1 Structure And Function of Body Sys Flashcards
musculoskeletal system of the human body consists of b____, j_____, m_______, and t______ configured to allow the great variety of movements characteristic of human activity.
bones, joints, muscles, and tendons
Muscles of the body do not act directly to exert force on the ground or other objects. Instead, they function by
pulling against bones that rotate about joints and transmit force to the environment.
approximately ## bones in the body,
206
axial skeleton consists of the
skull (cranium), vertebral column (vertebra C1 through the coccyx), ribs, and sternum.
The appendicular skeleton includes
the shoulder girdle; bones of the arms, wrists, and hands; the pelvic girdle; and the bones of the legs, ankles, and feet
Fibrous joints
(e.g., sutures of the skull) allow virtually no movement;
cartilaginous joints
(e.g., intervertebral disks) allow limited movement;
synovial joints
(e.g., elbow and knee) allow considerable movement. Sport and exercise movements occur mainly about the synovial joints, whose most important features are low friction and large range of motion.
Articulating bone ends are covered with
smooth hyaline cartilage and the entire joint is enclosed in a capsule filled with synovial fluid
Uniaxial joints,
such as the elbow, operate as hinges, essentially rotating about only one axis. The knee is often referred to as a hinge joint, but its axis of rotation actually changes throughout the joint range of motion.
Biaxial joints,
such as the ankle and wrist, allow movement about two perpendicular axes.
Multiaxial joints,
including the shoulder and hip ball-and-socket joints, allow movement about all three perpendicular axes that define space.
vertebral column is made up of
vertebral bones separated by flexible disks that allow movement to occur.
Each skeletal muscle is an organ that contains
muscle tissue, connective tissue, nerves, and blood vessels.
Fibrous connective tissue, or e______, covers the body’s more than 430 skeletal muscles.
epimysium, is contiguous with the tendons at the ends of the muscle
The tendon is attached to bone periosteum,.
a specialized connective tissue covering all bones;
any contraction of the muscle pulls on the tendon and, in turn, the bone
TRUE
Limb muscles have two attachments to bone:
Proximal (closer to trunk)
Distal (farther from the trunk)
The two attachments of trunk muscles are termed _______ (closer to the head) and _________ (closer to the feet).
superior, inferior
Muscle cells, often called muscle fibers, are
long (sometimes running the entire length of a muscle), cylin- drical cells 50 to 100 μm in diameter (about the diameter of a human hair).
Under the epimysium the muscle fibers are grouped in bundles (f______) that may consist of up to 150 fibers, with the bundles surrounded by connective tissue called p_________
fasciculi, perimysium.
Each muscle fiber is surrounded by connective tissue called e_________, which is encircled by and is contiguous with the fiber’s membrane, or s_________
endomysium, sarcolemma
The junction between a motor neuron (nerve cell) and the muscle fibers it innervates is called the motor end plate, or, more often, the
neuromuscular junction
A motor neuron and the muscle fibers it innervates are called a _____ ____. All the muscle fibers of a _____ ____ contract together when they are stimulated by the motor neuron.
motor unit
sarcoplasm, which is the cytoplasm of a muscle fiber, contains contractile components consisting of
protein filaments, other proteins, stored glycogen, fat particles, enzymes, and specialized organelles such as mitochondria and the sarcoplasmic reticulum.
myofibrils (1/100 the diameter of a hair) dominate the sarcoplasm. Myofibrils contain the apparatus that contracts the muscle cell, which consists primarily of two types of myofilament:
myosin and actin.
myosin filament consists of a (3)
globular head, a hinge point, and a fibrous tail.
The globular heads protrude away from the myosin filament at regular intervals, and a pair of myosin filaments forms a
cross- bridge, which interacts with actin.
The actin filaments (thin filaments about 6 nm in diameter) consist of two strands arranged in a double helix.
TRUE
A-band corresponds with the alignment of the
myosin filaments
I-band corresponds with the
areas in two adjacent sarcomeres that contain only
actin filaments
Z-line is in the middle of the I-band and appears as a thin, dark line running longitudinally through the I-band.
True
H-zone is the area in the center of the sarcomere where only ______ filaments are present.
myosin
Sarcoplasmic Reticulum
Parallel to and surrounding each myofibril is an intricate system of tubules which terminates as vesicles in the vicinity of the Z-lines. Calcium ions are stored in the vesicles.
T-tubules, or transverse tubules,
Run perpendicular to the sarcoplasmic reticulum and termi- nate in the vicinity of the Z-line between two vesicles.
_______ controls muscular contraction
Calcium (stored in vesicles)
