Muscle Anatomy

epimysium, perimysium, endomysium

3 layers of connective tissue that wrap around a muscle, its fascicles, and its individual muscle cells

Z line/disc

A dark thin protein band to which actin filaments are attached in a striated muscle fiber, marking the boundaries between adjacent sarcomeres.

motor unit

A motor neuron and all of the muscle fibers it innervates

muscle striations

A striped or striated pattern within myofibrils: alternating dark, thick filaments (A bands) and light, thin filaments (I bands)

perimysium

Connective tissue surrounding a fascicle

endomysium

Connective tissue surrounding an individual muscle fiber

tendon

Connects muscle to bone

Muscle Fiber Recruitment

Less force production: fewer or smaller motor units More force production: more or larger motor units

myosin

The contractile protein that makes up the thick filaments of muscle fibers

actin

The contractile protein that makes up the thin filaments of muscle fibers

fascia

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle. Fascia of multiple muscles connects; hence one tight muscle affects other ones.

muscle fiber

a single muscle cell

fascicle

bundle of muscle fibers - each muscle has multiple fascicles within it.

Brain location that contains upper motor neurons that initiate movement

cerebrum; frontal lobe; precentral gyrus (primary motor cortex)

epimysium

connective tissue that surrounds entire muscle and thickens into the tendons at either end of the muscle

A band of sarcomere

contains all of the thick myosin filaments plus any overlapping think actin filaments

sarcomeres

contractile units within myofibrils, the smallest contractile unit of a muscle

Cranial nerve that contain somatic motor fibers for facial expression

cranial nerve VII (facial)

cranial nerves that contain somatic motor fibers for eye muscle movement

oculomotor (cranial nerve III) trochlear (cranial nerve IV) abducens (cranial nerve VI)

sarcolemma

plasma/cell membrane of a muscle fiber/cell literally, "flesh husk"

myofibrils

protein structures that make up muscle fibers.

type of neurons that stimulate skeletal muscle

somatic motor neurons

motor neuron cell body location for skeletal muscles

spinal cord - ventral horn (referred to as "effector neuron" in this picture)

Aponeurosis

strong sheet of tissue that acts as a tendon to attach muscles to bone - one shown for example

H zone

thick filaments only (myosin)

I band

thin filaments only (actin)

cranial nerve that powers up the chewing muscles

trigeminal (cranial nerve V)