Muscles Flashcards
muscle cells/ fibers
are made up of excitable cells that are capable of contraction. these are responsible for movement of different types of body structures. it is responsible for the change in shape and size on internal organs. they are made of myocytes which are long and narrow. the contractile property of muscle fibers comes from myofibrils
external lamina of muscle fiber
it is secreted by muscle cells, and its structure resembles basement membrane and made up of glycoprotein laminin , collagen IV and and proteoglycan perlecan
skeletal muscles and cardiac muscles receive nerve supply from?
somatic nervous system and autonomic nervous system
non striated muscle fiber
present in smooth muscle fiber, involuntary and receives nerve supply from autonomic nerve supply
smooth muscles
they are present in the form of sheet, bundle and bands. they are present on viscera of body, intestines, stomach, uterus and urinary bladder. it is also knows as visceral muscle. it is also present in ciliary muscles of eye, muscle of iris, walls of blood vessels and lymphatics, prostrate gland stroma, arrector pili muscles.
smooth muscle fiber
spindle shaped (fusiform) cells which have thick in the central part but tapers towards both sides. they have maculae communicants (gap junction) that join each fiber and helps in communication and contraction of the whole muscle fiber. in longitudinal section they show mosaic pattern.
nucleus of smooth muscle cells
nucleus is rod shaped, present in central part of the fusiform cells. in longitudinal section, it shows corkscrew appearance
what does the cytopasl of smooth muscle cells contains
it has contractile apparatus actin and myosin, and cytoskeleton of intermediate filaments. it also contains SER, RER, glycogen granules and golgi apparatus, polysomes and mitochondria.
caveolae
invaginations of plasmalemma makes caveolae which function in signaling molecules. the caveolae contains receptors, ion channels and pumps. it allows Ca ions to move towards the inside of the muscle fiber and also vise versa.
cytoskeleton of smooth muscle cells
consist of network of desmin intermediate filaments and walls of blood vessels of smooth muscle cells contain vimentin
dense bodies
these are acting binding proteins which are either dispersed randomly or attached to sarcolemma. they act as the Z disk of skeletal muscle and causes contraction. the intermediate filaments are also inserted into dense bodies
nerve supply in smooth muscle cells
it takes place by sympathetic and parasympathetic divisions of autonomic nervous system which is pre ganglionic and unmyelinated.
there are two types or nerve fibers, multiunit that has a lot of nerve terminals and and rich nerve supply
present in iris muscle of eye and duct deferens. other is unitary which has poor nerve supply and nerve impulse transferred from one cell to another from gap junctions present in viscera of body and walls of blood vessels
functions of smooth muscles
contraction & relaxation of blood vessels for blood pressure and blood flow, in lungs (bronchioles) for movement of air inside to outside and vise versa, in urinary bladder to push urine outside. in uterus to push baby outside, in male reproductive tract to push semen and spermatozoa in the urethra, in prostrate gland and seminal vesicles at the time of ejaculations. ciliary muscles to control the curvature of lenses, pupillary muscle for dilation of size of pupil and opposite, erector pili muscles contract to make the hair stand .
connective tissues associated with skeletal muscle fibers
epimysium- surrounds the whole muscle including blood vessels nerves
perimysium- surrounds bundle (fascicles)
endomysium- surrounds each muscle fiber. present just above the external lamina and has fine collagenous fibers embedded in the proteoglycan matrix
do skeletal muscles branch or not?
they do not brach
diameter of skeletal muscles
50-60 micrometer
shape and location of nucleus
it is ovoid in shape and placed in the peripheral region of the muscle cell
muscle cell structure describe
muscles cells are cylindrical in covered by an external lamina whose collagenous fibers are embedded in the endomysium
muscle cells mononucleated or multinucleated and how
they are multinucleated made from the fusion of many mononucleated cells (myoblast)
contents of cytoplasm of skeletal muscle
contains myofibrils (1 micrometer ), sarcoplasmic reticulum, small amount of RER, golgi complex and glycogen granules and abundant mitochondria.
thick myofilaments
made up of myosin II. it has two heavy chains and one light chain. each heavy chain is shaped like a golf ball and has a thin tail and thick globular heads that wind around each other in rope like manner. each of the 2 globular heads is associated with myosin light chain
it spans the entire A JOINS protein on the m line from one side and joins the protein titin on the Z disk
thin myofilament
think myofilament is actin which joins the Z disk by alpha actinin
each actin exist as long filamamentous polymers called F-actin polymers. each F-actin has two strands which are composed of another globular protein subunit G-actin.
tropomyosin
it is 40nm long slender filaments that occupy the shallow grooves of F-actin double helix
troponin
has globular subunits TnT which binds with tropomyosin, TnI Which maintains the action myosin interaction and TnC which binds with calcium
structural organization of skeletal muscle fibers
the thick filaments occupy the A band (central region) the thin filamets extends from either side of Z disk thru adjacent I band and parted way into A band.
each thick filament is surrounded by 6 thin filaments
H zone is free of thin filaments
A band has both thick and think
I band has only think
thick and thin filaments anchor at what places
thin filaments anchors at the Z disk and Thick filaments are anchored at M line region of H zone
Z disk contains what?
contains Z matrix which has alpha actinin that helps in actin binding to the Z disk
what does M line contains
contains myomesin which is myosin binding protein
also contains enzyme creatinine kinase which catalyzes the transfer of phosphate to ADP
association of tubules of sarcoplasmic reticulum with T tubule
the tubules of SR run longitudinally, the later anastomosing b/w these longitudinal disposed tubules form a PERFORATED COLLAR around the myofibrils at the level of H zone. at the level of A-I junction these tubules join terminal cisternae which are in ring shaped around these myofibrils. there are two transversely disposed terminal cisternae at A-I junction but are separated by T TUBULES.
traid
the special arrangement of the two terminal cicsternae with T tubule is known as triad
cardiac muscle
it is only found in myocardium, striated and involuntary in nature. cardiac muscle fiber are formed by cardiomycetes which are arranged in a chain cell-to-cell and attached to each other by a junction located in a specialized region called as intercalated disk
a delicate network of collagenous and reticular fibers are present in between of cardiac muscle cells and represents the endomysium
cardiac muscle cells
cardiomyocytes are elongated, branching cells with irregular contours at their junction
nucleus of cardiac cells
oval pale staining single large nucleus
some cardiomyocytes are binucleated
what does the sarcoplasm of cardia muscle fiber contains
same thick thin filaments arrangement as skeletal muscle
contains a large amount of mitochondria, sarcoplasmic reticulum, Golgi complex, glycogen granules, fat droplets and lipofuscin pigment (present in old people)
location of mitochondria in cardiac muscles
small mitochondria are present bellow the sarcolemma in the perinuclear zone
and large mitochondria are densely packed in between of myofibrils
sarcoplasm of right and left atria contains what and does what
atrial granules, these granules contain hormone called arterial natriuretic factor
these are release when atria are distended due to large plasma volume and causes diuresis (exertion of large amount of urine by inhibiting reabsorption of Na by kidney tubules and collecting ducts)
intercalated disk
are darkly stained transverse bands present between muscle fiber cells of cardiac muscles. they are present at the level of Z line and have special junctional complex like desmosomes, fascia adherents and gap junctions
functions of the special junctional complexes
desmosomes and fascia adherents provide mechanical support and strength for the attachment of cardiomyocytes
and gap junctions provide electrical coupling between the adjacent cardiac muscles.
T tubules and sarcoplasmic reticulm of cardiac muscles
the T tubules of cardiac muscles have greater diameter than skeletal muscles and are present at the level of Z disk not A-I junction
also there is no triad formation, but the one small terminal cisternae joins with the T tubule making diad.
the sarcoplasmic reticulum has many branches that join and anastomose frequently baking plexiform pattern
regenerative properties of skeletal muscles
they have very little regenerative properties, although they have satellite cells which are a dormant form of myoblast, they re enter the cycle, proliferate and make up new cells and fuse to form skeletal muscles.
in case of a large injury, fibroblast make up collagenous fibers which make up the scar tissue filling the space made in at injury site
regenerative properties of smooth msucles
they are highly regenerative, the old smooth muscle cells undergo mitosis and make up new cells
in blood vessels pericytes take part in the repair process
regenerative properties of cardiac muscle
cardiac muscle has no regenerative properties, the fibroblast make up scar tissue filled by collagenous fibers
