Muscles

Question 1

muscle cells/ fibers

Answer 1

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

Question 2

external lamina of muscle fiber

Answer 2

it is secreted by muscle cells, and its structure resembles basement membrane and made up of glycoprotein laminin , collagen IV and and proteoglycan perlecan

Question 3

skeletal muscles and cardiac muscles receive nerve supply from?

Answer 3

somatic nervous system and autonomic nervous system

Question 4

non striated muscle fiber

Answer 4

present in smooth muscle fiber, involuntary and receives nerve supply from autonomic nerve supply

Question 5

smooth muscles

Answer 5

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.

Question 6

smooth muscle fiber

Answer 6

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.

Question 7

nucleus of smooth muscle cells

Answer 7

nucleus is rod shaped, present in central part of the fusiform cells. in longitudinal section, it shows corkscrew appearance

Question 8

what does the cytopasl of smooth muscle cells contains

Answer 8

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.

Question 9

caveolae

Answer 9

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.

Question 10

cytoskeleton of smooth muscle cells

Answer 10

consist of network of desmin intermediate filaments and walls of blood vessels of smooth muscle cells contain vimentin

Question 11

dense bodies

Answer 11

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

Question 12

nerve supply in smooth muscle cells

Answer 12

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

Question 13

functions of smooth muscles

Answer 13

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 .

Question 14

connective tissues associated with skeletal muscle fibers

Answer 14

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

Question 15

do skeletal muscles branch or not?

Answer 15

they do not brach

Question 16

diameter of skeletal muscles

Answer 16

50-60 micrometer

Question 17

shape and location of nucleus

Answer 17

it is ovoid in shape and placed in the peripheral region of the muscle cell

Question 18

muscle cell structure describe

Answer 18

muscles cells are cylindrical in covered by an external lamina whose collagenous fibers are embedded in the endomysium

Question 19

muscle cells mononucleated or multinucleated and how

Answer 19

they are multinucleated made from the fusion of many mononucleated cells (myoblast)

Question 20

contents of cytoplasm of skeletal muscle

Answer 20

contains myofibrils (1 micrometer ), sarcoplasmic reticulum, small amount of RER, golgi complex and glycogen granules and abundant mitochondria.

Question 21

thick myofilaments

Answer 21

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

Question 22

thin myofilament

Answer 22

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.

Question 23

tropomyosin

Answer 23

it is 40nm long slender filaments that occupy the shallow grooves of F-actin double helix

Question 24

troponin

Answer 24

has globular subunits TnT which binds with tropomyosin, TnI Which maintains the action myosin interaction and TnC which binds with calcium

Question 25

structural organization of skeletal muscle fibers

Answer 25

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

Question 26

thick and thin filaments anchor at what places

Answer 26

thin filaments anchors at the Z disk and Thick filaments are anchored at M line region of H zone

Question 27

Z disk contains what?

Answer 27

contains Z matrix which has alpha actinin that helps in actin binding to the Z disk

Question 28

what does M line contains

Answer 28

contains myomesin which is myosin binding protein

also contains enzyme creatinine kinase which catalyzes the transfer of phosphate to ADP

Question 29

association of tubules of sarcoplasmic reticulum with T tubule

Answer 29

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.

Question 30

traid

Answer 30

the special arrangement of the two terminal cicsternae with T tubule is known as triad

Question 31

cardiac muscle

Answer 31

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

Question 32

cardiac muscle cells

Answer 32

cardiomyocytes are elongated, branching cells with irregular contours at their junction

Question 33

nucleus of cardiac cells

Answer 33

oval pale staining single large nucleus

some cardiomyocytes are binucleated

Question 34

what does the sarcoplasm of cardia muscle fiber contains

Answer 34

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)

Question 35

location of mitochondria in cardiac muscles

Answer 35

small mitochondria are present bellow the sarcolemma in the perinuclear zone
and large mitochondria are densely packed in between of myofibrils

Question 36

sarcoplasm of right and left atria contains what and does what

Answer 36

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)

Question 37

intercalated disk

Answer 37

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

Question 38

functions of the special junctional complexes

Answer 38

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.

Question 39

T tubules and sarcoplasmic reticulm of cardiac muscles

Answer 39

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

Question 40

regenerative properties of skeletal muscles

Answer 40

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

Question 41

regenerative properties of smooth msucles

Answer 41

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

Question 42

regenerative properties of cardiac muscle

Answer 42

cardiac muscle has no regenerative properties, the fibroblast make up scar tissue filled by collagenous fibers