CH 9 MUSCULAR SYSTEM Flashcards
List three muscle types
Skeletal, Cardiac, Smooth
Skeletal muscle definition
attached to bones voluntary control striated multi-nucleated limited regeneration
Cardiac muscle definition
in heart walls involuntary striated short no regeneration controlled by pacemakers within heart intercalated discs autonomic nervous system regulation
Smooth muscle definition
in the walls of the hollow organs involuntary not striated spindle shaped fast regeneration autonomic nervous system regulation
Voltage
gated channels open when membrane potential changes
Ligand
gated channels open when chemicals(such as neurotransmitters) attach to them
ion channels
allow ions to diffuse across the cell membrane
gated channels
these open and close, when closed do not allow any diffusion of ions
Myosin
protein shaped like a double headed golf club
Each thick filament contains _____ ______ molecules
300 myosin
Central position of thick filament is ____, but its ends are _____ with a staggered array of myosin heads
smooth, studded
thin filaments of muscle is made of ___
actin
Actin
2 thin strands of protein that wind around each other and contains myosin binding sites (that the myosin heads attach to)
When muscle is relaxed, ______ blocks myosin binding site on actin
tropomyosin
Smooth muscle gross anatomy
arranged in layers in walls of hollow organs, cells in adjacent layers have opposite orientation
Longitudinal layer
muscle fibers run parallel to the long axis of the organ. when the muscle contracts, the organ dilates and shortens
Circular layer
fibers run around the circumference of the organ. Contraction of this layer constricts the lumen of the organ and causes the organ to elongate.
Varicosity
large bulb-like swelling in the neuron
Stimulation for contraction may be _______ innervation, _______, _____ conditions
autonomic, hormonal, local
Skeleton muscles has 3 connective tissue sheaths ( all continuous with one another) which are
Epimysium, Perimysium, Endomysium
Epimysium
dense connective tissue, surrounds whole muscle
Perimysium
fibrous connective tissue, surrounds fascicles
Endomysium
Sheath of fine areolar connective tissue with reticular fibers, surrounds each muscle fiber (cell)
Sacroplasm
stores glycogen, myglobin, and creatine phosphate all are related to energy needs
Nucleus
Multinucleated because they originate from fusion of several myoblast cells nuclei are pushed to side
Myofibril
Rod-like structures that fill the cell contains bundles of proteins that compose the contractile units, about 2 micrometers in diameter, extend the entire length of the muscle fiber
Thick/thin filaments
the proteins of the myofibrils
Sacromere
the contractile units formed by the thick and thin filaments of the myofibril
Muscle-atrophy
wasting away of muscles, individual muscle fibers decrease in size due to lack of use, or disturbance of nerve supply.in about 6 months to 2 years, the muscle will be a quarter of its original size, and will be replaced by fibrous c.t. a process that when complete cant be reversed
4 types of attachments
origin, insertion, direct(fleshy), indirect
Origin
attachment to bone that does not move during contraction
Insertion
attachment to bone that moves during contraction
Direct
epimysium of muscle fused to periosteum of bone or perichondrium of cartilage
indirect
muscles connective tissue wrappings extend beyond muscle as a ropelike tendon or aponeurosis. indirect is much more common due to durability and small size.
4 steps of skeletal muscle contraction- relaxation
excitation, excitation-contraction coupling, contraction (with power stroke), relaxation, cardiac muscle contraction is very similar to skeletal muscle contraction
muscle cells typically have a ____ resting membrane potential
-70mv
each muscle fiber has only one ___________ junction, located midway along the fibers length
neuromuscular
list the steps for excitation
nerve impulse reaches axon –> ACh is released into cleft –> ACh attaches to receptors (ligand gated ion channels) –> Na floods more quickly than K into the cell and the sarcolemma depolarizes –> Action potential
Excitation- contraction coupling neighboring voltage gatedd Na channels open and …..
depolarization sweeps across sacrolemma and into T-Tubules –> causes Ca to be released from terminal cisternae into cytoplasm –> ca attaches to troponin –> troponin changes shape and pulls the tropomyosin off the myosin binding sites on the actin –> myosin heads bind to the exposed binding sites
muscle contraction- power stroke steps
when cell is resting, ca levels in the cell are low and myosin binding sites on actin are physically blocked by tropomyosin. when terminal cisterns releases ca into cytoplasm –> calcium attaches to tropinin –> troponin/tropomyosin complex moves which opens the myosin binding sites on the actin –> power strokes occur
Contraction is the result of ______ shortening
sacromeres
T or F: when relaxed the think and thick filaments overlap slightly
TRUE
Contractio cycle (4 steps) (continuous until relaxation)
- ATP hydrolysis
- attachment of myosin to actin to form crossbridges
- power stroke
- detachment of myosin from actin
Contraction- relaxation steps
cycle repeats to shorten sacromeres (muscle contracts) –> cycle is broken when calcium is reabsorbed into terminal cisterns –> tropinin/tropomyosin move back to cover myosin binding sites on actin –> sacromeres return to original length (muscle relaxes)
Autorhythmic cells-pacemaker cells-
set heart rate 70bpm, auto or self generate action potentials and stimulate neighboring cells to generate and propagate action potentials