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Chapter 6 Muscles

the ability of skeletal muscle to shorten with force contractility
the capacity of skeletal muscle to respond to a stimulus excitability
the ability to be stretched extensibility
ability to recoil to their original resting length after they have been stretched elasticity
each skeletal muscle is surrounded by connective tissue sheath called epimysium
another connective tissue located outside the epimysium fascia
a muscle that is composed of numerous visible bundles is called fasciculi
fasciculi are surrounded by loose connective tissue called perimysium
fasciculi are composed of single muscle cells called fibers
each fiber is surrounded by a connective tissue sheath called endomysium
a threadlike structure that extends from one end of the fiber to the other myofibrils
cytoplasm of each fiber is filled with myofibrils
two major kinds of protein fibers actin and myosin myofilaments
thin myofilaments, resemble two minute strands of pearls twisted together actin myofilaments
thick myofilaments, resemble bundles of minute golf clubs myosin myofilments
actin and myosin myofilaments form highly ordered units called sarcomeres
basic structural and functional unity of the muscle sarcomeres
charge difference across the membrane is called resting membrane potential
brief reversal back of the charge is called action potential
nerve cells that carry action potentials to skeletal muscle fibers motor neurons
each branch that connects to the muscle and is near the center of a cell is neuromusclular junction or synapse
a single motor neuron and all the skeletal muscle fibers it innervates are called motor unit
enlarged nerve terminal is presynaptic terminal
space between the presynaptic terminal and the muscle cells is the synaptic cleft
muscle fiber is postsynaptic terminal
each persynaptic terminal contains synaptic vesicles
synaptic vesicles that secrete a neurotransmitter is called acetylcholine
sliding of actin myofilaments past myosin myofilaments during contraction is called sliding filaments mechanism
a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle contraction muscle twitch
muscle fiber will not respond to stimulus until that stimulus reaches a level called threshold
time between application of a stimulus to a motor neuron and the beginning of a contraction is the lag phase
time of contraction is the contraction phase
time during which the muscle relaxes is the relaxation phase
where the muscle remains contracted without relaxing tetany
increase in number of motor units being activated is called recruitment
what is needed for energy for muscle contraction ATP (adenosine triphospate)
rest they cant stockpile ATP but they can store another high-energy molecule called creatine phosphate
without oxygen; example lifting anaerobic respiration
with oxygen; example running aerobic respiration
what is 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 oxygen debt
results when ATP is used during muscle contraction faster than it can be produced in the muscle cells muscle fatigue
two types of muscle contractions isometric and isotonic
the length of the muscle does not change, but the amount of tension increases during the contraction process (equal distance) isometric
the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes (equal tension) isotonic
refers to constant tension produced by muscles of the body for long periods of time muscle tone
contract quickly and fatigue quickly fast- twitch fibers
contract more slowly and more resistant to fatigue slow- twitch fibers
define mastication chewing
define all four pairs of mastication muscles two pair of pterygoids, temporalis, and masseter
raises the eyebrows occipitofrontalis
closes the eyelids and causes "crows feet" wrinkles in the skin at the lateral corners of the eye orbicularis oculi
puckers the lips orbicularis oris
flattens the cheeks buccinator
smiling muscle zygomaticus
sneering levator labii superioris
frowning depressor anguli oris
change the shape of the tongue intrinsic tongue muscles
move the tongue extrinsic tongue muscle
lateral neck muscle and prime mover. rotates and abducts the head sternocleidomastoid
group of muscles on each side of the back. responsible for keeping the back straight and the body erect erector spinae
rotates scapula trapezius
pulls scapula anteriorly serratus anterior
adducts and flexes the arm pectoralis major
medially rotates, adducts, and powerfully extends the arm latissimus dorsi
attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb deltoid
extends the forearm. occupies the posterior compartment of the arm triceps brachii
flexes the forearm. occupies the anterior compartment of the arm biceps brachii
flexes forearm brachialis
flexes and supinates the forearm brachioradialis
strong band of fibrous connective tissue that covers the flexor and extensor tendons and holds them in place around the wrist so that they do not "bowstring" during muscle contraction retinaculum
flexes the wrist flexor carpi
extends the wrist extensor carpi
flexes the fingers flexor digitorum
extends the fingers extensor digitorum
buttocks. contributes most of the mass of the buttocks. gluteus maximus
Created by: kgedwards



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