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Anatomy

Muscles

QuestionAnswer
the ability to shorten with force contractility
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
help to produce heat essential for maintenance of normal body temp. muscles
skeletal muscle is surrounded by a connective tissue sheath called epimysium
another connective tissue located outside the epimysium fascia
a muscle is composed of numerous visible bundles called muscle fasciculi (fascicle)
fiber is surrounded by connective tissue sheath called endomysium
cytoplasm of each fiber is filled with myofibrils
myofibrils consist of 2 major kinds of protein fibers actin myofilament myosin myofilament
actin & myosin myofilaments form highly ordered units called sarcomeres
thin myofilaments resembles 2 minute strands of pearls twisted together actin myofilament
thick myofilamenys resembles bundles of minute golf clubs myosin myofilament
the arrangement of actin & myosin give a banded appearance
on each side of Z line is a light area I band
the darker central region in each sarcomere is called A band
center of each sarcomere is another light area called H zone
myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called M line
each sarcomere extends from one Z line (disc) to another Z line (disc)
the charge difference across the membrane is called resting membrane potential
the brief reversal back of the charge is called action potenial
nerve cells that carry action potentials to skeletal muscle fibers motor neurons
each branch that connects to the muscle forms neuromusclular junction
near the center of the cell synapse
a single motor neuron & all the skeletal muscle fibers it innervates are called motor unit
enlarged nerve terminal presynaptic terminal
the space between the presynaptic terminal & the muscle cell synaptic cleft
the muscle fiber postsynaptic terminal
each presynaptic terminal contains synapyic vesicles
secretes a neurotransmitter called acetylcholine
the acetylcholine diffuses across the synaptic cleft & binds to receptor molecules in the muscle cell membrane called sarcolemma
acetylcholine released into the synaptic cleft between the neuron & muscle cell is rapidly broken down by enzymes acetylcholinesterase
occurs as actin & myosin myofilaments slide past one another causing the sarcomeres to shorten muscle contraction
the sliding of actin myofilaments past myosin myofilaments during contraction is called sliding filament mechanism
a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers muscle twitch
a muscle fiber will not respond to stimulus until that stimulus reaches a level called threshold
the muscle fiber will contract maximally this phenomenon is called all-or-none response
the time between application of a stimulus to a motor neuron & the beginning of a contraction lag phase
time of contraction contraction phase
time during which the muscles relaxes relaxation phase
where the muscle remains contracted without relaxing tetany
the increase in number of motor units being activated recruitment
needed for energy for muscle contraction ATP (adenosine triphosphate)
ATP is produced in the mitochondria
short-lived & unstable ATP (adenosine triphosphate)
ATP degenerates to the more stable called ADP (adenosine diphosphate)
it is necessary for muscle cells to constantly produce ATP; when at rest they can't stockpile ATP but they can store another high-energy molecule called creatine phosphate
without oxygen anaerobic respiration
with oxygen (more efficient) aerobic respiration
the amount of oxygen needed in chemical reactions to convert lactic acid to glucose & 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
(equal distance) the length of the muscle does not change, but the amount of tension increases during the contraction process isometric
(equal tension) the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes isotonic
constant tension produced by muscles of the body for long periods of time; keeps head up & back straight muscle tone
contract quickly & fatigue quickly; well adapted to perform anaerobic metabolism Ex. white meat fast-twitch fibers
contract more slowly 7 more resistant to fatigue; better suited fir aerobic metabolism Ex.dark meat slow-twitch fibers
the points of attachment of each muscle are called origin & insertion
at these attachment points the muscle is connected to the bone tendon
(head) the most stationary end of the muscle origin
the end of the muscle undergoing the greatest movement insertion
portion of the muscle between the origin & the insertion is called belly
muscles that work together to accomplish specific movements are called synergists
muscles that work in opposition to one another antagonists
among a group of synergists, if one muscle plays the major role in accomplishing the desired movement prime mover
most muscles have names that are descriptive, some are named according to their location, size, orientation of fibers, shape, origin, insertion, & function nomenclature
raises the eyebrows occipitofrontalis
closes eyelids orbicularis oculi
2 kissing muscles orbicularis oris & buccinator
puckers the lips orbicularis oris
flattens the cheeks " trumper"s muscles" buccinator
smiling muscle zygomaticus
sneering levator labii superoris
frowning depressor anguli oris
chewing mastication
chewing muscles temporalis & masseter
tongue muscles intrinsic & extrinsic
changes the shape of the tongue intrinsic
moves the tongue extrinsic
lateral neck; prime mover; rotates and extends the head strenocleidowastoid
twisted neck; wry neck torticollis
extends the forearm triceps brachii
flexes the forearm biceps brachii
flexes forearm brachialis
flexes and supinates the forearm brachioraialis
flexes the wrist flexor carpi
extends the wrist extensor carpi
flexes the fingers flexor digitorum
extends the fingers extensor digitorum
buttocks gluteus maximus
hip muscle & common injection site gluteus medius
extends the leg; anterior thigh muscle quadriceps femoris
"tailors muscle", flexes the thigh sartorius
flexes the leg and extends the thigh: posterior thigh muscle hamstring
form the calf muscle gastrocnemius and soleus
flex the foot and toes calcaneal tendon (Achilles tendon)
the lateral muscles of the leg peroneus
20 muscles within the foot intrinsic foot
19 hand muscles intrinsic hand muscles
located between the metacarpals; responsible for abduction & adduction of the fingers interossi
strong band of fibrous connective tissue that cover the flexor & extensor tendons & holds them in place retinaculum (bracelet)
group of muscles on each side of the back erector spine
elevate the ribs during inspiration external intercostals
contract during forced inspiration internal intercostals
tendinous area of the abdominal wall called linea alba
on each side of the linea alba is the rectus abdominis
cross the rectus abdominis at three or more locations tendinous inscriptions
rotates scapula trapezius
pulls scapula anteriorly serratus anterior
adducts and flexes the arm pectoralis major
medially rotates,adducts, & powerfully extends the arm 'swimmer muscles" latissimus dorsi
attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb deltoid
Created by: alexishodge21