function of muscles - ✔️✔️are for body movement, maintenance of posture, respiration, production of
body heat, communication, constriction of organs and vessels, heart beat.
skeletal muscles - ✔️✔️- are primarily voluntary by somatic motor neurons which are multinucleated. It
also functions for your respiratory system when it moves air in and out of the body and moves blood
back to our heart. MULTINUCLEATED.
- are usually attached to bones by tendons, the origin of the muscle is closest to the truck or more
stationary bone.
Insertion is more distal or more mobile attachment.
cardiac muscle - ✔️✔️which are primarily involuntary and function for spontaneous electrical activity, can
be altered by autonomic NS and hormones.
smooth muscle - ✔️✔️- is primarily involuntary for autonomic control, spontaneous, hormones,
paracrines or autocrines.
- Provides mechanical control of digestive tract, urinary tract, reproductive tract, blood vessels and
airways.
organization of muscles - ✔️✔️Muscles are made of fascicles made of individual muscle fibers made of
myofibrils made of sarcomeres made of thick and thin filaments.
thin filaments - ✔️✔️contain F- actin that is the back bone, they are double stranded alpha helical
polymer of G- actin molecules and have binding sites for thick filaments (myosin).
tropomyosin - ✔️✔️- is two identical alpha helices that coil around each other and sit in the two grooves
formed by actin strands, regulating the binding of myosin to actin.
- During muscle rest, the myosin is non- touchable but when active, tropomyosin will move them to
bind.
troponin complexes - ✔️✔️- are heterotrimer consisting of:
,1. Troponin T (TnT) binds to a single molecule of tropomyosin.
2. Troponin C (TnC) is the Ca2+ binding site.
3. Troponin I (TnI) is under resting conditions and bound to actin inhibiting contraction.
thick filaments - ✔️✔️consist of bundles of myosin molecules where one myosin molecule are 2
intertwined heavy chains.
myosin molecules - ✔️✔️are made up of a myosin head containing regions for binding actin as well as a
site for binding and hydrolyzing ATP.
heavy chain - ✔️✔️consists of a light chain 1 that is the essential light chain stabilizing myosin heads and
light chain 2 that is a regulatory light chain regulating ATP activity of myosin.
titin - ✔️✔️is a very large protein extending from M line to Z line, appears to be involved in stabilization
and the elastic recoil behavior of muscle.
nebulin - ✔️✔️is a large protein that wraps around the thin filament, believed to regulate the length of
thin filaments and contribute to the structural integrity of myofibrils.
Sacromere - ✔️✔️consists of a z disk, i band, a band, h zone, and m line
z disk - ✔️✔️is a zigzag protein structure that is the attachment site for the THIN filaments.
i and a bands - ✔️✔️- are the lightest band of sarcomere, region occupied only by THIN filaments.
- is the darkest band of sarcomere, encompasses the entire length of the thick filament, including very
dark areas where THIN and THICK filaments overlap.
h zone and m line - ✔️✔️- is the central region of A band, consisting only of THICK filaments.
- consists of proteins forming the attachment site for the THICK filaments, equivalent to z disk for thin
filaments.
, transverse tubules - ✔️✔️are continuations of sarcolemma plasma membranes. They help the AP
generate into the interior region of the muscle fiber of the sarcoplasm, they also surround each
sarcomere in a certain area (A - I band).
MUSCLE FIBERS
sarcoplasmic reticulum - ✔️✔️is the Ca2+ storage organelle that surrounds each sarcomere as well. They
contain a T tubule in b/w each reticulum and a terminal cisternae in them.
MUSCLE FIBERS
terminal cistermae - ✔️✔️is the swollen region of the reticulum where the majority of the Ca is stored.
MUSCLE FIBERS
Mitochondrion - ✔️✔️where ATP is produced but some skeletal muscles don't have a lot of these.
MUSCLE FIBERS
initiation of skeletal muscle contraction - ✔️✔️1. Events in the CNS: areas of the brain responsible for
voluntary movement and the descending tracts in the spinal cord.
2. Events in neuromuscular junction: is a point of synaptic contact b/w somatic motor neurons and
individual muscle fibre.
3. Excitation- contraction coupling: an AP initiated in the skeletal muscle fibre results in an increase in
intracellular Ca2+.
4. Ca2+ signal
5. Contraction relaxation cycle: broken down into muscle twitch and sliding filament theory.
Voluntary movement also comes from the primary motor cortex.
Premotor cortex, basal ganglia, thalamus, midbrain, and cerebellum.
corticospinal tract - ✔️✔️is a descending tract (ventral and interior lateral white matter)
PRIMARY MOTOR CORTEX
upper motor neurons - ✔️✔️is the brain to spinal cord and synapses with a second neuron (alpha motor
neuron)
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