CHAPTER 08: MUSCLE PHYSIOLOGY

Question 1

A band

Answer 1

One of the dark bands that alternate with light (I) bands to create a striated appearance in a skeletal or cardiac muscle fiber when these fibers are viewed with a light microscope

Question 2

actin

Answer 2

The contractile protein that forms the backbone of the thin filaments in muscle fibers

Question 3

aerobic exercise

Answer 3

Exercise that can be supported by ATP formation accomplished by oxidative phosphorylation because adequate O2 is available to support the muscleUs modest energy demands; also called endurance-type exercise

Question 4

alpha motor neuron

Answer 4

A motor neuron that innervates ordinary skeletal muscle fibers

Question 5

anaerobic exercise

Answer 5

High-intensity exercise that can be supported by ATP formation accomplished by anaerobic glycolysis for brief periods of time when O2 delivery to a muscle is inadequate to support oxidative phosphorylation

Question 6

atrophy

Answer 6

Decrease in mass of an organ

Question 7

calmodulin

Answer 7

An intracellular Ca2 binding protein that, on activation by Ca2, induces a change in structure and function of another intracellular protein; especially important in smoothmuscle excitation-contraction coupling

Question 8

cardiac muscle

Answer 8

The specialized muscle found only in the heart

Question 9

contractile component

Answer 9

The sarcomere-containing myofibrils within a muscle fiber that are capable of shortening on excitation

Question 10

contractile proteins

Answer 10

Myosin and actin, whose interaction brings about shortening (contraction) of a muscle fiber

Question 11

cross bridges

Answer 11

The myosin moleculesU globular heads that protrude from a thick filament within a muscle fiber and interact with the actin molecules in the thin filaments to bring about shortening of the muscle fiber during contraction

Question 12

end-plate potential (EPP)

Answer 12

The graded receptor potential that occurs at the motor end plate of a skeletal muscle fiber in response to binding with acetylcholine

Question 13

excitation-contraction coupling

Answer 13

The series of events linking muscle excitation (the presence of an action potential) to muscle contraction (filament sliding and sarcomere shortening)

Question 14

excitatory postsynaptic potential (EPSP)

Answer 14

A small depolarization of the postsynaptic membrane in response to neurotransmitter binding, thereby bringing the membrane closer to threshold

Question 15

fatigue

Answer 15

Inability to maintain muscle tension at a given level despite sustained stimulation

Question 16

functional syncytium

Answer 16

A group of smooth or cardiac muscle cells that are interconnected by gap junctions and function electrically and mechanically as a single unit

Question 17

functional unit

Answer 17

The smallest component of an organ that can perform all the functions of the organ

Question 18

gamma motor neuron

Answer 18

A motor neuron that innervates the fibers of a muscle-spindle receptor

Question 19

glycolysis

Answer 19

A biochemical process that takes place in the cellUs cytosol and involves the breakdown of glucose into two pyruvic acid molecules

Question 20

gradation of contraction

Answer 20

Variable magnitudes of tension produced in a single whole muscle

Question 21

hyperplasia

Answer 21

An increase in the number of cells

Question 22

hypertrophy

Answer 22

Increase in the size of an organ as a result of an increase in the size of its cells

Question 23

I band

Answer 23

One of the light bands that alternate with dark (A) bands to create a striated appearance in a skeletal or cardiac muscle fiber when these fibers are viewed with a light microscope

Question 24

isometric contraction

Answer 24

A muscle contraction in which the development of tension occurs at constant muscle length

Question 25

isotonic contraction

Answer 25

A muscle contraction in which muscle tension remains constant as the muscle fiber changes length

Question 26

lactic acid

Answer 26

An end product formed from pyruvic acid during the anaerobic process of glycolysis

Question 27

lateral sacs

Answer 27

The expanded saclike regions of a muscle fiberUs sarcoplasmic reticulum; store and release calcium, which plays a key role in triggering muscle contraction

Question 28

length-tension relationship

Answer 28

The relationship between the length of a muscle fiber at the onset of contraction and the tension the fiber can achieve on a subsequent tetanic contraction

Question 29

motor activity

Answer 29

Movement of the body accomplished by contraction of skeletal muscles

Question 30

motor unit

Answer 30

One motor neuron plus all the muscle fibers it innervates

Question 31

motor unit recruitment

Answer 31

The progressive activation of a muscle fiberUs motor units to accomplish increasing gradations of contractile strength

Question 32

multiunit smooth muscle

Answer 32

A smooth muscle mass that consists of multiple discrete units that function independently of each other and that must be separately stimulated by autonomic nerves to contract

Question 33

muscle fiber

Answer 33

A single muscle cell, which is relatively long and cylindrical in shape

Question 34

myofibril

Answer 34

A specialized intracellular structure of muscle cells that contains the contractile apparatus

Question 35

myosin

Answer 35

The contractile protein that forms the thick filaments in muscle fibers

Question 36

optimal length

Answer 36

The length before the onset of contraction of a muscle fiber at which maximal force can be developed on a subsequent tetanic contraction

Question 37

oxidative phosphorylation

Answer 37

The entire sequence of mitochondrial biochemical reactions that uses oxygen to extract energy from the nutrients in food and transforms it into ATP, producing CO2 and H2O in the process

Question 38

regulatory proteins

Answer 38

Troponin and tropomyosin, which play a role in regulating muscle contraction by either covering or exposing the sites of interaction between the contractile proteins

Question 39

sarcomere

Answer 39

The functional unit of skeletal muscle; the area between two Z lines within a myofibril

Question 40

sarcoplasmic reticulum

Answer 40

A fine meshwork of interconnected tubules that surrounds a muscle fiberUs myofibrils; contains expanded lateral sacs, which store calcium that is released into the cytosol in response to a local action potential

Question 41

series-elastic component

Answer 41

The noncontractile portions of a skeletal muscle fiber, including the connective tissue and sarcoplasmic reticulum

Question 42

single-unit smooth muscle

Answer 42

The most abundant type of smooth muscle; made up of muscle fibers that are interconnected by gap junctions so that they become excited and contract as a unit; also known as visceral smooth muscle

Question 43

skeletal muscle

Answer 43

Striated muscle, which is attached to the skeleton and is responsible for movement of the bones in purposeful relation to one another; innervated by the somatic nervous system and under voluntary control

Question 44

slow-wave potentials

Answer 44

Self-excitable activity of an excitable cell in which its membrane potential undergoes gradually alternating depolarizing and hyperpolarizing swings

Question 45

smooth muscle

Answer 45

Involuntary muscle innervated by the autonomic nervous system and found in the walls of hollow organs and tubes

Question 46

stretch reflex

Answer 46

A monosynaptic reflex in which an afferent neuron originating at a stretch-detecting receptor in a skeletal muscle terminates directly on the efferent neuron supplying the same muscle to cause it to contract and counteract the stretch

Question 47

tension

Answer 47

The force produced during muscle contraction by shortening of the sarcomeres, resulting in stretching and tightening of the muscleUs elastic connective tissue and tendon, which transmit the tension to the bone to which the muscle is attached

Question 48

tetanus

Answer 48

A smooth, maximal muscle contraction that occurs when the fiber is stimulated so rapidly that it does not have a chance to relax at all between stimuli

Question 49

thick filaments

Answer 49

Specialized cytoskeletal structures within skeletal muscle that are made up of myosin molecules and interact with the thin filaments to accomplish shortening of the fiber during muscle contraction

Question 50

thin filaments

Answer 50

Specialized cytoskeletal structures within skeletal muscle that are made up of actin, tropomyosin, and troponin molecules and interact with the thick filaments to accomplish shortening of the fiber during muscle contraction

Question 51

transverse tubule (T tubule)

Answer 51

A perpendicular infolding of the surface membrane of a muscle fiber; rapidly spreads surface electric activity into the central portions of the muscle fiber

Question 52

tropomyosin

Answer 52

One of the regulatory proteins found in the thin filaments of muscle fibers

Question 53

troponin

Answer 53

One of the regulatory proteins found in the thin filaments of muscle fibers

Question 54

twitch

Answer 54

A brief, weak contraction that occurs in response to a single action potential in a muscle fiber

Question 55

twitch summation

Answer 55

The addition of two or more muscle twitches as a result of rapidly repetitive stimulation, resulting in greater tension in the fiber than that produced by a single action potential

Question 56

Z line

Answer 56

A flattened disclike cytoskeletal protein that connects the thin filaments of two adjoining sarcomeres