Animal Physiology Chapter 10 Vocabulary

Front 1

Striated muscle

Back 1

Muscle characterized by sarcomeres aligned in register; includes skeletal and cardiac muscle.

Front 2

Smooth muscle

Back 2

Muscle without sarcomeres and hence without striations, whose myofilaments are nonuniformly distributed within small, mononucleated, spindle-shaped cells.

Front 3

Skeletal muscle

Back 3

The striated muscle whose neurogenic contraction is responsible for moving the bodies of animals.

Front 4

Cardiac muscle

Back 4

Heart muscle; individual fibers differ from skeletal muscle fibers in being small, elongated, tapered, and mononucleated. Includes noncontractile conducting fibers and contractile fibers.

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Muscle fibers

Back 5

A skeletal muscle cell.

Front 6

Myofibrils

Back 6

A longitudinal unit of a muscle fiber, made up of sarcomeres and surrounded by sarcoplasmic reticulum.

Front 7

Sarcomeres

Back 7

The contractile unit of a myofibril, bounded at each end by a Z disk.

Front 8

Myofilaments

Back 8

Each sarcomere contains two kinds of long, thin proteins called myofilaments arranged in a precise geometric pattern.

Front 9

Thin filaments

Back 9

A myofilament that contains actin and regulatory proteins such as troponin and tropomyosin.

Front 10

Actin

Back 10

A ubiquitous protein that participates in muscle contraction and other forms of cellular motility. G-actin is the globular monomer that polymerizes to form F-actin, the backbone of the thin filaments of muscle.

Front 11

Thick filaments

Back 11

A myofilament made primarily of myosin.

Front 12

Myosin

Back 12

A protein that makes up the thick filaments and cross-bridges in muscle fibers; it is also found in many other cell types and is associated with cellular motility.

Front 13

Cross-bridges

Back 13

Spirally arranged projections from myosin thick filaments that bind to sites on actin thin filaments during muscle contraction.

Front 14

Tropomyosin

Back 14

A long protein molecule located in the grooves between actin filaments of muscle; inhibits muscle contraction by blocking the binding of myosin cross-bridges to actin filaments.

Front 15

Troponin

Back 15

A calcium-binding complex of globular proteins associated with actin and tropomyosin in the thin filaments of muscle. When troponin binds Ca2+, it undergoes a conformational change, causing propomyosin to reveal myosin-binding sites on the actin filament.

Front 16

Length-tension relation

Back 16

Relation between the amount of overlap between actin and myosin filaments and the tension developed by an active sarcomere; also, the relation between the initial length of a whole muscle and the maximum tension it can produce during isometric contraction.

Front 17

Sliding-filament theory

Back 17

The theory that muscle sarcomeres shorten when actin thin filaments are actively pulled toward the middle of myosin thick filaments by the action of myosin crossbridges.

Front 18

Actomyosin

Back 18

A complex of muscle proteins formed when myosin cross-bridges bind to actin.

Front 19

Isometric contraction

Back 19

Contraction during which a muscle does not shorten significantly.

Front 20

Isotonic contraction

Back 20

Contraction in which the force generated remains constant while the muscle shortens.

Front 21

Excitation-contraction coupling

Back 21

In muscle fibers, the process by which electrical excitation of the plasma membrane leads to activation of the contractile process.

Front 22

Transverse tubule (T tubule)

Back 22

Tubules found in striated muscle fibers that are continuous with the plasma membrane, extend deep into the fiber, and are closely apposed to the terminal cisternae of the sarcoplasmic reticulum.

Front 23

Sarcoplasmic reticulum (SR)

Back 23

A smooth, membrane-limited network surrounding each myofibril. Calcium is stored in the SR and released as free Ca2+ during excitation-contraction coupling.

Front 24

Calsequestrin

Back 24

A calcium-binding protein that contributes to the regulation of [Ca2+] in muscles.

Front 25

Ryanodine receptors

Back 25

Ryanodine receptors are tetrameric proteins that span the SR membrane. Half of them are lined up with proteins in the T-tubule membrane, called dihydropyridine receptors for their ability to bind dihydropyridine drugs.

Front 26

Dihydrophridine receptors

Back 26

Ryanodine receptors are tetrameric proteins that span the SR membrane. Half of them are lined up with proteins in the T-tubule membrane, called dihydropyridine receptors for their ability to bind dihydropyridine drugs. The dihydropyridine receptors have been more precisely identified as a type of voltage-gated calcium channel, called an L-type channel, which explains how they can respond to APs traveling along the membrane of T tubules.

Front 27

Active state

Back 27

In muscle fibers, the condition in which myosin cross-bridges are attached to actin, causing the fibers to resist a force that would pull them apart.

Front 28

Summation of contraction

Back 28

The addition of muscle tension due to repeated rapid stimulation of muscle.

Front 29

Tonic fibers

Back 29

Muscle fibers that contract very slowly and do not produce twitches. Found in the postural muscles of amphibians, reptiles, and birds, as well as in the muscle spindles and extraocular muscles of mammals. Tonic fibers normally produce no action potentials, and action potentials are not required to spread excitation, because the innervating motor neuron runs the length of the muscle fiber and makes repeated synapses all along it.

Front 30

Twitch fibers (phasic fibers)

Back 30

The most common striated vertebrate skeletal muscle; produces an all-or-none twitch in response to an all-or-none action potential.

Front 31

Half-width

Back 31

The length of time during which a transient physiological variable is at half of its maximum value or greater.

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Motor pool

Back 32

The collection of motor neurons that innervate a particular muscle.

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Motor unit

Back 33

The unit of motor activity , consisting of a motor neuron and all of the muscle fibers it innervates.

Front 34

Pacemaker fibers

Back 34

An excitable cell or tissue that fires spontaneously and rhythmically.

Front 35

Myogenic

Back 35

Initiated by rhythmic electrical activity within a muscle cell or cells in the absence of neuronal input.

Front 36

Single-unit smooth muscles

Back 36

A smooth muscle in which individual fibers are coupled through gap junctions, allowing excitation to spread through the muscle independent of neuronal activity; contraction in these muscles is often myogenic, driven by internal pacemaker cells.

Front 37

Multi-unit smooth muscles

Back 37

A smooth muscle in which individual muscle fibers contract only when they receive excitatory input from neurons.

Front 38

Caldesmon

Back 38

A calcium-binding regulatory protein that plays a role in the “latch” mechanism of some smooth muscles.

Front 39

Calmodulin

Back 39

A troponin-like calcium-binding regulatory protein found in essentially all tissues.