosin
TnC- Binds calcium
TnI- Regulates actin-myosin interaction
Important accessory protein in I band
titin- The largest protein in the body, with scaffolding and elastic properties which supports thick myofilaments and connects Z disc.
nebulin
another large accessory protein binds each myofilaments laterally, helps anchor them to alpha-actinin and specify the length of the actin polymers during myogenesis.
H zone
lighter zone in between myosin/ in the center of A band
walang actin filaments
H zone
bisects H zone
M line
-Contains myosin binding protein called myomesin that holds thick filaments in place and kreatine kinase, this enzyme catalizes transfer of phosphate group from phosphocreatine, a storage from high energy phosphate groups to ADP, helping to supply ATP for contraction of muscle.
muscle fiber also known as
muscle cell
myofibril
collection of myofilaments
myofilaments
actin and myosin
the functional unit of cardiac/skeletal muscle
sarcomere
specialized for calcium sequestration
nagtatago/naglalabas ng calcium
Sarcoplasmic reticulum
Transverse of T tubule
long fingerlike invagination of the cell that penetrate deeply into the sarcoplasm and encircle every myofibril near the aligned A and I band boundaries of sarcomere.
Adjacent to each side of every tubule are expanded terminal cisterns of the sarcoplasmic reticulum. This complex of a T tubule with two closely associated small cisterns of SR on each side is known as
triad
During contraction
neither thick or thin filaments change length
only I band shortened
contraction result as overlaping
thin and thick filaments of each sarcomere slide past one another
contraction is induced when
action potential arrive at a synapse, the neuromuscular junction, and is transmitted along the T tubule to the sarcoplasmic reticulum to trigger calcium release.
creation of calcium
electrical signal –> chemical signal —> release neurotransmitter (acetyl choline) –> go to synapse —> go to receptor of acetyl choline sa sarcolemma —> another action potential –> action potential run up to T tubule —> sarcoplasmic reticulum (stores calcium)
in resting mucle, the myosin heads can not bind G actin because
the binding sites are blocked by the troponin-tropomyosin complex on the F actin filaments.
calcium ions released upon
neural stimulation bind troponin C, changing the shape and moving tropomyosin on the F actin to expose myosin-binding site and allow cross-bridge to form.
Binding actin produces a
conformational change to pivot in the myosins, which pulls thin filaments farther into the A band towards the Z disc.
Energy for the pivot and pulling of the actin is provided by the
hydrolysis of ATP bound to the myosin heads.
___ is an autoimmune disorder that involves circulating antibodies against proteins of acetylcholine receptors. Antibody binding to the antigenic sites interferes with acetylcholine activation of their receptors, leading to intermittent periods of skeletal muscle weakness. As the body attempts to correct the condition, junctional folds of sarcolemma with affected receptors are internalized, digested by lysosomes, and replaced by newly formed receptors. These receptors, however, are again made unresponsive to acetylcholine by similar antibodies, and the disease follows a progressive course. The extraocular muscles of the eyes are commonly the first affected.
Myasthenia gravis
Striated muscles and myotendinous junctions contain
sensory receptors acting as proprioceptors (L. proprius, one’s own + capio, to take), providing the central nervous system (CNS) with data from the musculoskeletal system.
proprioceptors
sensory receptors that puts our limbs in space
*we are aware
specialized receptors located within joints muscles and tendons
proprioceptors
these receptors are sensitive to both tension and pressure, they play a role in relaying info concerning muscle dynamics to the conscious subconscious part of CNS
They provide brain with info concerning kinesthetic sense or conscious appreciation of the position of body parts with respect to gravity
proprioceptors
Most of the proprioceptive info is processed at a
subconscious level, so we do not havee to dictate conscious activity towards tasks such as maintining posture or position of body parts.
Examples of propprioceptors
Golgi tendon organs. They are located in tedons near the myotendonous junction and are in series, that are attached end to end, with extrafusial muscle fibers.
stretch detectors among muscle fascicles
muscle spindles
Muscle spindles are
skeletal muscle sensory receptors within the body of a muscle that primarily detect changes in length of muscle contributing to fine motor control and providing axial and limb position info to CNS.
Muscles that are often active with slow contractions for long periods tend to have
more mitochondria for oxidative phosphorylation and ATP production and to have a higher density of surrounding capillaries. Such fibers have high levels of the cytoplasmic protein myoglobin, which contains iron and stores oxygen molecules, giving such fibers a red color in fresh tissue.
Muscles specialized for short-term work and fast contractions are typically
larger in diameter and depend more heavily on anaerobic (glycolytic) metabolism of glucose, much of which is derived from stored glycogen
longitudinal arrays of contractile filaments in cytoplasm of muscle cells
myofibrils
myofibrils are composed of
thick (myosin) and thin (actin) filaments
segment of a myofibril that forms the basic functioning unit of skeletal muscle
sarcomere
During embryonic development, the mesoderm cells of the primitive heart tube
align into chainlike arrays. Rather than fusing into multinucleated cells, as in developing skeletal muscle fibers
Cardiac muscle cells forms
complex junction between interdigitating processes.
Cells within a fiber often
branch and bind to cells in adjacent fibers.
Cardiac muscle cells has cross striations comparable to
skeletal muscle fibers
Each cardiac muscle cells containis how many nucleus?
one sometimes 2
unique and distinguishing characteristic of cardiac muscle is the presence of
dark-staining transverse lines that cross the chains of cardiac cells at irregular intervals where the cells join. These intercalated discs represent the interface between adjacent muscle cells and contain many junctional complexes. Transverse regions
of these steplike discs have many desmosomes and fascia
adherentes
Cardiac muscle has more mitochondria
reflecting their need for continues aerobic metabolism
major fuel of the heart. Stored as tryglyceride which can be seen in numerous lipid droplets in many cardiac cells.
fatty acids
Muscle of ventricle is much thicker than
atria
Muscles of atria has
cytoplasmic granules
release atrial natriuretic factor (ANF) that acts on the target cells of the kidneys to affect sodium and water balance.
cardiac muscle contraction
intrinsic and spontaneous
____ is specialized for slow, steady contraction and is controlled by a variety of involuntary mechanisms
Smooth muscle
Fibers of smooth muscle (also called visceral muscle)
are elongated, tapering, and nonstriated cells, each of which is enclosed by a thin basal lamina and a fine network of reticular fibers, the endomysium.
Each cell of smoth muscle has
single long nucleus located in cells central, broadest part.
____ of smooth muscle cells contain several pumps and ion channels and may serve to organize proteins signaling calcium release at myofibrils.
Caveolae
in smooth muscles, bundles of thin and thick myofilaments
crisscross obliquely through the cells
actin filaments lack
troponin, using instead calmoudin and calcium sensitive myosin light chain kinase (MLCK) in the contraction mechanism.
smooth muscle fibers lack
MEP’S
Because smooth muscle is most often spontaneously active without nervous stimuli, its nerve supply serves primarily to
modify activity rather than to initiate it.
Smooth muscle receives both
adrenergic and cholinergic nerve endings that act antagonistically, stimulating or depressing its activity.
Smooth muscle contraction is determined largely by the
degree of autonomic innervation and the density of the gap junction; both conditions vary considerably in different organs.
Smooth muscle demonstrate the characteristic features of
secretory cells
ex: endomysium and basal lamina are produced and deposited by smooth muscle cells.
cross sectional
pabiolg
longitudinal
pahaba
nucleus of skeletal
cross section- gilid
longitudinal-
nucleus of cardiac and smooth muscle
cross section- nucleus
longitudinal- oval
cross sectional- circle
