Chapter 12

Front 1

Skeletal muscle

Back 1

the type of muscle that is generally connected to bone

Front 2

Tendons

Back 2

cords of elastic connective tissue that transmit force from skeletal muscles to bones

Front 3

Sarcolemma

Back 3

a muscle fibres plasma membrane

Front 4

Myofibrils

Back 4

banded, rodlike elements that contain a muscle fibres contractile machinery

Front 5

Sarcoplasmic reticulum (SR)

Back 5

modified smooth endoplasmic reticulum in muscle cells that surrounds the myofibril and stores calcium

Front 6

Transverse tubules (T tubules)

Back 6

structures that transmit action potentials from the sarcolemma into the cells interior, triggering the release of calcium from the sarcoplasmic reticulum

Front 7

Thick filaments

Back 7

filaments composed of myosin that form part of the contractile machinery of a muscle cell

Front 8

Thin filaments

Back 8

filaments composed of actin that form part of the contractile machinery of a muscle cell; also contain troponin and tropomyosin in striated muscle cells

Front 9

Sarcomeres

Back 9

the fundamental repeating units that make up myofibrils

Front 10

Actin

Back 10

the most common microfilament; found in thin filaments in muscle fibres; provides structural support for microvilli

Front 11

Myosin

Back 11

the contractile protein found in thick filaments in striated muscle

Front 12

Tropomyosin

Back 12

one of the two regulatory proteins in striated muscle; a long fibrous molecule that acts to block myosin-binding sites ion thin filaments when a muscle is not contracting

Front 13

Troponin

Back 13

one of the two regulatory proteins in striated muscle; binds calcium reversibly and is responsible for starting the crossbridge cycle by moving tropomyosin out of its blocking position

Front 14

Crossbridges

Back 14

protrusions on both ends of the thick filament that bind to actin and are responsible for generating the motion that causes muscle contraction

Front 15

Sliding-filament mechanism

Back 15

process of muscle contraction whereby thick and thin filaments slide past each other

Front 16

Crossbridge cycle

Back 16

the mechanism that drives muscle contraction

Front 17

Excitation-contraction coupling

Back 17

in a muscle cell, the sequence of events that links the action potential to the contraction

Front 18

End-plate potential (EPP)

Back 18

a depolarization of the motor end plate of a skeletal muscle fibre caused by acetylcholine binding to nicotinic cholinergic receptors

Front 19

Motor unit

Back 19

a motor neuron and all the muscle fibres it innervates

Front 20

Twitch

Back 20

the mechanical response of a muscle to a single action potential

Front 21

Latent period

Back 21

the time between a stimulus and the beginning of a response; in muscle physiology, the lag of a few milliseconds that occurs between the action potential in a muscle and when the muscle first begins to generate force

Front 22

Isometric twitch

Back 22

a twitch during which a muscle generates force by does not shorten

Front 23

Isotonic twitch

Back 23

a twitch during which a muscle shortens and lifts a constant load

Front 24

Series elastic component

Back 24

connective tissue that is in series with the sarcomeres of skeletal muscle

Front 25

Contractile component

Back 25

thick and thin filaments of muscle; compared to elastic components

Front 26

Treppe

Back 26

increase in muscle tension with repeated twitch contractions

Front 27

Summation

Back 27

in neurophysiology, the adding together of graded potentials that occurs within a neuron;l in muscle physiology, the adding together of twitches that occurs when a muscle is stimulated at high frequency

Front 28

Tetanus

Back 28

in a muscle being stimulated at high frequency, the plateau phase of the contraction, during which the tension is relatively constant

Front 29

Recruitment

Back 29

an increase in the number of active neurons

Front 30

Size principle

Back 30

the correspondence between the size of motor units and the order of recruitment

Front 31

Creatine Phosphate

Back 31

a compound in muscle cells that can donate a high-energy phosphate to ADP to form ATP

Front 32

Myoglobin

Back 32

an oxygen-binding protein found in certain muscle cells

Front 33

Slow oxidative fibres

Back 33

muscle cells with slow ATPase activity and high oxidative capacity

Front 34

Fast glycolytic fibres

Back 34

type of skeletal muscle with high myosin ATPase activity and high glycolytic capacity

Front 35

Fatigue

Back 35

a decline in a muscles ability to maintain a constant force of contraction in the face of long-term, repetitive stimulation

Front 36

Muscle spindle

Back 36

sensory receptor within skeletal muscle that detects changes in the length of the muscle

Front 37

Golgi tendon organ

Back 37

sensory receptor located near the junction between muscle and tendon that detects changes in muscle tension

Front 38

Calmodulin

Back 38

cytosolic calcium-binding protein; modulates the activity of intracellular proteins

Front 39

Multi-unit smooth muscle

Back 39

smooth muscle lacking gap junctions; thus each fibre acts as a unit

Front 40

Single-unit smooth muscle

Back 40

smooth muscle with gap junctions linking the cells together so they function as a unit

Front 41

Pacemaker potentials

Back 41

spontaneous depolarization in the resting membrane potential