muscles are so important because they make up how much of the body’s mass
nearly half of the body’s mass
what can muscles transform chemical energy into
can transform energy in the cells, called ATP into directed mechanical energy which is capable of exerting force
whats the 3 types of muscle
cardiac smooth skeletal
what are muscles 4 main characteristics
exciteabli contractibility Extensibility Elasticity
Excitability
(responsiveness) ability to receive and respond to stimuli
Contractability
Ability to shorten forcibly when stimulated
Extensibility
ability to be stretched
Elasticity
ability to recoil to resting length
what is skeletal muscle
an organ made up of diff. tissues with three features: NERVE AND BLOOD SUPPLY, CONNECTIVE TISSUE SHEATHS, and ATTATCHMENTS
each muscle receives a nerve, artery, and vein. How are they consciously controlled
Consciously controlled skeletal muscle has nerves supplying every fiber to control activity
contracting muscle fibers require huge amounts of what two things?
oxygen and nutrients they also need waste products to be removed quickly
what are the two functional groups
Prime mover(agonist) Antagonist
Prime mover
aka Agonist Major responsibility for producing specific movement
Antagonist
Opposes or reverses particular movement
Prime mover and antagonist are located where
opposite sides of joint across which they act
Synergist
helps prime movers adds extra force to same movement reduces undesireable or unnecessary movement
Fixator
-Synergist that immobilizes bone or muscles origin -Gives prime mover stable base on which to act
Some muscle may be….
- prime mover of one movement - antagonist for diff. movement -synergist for third movement
whats the 7 ways muscles are named?
location, shape, size, direction of muscle pairs(fascicles), number of origins, location of attatchments Muscle action
muscle location
bone or body region w/ which muscle associated ex: temporalis
whats an ex. of a muscle named for the direction of muscle fibers
Rectus, transversus -All skeletal muscles consist of fascicles (bundles of fibers) -fibers arrangements vary, resulting in muscles w/ different shapes and functional capabilities -the most common patterns of arrangements
whats the 3 most common patterns of arrangement
Circular Congruent Parrallell Pennate
insertion
attatchment to movable bone
origin
attatchment to immovable or less movable bone
direct attachment
epimysium fused to periosteum of bone or perichondrium of cartilage
Indirect
connective tissue wrappings extend beyond muscle as ropelike tendon or sheet-like aponeurosis
describe Muscle Action
-when muscles are named for the movement they produced action words such as flexor,extensor, or abductor
what is each skeletal muscle and muscle fiber covered in
Connective tissue
what do connective tissue sheaths do
support cells and reinforce whole muscle
whats the order of sheaths from external to internal
epimysium perimysium Endomysium
Epimysium
Dense irregular connective tissue surrounding entire muscle; may bend with fascia
Perimysium
Fibrous connective tissue surrounding fascicles(groups of muscle fibers)
Endomysium
Fine areolar connective tissue surrounding each muscle fiber
Whats the characteristics of skeletal muscle
long cylindrical cells that contain multiple nuclei
Sarcolemma
muscle fiber plasma membrane
sarcoplasm
muscle fiber cytoplasm
what does skeletal muscle contain
contains many glycosomes for glycogen storage, as well as myoglobin for oxygen storage
what are the 3 modified organelles
Myofibrils
Sarcoplasmic reticulum
T Tubules
describe Myofibrils
densely packed, rodlike elements
- single muscle fiber can contain 1000s
- Accounts for 80% of muscle cell volume
What are myofibrils features
Striations
sarcomeres
myofilaments
Striations
stripes formed from repeating series of dark and light bands along length of each myofibril
what are A bands
a-dark regions
whats the h zone
lighter region in middle od dark A band
whats the M line
line of protein(myomesin) that bisects H zone vertically
whats the I band
Lighter regions -z disc(line)- coin-shaped sheet of proteins on midline of light
list 4 things about a sarcomere
-Smallest contractile unit (functional unit) of muscle fiber -Contains A band w/ half of an I band at each end -Consists of area between Z discs -Indivisual sarcomeres align end to end along myofribril, like boxcars of train -band
what are myofiliments
orderly arrangement of actin and myosin myofilaments within sarcomere
Actin
thin filaments -extend length of A and -Anchored to Z discs
Myosin
thick filaments -Extend length of A band -Connected M line -Sarcomere cross section shows hexagonal arrangement of one thick filament surrounded by 6 thin filaments
whats the molecular composition of myofilaments( in thick filaments)
thick filaments: composed of protein myosin that contains two heavy and four light polypeptide chains
what does the molecular composition of myofiliaments contain( in thick filaments)
-heavy chains intertwine to form myosin tail Light chains form myosin globular head
–During contraction, heads link thick and thin filaments together, forming cross bridges
in molecular composition of myofilaments, what are offset of each other (in thick filaments)
Myosins are offset from each other, resulting in staggered array of heads at different points along thick filament
In molecular composition of myofilaments, what are the thin filaments made up of
Composed of fibrous protein actin
what role does actin play in molecular composition of myofilaments in thin filaments
Actin is ploypeptide made up of kidney-shaped G actin (globular) subunits
what role does G actin play in molecular composition of myofilaments (in thin filaments)
G actin subunits bears active sites dor myosin head attatchement during contraction
-G actin subunits link together to form long, fibrous F actin(filamentous
what role does F actin play in molecular composition of thin filaments
Two F actin strands twist together to form a thin filaments
whats tropomyosin and troponin
regulatory proteins bound to actin
what does each thick filament consist of
many myosin molecules whose heads protrude at opposite ends of the filament
what does a thin filament consists of two strands of
actin subunits twisted into a helix plus two types of regulatory proteins (troponin and tropomyosin)