L26 Flashcards
Function of cardiac, skeletal, and smooth muscle
cardiac
-pumping blood
skeletal
- produces movement, posture, body position, + maintain body temp.
-voluntary
-good for long contractions
smooth
-storing + moving substances in body
-makes up iris, uterus, bladder
structural organisations of a muscle + layers of connective tissue
-muscle, fasicles, bundles of muscle cells, muscle fibres, single muscle cell (biggest to smallest)
-veins, arteries, and nerves pass between the fasicles
- epimysium (external sheath), perimysium (encases fasicles), and endomysium (encased fibres) (outside to inside)
explain skeletal muscle fibres
-long, large, multinucleated (near periphery), striated
-has sacrolemma + sarcoplasma
- in skeletal muscles, attached to bone
-contains tightly packed myofibrils (bundles of protein myofilaments within the muscle fibres) made of thick (myosin) + thin (actin) myofilaments
-myofibirils provide efficiency of packing in, so more cross bridges formed, stronger contraction
define transverse tubule system
-branched network of tubules that runs across fibre
-allows rapid passage of depolarisation into the interior of the fibre
define sarcoplasmic reticulum
-reservior of calcium
-release when muscles depolarises (internal is a well full of calcium + mitochondria)
draw a sarcomere + explain the bands
- light band- I band, thin filaments
- dark band- A band, absorb light, thick filaments
-bands make the striations
titian- coil, anchors on z disc, makes sure filaments stay in place + recoil when the muscle relaxes
Z-disc- narrow, plate shaped, dense material separates 1 sarcomere from the next
A-band, dark, middle part of sarcomere, extends entire length of thick filaments, includes parts of thin filaments that overlap thick filaments
I-band, lighter, less dense, contains thin filament ONLY, Z disc passes through the centre of each I band
M-lines, part of the cytoskeleton, holds filaments in place, centre of H zone, contains proteins that hold thick filaments together at centre of sarcomere
H-zone- no overlap centre of each A band, contains thick filament ONLY
*refer to onenote
explain thick (myosin) filaments
-consists of a long tail + 2 heads
-tails anchor in the thick filament
-heads bind active sites on actin, forming cross bridges
-heads then rotate towards M line, pulling the thin filament along
explain thin (actin) filaments
actin- has binding sites for myosin heads
thin filaments- are 2 strings of actin winding around each other for strength, like 2 beaded strings, block dots on the beads are the binding sites, where myosin binds with actin
-tropomyosin- covers active site on actin
troponin- complex of 3 molecules that binds both actin + tropomyosin, also binds Ca2+
- troponin T, can be seperated into troponin C and troponin I, act as cardiac regulation proteins that control calcium interaction between actin + myosin
what happens during contraction
- H zones + I bands get shortened
-zones of overlap increase
-width of A band stays constant
-thick filament CANT get compressed
describe cardiac muscle
- branched, striated, uninucleated cells, with itnercalated discs
-as contracts propels blood ito circulatio - ivolutary control
-make up walls of heart
define intercalated discs.
-cell membranes od adjacen cels interwie + couple cells
-hold fibres together
-myofibrils achnor to intercalated discs
-contain gap junctions which allow ion movement, creating electrical cotinuity
-forms a functional syncytium (means cells act as a single unit)
-cells have automaticity
describe smooth muscle.
-spindle shaped cells, with a central nucleus
- no striations
-cells form sheets
-cells connected by gap junctions
-syncytium, act as a single unit
-propels substances along internal passageways
-involuntary control- controlled by pacemaker cells with automaticity
-walls of hollow organs
-also has actin, myosin, and Ca2+ is a trigger, just like striated
-corkscrew motion when contracting
-is smooth, because myosin thick filaments are at rest, are depolarised
