Muscular System - Anatomy & Physiology

orbicularis oris location

surrounds motth, closes and protrudes the lips

orbicularis oculi location

surrounds the eye

orbicularis oculi function

blinks and closes eye

orbicularis oris function

closes and protrudes the lips

frontalis function

raises eyebrows

frontalis location

forehead/frontal bone

temporalis location

temporal bone

temporalis function

closes the jaw

masseter location

large cheek muscle spanning from temporal bone to the mandible

masseter function

jaw closing/movement

zygomaticus location

cheek, mouth to cheekbone

zygomaticus function

raises corners of mouth, smiling

sternocleidomastoid location

lateral neck

sternocleidomastoid function

inferior rotation of head (bowing)

pectoralis major location

upper chest

pectoralis major function

adduct and flexes the humerus (arm)

deltoid location

covers shoulder

deltoid function

abducts humerus, raises the arm

bicep brachii (2) location

anterior humerus

bicep brachii (2) function

flexes the elbow

external oblique location

lateral abdomen

external oblique function

flexes and rotates the torso

rectus abdominis location

medial anterior abdomen (6 pack)

rectus abdominis function

anterior flexion of the torso (crunches) & posture

transverse abdominis location

lateral hip

transverse abdominis function

compresses the abdomen for posture

sartorius location

lays across the thigh, from lateral him to medial knee

sartorius function

crosses the leg “tailor’s muscle”, synergist

iliopsoas location

medial thigh/groin

iliopsoas function

flexes hip and adducts the leg

adductor group location

medial thigh/groin

adductor group function

adduct the legs together

rectus femoris location

anterior femur, runs across knee

rectus femoris function

extends knee, flexes the thigh at the hip

vastus lateralis location

lateral/anterior femur

vastus lateralis function

extends the knee

abductor group location

lateral thigh/hip

abductor group function

abduct legs

vastus medialis location

medial anterior femur

vastus medialis function

extends the knee

vastus intermedius location

intermediate femur, deep to the rectus femoris

vastus intermedius function

extends the knee

fibularis longus location

lateral lower leg, on fibula

fibularis longus function

plantar flexion and eversion of the foot

tibialis anterior location

shin

tibialis anterior function

dorsi flexion of the foot

trapezius location

posterior superior back and neck

trapezius function

extends head (look up) and shrugs shoulders

rear deltoid location

posterior shoulder

rear deltoid function

posterior abduction

latissimus deltoid location

lower back “v-shape”

latissimus deltoid function

adducts the arm

tricep brachii (3) location

posterior humerus

tricep brachii (3) function

extends elbow

gluteus maximus location

buttocks

gluteus maximus function

extends the hip for walking/climbing

gluteus medius location

superior hip, deep to gluteus maximus

gluteus medius function

posterior thigh abduction (donkey kick); synergist

biceps femoris location

posterior femur

biceps femoris function

flex the knee and extends the hip

semitendinosus location

posterior femur

semitendinosus function

flex the knee and extends the hip

semimembranosus location

posterior femur

semimembranosus function

flex the knee and extends the hip

gastrocnemius location

calf; posterior tibia

gastrocnemius function

plantar flexion of foot (tip-toes)

three types of muscle tissue

skeletal, cardiac, smooth

skeletal muscle tissue functions

move bones, generate heat (friction of contraction), maintain posture, facial expressions

epimysium

outermost connective tissue covering of a muscle; extends from the tendons that attack muscle to bone

fascicles

bundle of tens of thousands of individual muscle fibers (cells)

perimysium

surrounding of each fascicle

muscle fiber

actual muscle cells; each covered by an endomysium

myofibrils

repeated contractile units that compose muscle fiber

myofibril composition

light and dark bands that give appearance of striations; myofilaments

myofilaments

overlapping protein fibers that make up myofibrils

actin

thin (myo)filaments

myosin

thick (myo)filaments

sarcomere

place of filament overlap (actual contractile unit)

irritability

ability to receive and respond to stimulus (nerve impulse)

contractility

ability to contract in response to a nerve impulse

first step of nerve stimulus

impulse reaches end of neuron at neuromuscular junction

second step of nerve stimulus

neurotransmitter (acetylcholine) is secreted into synaptic cleft between dendrite and muscle cell

third step of nerve stimulus

ACh binds to receptors on the sarcolemma (endomysium), opends gated sodium channels

fourth step of nerve stimulus

Na+ rush into cell, building action potential

final step of nerve stimulus

action potential reaches threshold, impulse moves down the entire muscle fiber, causing contraction

action potential releases

Ca+ (calcium) from sarcoplasmic reticulum

Ca+ bind to

actin (thin) filaments, exposing binding sites for myosin

cross-bridges

formation of bound myosin filament heads to newly exposed actin filaments

shortening of myofibrils caused by

pulling of myosin heads towards center of sarcomere

ATP energy

required to recock myosin heads / reattach to actin filaments

relaxation occurs

when action potential subsides (calcium is reabsorbed, sarcomere returns to resting state

all or none

individual muscles will contract fully, never partially

graded contraction

varying of the number of muscle cells that contract and the rate at which they contract, depending on force needed

aerobic cellular respiration

assembling of ATP energy in mitochondria, requires oxygen

muscle fatigue

occurs when oxygen levels drop, causing cell resp. to slow and limiting ATP available for contraction

anaerobic respiration

breakdown of glucose w/o oxygen, increases lactic acid fermentation, causes cramping

lack of ATP effect

muscle failure

twitch

single muscle contraction

summing

successive contractions that lead to stronger and smoother contractions

tetanus

contraction & relaxation occurring so rapidly that no apparent relaxation occurs, results in cramping