Muscles Flashcards
Role of muscles
supply force for movement
restrain movement (stabilize body)
control viscera
form sphincters that control the passage of materials
heat production
produce electricity
somatic muscle
attaches to the bone or cartilage
visceral muscle
attaches to organs, vessels, and ducts
voluntary muscle
under conscious control
involuntary muscle
not under conscious control
nucleate tell us
how many nucleo the muscle cell has
striated vs unstriated
striated filaments are aligned in rows
unstriated filaments are not aligned in rows
3 types of muscle
skeletal, smooth, and cardiac
Smooth muscle
unstriated, mononucleate, cells are joined in sheets that wrap around organs that they exert control over, cells are electrically coupled (can pass signal), visceral muscles and involuntary
skeletal muscle
voluntary, striated, multinucleate, filled with sarcomeres, attach to the skeleton but also surround the digestive and urinary tract
cardiac muscle
striated, multinucleate, branched, and joined by intercalated disks, waves of contraction are spread through intercalated disks
skeleton muscle actions
contract pulling on the skeleton to create movement
origin of muscle
attached to immobile part of bone
insertion of muscle
attached to the more mobile bone
antagonistic muscles
move skeletal elements in opposite directions, muscles can only create force in one direction via contraction so they are often paired as antagonistic sets
synergistic muscles
muscles that work together, multiple redundant muscles allow for each to reach peak force at different times (get around limitations)
skeletal muscle structure
composed of muscle bundles that contain multiple muscle cells (fibers), fascicles (muscle cells packed together) surrounded by epimysium, attached to bone via tendons
tendons
connective tissue surrounding muscle that extends to periosteum around bones, less energetically costly to maintain than muscle, allow long connection for short muscles
myofibrils
Composed of chains of repeating units called sarcomeres
z bands
separate sarcomeres
myofilaments
overlapping filaments in sarcomeres
myosin
thick filaments with protruding heads, heads are tilted to the side, have binding sites for ATP and actin, heads can hydrolyze ATP (releasing phosphate and energy) active during contraction
actin
thin filament with two other proteins attached
resting state of contraction
no stimulation from the nervous system, muscle is soft, shape maintained by collagenous fiber around it, not force generated, can be stretched
active state of contraction
nerves stimulate the muscle past the threshold point, contraction generates a tensile force that tries to move bone/mass attached to muscle, resistance to the movement is the load (mass being pulled)
describe muscle contraction
muscle structure shortens, the white region becomes thinner, and the black region maintains its width
how does length affect muscle force
length of sarcomere alter the ability of muscle to produce force, the greatest force is in the middle length, and longer has less connection between myosin, shorter does not have enough room for myosin
how does velocity affect muscle force
speed of muscle contraction alters for available, binding and unbinding takes time, slower the contraction the more force, if filaments move too fast fewer heads can bind to create force
describe power limit
cant increase force and velocity at the same time, there is a trade-off
red muscle vs white muscle
red muscle contains myoglobin, resistant to fatigue, useful for high endurance activities
white muscle is low in myoglobin, contracts rapidly, fatigues easily, and is good for quick reactions
tonic fibers
slow contracting, produce low force, common in amphibians rare is mammals
twitch fibers
faster contraction -> higher forces, divided into fast and slow twitch muscles
myosin heavy chain (mhc)
motor protein used to identify fiber types
where does ATP fuel source of slow and fast twitch fibers come from
slow twitch fibers rely on ATP from aerobic respiration
fast twitch fibers rely on ATP from anaerobic respiration
rate modulation
increase or decrease the rate at which nerve impulses are delivered to the muscle
motor unit
single neuron and the unique set of fibers it innervates (stimulates)
how to modulate the amount of force used to lift different mass with same muscle
rate modulation and motor unit