muscle histo Flashcards
characteristics of muscle tissue
- striated or smooth
- voluntary or involuntary
- all specialized for contraction
types of muscle tissue
1.skeletal
2. smooth
3. cardiac
order of muscle components from largest to smallest
-muscle
-muscle fascicle
-muscle fibre
-myofibrils
-actin and myosin filaments
what does the epimysium surround
muscle
what does the perimysium surround
muscle fascicle
what does the endomysium surround
muscle fibre
function of epi,peri,endomysium
reduce friction between layers of muscle tissue
muscle to tendons and apeneuroses
collage of fibres from endo,peri,epimusium that blend together into the tendon and apeneuroses for attachment
tendons to bony attachment
collage of fibres from tendons and apeneuroses interwoven with fibres of the periosteum
how is tendon/apeneurosis attached to periosteum
cemented to matrix of bone as sharpeys fibres (connect periosteum to bone)
how is blood and nerve supplied to muscle
vessels and nerves form neuromuscular bundle
-branch within the CT coverings and reach individual muscle fibres
what is the sarcolemma
cell membrane of skeletal muscle fibre
what is sarcoplasm
cytoplasm of skeletal muscle fibre
what are transverse tubules
-indentations of sarcolemma
-form network of tubes extending into sarcoplasm that ensure contraction signal is received at the same time throughout fibre
what are myofibrils
protein filaments made up of actin and myosin
what is the sarcoplasmic reticulum and what does it store and do
endoplasmic reticulum of skeletal muscle fibre
-stores Ca2+ and forms sleeve around each myofibril
what are terminal cisterna
expansions fo sarcoplasmic reticulum on either side of T-tubules
what is a triad
pair of terminal cisternae with one intervening T-tubule
which filament is the thin filament
actin
which filament is the thick filament
myosin
what is a sarcomere
component of the myofibril for muscle contraction composed of actin and myosin
what is G actin (globular actin)
molecule with active binding site capable of binding to a thick filament
what is F actin (filamentous actin)
polymers of G molecule which form a filament
what is tropomyosin
-covers active sites of G actin
-prevents actin myosin interactions
what is troponin
-has binding site for calcium
-signals for tropomyosin to move off active site with increase calcium presence
how many thin filaments surround a thick
6
parts of the sarcomere
z line
m line
h zone
i band
a band
zone of overlap
what is the z line
thin filaments attach together and delineate the sarcomere
what is the m line
thick filaments attach together and extend toward z lines
what is in h zone
only thick filaments (myosin)
what is in i band
only thin filaments (actin)
what is a band
length of thick filament
-zone of overlap and h zone
what is in zone of overlap
thin and thick filaments
what are ends of sarcomere
z lines
with contraction, what happens to;
length of sarcomere
size of h and i bands
length of a band
length of zone of overlap
-shortened
-shortened
-constant
-increased
what initiates muscle contraction
Ca2+
how does muscle contraction happen
in presence of calcium, actin site becomes available, myosin head binds (cross-bridges), crossbridges rotate toward centre of sarcomere
what causes cross bridges to detach after they rotate
ATP binds to myosin
why is muscle relaxation largely passive
1.tissue elasticity
2. pull of antagonist muscles
3.gravity
what is a motor unit
motor neuron and all muscle fibres it innervates
what type of motor neuron is the motor neuron in motor unit
lower motor neuron
how do we have precision in actions
ration of motor neuron to number of muslce fibres changes - more fibres = less precise
how is there smooth contraction of muscle
fibres of each motor unit are intermingled within one muscle
can only some muscle fibres from one motor unit contract while others dont
no - all contract or none
how do we avoid burnout
some motor units contract while others rest
what is a isotonic contraction and what are the types
no change in tension while muscle changes length
-concentric
-eccentric
what is the difference between concentric and eccentric isotonic contraction
concentric
-shortening, joint angle gets smaller, overcoming weight, against gravity
eccentric
-lengthening, joint angle gets bigger, controlled lowering of weight, gravity would otherwise pull object down
what is a isometric contraction
no change in length
-tension generated is not enough to exceed resistance of object to be moved and muscle does not change length
what are the factors affecting tension
- sarcomere length
- frequency of stimulation
- motor unit size
- recruitment of motor units
what happens with muscle hypertrophy
-more mitochondria
-higher glycogen reserves
-more glycogen enzymes
-increased myofibrils with increased myofilaments
how does muscle hypertrophy happen
repeated stimulation of muscle near maximal tension
what are the 3 muscle fibre types and what are they for
- slow oxidative - postural, antigravity muscles
- fast glycolytic - fine control like hand and eye
- fast oxidative-glycolytic - largest fibres - leg
what determines the proportion of fibres within a muscle
function and genetics
specifically, ratio of slow oxidative and fast glycolytic fibres are determined by what
genetics
can fibres in the same motor unit be different types
no
where is cardiac muscle found and what are characteristics
-only heart
-striated, involuntary
what are cardiocytes
cells that form branching network and join at the intercalated discs
what are intercalated discs
-gap junctions provide intercellular communication
-desmosomes provide anchorage for intermediate filaments of cytoskeleton
what are pacemaker cells
set basic rate of contraction - impulses conducted through gap junctions
what is contraction of cardiac muscle modulated by
autonomic nervous system
can cardiac muscle regenerate
no
what junctions hold cardiac muscle fibres together
tight
where is smooth muscle and what are characteristics
-respiratory, circulatory, digestive, reproductive tracts
- non striated, involuntary
why is smooth muscle non-striated
spindle shaped cells - myofilaments are arranged irregularly
what are pacesetter cells
set basic rate of contraction in smooth muscle
what modulates smooth muscle contraction
ANS
can smooth muscle regenerate and repair
yes
