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
cross section area of muscle and force
total force a muscle can produce is proportional to the cross section of its myofibrils (length doesnt matter)
parallel fibers
lie along line of force generation
pinnate fibers
lie oblique (slanted) to a line of force generation, insert at the common tendon
pinnate vs parallel for force and movement
pinnate have greater for production because more myofibrils are packed into a given area (carry heavier loads)
parallel can shorten and move longer distance (carry lighter loads)
active component of muscle organ
sliding filaments
elastic component of muscle organ
tendon (store energy, energy released when stretched)
active tension
tension created by the muscle itself
passive tension
the tension required to stretch the elastic components
total tension
overall tension measured in muscle, active+passive
how do lever mechanics affect muscles
can alter force production, muscle insertion near joint results in fast large motion with little force, muscle attaching farther from joint results in short powerful motion
low gear muscles (synergistic)
more force advantage, used to overcome inertia during initial movement
high gear muscles (synergistic)
more speed advantage to create rapid movements
concentric
muscle contraction shortens
isometric
contraction and no length change
eccentric
muscle lengthens and then contracts
homologous trait
shared ancestry
depressor mandibular and digastric functions
depress the lower jaw
diaphragm and phrenic nerve innervation
diaphragm is innervated by the phrenic nerve
name homology criteria and which one is the best and why
Attachment, function, innervation, and development (best)
common developmental origin correlates with ancestry (track as it migrates)
what does skeletal muscle arise from and what happens to the tissue
paraxial mesoderm, tissue becomes segmented into somites that further divide
myotomes
tissue that gives rise to the axial musculature
myomeres
arise directly from myotomes, keep the segmented structure
myosepta
connects neighboring myomere blocks that extend inwards and attach to the vertebral column
horizontal septa
runs along the length of the body and divides axial muscles into epaxial (dorsal) and hypaxial (ventral)
myomeres in fish
arranges in zig zag pattern that allows for each block to influence multiple axial segments
appendicular muscles in fish
muscle sheets extend to cover both sides of the fin, muscles act to pull the fins up and down, and in some groups, muscles are added for rotation
axial muscles in tetrapods
axial musculature is reduced and differentiated by region, legs take over locomotion functions, hypaxial muscles remain robust
appendicular muscles in tetrapods
expanded and complicated, limbs are more important for locomotion
appendicular muscles in running or walking (cursorial) animals
bunch their limbs near the body (center of mass), utilize long tendons to work the limbs, reduce weight of the limbs being moved (fewer muscles at extremes)
appendicular muscle in jumping animals
greatly expanded leg musculature, robust forelimb muscle taking the impact of landing (eccentric contraction to work against the ground)
axial musculature of birds
synsacrum stabilizes the posterior of the vertebral column; axial musculature is further reduced (more at the center of mass)
appendicular muscles of flying animals
forelimb muscles are greatly expanded but are much to keep limbs light, and tendons aid in the movement of the claws (not much muscle down there)
constrictor muscles and adductor muscles in fish
constrictor: outer sheet of muscle that straightens brachial arches
adductor: bend the brachial arches
antagonistic actions of muscles pump water over the gills
adductor mandibulae
enlarged version of the adductor muscle
preorbitals
muscles in sharks that aids adductor in closing the jaws
jaw adductor in tetrapods
remains massive muscle, attachments change to cranium instead of separate palatoquadrate bone
massester and temporalis in mammals
adductor separated into two muscles
massester is from zygomatic arch to masseteric fossa
temporalis is from the temporal bone to the coronoid process
hyoid arch
modified branchial arch, dorsal constrictors become mandibular depressors in tetrapods, ventral constrictors are differentiated (some become constrictor colli)
constrictor colli
source of mammalian facial muscles, alter feeding and communication
pectoral sliding
holds the pectoral girdle in place, a set of muscles that suspend the anterior portion of the body
How can muscle size be altered
muscle increase from exercise and muscle decrease from lack of activity and disease
exercise
whenever a muscle contracts
chronic overload
denotes sustained muscle activity used for training purposes
hypertrophy
term for the increase in tissue size/ mass due to stimuli
where does new muscle mass come from
most comes from muscle fibers getting larger, there are more myofilaments added and an increase in cross-sectional area
Proportion of fiber types in human untrained, long distance runners and sprinters
untrained individuals have an even number of slow and fast twitch
long distance have a larger proportion of slow twitch
Sprinters have a larger proportion of fast twitch
Is there evidence that support that muscle fiber type can change through training
there is experimental evidence against and in favor
what happened to mice in micogravity?
they had a decrease in slow twitch fibers and increase in fast twitch
what is the mechanism of fiber change
different types of myosin in the fibers
differences in the way ATP is broken down during contraction
differences in innervation
muscular atrophy
decrease in muscle mass due to a lack of activity
disuse of muscle results in down regulation of synthesis and activation of degradation pathway (wasted resource so breaks down)
also caused by disease
muscular dystrophy and types
cause gradual degradation of skeletal muscle
generally caused by mutation on X chromosome ( in males)
duchenne muscular dystrophy is most common and occurs most in males (20s)
becker is onset later in life with slower progression (40s)
steinert’s adult onset affects face and neck prevents relaxation
congenital early onset affects males and females
muscle bone interaction
during development, bone loading via repeated muscle action (contraction) helps bone develop
diseases like DMD that make muscle weaker have adverse effect on bone development
DMD effect on bone
in lab mice jaw of those with dystrophin deficiency were altered jaw forms from more than just diet
cause of muscular dystrophy
mutation in gene that codes for dystrophin, dystrophin is part of protein complex in cell membrane of muscle fiber
function of dystrophin
creates mechanical link between myofilaments making up the cell and surrounding matrix
aid in signaling to the muscle fibers
(provides structural support)
DMD escaper dogs
have dystrophin mutations that do not show symptoms
have increased expression in Jagged1 that is involved in cell repair, able to counteract lack of dystrophin
