Muscular System

skeletal muscle (striated)

most abundant muscle tissue, voluntary muscle, multinucleated

multinucleated

contain more than one nucleus per cell

visceral muscle (smooth)

found in the internal organs, involuntary muscle, smooth muscle cell only has one nucleus

cardiac muscle

found only in the heart, involuntary muscle, undergoes consistent rhythmic contractions, contains one to two nuclei per cell

sarcolemma

cell membrane of muscle cell

sarcoplasm

cytoplasm of muscle cell

sarcoplasmic reticulum

endoplasmic reticulum of muscle cell

sarcosomes

mitochondria of muscle cells

supraspinatus muscle (muscle group)

extensor muscle of the shoulder joint, muscles that attach the humerus to the neck and spine aid the supraspinatus in straightening the shoulder

infraspinatus muscle (muscle group)

flexes the shoulder joint in conjunction with muscles that attach the humerus to the spine or sternum

pectoral muscles

adduct the leg (pull it medially) by attaching the humerus to the sternum

trapezius muscles

abduct the leg (pull it laterally) by attaching the scapular spine to the dorsal spine

biceps brachii muscle

attaches the distal scapula to the radius, causing the shoulder to extend and the elbow to flex

triceps muscle

originates on the caudal edge of the scapula and proximal humerus and ends at the olecranon (elbow) of the ulna; when triceps muscles contract, the shoulder flexes and the elbow extends

gluteal muscles

abduct the limb and extend the hip joint (pull the leg back), originates on the pelvic bones and end at proximal femur, counteracted by several muscles on the medial surface of thigh that adduct

bicep femoris muscle & semitendinosus muscle & semimembranosus muscle

called the hamstrings, attach to the caudal aspects of the pelvis and to the tibia and calcaneus; when they contract, the hip joint extends, knee flexes, and ankle extends

quadriceps femoris muscle

opposes hamstring muscles, originated on both the pelvis and femur and ends at the patella; the contraction extends the knee joint and flexes the hip joint

gastrocnemius muscle

in the calf of the leg, extends the tarsal joint and flexes the digits

myofibers

densely packed groups of elongated cells that make up skeletal muscle

fascicles

bundles of myofibers

myofibrils

small structures that make up myofibers

myofilaments

actin (thin) & myosin (thick) proteins that make up myofibrils

actin

thin protein that makes up myofibrils

myosin

thick protein that makes up myofibrils

capillaries

keep the muscle supplied with oxygen and glucose that is needed to power the muscle contractions

sarcomere

segment of myofibrils, smallest contracting unit of a muscle

dense bodies

small globs of protein found only in smooth muscle, contains small amounts of actin and myosin, aids in contraction

neurotransmitters

substance secreted by involuntary nerve endings, stimulates or inhibits contraction

tone

smooth muscle has the ability to maintain a steady state of contraction, maintained by hormones

intercalated discs

connects cardiac muscle cells, have a low resistance to electrical current and aids in the conduction of electrical currents

syncytium

a multinuclear cell-like structure, describes cardiac muscle cells (closely bound and excitation signal travels easily from one cell to another)

extensor muscle

muscle that straightens a joint

flexor muscle

muscle that bends a joint