Chapter 4

Question 1

Muscular strength reflects the primary function of muscle: transformation of
X energy into X energy to generate force, perform work, and
produce movement

Answer 1

chemical
mechanical

Question 2

In addition, muscle tissues:
- stabilize body position
- regulate X volume
- generate X
- propel fluids and food
matter
- provides protection

Answer 2

organ
heat

Question 3

Muscular tissue consists of elongated cells called muscle fibers or X that
can use ATP to generate force

Answer 3

myocytes

Question 4

Based on location and certain structural and functional features, muscular tissue
is classified into three types:

Answer 4

skeletal, cardiac, and smooth

Question 5

Skeletan muscle tissue:
* It is striated: alternating light and dark protein bands (striations).
* Works mainly in a voluntary manner: activity consciously controlled by somatic nervous
system.
* Others skeletal muscles are controlled subconsciously. E.g. diaphragm while breathing.

Answer 5

ok

Question 6

Cardiac muscle tissue:
* Located only in the heart wall. Ture/false?

Answer 6

true

Question 7

Cardiac muscle tissue:
* It is non-striated, and its action is involuntary: natural pacemaker initiates each
contraction (autorhythmicity) and hormones and neurotransmitters adjust heart rate

true/false

Answer 7

false: it is striated

Question 8

Smooth muscle tissue:
* Located in the walls of hollow internal structures (blood vessels, airways, and most
organs in the abdominopelvic cavity). Also found in the skin, attached to hair follicles.
* Nonstriated.
* Action usually involuntary (true/false?)

Answer 8

true, but some have autorhythmicity

Question 9

Cardiac muscle and smooth muscle are regulated by autonomic/somatic nervous system and by
hormones released by endocrine glands.

Answer 9

autonomic

Question 10

FUNCTIONS OF MUSCLE TISSUE

1. producing body movements
2. stabilizing body positions
3. Storing and moving substances within the body. (E.g. Smooth muscle called X
   prevent outflow of the contents of a hollow organ)
4. Generating heat

Answer 10

sphincters

Question 11

PROPERTIES OF MUSCLE TISSUE

1. Electrical excitability
   ability to respond to certain stimuli by producing electrical: muscle action potentials. Two types of stimuli trigger them:

X electrical signals arising in the muscular tissue itself: heart’s
pacemaker.
X stimuli: neurotransmitters released by neurons, hormones distributed by
the blood or local changes in pH.

Answer 11

Autorhyhmic
Chemical

Question 12

PROPERTIES OF MUSCLE TISSUE

2. Contractility
3. Extensibility
4. Elasticity (ability of muscular tissue to return to its original length and shape)

Answer 12

k

Question 13

ANATOMY OF A SKELETAL MUSCLE FIBER

Skeletal muscle cells or muscle fibers are single contractile muscle cells that form
skeletal muscles.

• Each skeletal muscle fiber arises during embryonic development from the fusion of
  myoblasts (mesodermal cells), thus each mature skeletal muscle fiber has a X nuclei.
• The plasma membrane of a muscle cell is called X.
• The cytoplasm of a muscle fiber is called Xplasm.

Answer 13

hundred or
more

sarcolemma

sarco

Question 14

The sarcolemma contains numerous invaginations (pits) called X tubules.
* Transverse tubules (filled with interstitial fluid) tunnel in from the surface toward the
center of each muscle fiber: permits muscle action potentials quickly spreading
throughout the muscle fiber (excites all parts of the muscle fiber at essentially the
same instant).

Answer 14

transverse

Question 15

Sarcoplasm appears stuffed with little threads (like sausages): X, the contractile organelles of
skeletal muscle.

Answer 15

myofibrils

Question 16

The endoplasmic reticulum (called X reticulum) encircles each myofibril

Answer 16

sarcoplasmic

Question 17

The mitochondria lie in circles throughout the muscle fiber, next to proteins that use ATP
during contraction.

true/false

Answer 17

false, in rows (see p.13)

Question 18

• Dilated end sacs of the sarcoplasmic reticulum (x cisterns) butt against the T
  tubule from both sides.
• A transverse tubule and the two terminal cisterns on either side of it form a X

Answer 18

terminal
triad.

p.14

Question 19

In a relaxed muscle fiber, the sarcoplasmic reticulum stores X ions .
Release of X from the terminal cisterns of the sarcoplasmic reticulum triggers
muscle contraction.

Answer 19

calcium(Ca2+)

Question 20

• Within myofibrils are smaller protein structures: myo…
• Thin filaments are composed of the protein A.
• Thick filaments are composed of the protein B.
• A and B are the contractile proteins that generate force during muscle
  contractions.

Answer 20

filaments
A actin
B myosin

Question 21

There are two X filaments for every Y filament in the regions of filament
overlap.

Answer 21

X thin
Y thick

Question 22

The filaments inside a myofibril do not extend the entire length of a muscle fiber.
Instead, they are arranged in compartments called X which are the basic
functional units of a myofibril.

Answer 22

sarcomeres

Question 23

Narrow, plate-shaped regions of dense protein material called A separate one
sarcomere from the next. Thus, a sarcomere extends from one A to the next A

Answer 23

A Z discs

Question 24

The components of a sarcomere are organized into a variety of bands and zones:

• A band: darker middle part of the sarcomere. It extends the X
• I band: lighter (less dense area). It contains the rest of the X filaments but no
  A filaments.

Z disc passes through the center of each I band: narrow, plateshaped regions of dense protein material.

Answer 24

entire length of the
thick filaments.

X thin
A thick

Question 25

The alternating dark A bands and light I bands create the striations that can be seen in both myofibrils and in whole skeletal and cardiac muscle fibers. True/false

Answer 25

true

Question 26

Within the A band, different areas can be distinguised: * The center of the A band is the .... zone: contains thick but not thin filaments. At the middle of the H zone there is the .... line: contains supporting proteins that hold the thick filaments together. * Each end of the A band is a zone of overlap between thick and thin filaments. Is this zone still part of the sarcomere?

Answer 26

H: hart, is het midden van de A-band met alleen dikke filaments M: metsellijn, houdt de dikke filaments bij elkaar * Each end of the A band is a zone of overlap between thick and thin filaments: ook dit deel is nog onderdeel van het sarcomeer (zie p.20 of daarvoor)

Question 27

thick or thin filament: It is made up of 300 myosin molecules

Answer 27

thick

Question 28

thick or thin filament: It is mainly made up of actin, although it also contains troponin and tropomyosin: regulatory proteins that help turn contraction on and off

Answer 28

thin

Question 29

Each myosin molecule has a doubleheaded globular region attached to a long double-stranded helical chain. * The myosin tails form the axis of the thick filament, and the myosin heads project outward toward the surrounding thin filaments. thick or thin filament?

Answer 29

thick

Question 30

Actin molecules join together to form a filament coiled into a helix. * On each actin molecule there is a myosin binding site. thick/thin?

Answer 30

thin

Question 31

During muscle contraction, the muscle shortens but lengths of the thick and thin filaments do not change. true/false

Answer 31

true

Question 32

The thick and thin filaments slide past one another: sliding filament mechanism. * Muscle contraction occurs because myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the ... line

Answer 32

M

Question 33

Muscle contraction: the thin filaments slide inward and meet at the center of a sarcomere. They may even move so far inward that their ends overlap. As the thin filaments slide inward, the .. band and .. zone narrow and eventually disappear altogether when the muscle is maximally contracted.

Answer 33

I (alleen dunne filaments) H (hart)

Question 34

However, during contraction, the width of the .... band and the individual lengths of the thick and thin filaments remain unchanged. Since the thin filaments on each side of the sarcomere are attached to ...., when the thin filaments slide inward, the ..... come closer together. Does that make the sarcomere shorter?

Answer 34

A Z discs Z discs Yes the sarcomere shortens

Question 35

Shortening of the sarcomeres causes shortening of the whole muscle fiber, which in turn leads to shortening of the entire muscle. true/false

Answer 35

true

Question 36

Put in the right order of events: 1. The myosin binding sites located on the actin molecule are "free" 2. The sarcoplasmic reticulum releases Ca2+ into the sarcoplasm. 3. Ca2+ binds to troponin 4. The contraction cycle begins: the repeating sequence of events that causes the filaments to slide. 5. The troponin-Ca2+ complex binds to tropomyosin (which is blocking the actin-myosin binding sites), displacing it.

Answer 36

2. 3. 5. 1. 4.

Question 37

very important: A and B permits myosinactin binding (thick and thin filament attachment, respectively).

Answer 37

A Ca2+ B troponin

Question 38

The contraction cycle consists of four steps. Put in right order 1. Power stroke 2. Detachment of myosin from actin 3. ATP hydrolysis 4. Attachment of myosin to actin

Answer 38

3. ATP hydrolysis (ATP-> ADP) 4. Attachment of myosin to actin 1. Power stroke 2. Detachment of myosin from actin (bc of binding ATP) p.27

Question 39

Rigor mortis: after death, cellular membranes become leaky. Calcium ions leak out of the ... into the sarcoplasm and allow myosin heads to bind to actin. ATP synthesis ceases shortly after breathing stops, however, so the crossbridges cannot detach from actin.

Answer 39

sarcoplasmic reticulum

Question 40

ATP permits myosin attachment from actin (thick and thin filament). true/false

Answer 40

false: detachment

Question 41

A muscle fiber contracts in response to one or more muscle action potentials propagating along its sarcolemma and through its system of T tubules. * Muscle action potentials arise at the X junction: the synapse between a somatic motor neuron and a skeletal muscle fiber. (dus waar de neuron gwn de spier raakt)

Answer 41

neuromuscular

Question 42

Neural part: the end of the motor neuron (axon terminal) divides into a cluster of synaptic end bulbs which contain hundreds of synaptic vesicles filled with the neurotransmitter ..... * Muscular part: motor end plate of the muscle fiber (abundant in junctional folds) which contain high number of .....

Answer 42

acetylcholine acetylcholine receptors