Download VOCABULARY Skeleton the bones of a human or an animal

VOCABULARY
Skeleton
the bones of a human or an animal considered as a
whole, together forming the framework of the body.
Axial skeleton
the skeleton of the head and trunk.
Appendicular skeleton
the part of the skeleton that includes the pectoral girdle
and the pelvic girdle and the upper and lower limbs
Periosteum
the normal investment of bone, consisting of a dense,
fibrous outer layer, to which muscles attach, and a
more delicate, inner layer capable of forming bone.
Compact bone
the compact noncancellous portion of bone that
consists largely of concentric lamellar osteons and
interstitial lamellae.
Cancellous bone
light, porous bone enclosing numerous large spaces
that give a honeycombed or spongy appearance. The
bone matrix, or framework, is organized into a threedimensional latticework of bony processes, called
trabeculae, arranged along lines of stress. The spaces
between are often filled with marrow
Bone marrow
the soft, fatty, vascular tissue that fills most bone
cavities and is the source of red blood cells and many
white blood cells.
Skeletal muscle
a usually voluntary muscle made up of elongated,
multinucleated, transversely striated muscle fibers,
having principally bony attachments. Also called
striated muscle.
Antagonistic pairs
a pair of muscles that work against each other
Muscle fiber
one of the structural cells of a muscle.
Myofibril
a contractile fibril of skeletal muscle, composed
mainly of actin and myosin.
Myofilament
a threadlike filament of actin or myosin that is a
component of a myofibril.
Sarcomere
any of the segments of myofibril in striated muscle
fibers.
Z line
Any of the dark thin protein bands to which actin
filaments are attached in a striated muscle fiber and
that mark the boundaries of adjoining contractile units.
I band
a pale band across a striated muscle fiber that consists
of actin, is much less birefringent topolarized light
than the A bands, is situated between two A bands, and
is bisected by a narrow dark-staining Z line called also
isotropic band
A band
one of the cross striations in striated muscle that
contain myosin filaments and appear dark under the
light microscope and light inpolarized light
H zone
a narrow and less dense zone of myosin filaments
bisecting the A band in striated muscle
Sliding-filament model
the process by which muscles contract
Tropomyosin
any of a group of muscle proteins that bind to
molecules of actin and troponin to regulate the
interaction of actin and myosin.
Troponin complex
a group of proteins that control the position of
tropomyosin on thin filaments
Actin
a globulin that is present in muscle plasma and that in
connection with myosin plays an important role in
muscle contraction.
Myosin
the principal contractile protein of muscle
Sarcoplasmic reticulum a system of membrane-bound tubules that surrounds
muscle fibrils, releasing calcium ions during
contraction and absorbing them during relaxation.
Motor neuron
a nerve cell that conducts impulses to a muscle, gland,
or other effector.
Motor unit
a motor neuron and the muscle fibers innervated by its
axon.
Action potential
the change in electrical potential that occurs between
the inside and outside of a nerve or muscle fiber when
it is stimulated, serving to transmit nerve signals.
Tetanus
a state of sustained contraction of a muscle during
which the muscle does not relax to its initial length or
tension, induced by a rapid succession of stimuli.
Cardiac muscle
a specialized form of striated muscle occurring in the
hearts of vertebrates.
Smooth muscle
involuntary muscle tissue in the walls of viscera and
blood vessels, consisting of nonstriated, spindleshaped cells.