A & P - College Network - Chapter 6 Muscle

Front 1

Absolute Refractory Period

Back 1

Early in the refractory period a period restimulation is effectively impossible.

Front 2

Acetylcholine

Back 2

A neurotransmitter. When actylcholine interacts with receptors on the muscle fiber, an action potential is initiated in muscle fiber membrane.

Front 3

Actin

Back 3

Protein component of the sarcomere. The thin polymerized filaments in the contractile machinery of all muscle.

Front 4

Action Potential

Back 4

Rapid, brief (several msec in duration) changes in the membrane potential of a neuron or muscle cell.

Front 5

Active Tension

Back 5

Can be determined by subtracting the predetermined passive tension curve from the total tension curve.

Front 6

Agonists

Back 6

Muscles that are responsible for a particular movement.

Front 7

All-or-Nothing Principle

Back 7

Each skeletal muscle fiber either contracts maximally or not at all.

Front 8

Alpha Actinin

Back 8

Attaches thin filaments to Z disc and determines their spacing.

Front 9

Aponeurosis

Back 9

The attachment of muscle to bone may be direct, or the connective tissue may extend beyond the muscle to form a cord-like tendon or a sheet-like aponeurosis.

Front 10

Ca++ Release Channels

Back 10

Parts of the voltage sensors that face interior of cell make a close connection with the second component of the endfeet, the Ca++ release channels in membrane of the sarcoplasmic reticulum. In unexcited state the voltage sensors block the Ca++ release channels. Excitation causes the voltage sensors to unblock the Ca++ release channels, releasing Ca++ into the surrounding myofibrils.

Front 11

CapZ

Back 11

Forms the Z discs.

Front 12

Contractile Machinery

Back 12

Consists of thin filaments composed of polymerized actin and thick filaments composed of aggregations of myosin

Front 13

Contractile Proteins

Back 13

Actin and myosin, protein components of the sarcomere.

Front 14

Convergent

Back 14

When the arrangement of the fascicles converge from broad origin toward a tendon so that the muscle is fan shaped.

Front 15

Creatine Phosphokinase

Back 15

The enzyme that catalysts the transfer of phosphate groups from CrP to ADP and from ATP to Cr

Front 16

Crossbridges

Back 16

Attachments made by myosin heads to actin binding sites that generate force during muscle contraction.

Front 17

Dense bodies

Back 17

Attaches some of the network of actin thin fillaments within the interior of smooth muscle cells. These bodies are the functional equivalent of the Z disc in striated muscle.

Front 18

Disuse Atrophy

Back 18

A dramatic loss of muscle mass due to long-term immobilization of a muscle.

Front 19

Endomysium

Back 19

A layer of connective tissue that wraps each individual muscle fiber.

Front 20

Epimysium

Back 20

A covering that surrounds all of the fascicles.

Front 21

Excitation-Contraction Coupling

Back 21

A process that will result in a detectable mechanical response of the muscle, as the action potential sweeps across the muscle surface.

Front 22

Fascicles

Back 22

Bundles of fibers enclosed in connective tissue sheaths of perimysium.

Front 23

Fast Twitch (Type II)

Back 23

Skeletal muscle fibers. Type II muscles expresses a myosin that cycles more rapidly than that expressed by Type I fibers.

Front 24

First Class Lever

Back 24

The fulcrum lies between the effort and the load so that moving the effort arm in one direction moves the load in the other direction.

Front 25

Graded Strength Principle

Back 25

The force delivered by a muscle may increase in proportion to the intensity of the stimulus delivered to its motor nerve, even though each motor nueron and each fiber obeys the all-or-nothing rule.

Front 26

Hyperplasia

Back 26

An increase in the number of muscle cells.

Front 27

Hypertrophy

Back 27

With conditioning skeletal muscles undergo adaptive changes that are visible mainly as an increase in size of the cells.

Front 28

Intercalated Discs

Back 28

Structures that make durable end-to-end connections between the plasma membranes of adjacent fibers in cardiac muscle.

Front 29

Isometric Contraction

Back 29

The muscle is not allowed to shorten, although tension does develop in the muscle.

Front 30

Isotonic Contraction

Back 30

The muscle is allowed to shorten and lift a load.

Front 31

Latent Period

Back 31

A measurable delay between muscle excitation and the onset of tension development or shortening in the muscle.

Front 32

Length-Tension Curve

Back 32

The curve shows that the active tension is maximal when the muscle is near its rest length.

Front 33

Leverage

Back 33

The central principle of leverage is effort x length of effort arm = load x length of load arm.

Front 34

Mechanical Advantage

Back 34

Leveraging using a small force operating over a large distance to move a heavy load a short distance.

Front 35

Mechanical Disadvantage

Back 35

Leverage allowing a strong force to move a light load rapidly through distance.

Front 36

Motor Unit

Back 36

A motor neuron, together with its muscle fibers.

Front 37

Multiunit Smooth Muscle

Back 37

Muscle not connected by gap junctions and typically is not spontaneously active. Such muscle is found in the iris of the eye and in the arrector pili muscles attached to individual hairs.

Front 38

Muscle Triad

Back 38

Formed by T tubules lying between two terminal cisternae.

Front 39

Myoblasts

Back 39

Stem cells that fuse to from skeletal muscle during embryonic development, with the result that the mature cells are long cylinders with multiple nuclei.

Front 40

Myofibrils

Back 40

Each fiber contains a number of parallel structures called myofibrils that constitute the actual contractile machinery of the fiber. Each myofibril is composed of a highly orderly arrangement of macromolecular filaments organized in repeating units called sarcomeres.

Front 41

Myoglobin

Back 41

An intracellular oxygen carrier.

Front 42

Myosin

Back 42

Protein component of sarcomere. Aggregations of thick filaments in the contractile machinery of all muscle.

Front 43

Myosin Light-Chain Kinase (MLCK)

Back 43

An enzyme that phosphorylates a portion of the myosin head.

Front 44

Nebulin

Back 44

Structural proteins associated with thin filaments; serves as a molecular yardstick that limits the length of thin filaments.

Front 45

Neuromuscular Junction

Back 45

The connection between a motor neuron and a skeletal muscle fiber.

Front 46

Nodal Fibers

Back 46

Contained within heart muscle that are spontaneously active and can serve as pacemakers for the entire heart.

Front 47

Operating Range

Back 47

The optimal range of contractile performance created by the leverage arrangements imposed by the skeleton that restricts muscle length.

Front 48

Origin

Back 48

Less movable attachment of muscle.

Front 49

Oxygen Debt

Back 49

A sustained increase in oxygen uptake that follows exercise. In order to incur an oxygen debt, the exercise must be of such intensity that it demands significant recruitment of Type IIb fibers.

Front 50

Pacemakers

Back 50

Some heart muscle fibers that are spontaneously active.

Front 51

Passive Tension

Back 51

The curve of passive tension of a muscle has a value of zero at rest length and rises as the length is made greater than rest length.

Front 52

Pennate

Back 52

The arrangement of muscle looks like a feather with the fascicles (the barbs of the feather) projecting at an angle from a tendon (the shaft of feather) that runs the whole length of the muscle.

Front 53

Pharmomechanical Route

Back 53

The second messages set in motion by autonomic transmitters may control release of Ca++ from the intracellular stores without involvement of a change in membrane potential.

Front 54

Pink Fibers

Back 54

Slowly fatiguing Type IIa fibers that contain some myoglobin.

Front 55

Power Stroke

Back 55

A rotation of the head that applies force to the thin filament.

Front 56

Red Fibers

Back 56

Type I fibers that are a red color due to myoglobin.

Front 57

Refractory Period

Back 57

Follows each action potential.

Front 58

Relative Refractory Period

Back 58

A period during which it is more difficult to restimulate the muscle.

Front 59

Rest Length

Back 59

Skeletal muscles that are removed from the body assume a standard length.

Front 60

Sarcomore

Back 60

The basic functional unit of the contractile machinery of striated muscle.

Front 61

Sarcoplasmic Reticulum (SR)

Back 61

The site within the cell where Ca++ is stored.

Front 62

Second Class Lever

Back 62

The load is attached between the effort and the fulcrum. The closer the load is to the fulcrum relative to the position of the effort, the greater the mechanical advantage.

Front 63

Series Elastic Elements

Back 63

Stretch components that are part of the contractile machinery.

Front 64

Shivering

Back 64

Involuntary contractions of the skeletal muscle initiated when the core body temperature falls below its central setpoint, resulting in an increase in heat production.

Front 65

Single-Unit Smooth Muscle

Back 65

A type of smooth muscle that contains excessive gap junction connections, making it possible for a large number of neighboring cells to contract simultaneously as if they were one unit. Such muscle is found in the GI tract and in blood vessels.

Front 66

Skeletal Muscle

Back 66

One of 3 types of muscle, these muscles are attached to the skeleton and controlled by the somatic motor branch of the nervous system.

Front 67

Sliding Filament Theory

Back 67

A theory of muscle contraction that states that each thick filament has one end overlapping slightly with the thin filaments of one Z disc and the other end among the thin filaments of the other Z disc. Shortening of the distance between hairbrushes occurs as the thick filaments pull both sets of thin filaments toward the center.

Front 68

Slow Twitch (Type I)

Back 68

Skeletal muscle fibers. Type I muscle expresses a myosin that cycles less rapidly than that expressed by Type II fibers.

Front 69

Somatic Branch

Back 69

The branch of motor system that controls skeletal muscle.

Front 70

Spatial Summation

Back 70

The force summation in muscle generated by the newly added motor units to increase force production summates with the force produced by the units already active.

Front 71

Striated

Back 71

Muscle that has a striped appearance due to being tightly organized sarcomores, as in skeletal muscle and cardiac muscle.

Front 72

Structural Proteins

Back 72

A protein component of sarcomores, consisting of nebulin, titn, CapZ, and alpha actinin.

Front 73

Temporal Summation

Back 73

A form of summation in muscle contraction: If the muscle is restimulated within a few tens of msec, the force or shortening generated in the second twitch can summate, or add on top of, the initial one, making a stepwise increase in tension or decrease in length.

Front 74

Terminal Cisterna

Back 74

A vessel formed by the SR, near the Z disc of each sarcomore.

Front 75

Tetanus

Back 75

A smooth rise in muscle tension or decrease in length resulting from the further reduction of the interval between successive impulses.

Front 76

Thin Filaments

Back 76

Double strands of polymerized actin.

Front 77

Third Class Lever

Back 77

Effort is applied between the load and the fulcrum. The load is moved rapidly, but with mechanical disadvantage--the disadvantage increases with the length of the load arm.

Front 78

Titin

Back 78

Connects the ends of thick filaments to Z disc to prevent sarcomores from falling apart; believed to be largely responsible for the series elastic properties of muscle.

Front 79

Transverse Tubules

Back 79

Finger-like projections of plasma membrane (T tubules) that project into the interior of the muscle fiber and pass close to each terminal cisterna.

Front 80

Voltage Sensors

Back 80

The protein components of the endfeet that sense the action potential passing along the T tubule.

Front 81

White Fibers

Back 81

Rapidly fatiguing Type IIb fibers contain some myoglobin.

Front 82

Z Discs

Back 82

Part of the contractile machinery of the muscle to which thin filaments are attached.