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chapter 6


contractility the ability of skeletal muscle to shorten with force
excitability the capacity of skeletal muscle to respond to a stimulus
extensibility the ability to be stretched
elasticity the ability to go back to original resting form after being stretched
epimysium connective tissue surrounding the skeletal muscle
fascia another connective tissue located outside the epimysium
perimysium loose connective tissue that surrounds muscle fasciculi
fibers single muscle cells that make up the fasciculi
endomysium connective tissue that surrounds each fiber
myofibrils cytoplasm of each fiber
actin myofilaments thin myofilaments
myosin myofilaments thick myofilaments
sarcomeres actin and myosin myofilaments form highly ordered
resting membrane potential the charge difference across the membrane
action potential the brief reversal back of the charge
motor neurons nerve cells that carry action potentials to skeletal muscle fibers
neuromuscular junction or synapse each branch
motor unit a single motor neuron and all the skeletal muscle fibers it innervates
presynaptic terminal the enlarged nerve terminal
synaptic cleft the space between the presynaptic terminal and the muscle
postsynaptic terminal the muscle fibers
synaptic vesicles each presynaptic terminal
acetylcholine neurotransmitter
sliding filament mechanism the sliding of actin myofilaments past myosin myofilaments during contraction
muscle twitch a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscles
threshold which point the muscle fiber will contract maximally
lag phase the time between application of a stimulus to a motor neuron and the beginning of a contraction
relaxation phase the time which muscle relaxes
tetany where the muscle remains contracted without relaxing`
recruitment the increase in number of motor units being activated
creatine phosphate can store another high energy molecule
anaerobic respiration without oxygen
aerobic with oxygen
oxygen debt the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells
muscle fatigue results when atp is used during muscle contraction faster than it can be produced in the muscle cells
isometric the length of the muscle does not change, but the amount of tension increases during the contraction process
isotonic the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes
muscle tone refers to constant tension produced by muscles of the body for long periods of time
fast-twitch fibers contract quickly and fatigue quickly
slow-twitch fibers contract more slowly and are more resistant to fatigue
origin the most stationary end f the muscle
insertion the end of the muscle undergoing the greatest movement
belly the muscle between the origin and insertion
synergists muscles that work together to accomplish specific movements
antagonists muscles that work in opposition to one another
occipitofrontalis raises the eyebrows
orbicularis oculi closes the eyelids. "crows feet"
orbicularis oris puckers the lips
buccinator flattens the cheeks
zygomaticus smiling muscle
levator labii superioris sneering
depressor anguli oris frowning
matication chewing
sternocleidomatoid lateral neck muscle and prime mover
thoracic muscles that move the thorax
erector spinae group of muscles that keep the back straight and the body erect
trapezius rotates scapula
serratus anterior pulls scapula anteriorly
z line thin line of actin, starts and finished sarcomeres
I band on both sides of the z line, light area,actin
A band dark area of sarcomere
H zone between A zones
M line dark line down the center
deltoid attaches the humerus to the scapula and clavicle
triceps brachiii extends the forearms
biceps brachii flexes the forearms
brachioradialis flexes and supinates the forearm
flexor carpi flexes the wrist
flexor digitorum flexes the fingers
extensor digitorum extends the fingers
gluteus medius hip muscles
sartorius flexes the thigh
quadriceps femoris extends the legs, anterior thigh muscle
hamstring posterior thigh muscle, flexes the legs and extends the thigh
latissimus dorsi extends arm powerfully, rotates, and adducts the arms
pectoralis major adducts and flexes the arm
Created by: krmcent1