BIO120 MUSCLE BASICS

what is the primary function of muscles?

convert chemical energy into mechanical energy

the bulk of the body's muscle is made up of what?

striated muscles

sarcopenia

muscle mass loss, effect of aging

smooth muscles

found around viscera, regulates lumen size

cardiac muscles

circulates blood and deliver nutrients to cells

skeletal muscles

locomotion, heat generation via shivering

what are the characteristics of skeletal muscles?

voluntary movement, striated, multi nucleated, cylindrical, found in bundles

sarcolemma

cell membrane that protects the interior of the muscle cell/fiber. propagates action potenetial to t tubules

mitochondria

produces ATP for the muscle

what does the sarcolemma surround?

myofibrils, nuceli, and mitochondria

myofibrils

makes up the bulk of the muscle fiber/cell, has myosin and actin

actin

thin filament that is pulled by myosin during a muscle contraction

what are myofibrils made up of?

myofilaments: actin and myosin

myosin

thick filament that is pulled by actin towards the m line during a muscle contraction

how many thin filaments surround every thick filament in each myofibril?

6

how many thick filaments surround every thin filament in each myofibril?

3

what are the myosin and actin arranged into?

subunits called sarcomeres

sarcomeres

contractile unit of muscle. divided into different regions, zones, or bands

A band

both myosin and actin, overlapping

H zone

myosin heavy, only myosin

I band

only actin

M line

center of sarcomere, has thick filaments with some proteins

Z disc

border of sarcomere

what length do sarcomeres go by?

from Z disc to Z disc

sarcoplasmic reticulum (SR)

repository for calcium

t tubule

transverse tubule, propagates depolarization wave from sarcolemma to the SR

transverse tubule opening

allows action potential to get close to the SR

terminal cisternae

on either side of t tubule, stores and releases calcium

triad

2 terminal cisternae + 1 t tubule

what makes up a muscle cell/fiber?

bundles of myofibrils + its sarcolemma

endomysium

protective covering of muscle fibers/cells

fascicles

collagenic membranes that wrap bundles of sheathed muscle fibers/cells, surrounded by perimysium

perimysium

collagenic membrane covering fascicles

epimysium

most outer covering. CT overcoat of fasciles. bundles of epimysium are called muscles

tendons

form when epimysia blend. binds muscles to bones, pathway for nerves and blood vessels

aponeuroses

flat structures that form when epimysia blend

sarcoplasm

gel like substance that holds filaments and nucleus

glycogen granules

used by mitochondria to make ATP

nerve fiber with myelin sheath

propagates depolarization wave

synaptic vesicle

contrains acetylcholine

synaptic bulb

allows acetylcholine to enter the synaptic cleft

synaptic cleft

send neurotransmitters to receptors on sarcolemma

motor end plate/sarcolemma with receptors

takes a chemical reaction and converts it into a depolarization wave and sends it to the t tubules

motor unit

a motor neuron and all the muscle cells it stimulates

neuromuscular junction

junction between a neuron and muscle cells

axon terminals

branches of motor neuron axons

how can skeletal muscles be classified?

by direction, relative size, number of origins/heads, shape, and action

vocab for classifying skeletal muscles by direction

rectus is straight, transverse is at right angles, and oblique is inclined/slanted

vocab for classifying skeletal muscles by relative size

maximus is largest, minimus is smallest, longus is long, brevis is short

vocab for classifying skeletal muscles by number of origins/heads

biceps is 2 heads, triceps is 3 heads, and quadriceps is 4 heads

vocab for classifying skeletal muscles by shape

deltoid is triangular, trapezius is trapezoidal

vocab for classifying skeletal muscles by action

adductors, abductors, extensors, flexors

what is the diameter of muscle fibers

10 to 100 mu meters

what is the length of muscle fibers

6 to 25 mu meters

origin

stationary attachment of muscle

insertion

movable attachment of muscle

belly

thicker, middle region of muscle between origin and insertion

agonists

prime mover for particular movements

synergists

aids the agonists by reducing unnecessary movements

antagonists

produces the reverse movement

fixators

stabilize the origin of an agonist so that all the tension is exerted at the insertion

flexors

muscles thst contract a joint or limb, decreasing the angle between the origin and insertion

extensors

muscles that extends or straightens a limb, increasing the angle between the origin and insertion