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Muscular System P.1 Frida Hernandez, *sarcoplasmic…
Muscular System
P.1
Frida Hernandez
Intro
Organs
that generate different types of movement
3 Types
: Skeletal, Smooth, and Skeletal
Skeletal Muscles
600 skeletal muscles in the body
Sk.M Fibers
Single, long, cylindrical muscle cell
contract only when stimulated by a motor
neuron
Cell membrane of M.F:
Sarcolemma
Cytoplasm of M.F:
Sarcoplasm
Sarcoplasm contains:
Myofibrils
Myofibrils has:
Thick Filament
(w/ protein myosin),
Thin Filament
(w/ protein actin, troponin, and tropomyosin)
Communicate w/
neurotransmitters
C.T
covers muscles
Dense C.T, surrounds and separates muscles; called
Fascia
Extends beyond muscles, and fused to the periosteum of bones; called
Tendons
Blends w/
epimysium
(arround Sk.M)
Some muscles connected by broad sheets of C.T; called
Aponeuroses
Skeletal muscles are named according to any of these:
size, shape, location, action, number of attachments, direction of its fibers
, or combinations of the above.
Smooth Muscles
Elongated w/ tapered ends, lacking striations, and underdeveloped SR*
Contains
thick
and
thin
filament
Similar
to Sk.M contraction
Reaction b/w
actin
and
myosin
. Stimulated by membrane impulses.
⇧
in calcium ions in cells. ATP energy used
Differences
to Sk.M contraction
Acetylcholine (ACh) and norepinephrine stimulate and inhibit smooth
muscle contraction. Only ACh stim. muscle contraction
Hormones stim. smooth muscles
he enzyme acetylcholinesterase, in the motor end plate, rapidly decomposes the acetylcholine
Slower to contract or relax; contractions are longer (same ATP amount); change length w/o tautness
Sarcomere, Myosin, or Actin
Troponin
and
tropomyosin
are
2
proteins associated with the surface of the actin molecules; together, these
3
proteins form the
thin
filaments
Head bends, than releases, and finally attaches to next actin pulling it towards the center
Upon receipt of the muscle impulse, the
sarcoplasmic reticulum
releases
its stored calcium to the cytosol of the muscle fiber
Energy for muscle fiber contraction comes from molecules of
ATP
; rely on cellular respiration to generate
ATP
Cardiac Muscles
Found
only
in the heart ❤️
Consist of branching and striated cells that interconnect in three-dimensional networks
Complex membrane junctions, called
intercalated discs
, join cells and transmit the force of contraction from one cell to the next
Self exciting (involuntary)
*sarcoplasmic reticulum