Download Muscle System Lecture Notes JAShaw

CHAPTER 9 & 10
MUSCLE SYSTEM
IDENTIFICATION
Muscle Identification
Lecture Notes:
A.
Skeletal muscles produce movement by
pulling on insertion bones across joints.
B.
Bones serve as levers and joints as fulcrums
of these levers.
C.
Muscles that move a body part usually do
not lie over that part, but proximal to it.
D.
Skeletal muscles almost always act in groups
rather than singly--i.e. most movements produced by
coordinated action of several muscles
1.
prime mover-- major muscle producing
action
2.
synergists-- muscles that help produce an
action
3.
antagonists-- muscles that produce an
opposite action as compared to the prime
mover and synergists, must relax as prime
mover and synergists contract.
E.
Hints on how to deduce actions:
1.
Start by making yourself familiar with the names,
shapes, and general locations of the larger muscles.
2.
Try to deduce which bones the two ends of a muscle
attach to from your knowledge of the shape and general
location of the muscle.
3.
Make a guess as to which bones moves when the
muscle shortens.
a.
insertion--the bone that is moved by the muscle
b.
origin-- the bone that remains relatively stationary is
its origin.
4.
Deduce a muscle's actions by applying the
principle that its insertion moves toward its origin.
5.
To deduce which muscle produces a given action, start
by inferring which is the insertion bone.
F.
Names:
1.
action
a.
flexors--decrease the angle of a joint
b.
extensors-- increase the angle of a joint
c.
abductors-- move the bone away from midline
d.
adductors-- move the part toward the midline
e.
rotators-- cause a part to pivolt upon its axis
f.
levators-- raise a part
g.
depressors --lower a part
h.
sphincters-- reduce the size of an opening
i.
tensors-- tense a part, that is, make it more rigid
j.
supinators-- turn the hand palm upward
k.
pronators -- turn the hand palm downward
2.
direction of its fibers
a.
b.
c.
3.
transverse
oblique
rectus
location
a.
b.
frontalis
temporalis
4.
number of divisions composing a muscle
a.
b.
biceps
triceps
a.
b.
its shape
longus
brevis
5.
6.
points of attachment
a.
sternocleidomastoid
Frontalis
Epicranial aponeurosis
Orbicularis oculi
Temporalis
Nasalis
Zygomaticus
Occipitalis
Orbicularis oris
Trapezius
Buccinator
Masseter
Sternocleidomastoid
Sternocleidomastoid
Trapezius
Pectoralis major
Deltoid
Serratus anterior
Latissimus dorsi
Linea alba
Abdominal aponeurosis
External oblique
Internal oblique
Rectus abdominis
Transverse abdominis
Sternocleidomastoid
Trapezius
Deltoid
Infraspinatus
Teres major
Latissimus dorsi
External oblique
Lumbodorsal Fascia
Biceps brachii
Triceps brachii
Brachialis
Pronator teres
Flexor carpi ulnaris
Palmaris longus
Flexor carpi radialis
Brachioradialis
Deltoid
Biceps brachii
Triceps brachii
Brachioradialis
Brachialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digiorum
Anconeus
Extensor carpi ulnaris
Flexor carpi ulnaris
Gluteus medius
Iliopsoas
Tensor fasciae latae
Pectineus
Adductor longus
Adductor magnus
Gracillis
Gastrocnemius
Sartorius
Vastus lateralis
Rectus femoris
Vastus medialis
Fibularis longus
Extensor digitorum longus
Soleus
Tibialis anterior
Gluteus medius
Gracillis
Gluteus maximus
Adductor magnus
Tensor fasciae latae
Biceps femoris
Semitendinosus
Semimembranosus
Gastrocnemius
Achilles tendon
Soleus
3 major muscle
groups of the thigh
Left thigh
Biceps femoris
Semitendinosus
Semimembranosus
hamstrings
lateral
adductors
quadriceps
Adductor magnus
Rectus femoris
Adductor longus
anterior
Adductor brevis
Vastus laterialis
Vastus medialis
Vastus intermedius
Origins and Insertions
Masseter
Origin:_zygomatic arch______________________
Insertion:_mandible_________________________
Action:_closes jaw__________________________
Diaphragm
Origin:__bottom of ribs_____________________
Insertion:__central tendon__________________
Action:__causes inspiration________________
Deltoid
Origin:__clavicle & scapula_________________
Insertion:___humerus_________________________
Action:___abducts arm______________________
Hamstrings:
Biceps femoris
Origin:___ischium & femur__________________
Insertion:___fibula and tibia________________
Action:__extends thigh & flexes knee_______
Semitendinosus
Origin:__ischium_____________________________
Insertion:__tibia______________________________
Action:__extends thigh & flexes knee________
Semimembranosus
Origin:__ischium_____________________________
Insertion:__tibia______________________________
Action:__extends thigh & flexes knee________
Quadriceps:
Rectus Femoris
Origin:___iliac__________________________________
Insertion:__patella & tibia_____________________
Action:__extends knee & flexes thigh_________
Vastus lateralis
Origin:___femur_________________________________
Insertion:__patella & tibia_____________________
Action:__extends knee & flexes thigh_________
Vastus medialis
Origin:___femur_________________________________
Insertion:__patella & tibia_____________________
Action:__extends knee & flexes thigh_________
Vastus intermedius
Origin:___femur_________________________________
Insertion:__patella & tibia_____________________
Action:__extends knee & flexes thigh_________
Arm:
Tricps brachii
Origin:___scapula , humerus & humerus____
Insertion:__ulna________________
Action:__extends forearm___________
Biceps brachii
Origin:___scapula & scapula
Insertion:__radius_______________
Action:__flexes forearm___________
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MUSCLE SYSTEM
LECTURE NOTES
I. The Muscle System:
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A. functions:
1. movement by contraction
2. maintains posture
3. stabilizes joints
4. generates heat
B. review of muscle tissues:
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1. smooth
a. visceral
b. nonstriated
c. involuntary
d. functions in slow, sustained, long-lasting wave-like
contractions (tight-junctions)
2. cardiac
25
a. heart
b. striated
c. involuntary
d. functions in rapid, rhythmic contractions (intercalated
discs)
3. striated
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a. skeletal muscle , makes up the skeletal system
b. striated
c. voluntary
d. functions in rapid, strong contractions but tires easily
C. Gross structure: striated muscle
1. skeletal muscle organ composed of
a. muscle fibers (cells)
b. CT
c. blood vessels
d. nerve fibers
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2. CT wrappings:
a. endomysium- covers and surrounds the individual muscle
fibers
b. perimysium- bundles together several m.fibers into a unit
called a fascicle (fasciculi).
c. epimysium- covers and surrounds the fascicles and unites
the entire muscle organ.
d. deep fascia- binds muscles into functional groups and
extends to wrap other structures as well.
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Muscle Organ
epimysium
perimysium
myofiber
fascicle
endomysium
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3. attachments:
30
a. direct (fleshy)- the epimysium of the muscle is fused to the
periosteum of a bone.
direct attachment
b. indirect- the epimysium of the muscle extends beyond
the muscle into a tendon or an aponeurosis which then
anchors the muscle to a bone. more common
tendons
1) origin- stationary attachment
2) insertion- movable attachment
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D. Microscopic structure
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1. muscle cell = muscle fiber also known as a myofiber.
a. Myofibers are composed of smaller rod shaped units called
myofibrils.
b. muscle fibers are contained by the cell membrane which is
called the sarcolemma.
c. myofibrils are surrounded by the fluid cytoplasm called
sarcoplasm.
muscle fiber / myofiber
sarcoplasm
myofibril
sarcolemma
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2. each muscle fiber is an elongated cell
(cylindrical) that is multi-nucleated with the nuclei
found on the periphery of the fiber.
multi-nucleated cells
peripheral nuclei
34
3. each muscle fiber contains numerous (100's1000's) myofibrils which contain the protein
filaments that show distinct banding we call
striations.
myofibrils
striations
light & dark banding
35
a. composed of 2 protein filaments--myofilaments
36
1) actin myofilament (actually composed of actin,
tropomysin and troponin) (thin)
a) troponin-prevents bonds between actin and myosin
filaments.
b) tropomysin-provides a straight shape for the actin filament.
actin
tropomysin
troponin
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2) myosin myofilament (thick) protein filaments
Myosin molecules have a rodlike tail ending in
two round “ heads”. These are usually called
“cross bridges” because they will form a chemical
bond with the actin myofilament.
38
3) structure of the striations;
39
a) dark bands are called A-bands
b) in the middle of the A-band is a lighter band --the H-band
c) in the middle of the H-band there is a darker line known as
the M-line.
d) on each side of the A-band there is a light band referred to
as the I-band
e) the I-band is crossed by a darker band; the Z-band or Z-line
f) the area between 2 Z-lines composes a sarcomere; the unit
of structure and function
Z line
sarcomere
Z line
M
40
I
H
A
I
41
b. during
contraction the
filaments (actin and
myosin) slide over
each other-shortening the
muscle fiber.
1) there are "cross bridges" that reach from the
myosin to the actin in order for the sliding to
occur
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cross bridges
4. T-system- a system of tubules that extend transversely
into the sarcoplasm, they enter the sarcoplasm at the level
of the z-line. T- tubules are part of the sarcolemma and
allow the for communication to occur with the inside of
the cell.
T-tu
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Z lines
5. SR--sarcoplasmic
reticulum--another
system of tubules,
separate from the Ttubules and differs from
it in that the tubules of
the sarcoplasmic
reticulum run parallel to
the muscle fiber and
end in closed sacs at the
ends of the sarcomere,
above and below each Zline. Ca ++ ions are
held in the SR.
SR
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a. triad- the term applies to a triple-layered structure of a
T-tubule sandwiched between sacs of the sarcoplasmic
reticulum; close association allows for communication
from one part of the fiber to another.
triad
45
E. Functioning:
1. sliding filament theory of contraction;
a. individual sarcomeres
shorten and the distance
between 2 Z lines
decreases.
b. myosin and actin
filaments do not change
length but slide over one
another.
c. in a relaxed sarcomere,
actin and myosin overlap
just slightly.
46
A
I
H
d. in a contracted
sarcomere, actin and
myosin overlap a greater
amount
1) the I-band decrease
2) the H-band decreases
3) the A band remains
unchanged in length and
increases in volume.
47
I
H
A
e. Contraction mechanics:
1) Myosin will form cross bridges with actin only after Ca++
ions have been released by the SR. The Ca ++ ions allow the
formation of cross bridges by bonding with troponin. This
rolls tropomyosin out of the way allowing myosin to bond
with the binding site on actin forming the cross bridges.
48
2) Cross bridges form
49
3) The myosin heads flex and pull the actin
myofilament toward the center of the sarcomeres.
50
4) Cross bridges then detach.
51
5) Myosin heads return to their “relaxed” position.
52
6) The process of forming cross bridges, flexing,
detaching, relaxing, continues over and over for as long
as the stimulus to contract continues.
53
F. Control of contraction:
1. A skeletal muscle is activated by its specific motor
nerve when stimulated.
a. Nerves make contact with
muscle fibers with
specialized nerve endings
called neuromuscluar
junctions.
1) telodendrites (axonal
endings) from nerves
make close contact
with the sarcolemma of
the myofiber.
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neuromuscular junctions
telodendrites
2) The membranes of the neuron are separated from the
sarcolemma by a tiny space called the synaptic cleft.
3) the telodendrites have
may synaptic vesicles
(sacs) which contain a
chemical neurotransmitter
called acetylcholine.
nerve ending (telodendrite)
synaptic cleft
synaptic vesicles
myofiber sarcolemma
55
acetylcholine
4) when the nerve sends a stimulus to the myofiber, the
synaptic vesicles release the neurotransmitter, which diffuses
across the synaptic cleft and to the sarcolemma of the
myofiber.
b. This stimulates the sarcolemma by producing
electro-chemical reactions.
1) the sarcolemma in a relaxed myofiber is polarized. It has a
+ charge on the outside of its membrane separated from a charge on the inside. The difference in charge is controlled
by the permeability of the membrane. K+ ions are permeable
and enter the cell while Na+ ions are not easily permeable and
are pumped out by the membrane. This produces a large
number of Na+ ions building up around the outside of the cell
producing a + charged membrane on the outer side. Even
though there are K+ ion inside, there are other ions that are inside, the inner side of the membrane remains - in charge.
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+
Na+ Na
Na+
Na+
Na+
Na+
+ +_ + +_ + + _+ +_+ +
+ + + +_ +_ + +_ + _+ + + +_ + +_
_
Na+
Na+
__
_
_
_
_K+ _ K+
_ _ _
K+ _ _
_ K+ _
_
_
_ _
_
_
_ _ __
_
+
_
_ K+ _ _K+ _ K+ _
_ K _
_
_ _
__ _ _
_
_
_
+
_
_
+ _
_
K
K
+
_
_ _ K+
_
+ _ _K _
_
K
_ _
_
_ _ _ _ _
_ _ _
++++++++++++++++++++++++
Na+
Na+
Na+
Na+
polarized membrane
57
Na+
Na+
Na+
58
2) when acetylcholine is released, it changes the
permeability of the sarcolemma. Now, the Na+ ions
come rushing in and the K+ ions rush out. This
causes a flip-flop of the charges and depolarizes
the sarcolemma. If the stimulus is large enough
then depolarization will be self-propagating and
move along the entire membrane of the myofiber.
This is known as an action potential.
Na+
++++++ ++++++++++++++++++
---------------------------------K+
---------------------------------++++++++++++++++++++++++
polarized membrane
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Na+
Na+
+ + + + - - - - - - - - - - +_ + + + + + + + + +
----+-+-+-+-+-+-+- + ----------K+
---------------------------------++++++++++++++++++++++++
depolarization of the membrane
60
neuromuscular junction
Na+
Na+
Na+
- + - + - + - + - + - + - +_ - + - + + + + + +
-+-+-+-+-+-+-+-+-+ -+-+------K+
K+
K+
---------------------------------++++++++++++++++++++++++
depolarization of the membrane
61
Na+
Na+
Na+
Na+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + -_+ - + - + - + - + - +
K+
K+
K+
K+
---------------------------------++++++++++++++++++++++++
depolarization of the membrane
62
Na+
Na+
Na+
Na+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + -_+ - + - + - + - + - +
Na+
Na+
K+
K+
K+
K+
K+
K+
---------------------------------+ + + + + + + + + + + + + + + + + + + + + + + + Na+
Na+
Na+
depolarization of the membrane
63
Na+
Na+
Na+
Na+
Na+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + - _+ - + - + - + - + - +
Na+
Na+
K+
K+
K+
K+
K+
Na+
Na+
depolarization of the membrane
64
K+
K+
K+
-+-+-+-+-+--------- -+-+-+-+-+
-+-+-+-+-++++++++ -+-+-+-+-+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + - _+ - + - + - + - + - +
Na+
Na+
K+
K+
K+
K+
+
K+
K+
K+
K+
Na+
Na+
Na+
Na+
depolarization of the membrane
65
K+
K+
- + - + - + - + - + K- + - + - + - +- + - + - + - + - +
-+-+-+-+-+-+-+-+-+ -+-+-+-+-+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + - _+ - + - + - + - + - +
Na+
Na+
K+
K+
K+
K+
+
K+
K+
K+
K+
Na+
Na+
Na+
Na+
depolarization of the membrane
66
K+
K+
- + - + - + - + - + K- + - + - + - +- + - + - + - + - +
-+-+-+-+-+-+-+-+-+ -+-+-+-+-+
Na+
Na+
Na+
Na+
K+
K+
K+
K+
K+
K+
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - ++ - + - + - + - + - + - + - _+ - + - + - + - ++ - +
Na
Na+
K+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+ Na Na+
Na+
Na+
- + - + - +_- +
K+
- + - + - + - + - + - + - + - + - +- +
-+-+-+-+-+-+-+-+-+ -+-+-+-+-+
K+
K+
K+
K+
K+
depolarized membrane
67
-+-+-+ - + - + - + - + - +-+-+-+-+
- + - + - + - + - + - + - + - + - _+ - + - + - + - + - +
- + - + - + - + - + - + - + - + - +- + - + - + - + - +
-+-+-+-+-+-+-+-+-+ -+-+-+-+-+
depolarized membrane
68
c. As an action potential moves along the
sarcolemma, it will travel down the T-tubules into
the interior of the cell.
1) As the action potential moves through the triads it
stimulates the SR to release Ca++ ions into the sarcoplasm.
Ca ++ bonds to troponin, which had prevented actin from
bonding with myosin. With the barrier between actin and
myosin gone, the cross bridges form between actin and
myosin and the sliding of the filaments takes place
(contraction occurs).
69
d. Immediately following contraction, the nerve
ending releases a second chemical which counteracts the transmitter substance. (This is an
enzyme; usually cholinesterase) and reverses the
electro-chemical reactions.
1) The sarcolemma quickly recovers and pumps the Na+ ions
out re-establishing a polarized membrane and everything
reverses bringing the myofiber back to a relaxed state.
70
71
2. Muscle fibers function on the all or none
principle.
a. They either contract all the way or they do not contract at
all depending on the amount of the stimulus.
1) if the stimulus is too small, only a local disturbance occurs
and the cell does not contract
2) if the stimulus is large enough, the entire cell contracts.
72
3. Muscle organs function on a graded strength
response. This allows variations in the degree of
movement produced by the muscle. Two ways are
involved:
a. increasing the rapidity of stimulations &
b. increasing the number of motor units contracting.
1) a motor unit is a nerve-muscle functional unit.
A motor nerve has many telodendrite endings,
each which makes contact with a myofiber. When
that nerve sends a stimulus, all of the myofibers it
makes contact with will contract. So it works as a
unit. The average motor unit contains about 150
myofibers. A muscle organ is composed of
hundreds of motor units which are spread
throughout the muscle. By stimulating a single
motor unit, a weak contraction of the entire
muscle occurs. By stimulating hundreds of motor
units, a very strong contraction can occur.
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one motor unit
74
another motor unit
75
2 motor units
76
5 motor units
77
G. Anatomy of a Contractions:
1. myogram- a graph showing the response of a muscle
during contraction.
1.2
1
mvolts
0.8
0.6
0.4
0.2
0
latent contraction
78
relaxation
start of stimulation
recovery
2. muscle twitch- a response to a single brief
stimulus; may be divided into 4 intervals;
a. latent period--this is the interval following stimulation,
before contraction begins. This is the time required for
stimulation, energy production, travel of impulse, chemical
processes, and the beginning of contraction. No response is
seen on a myogram.
b. the contraction period directly follows the latent period.
The dark bands increase slightly in volume while the volume
of the light band decreases during the contraction period. The
shorten of the sarcomeres occurs.
79
c. The relaxation period is the reversal of the
process of contraction. It involves definite
chemical changes within the muscle as the cell
returns to its original length.
d. The recovery period is the short period of time required for
the cell to recover from these changes, this would involve
restoring ATP , Ca++, K+, Na+, etc.
80
81
1.2
mvolts
1
0.8
0.6
0.4
0.2
0
latent contraction
relaxation
start of stimulation
recovery
H. Types of contractions1. Muscle twitch-the response of a muscle to a single brief
threshold stimulus. The muscle contracts quickly and then
relaxes.
2. wave summation- where a second contraction begins
before the first contraction is complete. the second
contraction builds on the first producing a larger contraction.
3. tetanus- smooth sustained contractions, normal movements,
caused by continuous stimulation of a muscle.
82
3. treppe- staircase effect- contractions become stronger
as the muscle is worked, warm up period for athletes
83
4. muscle tone- a slight contracted state, keeps
the muscles firm, healthy, ready to respond to
stimulation, stabilizes joints and maintain
posture.
5. isotonic contractions- normal movements in which the
muscles shorten when producing movements.
6. isometric contractions- contraction of muscles and the
increase of tension but little or no movement occurs.
84
I. Energy for Contraction:
85
1. Energy which is released from ATP does the work of
rotating the cross bridges (chemical bonds created between
actin and myosin) to a different angle. As the cross bridges
flex, they move the thin filaments to which they are attached
in toward the center of the sarcomeres. This necessarily
shortens the sarcomere and the myofibrils.
2. Muscle fatigue- occurs when the ATP production is not fast
enough, our muscles can not contract.
3. Oxygen debt- occurs when our bodies can not
supply enough oxygen to maintain aerobic
respiration. We then use backup anaerobic
respiration to produce some ATP. But to restore
the body back to its normal condition, oxygen will
be required so we called it an oxygen debt.
4. Muscle contraction requires a large amount of energy. ATP
is the original source of energy for muscle contraction.
However, there is very little ATP stored in muscle tissue.
Muscle activity of any duration quickly uses up the supply of
stored ATP. There are at least 3 ways our bodies have to
produce ATP energy.
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a. During rest and for light to moderate energy demands,
ATP is supplied by aerobic cellular respiration from the
mitochondria. When an adequate supply of oxygen is
present, glucose molecules are completely metabolized
releasing sufficient energy for muscle activity. This is the
body's preferred way of producing its energy. It produces
the most ATP units per glucose molecule as compared to
the other 2 backup methods. For each glucose molecule,
36 ATP units are released and available for work.
1) glucose + O2 _________> energy + CO2 + H2O
ADP
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36 ATP
b. However, if the muscle activity is strenuous, energy from
cellular respiration will be too slow to meet the need for
energy. The muscle tissue contains a back-up compound,
creatine phosphate (CP) that is rich in energy too. This
compound releases a phosphate group to resynthesize ATP
from ADP. This produces ATP molecules so that muscle
contraction can continue for a short time.
1) CP + ADP __________> ATP + C
2) Later, when there is enough O2, the reverse reaction
occurs, producing more CP as stored energy.
3) C + ATP __________> CP + ADP
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c. As the level of CP decreases, and additional energy is
required, there is another compound, a starch, glycogen
that can release energy for muscle activity. Glycogen is
stored in muscle tissue. Glycogen can be converted directly
into lactic acid and release energy in the process. This is
done without O2 and is called anaerobic respiration or
lactic acid fermentation. The lactic acid will cause muscle
fatigue and an oxygen debt will be created in the body.
1) glycogen____________> lactic acid + 2 ATP units
2) When the body has had time to reduce its activity to a less
strenuous pace and oxygen is again plentiful, the lactic acid will be
removed by the blood, taken to the liver and with the aid of more
energy, reconverted into glycogen where it will be stored again in the
muscle.
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