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Objectives:
The students should be able to : -
1. recall the types of muscles
2. describe the functional characteristics of muscles
3. state the antagonistic muscle parts
4. describe the muscle fatigue and muscle tone
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The ability to move is an essential activity of the living human body
is made possible by
" the unique function of contractility " in muscles
What is contractility ?Contractility :
The ability or property of a substance,
especially of muscle, of shortening, or becoming reduced in size, or developing increased tension. ( Reference of this chapter )
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“ Movement ”
- is the main function of the muscular system
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Movement of the body ( locomotion )
Figure shows movement of
individual parts of the body
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Locomotion is movement or the ability to move from one place to another.
‘the muscles that are concerned with locomotion’
‘ Some people preferred walking to other forms of locomotion such as running, swimming, jumping ’
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Walking ( Locomotion )
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Jumping ( Locomotion )
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Related to the function of movement is the muscular system’s
second function:
- is the maintenance of posture and body position
Muscles
- often contract to hold the body still or in a particular position rather than to cause movement.
- hold up the body throughout the day without becoming tired.
Reference of this chapter
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Muscles help the body stay erect
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Muscles determine posture .
What is posture?
Posture is how you hold your body.“ how you hold yourself when you are moving, like when you are
walking, running, or bending over to pick up something.”
“ how you hold yourself when you are not moving, like when you are sitting, standing, or sleeping.”
Reference of this chapter
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Muscles maintain the Posture
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Examples of posture
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3. Another function related to movement
- the movement of the internal organs
- causes the movement of substances inside the body.
The cardiac and visceral muscles are primarily responsible for transporting
substances like blood or food from one part of the body to another.
Reference of this chapter
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Inaddition to playing a role in movement , muscle give
the body’s “characteristic form”.
The skeleton determines the over-all body shape, but the
muscle drape the skeleton produce the contours, perceive
as “ beautiful and graceful”.
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The contour and characteristic form of human body
Contour of
human body
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The skeleton of the human body
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Muscles drape the skeleton produce the contours
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A simplified image showing peristalsis
Muscles also perticipate the less obvious
movement of the internal organs.
Peristalsis is a radially symmetrical contraction and relaxation of
muscles that propagates in a wave down a tube, in an anterograde
direction.
In much of a digestive tract
such as the human gastrointestinal tract, smooth muscle tissue
contracts in sequence to produce a peristaltic wave, which propels a
ball of food (called a bolus while in the esophagus and upper
gastrointestinal tract and chyme in
the stomach) along the tract. Peristaltic movement comprises
relaxation of circular smooth muscles, then their contraction behind
the chewed material to keep it from moving backward, then
longitudinal contraction to push it forward.
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The final function of muscle tissue is the generation of body heat.
The body’s heat
The high metabolic rate of contracting muscle - -produces
"a great deal of waste heat"
Many small muscle contractions within the body produce
" our natural body heat“
Reference of this chapter
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Muscles
1. allow to move the body ( locomotion ) as well as move individual parts of the body
2. help the body stay erect and determine posture
3. also perticipate the less obvious movement of the internal organs
4. give the body’s “characteristic form”
5. drape the skeleton produce the contours,
perceive as “ beautiful and graceful”
6. produce most of the body’s heat
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Muscle Types in Mammals
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Muscle types in mammals
There are three types of muscle tissues.
1. Skeletal muscle
2. Cardiac muscle
3. Smooth muscle
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Muscle Types in Mammals
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Muscles and location
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1. Skeletal muscle
- Striped or striated muscle : often called voluntary muscle
( because its movement is voluntary ) .
- are also called somatic muscle.
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Organization of skeletal muscle
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Skeletal muscle cell (also called muscle fiber)
(A) These huge multinucleated cells form by the fusion of many muscle cell precursors, called myoblasts. In an adult human, a muscle cell is typically 50 μm in diameter and can be up to several centimeters long. https://www.ncbi.nlm.nih.gov/books/NBK26888/figure/A3066/?report=objectonly
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Microscopic structure of skeletal muscle fibers
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2. Cardiac muscle
- is a special type of striped muscle in the wall of heart ;
contraction is involuntary.
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The walls of the heart's chambers are composed almost entirely of muscle fibers.
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Muscle fiber
Cardiac muscle cells or fibers
Cardiac muscle cells
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Section of cardiac muscle fibers
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Microscopic structure of cardiac muscle fibers
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The heart wall
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3. Smooth muscle
- surrounds the walls of internal organs
such as gut , bladder , blood vessels and the uterus ;
contruction is involuntary.
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Microscopic structure of smooth muscle fibers
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Smooth muscle
Arrangement of smooth muscle in the walls of hollow organ.
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Cross section of intestine showing the longitudinal and circular layers smooth muscle
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Cross section of the blood vessel
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Cross section of the blood vessels
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Functional characteristics of muscles
All muscles ( Skeletal , Smooth and Cardiac ) have three
characteristics in common .
1. Contractibility
2. Extensibility
3. Elasticity
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Contractibility
“ a quality possessed by no other body tissue ”
a quality : to become smaller, narrower, shorter, etc.
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The sliding of actin along myosin shortens
the sarcomere, causing muscle contraction.
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When a muscle shorten or contracts
Reduces the distance between the parts of its contents
or
Reduces the space it surrounds
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Functional characteristics of muscle
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Contractibility , extensibility and elasticity of skeletal muscle
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When a muscle shorten or contracts
- reduces the distance between the parts of
its contents
Muscles can only contract.
They cannot actively extend, or lengthen
Fig : Contractibility , extensibility
and elasticity of skeletal muscle
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The contraction of skeletal muscles which connect a pair of
bone
brings the attachment points closer together
causes the bone to move
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Attachment
points
of biceps
Attachment
points
triceps
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Contractibility , extensibility and elasticity of cardiac muscle
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The walls of the heart's
chambers are composed
almost entirely of muscle
fibers.
Cardiac muscle is also an
involuntary type of muscle.
Its rhythmic, powerful
contractions force blood
out of the heart as it
beats.
Fig : Contractibility , extensibility
and elasticity of cardiac muscle
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Cardiac muscle stimulates itself to contract. The natural pacemaker of the heart is made of
cardiac muscle tissue that stimulates other cardiac muscle cells to contract.
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https://media.giphy.com/media/LZYul5Rtgr76E/source.gif
Network of tubules and sacs found within muscle
fibers
-Transverse tubules extend across the sarcoplasm
at right angles to the long axis of the muscle fiber
-Formed by inward extensions of the sarcolemma
-Membrane has ion pumps that continually
transport calcium ions inward from the
sarcoplasm
-Allow electrical impulses traveling along the
sarcolemma to move deeper into the cell
The human heart is a very efficient machine that beats on average about 80 times per minute for the entire lifespan of its owner. Direct
observations of rat cardiomyocytes, the individual muscle units of the heart, with a high-resolution light microscope have revealed that the
microtubules (wavy lines pictured here in red) buckle during each contraction, and act as load bearing springs that complement the contractile
apparatus. The microtubules help return the myocyte back to its original shape after contraction.
Contraction of cardiac muscle fiber
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When cardiac muscles contract
reduce the area in the chambers
pumping blood from the heart into the blood vessels
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Cardiac muscle contraction reduce the chambers of heart
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The area ( space )
of the chambers
Transverse section of the heart
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The area ( space )
of the right and
left ventricles
Transverse section of the heart
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Cardiac muscles contraction pumps the blood from the heart into the blood vessels
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Contractibility , extensibility and elasticity of smooth muscle
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Figure : contractibility , extensibility and elasticity of smooth muscle
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Contracted and uncontracted states of smooth muscle cell
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Smooth muscles
- surround blood vessels and intestine causing the
diameter of these tubes to decrease upon contraction
You cannot consciously control smooth muscle contraction, and your brain releases
hormones into your blood that control smooth muscle contraction.
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In this animation, the large
intestine is shown in a state of
peristalsis, which involves the
contraction and relaxation of
smooth muscle tissue to assist
the movement of food through
the digestive tract.
Intestinal Peristalsis
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A simplified image showing peristalsis
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Antagonistic muscle parts
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An antagonistic pair
The muscles of the body are arranged in pairs.
One produces movement in a single direction,
the other does so in the opposite direction.
This arrangement of muscles with opposite
action is known as “ an antagonistic pair ”.
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The opposite direction of antagonistic pairs
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The antagonistic muscle pair
One produces movement in a single direction,
the other does so in the opposite direction.
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Muscles
are attached to the bones by non elastic cords called
tendons
Muscles
attach to the bone of the skeleton
or
the bone of some other structure
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Most skeletal muscle is attached to bone on its ends by way of what we call tendons. As the
muscles contract, they exert force on the bones, which help to support and move our body
along with its appendages.
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https://books.google.com.mm/books?id=5LsaCgAAQBAJ&pg=PA121&lpg=PA121&dq=Skeletal+muscles+are+attached+to+bone+in+such+a+way
+as+to++bridge+the+Joints&source=bl&ots=0NWO4XR-hE&sig=tRhSUOX0e7QmPi-
S0VAoLh66yQ8&hl=en&sa=X&ved=0ahUKEwiorcuzkqLZAhVGw7wKHQlSC4kQ6AEIJTAA#v=onepage&q=Skeletal%20muscles%20are%20attac
hed%20to%20bone%20in%20such%20a%20way%20as%20to%20%20bridge%20the%20Joints&f=false
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Most skeletal muscle is attached to bone of some other structures by tendon such as eyeball.
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Bones are connected by joints.
Skeletal muscles
- are attached in such
a way as to bridge these Joints
So,
when skeletal muscle contracts
the bone to which it is attached
will move
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The muscle as a whole
- is surrounded by a thin sheet of connective tissue , epimysium
Within the muscle
perimysium surrounds and separates the bundles ( fascicles )
endomysium surrounds and separates the muscle cells( fibers )
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https://www.pearsonhighered.com/content/dam/region-
na/us/higher-ed/en/products-services/course-products/marieb-10e-
info/pdf/marieb-0321927028-chapter9.pdf
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https://giphy.com/gifs/anatomy-muscle-medicine-DIC01xaqHvx8k?utm_source=iframe&utm_medium=embed&utm_campaign=Embeds&utm_term=https%3A%2F%2Fwww.scientistcindy.com%2Fepithelial-tissues.html
https://www.scientistcindy.com/muscle-tissue.html
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Section of skeletal muscle
Skeletal muscle
- consists of many bundles
of muscles
A bundle of muscle cells
- is called a fascicle
A muscle cell
- consists of many myofibrils
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Each muscle fiber
- is wrapped by a layer of
loose connective tissue
called endomycium ( a
loose connective tissue ).
The endomycium
- not only lends physical
support to each muscle
fiber, but also supports the
small blood vessels and
nerve arborizations that
supply the tissue.
Examine fibers cut in long section with the low-power
objective. Individual skeletal muscke cells are called muscle
fibers.
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Skeletal striated muscle fibers in cross section showing the presence of several nuclei
(multinucleated cells) located in the cell periphery. Light microscope photomicrograph
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Skeletal Muscle
cross section ( CS )
long section ( LS )
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Muscle fibers never attach directly to
bone or cartilage
The attachment is always mediated
by connective tissue fibers
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Epimysium ( together with the perimysium
and endomysium layers of connective tissue )
generally extend beyond the fleshy part
of muscle, forming a thick rope-like tendon .
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a thick rope-like
tendon
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Origin and insertion
The origin
- is the part of a skeletal muscle
- is attached to a fixed structure or bone
- moves least during muscle contraction
The insertion
- is the other end of skeletal muscle
- is attached to a movable part ( bone )
- moves most during muscle contraction
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Attachment
points
of biceps
Attachment
points
of triceps
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Origin and Insertion of Biceps .
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A skeletal muscle attaches to bone (or
sometimes other muscles or tissues) at
two or more places. If the place is a
bone that remains immobile for an
action, the attachment is called an origin.
If the place is on the bone that moves
during the action, the attachment is
called an insertion.
The triceps brachii have four
points of attachment :
- one insertion on the ulna
- three origins
two on the humerus
and
one on the scapula
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Muscles always work in pairs
- The agonist is the primarily
responsible for producing a
movement
- The antagonist is the muscle
which relaxes while the
movement
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An antagonistic pair
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They never completely
relax – always a few
contracted fibres in
every muscle making
them slightly tense =
muscle tone.
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Before a prime mover can
cotract , the antagonist
must be equally relaxed.
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muscle physiology through viewing electromyograms (EMGs) of muscles. Pump up your gestural
greeting with extra muscular effort so you can visualize/hear the EMG better. Can you use your
two EMGs to verify which muscle is the agonist when you flex your arm? How about when you
extend your arm?
B) The antagonist muscle might show spiking as well, why do you think? Try to explore your arm
motions until you can completely relax the antagonist (no spikes).
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Fig. 24.14
Agonist- one muscle or group of muscles actively contract to produces
particular movement of a joint and is/are called a primary mover
or agonist. The agonist is the primarily responsible for producing
a movemet
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Extensors working and
contracting as agonist
Flexor working and
contracting as agonist
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Types of antagonistic movements
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Antagonistic Muscles and Action
Muscle ActionFlexor muscle - flexes or bends a joint
Extensor muscle - extends or straightens a joint
Adductor muscle - moves parts of the body towards the midline of the body
Abductor muscle - moves parts of the body away from the midline of the body
Levator muscle - raises the body parts
Depressor muscle - lowers the body parts
Pronator muscle - rotates the forearm so that the palm of the hand is turned
towards the body
Supinator muscle - rotates the forearm so that the palm of the hand is turned away
from the body
Protractor muscle - draws parts forward or out
Retractor muscle - retracts body parts
Contractor muscle - surrounds orifices ( as gill , anus ) to close them
( sphinctor muscle )
Dilator muscle - surrounds orifices ( as gill , anus ) to open them
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Directional terms
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Types of antagonistic movements
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Flexion and extension
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Flexion and extension
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Abduction and adduction
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https://basicmedicalkey.com/to-clinically-oriented-anatomy/
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Muscles and movements
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The action associated with kicking a
soccer ball involves a number of
levers working together. Consider
the kicking motion shown on the
right.
Protractor muscles and its movements
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Muscle fatigue
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Muscle fatigue
Muscle fatigue is the physiological inability to contract ,
caused by an accumulation of lactic acid in the muscle.
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During vigorous exercise,
Blood is unable to transport enough oxygen for the complete oxidation of glucose in the muscles.
In aerobic oxidation
Energy and pyruvic acid are released from sugar
The pyruvic acid is converted to carbon dioxide and waste.
However, in anaerobic oxidation ( insufficient oxygen )
the pyrubic acid is converted into lactic acid
Lactic acid normally leaves the muscle passing into blood stream
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https://www.pearsonhighered.com/content/dam/region-na/us/higher-ed/en/products-
services/course-products/marieb-10e-info/pdf/marieb-0321927028-chapter9.pdf
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Muscle fatigue ( reference )
- occurs when the muscles are no longer able to contract.
This condition is rare under most circumstances, because an individual will
stop their physical activity before true muscle fatigue sets in.
Marathon runners, however, will often collapse due to true muscle fatigue
since the extended period of physical activity severely depletes their energy
reserves.
( Reference )
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In order to recover from typical exercise and from muscle fatigue, oxygen
levels must be restored in the muscle.
To return oxygen levels to normal, the respiratory system is signaled to
increase the depth and rate of respiration causing rapid, deep breathing.
During the recovery process, creatine phosphate (PCr) and glycogen
stores are regenerated, and any accumulated lactic acid is removed from
the muscles.
( Reference )
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Muscle tone is accomplished by a complex interaction between the nervous
system and skeletal muscles that results in the activation of a few motor units.
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Muscle tone - does not produce active movement
- but it keeps the muscles firm , healthy and ready to
respond stimulation
Muscle tone can be seen when muscles are in a state of slight
tension and they are ready for action.
Skeletal muscle tone
- stabilize the joints and maintain posture
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