Chapter 10: Muscular Tissue

Question 1

THREE TYPES OF MUSCULAR TISSUE

Answer 1

 Skeletal muscle
 Cardiac muscle
 Smooth muscle

Question 2

FUNCTIONS OF MUSCULAR TISSUE

Answer 2

Producing body movements
 Stabilizing body positions
 Storing and mobilizing substances within the body
 Generating heat

Question 3

PROPERTIES OF MUSCULAR TISSUE

Answer 3

 Electrical excitability
 Contractility
 Extensibility
 Elasticity

Question 4

Narrow, plate-shaped regions of dense
material that separate sarcomere from the next

Answer 4

Z DISCS

Question 5

Dark, middle part of sarcomere that extends
entire length of thick filaments and includes those parts
of thin filaments that overlap thick filaments

Answer 5

A BAND –

Question 6

– Lighter, less dense area of sarcomere that
contains remainder of thin filaments but no thick
filaments. A Z disc passes through center of each __
band

Answer 6

I BAND

Question 7

Narrow region in center of each A band that
contains thick filaments but no thin filaments

Answer 7

H ZONE

Question 8

Region in center of H zone that contains
proteins that hold thick filaments together at center of
sarcomere

Answer 8

M LINE

Question 9

Proteins that generates force during muscle
contractions

Answer 9

SKELETAL MUSCLE FIBER PROTEINS
CONTRACTILE PROTEINS

Question 10

CP that makes up thick filament;
molecule consists of a tail and two myosin heads,
which binds to myosin binding sites on actin
molecules of thin filament during muscle
contraction.

Answer 10

 MYOSIN

Question 11

CP that makes up thin filament; each
actin molecule has a myosin-binding site
where myosin head of thick filament binds
during muscle contraction

Answer 11

ACTIN

Question 12

Proteins that help switch muscle contraction
process on and off

Answer 12

REGULATORY PROTEINS

Question 13

Regulatory protein that is a
component of thin filament; when skeletal fiber
muscle is relaxed, Tropomyosin covers
myosin-binding sites on actin molecules,
thereby preventing myosin from binding to
actin.

Answer 13

 TROPOMYOSIN

Question 14

Regulatory protein that is a
component of thin filament; When calcium
ions (Ca2+) bind to troponin, it changes
shape; this conformational change moves
tropomyosin away from myosin-binding sites
on actin molecules, and muscle contraction
subsequently begins as myosin binds to
actin.

Answer 14

TROPONIN

Question 15

 Proteins that keep thick and thin filaments of
myofibrils in proper alignment, give myofibrils
elasticity and extensibility, and link myofibrils to
sarcolemma and extracellular matrix

Answer 15

STRUCTURAL PROTEINS

Question 16

– Structural protein that connects Z disc
to M line of sarcomere, thereby helping to
stabilize thick filament position; can stretch and
then spring back unharmed, and thus accounts
for much of the elasticity and extensibility of
myofibrils

Answer 16

 TITIN –

Question 17

Structural protein of Z discs that
attaches to actin molecules of thin filaments
and to titin molecules

Answer 17

a-ACTININ

Question 18

– Structural protein that forms M
line of sarcomere; binds to titin molecules an d
connects adjacent thick filaments to one
another

Answer 18

MYOMESIN

Question 19

Structural protein that wraps
around entire length of each thin filament;
helps anchor thin filaments into Z discs and
regulate length of thin filaments during
development

Answer 19

NEBULIN

Question 20

Structural protein that links
thin filaments of sarcomere to integral
membrane proteins in sarcolemma, which are
attached in turn to proteins in connective tissue
matrix that surrounds muscle fibers; thought to
help reinforce sarcolemma and helps transmit
tension generated by sarcomeres to tendons.

Answer 20

DYSTROPHIN

Question 21

Organ made up of fascicles that contain muscle
fibers (cells), blood vessels, and nerves, wrapped
in epimysium

Answer 21

SKELETAL MUSCLE

Question 22

Bundle of muscle fibers wrapped in Perimysium

Answer 22

FASCICLE

Question 23

Long cylindrical cell covered by endomysium
and sarcolemma; contains sarcoplasm,
myofibrils, many peripherally located nuclei,
mitochondria, transverse tubules, sarcoplasmic
reticulum, and terminal cisterns. The fiber has a
striated appearance.

Answer 23

MUSCLE FIBER (CELL)

Question 24

Threadlike contractile elements within
sarcoplasm of muscle fiber that extend entire
length of fiber; composed of filaments

Answer 24

MYOFIBRIL

Question 25

Contractile proteins with myofibrils that are of two
types: thick filaments composed of myosin and
thin filamnets composed of actin, tropomyosin,
and troponin; sliding of thin filaments past thick
filaments produces muscle shortening

Answer 25

FILAMENTS (MYOFILAMENTS)

Question 26

Myosin pulls on actin, causing the thin filament to
slide inward
 Consequently, Z discs move toward each other and
the sarcomere shortens
 Thanks to the structural proteins, there is a
transmission of force throughout the entire muscle,
resulting in whole muscle contraction

Answer 26

The Sliding Filament Mechanism

Question 27

This concept connects the events of a muscle
action potential with the sliding filament mechanism

Answer 27

EXCITATION-CONTRACTION COUPLING

Question 28

 The force of a muscle contraction depends on the
length of the sarcomeres in a muscle prior to
contraction

Answer 28

LENGTH-TENSION RELATIONSHIP

Question 29

The events at the NMJ produce a muscle action
potential:
 Voltage-gated calcium channels in a neuron’s
synaptic end bulb open, resulting in an influx
of calcium. This causes exocytosis of a
neurotransmitter (NT) into the synaptic cleft
 NT binds to ligand-gated Na+ channels on the
motor endplate, which causes an influx of
Na+ into the muscle
 This depolarizes the muscle and results in
Ca2+ release from the sarcoplasmic
reticulum
 NT gets broken down by acetylcholinesterase

Answer 29

THE NEUROMUSCULAR JUNCTION (NMJ)

Question 30

Creatine kinase catalyzes the transfer of a
phosphate group from CP to ADP to rapidly
yield ATP

Answer 30

CREATINE PHOSPHATE

Question 31

When CP stores are depleted, glucose is
converted into pyruvic acid to generate ATP

Answer 31

ANAEROBIC GLYCOLYSIS

Question 32

 Under aerobic conditions, pyruvic acid can
enter the mitochondria and undergo a series
of oxygen-requiring reactions to generate
large amounts of ATP

Answer 32

 CELLULAR RESPIRATION

Question 33

is the inability to maintain force of
contraction after prolonged activity

Answer 33

MUSCLE FATIGUE

Question 34

The onset of fatigue is due to:

Answer 34

 Inadequate release of Ca2+ from SR
 Depletion of CP, oxygen, and nutrients
 Buildup of lactic acid and ADP
 Insufficient release of ACh at NMJ

Question 35

occurs due to changes in the central
nervous system and generally results in cessation
of exercise

Answer 35

CENTRAL FATIGUE

Question 36

Why do you continue to breathe heavily for a period of
time after stopping exercise?
 To “pay back” your oxygen debt!
The extra oxygen goes toward:
 Replenishing CP stores
 Converting lactate into pyruvate
 Reloading O2 onto myoglobin

Answer 36

OXYGEN CONSUMPTION AFTER EXERCISE

Question 37

The strength of a muscle contraction depends on how
many motor units are activated
 A motor unit consists of a somatic motor neuron
and the muscle fibers it innervates
 Activating only a few motor units will generally
result in a weak muscle contraction
 Activating many motor units will generally result
in a strong muscle contraction

Answer 37

CONTROL OF MUSCLE TENSION

Question 38

is the process in which the
number of active motor units increases
 Weakest motor units are recruited first, followed
by stronger motor units
 Motor units contract alternately to sustain
contractions for longer periods of time

Answer 38

MOTOR UNIT RECRUITMENT

Question 39

The brief contraction of all muscle fibers in a motor
unit in response to a single action potential
 Latent period
 Contraction period
 Relaxation period
 Refractory period

Answer 39

TWITCH CONTRACTION

Question 40

 Wave summation occurs when a second action
potential triggers muscle contraction before the
first contraction has finished
 Results in a stronger contraction
 Unfused tetanus
 Fused tetanus

Answer 40

FREQUENCY OF STIMULATION

Question 41

Even when at rest, a skeletal muscle exhibits a small
amount of tension, called tone
 Tone is established by the alternating, involuntary
activation of small groups of motor units in a
muscle

Answer 41

MUSCLE TONE

Question 42

tension is constant while muscle length
change

Answer 42

Isotonic

Question 43

• is great enough to overcome the
  resistance of the object to be moved, the
  muscle shortens and pulls on another
  structure, such as a tendon, to produce
  movement and to reduce the angle at a joint.

Answer 43

 Concentric

Question 44

• When the length of a muscle
  increases during a contraction

Answer 44

Eccentric

Question 45

– muscle contracts but does not change
length

Answer 45

Isometric –

Question 46

has the same arrangement as
skeletal muscle, but also has intercalated discs

Answer 46

Cardiac muscle

Question 47

 Intercalated discs contain desmosomes and gap
junctions that allow muscle action potentials to
spread from one muscle fiber to another
 Cardiac muscle cells have more mitochondria
and their contractions last 10 to 15 times longer
than skeletal muscle contraction

Answer 47

CARDIAC MUSCLE

Question 48

 Smooth muscle looks quite different than
cardiac and skeletal muscle. It is thick in the
middle, tapered on the ends, and is not striated
 It can be arranged as either single-unit or multiunit fibers
 Smooth muscle contractions start more slowly
and last longer than skeletal and cardiac muscle
contractions
 Smooth muscle can shorten and stretch to a
greater extent than skeletal and cardiac muscle
 Smooth muscle fibers shorten in response to
stretch!

Answer 48

SMOOTH MUSCLE

Question 49

Mature skeletal muscle fibers cannot undergo mitosis

Answer 49

REGENERATION OF MUSCLE TISSUE

Question 50

Enlargement of existing cells

Answer 50

Hypertrophy

Question 51

 An increase in the number of fibers

Answer 51

Hyperplasia

Question 52

 Stem cells found in association with blood
capillaries and small veins.

Answer 52

Smooth muscle and pericytes

Question 53

Most muscles are derived from ______ which
develops into somites

Answer 53

mesoderm

Question 54

Which, as the name suggests, forms the
skeletal muscles of the head, neck, and
limbs;

Answer 54

 Myotome

Question 55

Which forms the connective tissues,
including the dermis of the skin;

Answer 55

 Dermatome

Question 56

Which gives rise to the vertebrae

Answer 56

Sclerotome

Question 57

Between 30–50 years of age, about __% of our muscle
tissue is replaced by fibrous connective tissue and
adipose tissue. Between 50–80 years of age another
__% of our muscle tissue is replaced. Consequences
are:
 Muscle strength and flexibility decreases
 Reflexes slow
 Slow oxidative fiber numbers increase

Answer 57

10%, 40%