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NAME:
STUDY GUIDE CH 9 PACKET # 1
MUSCLE PHYSIOLOGY
Use web site that goes with your text. Focus on the Get Body Smart program dealing with
muscle tissue physiology.
I.
OVERVIEW OF MUSCLE TISSUES:
A. Muscle Types:
Skeletal
Smooth
Cardiac
B.
Similarities: List at least 3 ways the above muscle types are similar
C.
Skeletal Muscle Characteristics: List at least 5 general characteristics of skeletal
muscle.
D.
Cardiac Muscle Characteristics:
muscle.
E.
Smooth Muscle Characteristics: List at least 4 general characteristics of cardiac
muscle.
List at least 5 general characteristics of cardiac
1
II.
F.
Functions: List 4 functions of the muscular system.
G.
Functional Characteristics of Muscle: Define each
1.
Excitability =
2.
Contractility =
3.
Extensibility =
4.
Elasticity =
SKELETAL MUSCLE
Introduction: Each skeletal muscle is an organ made up of skeletal muscle fibers,
connective tissue coverings, blood vessels, and nerve fibers.
A.
Gross Anatomy: 1. Label the parts of a typical skeletal muscle.
Myofilament (filament)
Myrofibril
Tendon
Perimysium
Endomysium
Epimysium
Myofiber (muscle fiber)
Sarcoplasmic reticulum
Sarcolemma
2
2. Define the following parts that are Connective Tissue Wrappings:
 endomysium.
 fascicles
 perimysium.
 epimysium.
 deep fascia.
 tendon
 aponeuroses
B.
Microscopic anatomy
Label Figure 1 and Figure 2 using the terms in the box.
A band
Actin
H zone
I band
M line
Myofiber (skeletal
muscle fiber or
muscle cell))
Myofibril
Myosin
Sarcomere
Titin
FIGURE 1
Z line
3
Figure 2 = Microscopic anatomy
2. Skeletal muscle tissue possesses striations. Define the parts below that contribute to
these striations.
 sarcolemma
 sarcoplasmic reticulum
 mitochondria
 t- tubules (transverse tubules)
 myofibrils
4
 protein filaments (cytoskeletal elements)
 actin
 myosin
 A-Band
 I-Band
 sarcomere
 Z-line
 M- line
 Titin
3. Protein filaments - Label the following diagram using the terms in the box.
Actin
Cross bridges
Myosin
Tropomyosin
Troponin
5
4. What is the function of each protein?
a. troponin
b. tropomyosin
c. myosin head (crossbridges)
II. SKELETAL MUSCLE CONTRATION:
1.
"Sliding Filament Theory":
a.
most popular theory concerning muscle contraction;
b.
first proposed by Hugh Huxley in 1954
c.
Briefly explain the sliding filament theory
2.
Changes in muscle cell during contraction:
following changes during a muscle contraction:
Explain how each of the
a.
The distance between the Z-lines of the sarcomeres
b.
The I-Bands (light bands)
c.
The A-Bands
6
3.
The Role of Calcium in Contraction Mechanism:
a.
In a resting muscle cell (i.e. in the absence of calcium ions), what
happens to the tropomyosin?



b. When calcium ions (Ca++) are present, explain what happens to both
tropomyosin and troponin.
3. Sarcoplasmic contents
a.Label the following diagram using the terms in the box.
Cisternae of
sarcoplasmic
reticulum
Mitochondria
Myofibrils
Myofilaments
Nucleus
Openings into
transverse tubules
Sacroplasmic
reticululm
Sarcolemma
Sarcoplasm
Transverse tubule
b. Give a function of each of the following when a muscle fiber contracts. Triad
 Cisternae of sarcoplasmic
reticulum
 Mitochondria
7
 Myofibrils
 Myofilaments
 Openings into transverse tubules
 Sacroplasmic reticululm
 Sarcolemma
 Sarcoplasm
 Transverse tubule
c. In class you will take notes as to what is occurring in each of the following steps of the
sliding filament theory.
8
9
CH. 9 MUSCLE PHYSIO.
STUDY GUIDE #2
NAME:
6. Stimulation of Skeletal Muscle Cell
a. In order for a skeletal muscle to contract, its fibers must first be stimulated by a
_______________________________________.
b. Definitions - Define these terms.:
1. Neuromuscular Junction (NMJ)
2. Motor Unit
3. Motor End-Plate
4. Neurotransmitter
c. Label the neuromuscular junction diagrams below using terms in box:
Muscle fiber
nucleus
Neuromuscu
lar junctions
Portion of
motor
neuron
Portions of
skeletal
muscle
10
Folded
sarcolemma
Mitochondria
Motor end plate
(used twice)
Motor neuron
fiber
Muscle fiber
nucleus
Myofibril of
muscle fiber
Nerve fiber
branches
d. Write the Sequence of Events in Skeletal Muscle Stimulation/Contraction (page287)
Synaptic cleft
Synaptic
vesicles
e. Write the Sequence of Events in the Relaxation Mechanism of a myofiber (page287)
`
11
The Energy for a Muscle Contraction
Complete the following statement and answer the following questions:
A. Introduction
1. The energy used to power the interaction between actin and myosin
comes from ______________.
2. ATP stored in skeletal muscle lasts only about six seconds
3. ATP must be ____________continuously if contraction is to continue
4. There are three pathways in which ATP is regenerated. What are these
3 pathways?
B. Coupled Reaction with Creatine Phosphate (CP) – Label the diagram using the
terms in the box.
ADP
ATP
Creatine
Creatine phosphate
Energy for muscle
contraction
Energy from cellular
respiration
When cellular ATP is
low
12
When cellular ATP is
high
C. Read the following information about Creatine phosphate Supplements used
by Athletes
The theory favoring the use of creatine as a supplement is that by increasing the supply of
creatine phosphate, ATP can be regenerated faster, thus speeding up recovery from bouts of
intense, short-term exercise. It does actually work in some people, although there seems to be a
genetic predisposition to effectiveness being necessary also. Creatine use is associated with
increase in muscle bulk, due to two factors: the increased amount of work allowed by quicker
regeneration of ATP and the fact that creatine in muscle cells binds water, thereby physically
increasing bulk. The latter effect is lost when the person stops taking creatine, and the bulk that
comes from water retention is lost quickly.
Creatine phosphate is produced naturally in the liver and kidneys, about 2 grams/day. Adults
can store about 120 to 184 grams of creatine in their muscles depending on what they eat. The
extra amounts of creatine in the body can maximize energy output for short-duration activities
and delay fatigue. A number of studies have demonstrated that taking creatine supplements
increases the rate of energy production in the muscle cells and allows muscle fibers to work
harder over a longer time period. The problem is that we do not know the long-term effects of
taking creatine, and studies have reported liver and kidney damage with daily doses of 40
grams or more. You should check with your physician before you start to take creatine
supplements.
D. Anaerobic Respiration
1. The steps of this type of respiration are called ______________.
2. Steps occur in the ______________of the cell.
3. This respiration results in production of ________and 2_________.
E. Aerobic Respiration –
1. The 2 steps of aerobic respiration are called __________and __________.
2. ___________is required for aerobic respiration.
3. The steps of aerobic respiration occur in the ____________of the cell.
4. Aerobic respiration results in the release of _______, ________and _________.
5. Oxygen is transported on blood hemoglobin and transferred to_
____________, an
oxygen binding pigment found in muscle
* Read box on page 289, which illustrates how a runner utilizes the sources discussed above.
Summarize this utilization below.
13
6. Fill in all * boxes below.
*
*
*
*
*
*
*
*
F. Oxygen Debt
1. What is meant by the Lactic acid threshold?
2. Under anaerobic conditions, _____________breaks down __________into
________________and converts it to_________________.
3. Lactic acid is carried by the blood to the______________.
4. Liver cells can convert lactic acid to_________________.
5. ___________________ reflects the amount of oxygen liver cells require to
convert the accumulated lactic acid into glucose, plus the amount the muscle cells
require to resynthesized ATP and creatine phosphate, and restore their original
concentrations.
G. Muscle fatigue
4.
Define muscle fatigue
14
H.
5.
If no oxygen is available in muscle cells to complete aerobic respiration,
pyruvic acid is converted to what compound?
6.
What effect does this compound (answer in # 2 above) have on the muscle?
7.
How can lactic acid soreness be dealt with?
8.
Explain why some persons are more prone to lactic acid soreness than others?
9.
A ______________is a painful condition in which a muscle undergoes a
sustained, involuntary contraction.
Heat Production From Muscle Contraction
A.
Almost half of the energy released during muscle contraction is lost to
____________which helps maintain our body temperature at_______.
B.
Excessive heat is lost through many negative feedback mechanisms
(discussed in chapter 1) including what mechanisms?
15
V.
MUSCULAR RESPONSES
A. Threshold Stimulus
a.
Define threshold stimulus
b.
A skeletal muscle fiber’s resting membrane potential must be
depolarized from –100mV to –70mv before an impulse begins;
Therefore the threshold stimulus is +30mV.
B. Recording a Muscle Contraction
a. What is a myogram? Define and sketch below.
b. What is a twitch?
c. What is the latent period?
d. What is the contraction period?
e. What is the relaxation period?
f. What is the refractory period?
16
C. All-or-Nothing Response
Muscle fibers (myofibers) exhibit an all-or-nothing response. Explain what
this means?
D. Staircase Effect (treppe)
a. Most muscle fiber contraction is “all-or-nothing”.
b. However a muscle fiber that has been inactive can be subjected to a series
of stimuli and:

the fiber undergoes a series of twitches with relaxation
between, and

the strength of each successive contraction increases slightly.
c. This phenomenon is small and brief and involves excess calcium in
sarcoplasm.
d. Treppe - muscle contracts more forcefully in response to same strength
stimulus. The inactive muscle undergoes a series of contractions. The
strength of each successive contraction increases until the optimum is met.
This is called the staircase phenomenon. This may be caused by an increase
in calcium ions in sarcoplasm or a change in temperature or pH.
Draw a graph of treppe below.
17
E. Summation:
a. When several stimuli are delivered in succession to a muscle fiber, it
cannot completely relax between contractions.
b. The individual twitches begin to combine and the muscle contraction
becomes sustained.

In a sustained contraction, the force of individual twitches
combines in a process called ______________________.

When the resulting sustained contraction lacks even slight
relaxation, it is called ___________________________.
Draw a graph of summation below.
Draw a graph of tetanus below.
F. Motor Units:
a. Write a definition of a motor unit:
b. Because the motor neuron branches into several motor nerve endings, it
can stimulate many skeletal muscles fibers simultaneously, which then
contract simultaneously.
c. The number of muscle fibers in a motor unit varies from 10-hundreds.
d. Sketch a motor unit.
G. Recruitment of Motor Units
a. Because a whole muscle is composed of many
_________________________controlled by many
different_________________________________,simultaneous
contraction of all units does not necessarily occur.
b. As the intensity of stimulation increases, recruitment of motor units
increases, until all contract simultaneously.
18
The brain combines two control mechanisms to regulate the force a single muscle produces. The first is
RECRUITMENT. The motor units that make up a muscle are not recruited in a random fashion. Motor
units are recruited according to the Size Principle. Smaller motor units (fewer muscle fibers) have a small
motor neuron and a low threshold for activation. These units are recruited first. As more force is
demanded by an activity, progressively larger motor units are recruited. This has great functional
significance. When requirements for force are low, but control demands are high (writing, playing the
piano) the ability to recruit only a few muscle fibers gives the possibility of fine control. As more force is
needed the impact of each new motor unit on total force production becomes greater. It is also important
to know that the smaller motor units are generally slow units, while the larger motor units are composed
of fast twitch fibers.
H. Muscle Tone
a. Even when a muscle is at rest, a certain amount of sustained contraction is
occurring in its fibers. This is called muscle tone.
b. Why is muscle tone important?
I. Types of Contractions:
a.
Isotonic contractions - Define and give examples

b.
Isometric contraction – Define and give examples
19
J. Fast and Slow Muscle Fibers
a. Muscle fibers vary in contraction speed (i.e. slow or fast twitch).
b. Define myoglobin:
c. Slow-Twitch Fibers are also called _____________.
1.Some important characteristics of slow –twitch are:
2. Examples of sports utilizing slow –twitch are:
d. Fast-twitch fibers are also called____________________.
1.Some important characteristics of fast –twitch are:
2. . Examples of sports utilizing fast –twitch are:
d.
Explain the difference between dark meat and white meat.
20
VI. Muscles Atropy and Hypertrophy
A.
Explain what atrophy is and why it occurs.
B.Explain what hypertrophy is and why it occurs.
1. So what really happens when weight lifters “bulk up”?
VII.The Aging Muscular System
What are some effects of aging on the muscles?
VIII. Muscular disorders:
A. myalgia- muscle pain
B. strain- overstretching of a muscle; no tear
C. sprain- overstretching and tear of a muscle
21
D. paralysis- loss of muscle movement/function; neuro-muscular abnormality
E. botulism- the bacteria Clostridium botulinum, from undercooked foods,
produces a toxin which prevents ACh release at the N-M Junction no muscle
stimulation/ no muscle movement paralysis death
F. muscle hypertrophy- increased #/diameter of myofilaments increased size;
no new myofibers produced
G. muscle atrophy- decreased # of mitochondria/decreased myofilament
diameterdecreased muscle size (up to less than 1/2 its normal size)
H. fibrosis- dead myofibers replaced by fibrous/dense CT
I. Muscular Dystrophy- a group of muscle-destroying ds.’s inherited
(almost Exclusively) as a sex-linked recessive trait
1. Duchenne’s MD: most common/serious MD- its possible etiology is lack
of Dystrophin: a protein that maintains the integrity of the sarcolemma
J. Myasthenia Gravis- extreme muscle fatigue Auto-immune ds.- one's own
body makes antibodies against one’s own ACh receptors
K. Class notes on nerve gas and its effects on the NMJ
L. A REMINDER: You are responsible for the disorders at the end of the chapter.
They will be in either multiple choice form or matching on the test.
22
CHAPTER 9: THE MUSCULAR SYSTEM
IX.
SMOOTH MUSCLE TISSUE:
A.
Introduction: The contraction mechanism of smooth muscle is similar to that of
skeletal muscle in that interaction occurs between actin and myosin, however the
transverse tubules and sarcoplasmic reticula are greatly reduced, and troponin is
absent.
B.
Two types:
1.
Multi-unit smooth muscle
a.
location:

irises of eyes

walls of blood vessels
b.
Contraction is rapid and vigorous (similar to skeletal muscle tissue).
2.
Visceral smooth muscle
a.
Location = the walls of hollow organs
b.
Contraction is slow and sustained.

Rhythmicity = pattern of repeated contractions;

Peristalsis = wave-like motion that helps push substances
through passageways.
c.
Structure:

random arrangement of actin and myosin filaments.

Two layers of muscle surround the passageway.
1.
inner circular layer
2.
outer longitudinal layer
C.
Contraction Mechanism:
1. A protein, calmodulin binds to calcium ions (no troponin) and activates the
contraction mechanism.
2. Most calcium diffuses in to smooth muscle cells from the extracellular fluid
(reduced SR).
3. Norepinephrine and acetylcholine are smooth muscle neurotransmitters.
4. Contraction is slow and sustained.
23
X. CARDIAC MUSCLE TISSUE:
Will be studied in greater detail in later in chapter on cardiovascular system
A.
Location:
1.
Only in heart.
B.
Anatomy:
1.
Striated uni-nuclear cells joined end-to-end forming a network.
a.
Cell junctions are called intercalated discs.

gap junctions
2.
Arrangement of actin and myosin not as organized as skeletal muscle.
3.
Contains sarcoplasmic reticula, transverse tubules, and numerous
mitochondria:
a.
Sarcoplasmin reticulum is less developed than SR in skeletal muscle
and stores much less calcium.
C.
Physiology
1.
Self-exciting tissue (i.e. “Pacemaker”);
2.
Rhythmic contractions (60-100 beats/minute);
3.
Involuntary, all-or-nothing contractions
a.
Function as a “syncyntium” (all-or-nothing)
4.
Pumps blood to:
a.
Lungs for oxygenation;
b.
Body for distribution of oxygen and nutrients.
24
CHAPTER 9: THE MUSCULAR SYSTEM
V.
SKELETAL MUSCLE ACTIONS
A.
B.
C.
D.
Introduction: Skeletal muscles generate a great variety of body movements. The
action of a muscle primarily depends upon the joint associated with it and the manner
in which the muscle is attached on either side of that joint.
Origin and Insertion: Recall that skeletal muscles are usually attached to a fixed
body part and a movable body part: See Fig 9.20, page 297.
1.
The origin of a muscle is its immovable (anchored) end.
2.
The insertion of a muscle is the movable end of a muscle.
*When a muscle contracts and shortens, its insertion is pulled toward its origin.
Review of Skeletal Muscle Actions:
1.
Flexion = decreasing the angle between 2 bones;
a.
Dorsiflexion = decreasing the angle between the foot and shin;
b.
Plantar flexion = pointing toes;
2.
Extension = increasing the angle between 2 bones;
3.
Abduction = moving a body part away from the midline;
4.
Adduction = moving a body part toward the midline;
5.
Circumduction = movement in a circular (cone-shaped) motion;
6.
Rotation = turning movement of a bone about its long axis; (i.e.atlas/axis);
7.
Supination = thumbs up;
8.
Pronation = thumbs down;
9.
Inversion = sole of foot in;
10.
Eversion = sole of foot out;
11.
Elevation = lifting a body part; (i.e. shoulder shrug);
12.
Depression = returning a body part to pre-elevated position.
FUNCTIONAL GROUPS OF MUSCLES
1.
Prime Mover (agonist) = the primary muscle responsible for a movement.

The biceps brachii in flexing the arm at the elbow,
2.
Antagonist(s) = the muscle(s) in opposition to the action of
the prime mover. The antagonist relaxes (or stretches) during the prime
movement.

The triceps brachii is the antagonist of the biceps brachii
when we flex the arm at the elbow.
3.
Synergist(s) = muscles that assist the prime mover.

The brachialis helps the biceps brachii during elbow flexion.
4.
Fixators = muscle groups that stabilize the origin of the prime
mover (i.e. hold it in place) so that the prime mover can act more
efficiently.

The scapula is the origin for many arm muscles, but it must be
held in place by fixator muscles in order to function in this way.
a.
serratus anterior
b.
pectoralis minor
25
CHAPTER 9: THE MUSCULAR SYSTEM
VI.
NAMING SKELETAL MUSCLES
CHARACTERISTIC
EXAMPLES
EXAMPLES IN HUMANS
Direction of fascicles relative
to midline
rectus = parallel
transverse = perpendicular
oblique = at 45o angle
Rectus abdominis
Transversus abdominis
External Oblique
Location (i.e. the bone or
body part that a muscle
covers)
frontal bone
tibia
Frontalis
Tibialis Anterior
Relative Size
maximus = largest
longus = longest
brevis = shortest
Gluteus maximus
Palmaris longus
Peroneus longus
Number of Origins (Heads)
biceps = 2 origins
triceps = 3 origins
Biceps brachii
Triceps brachii
Shape
deltoid = triangle
trapezius = trapezoid
serratus = saw-toothed
orbicularis = circular
Deltoid
Trapezius
Serratus anterior
Orbicularis oris
Location of Origin and/or
Insertion
origin = sternum
insertion = mastoid process
Sternocleidomastoid
Action of Muscle
flexion
extension
adduction
Flexor carpi radialis
Extensor digitorum
Adductor longus
26
CHAPTER 9: THE MUSCULAR SYSTEM
VII.
MAJOR SKELETAL MUSCLES (Keyed at the end of this outline)
Use the figures and tables on pages 298-325 to complete the following information.
If a muscle is starred (*), please include its origin and insertion. Also see References
Plates on pages 332-336.
A.
Muscles of Facial Expression:
See Fig 9.22 on page 298, and Table 9.3 on page 299.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Epicranius
Frontalis
Occipitalis
Orbicularis oris
Zygomaticus (*)
Buccinator
Platysma
Orbicularis oculi
B.
Muscles of Mastication: See Fig 9.22 on page 298, and Table 9.4 on page 300.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Masseter(*)
Temporalis
27
CHAPTER 9: THE MUSCULAR SYSTEM
VII.
Major Skeletal Muscles (continued)
C.
Muscle that moves the Head:
See Fig 9.23 on page 301, and Table 9.5 on page 302.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Sternocleidomastoid (*)
D.
Muscles that move the Pectoral Girdle:
See Fig 9.25 on page 304, Fig 9.26 on page 305, and Table 9.6 on page 304.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Trapezius (*)
Pectoralis minor
Serratus anterior
E.
Muscles that move the Arm (Humerus):
See Fig 9.25, page 304, Fig 9.26, page 305, and Table 9.7, page 306.
NAME OF MUSCLE
LOCATION/
DESCRIPTION
ACTION
Pectoralis major (*)
Latissimus dorsi
Deltoid
28
4.
Sequence of Events in Sliding of Actin filaments during Contraction:
See Fig 9.11, page 286.
When calcium ions are present, the myosin binding sites on actin are exposed:
a.
Cross-bridge attaches.

ATP breakdown provides energy to “cock” myosin head.

“Cocked” myosin head attaches to exposed binding
site on actin.
b.
Cross-bridge (myosin head) springs from cocked position and pulls
on actin filamant.
a.
Cross bridges break.

ATP binds to cross-bridge (but is not yet broken down)

Myosin heads are released from actin.
* As long as calcium ions and ATP are present, this walking continues until
the muscle fiber is fully contracted.
29
CHAPTER 9: THE MUSCULAR SYSTEM
II.
SKELETAL MUSCLE (continued).
E.
SKELETAL MUSCLE CONTRATION
5.
Stimulation of Skeletal Muscle Cell:
In order for a skeletal muscle to contract, its fibers must first be stimulated
by a motor neuron.
See Figure 9.9, page 283.
a.
Definitions:




6.
Neuromuscular Junction (NMJ) = the site where a motor
nerve fiber and a skeletal muscle fiber meet; (also called a
synapse or synaptic cleft)
Motor Unit = one motor neuron and many skeletal muscle
fibers; See Fig 9.17, page 292.
Motor End-Plate = the specific part of a skeletal muscle
fiber's sarcolemma directly beneath the NMJ.
Neurotransmitter = chemical substance released from a
motor end fiber, causing stimulation of the sarcolemma of
muscle fiber; acetylcholine (ACh).
Sequence of Events in Skeletal Muscle Stimulation/Contraction:
See Table 9.1, page 287.
a.
b.
c.
Introduction: The function of skeletal muscle is to move bones of the
skeleton under voluntary control. Contraction of a skeletal muscle
fiber is a complex interaction of several cellular and chemical
constituents. The final result is a movement whereby actin and
myosin filaments slide past one another. Accordingly, the muscle
fiber shortens and pulls on its attachments.
The process begins when a motor impulse is initiated by the brain,
travels down the spinal cord, into a motor neuron, which branches
into many motor nerve fibers/endings;

Each motor nerve fiber
extends to the motor end-plate of a skeletal muscle fiber
forming a neuromuscular junction (NMJ);
When the motor impulse reaches the end of the motor nerve
fiber/ending, the membrane is depolarized (-70mV to -55mV);

calcium ions rush into motor nerve fiber, and

neurotransmitter (Acetylcholine) is released
into the NMJ (via exocytosis).
30
CHAPTER 9: THE MUSCULAR SYSTEM
II.
SKELETAL MUSCLE (continued).
D.
SKELETAL MUSCLE CONTRATION
6.
Sequence of Events in Skeletal Muscle Stimulation/Contraction
b.
c.
d.

g.
h.
i.
j.
7.
Relaxation Mechanism:
a.
b.
Acetylcholinesterase is an enzyme present in the NMJ;
It immediately destroys acetylcholine, so the motor end-plate is no
longer stimulated (i.e. it cannot cause continuous muscle contraction).
Calcium ions are transported from sarcoplasm back into sarcoplasmic
reticulum.
Linkages between actin and myosin are broken.
The muscle fiber relaxes.
c.
d.
e.
8.
Acetylcholine diffuses across the NMJ & stimulates/depolarizes the
motor end-plate (sarcolemma) of a skeletal muscle fiber from 100mV to –70mV;
The muscle impulse travels over the surface of the skeletal muscle
fiber and deep into the muscle fiber by means of the transverse
tubules;
The muscle impulse reaches the sarcoplasmic reticulum, which
releases calcium ions into the sarcoplasm of the muscle fiber;
This is termed “excitation contraction coupling”.
Calcium binds to troponin, moving tropomyosin and exposing myosin
binding sites on actin filament;
Crossbridges (linkages) form between actin and myosin;
Actin filaments are pulled inward by myosin cross-bridges;
The muscle fiber shortens as contraction occurs.
Energy for Muscle Contraction:
a.
b.


Introduction: The energy used to power the interaction between actin
and myosin comes from ATP.
ATP stored in skeletal muscle lasts only about six seconds.
ATP must be regenerated continuously if contraction is to continue.
There are three pathways in which ATP is regenerated:
1.
Coupled Reaction with Creatine Phosphate (CP)
2.
Anaerobic Cellular Respiration
Aerobic Cellular Respiration
31
32