Chapter 9: Muscular System

Front 1

Functions of Muscular System

Back 1

Movement of body; Maintenance of posture; Respiration; Production of body heat; Communication
Constriction of organs and vessels; Contraction of heart

Front 2

Contractility

Back 2

Ability of muscle to shorten forcefully.

Front 3

Excitability

Back 3

Capacity of muscle to respond to a stimulus.Normally, the stimulus is from nerves that we consciously control.

Front 4

Extensibility

Back 4

Muscle can be stretched beyond its normal resting length and still be able to contract.

Front 5

Elasticity

Back 5

Ability of muscle to recoil to its original resting length after it has been stretched.

Front 6

Skeletal Muscle

Back 6

With its associated connective tissue, constitutes about 40% of the body's weight and is responsible for locomotion, facial expressions, posture, respiratory functions, and many other movements. The nervous system voluntarily, or consciously, controls the functions of the skeletal muscles.

Front 7

Smooth Muscle

Back 7

Most widely distributed type of muscle in the body. It is found in the walls of hollow organs and tube, in the interior of the eye, and in the walls of blood vessels, among other areas.

Front 8

Cardiac Muscle

Back 8

Found only in the heart, and its contractions provide the major force for moving blood through the circulatory system. Autorhythmic, they contract spontaneously at somewhat regular intervals, and nervous or hormonal stimulation is not always required to contract them.

Front 9

Skeletal Muscle Fibers

Back 9

Muscle cells

Front 10

Fasciculi

Back 10

Numerous visible bundles that make up a muscle.

Front 11

Perimyseum

Back 11

Heavier connective tissue layer that surrounds each fasciculus.

Front 12

Epimysium

Back 12

Layer of connective tissue that surrounds the entire muscle.

Front 13

Muscular Fascia

Back 13

Dense irregular collagenous connective tissue, located superficial to the epimysium, separates and compartmentalizes individual muscles or groups of muscles. I

Front 14

Motor Neurons

Back 14

Specialized nerve cells that stimulate muscles to contract. Their cell bodies are located in teh brain and spinal cord, and their axons extend to skeletal muscle fibers through nerves.

Front 15

Striated

Back 15

As seen in longitudinal section, alternating light and dark bands give the muscle fiber a striped appearance.

Front 16

Myoblasts

Back 16

Less mature, multinucleated cells that muscle fibers develop from. Multiple nuclei result from the fusion of myoblast precursor cells, not from the division of nuclei within myoblast. Converted to muscle fibers as contractile proteins accumulate within their cytoplasm. Shortly after the myoblasts form, nerves grow into the area and innervate the developing muscle fibers.

Front 17

Hypertrophy

Back 17

Enlargement of muscles after birth in children and adults results from an increase in the size of each muscle fiber, not from a substantial increase in the number of muscle fibers.

Front 18

Sarcolemma

Back 18

The plasma membrane of a muscle fiber.

Front 19

External Lamina

Back 19

Deeper and thinner of the two delicate connective tissue layers located just outside the sarcolemma.Consists mostly of reticular (collagen) fibers and is so thin that it cannot be distinguished from the sarcolemma when view under a light microscope.

Front 20

Endomysium

Back 20

Second layer of the two delicate connective tissue layers located just outside the sarcolemma. Consists mostly of reticular fibers, but is a much thicker layer.

Front 21

Transverse Tubules (T Tubules)

Back 21

Tubelike invaginations along the surface of the sarcolemma, at regular intervals along the muscle fiber and extending inward to a myofibril of striated muscles.

Front 22

Sarcoplasmic Reticulum

Back 22

Highly organized smooth endoplasmic reticulum. Associated with T Tubules.

Front 23

Sarcoplasm

Back 23

Other organelles, such as the numerous mitochondria and glycogen granules, are packed in the cell and constitute the cytoplasm.

Front 24

Myofibrils

Back 24

Bundles of protein filaments contained in the sarcoplasm. Extends from one end of the muscle fiber to the other. Contains two types of proteins.

Front 25

Myofilaments

Back 25

Extremely fin molecular thread helping form the myofibrils of muscle; thick myofilaments are formed of myosin, and thin myofilaments are formed of actin.

Front 26

Actin Myofilaments

Back 26

Thin myofilaments within the sarcomere; composed of two F actin molecules, tropomyosin, and troponin molecules.

Front 27

Myosin

Back 27

Thich myofilament of muscle fibrils; composed of myosin molecules.

Front 28

F Actin Molecule

Back 28

Coiled to form a double helix, which extends the length of the actin myofilament. Each F actin strand is a polymer of approx. 200 small, globular units called globular acting (G actin). Each G actin monomer has an active site, to which myosin molecules can bind during muscle contraction.

Front 29

Tropomyosin

Back 29

Elongated protein that winds along the groove of the F actin double helix. He molecule is sufficiently long to cover seven G actin active sites.

Front 30

Troponin

Back 30

Composed of three subunits: one that binds to actin, a second that binds to tropomyosin, and a third that has a binding site for Ca2+. Spaced between the ends of the tropomyosin and molecules in the groove between the F actin strands.