chapter 10 muscular tissue
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Chapter 10 Muscular Tissue. Lecture slides prepared by Curtis DeFriez, Weber State University. Excitation-Contraction Coupling. We will come back to the term excitation-contraction coupling in a little bit Before we can describe the entire process, from thinking of moving a - PowerPoint PPT PresentationTRANSCRIPT
Copyright © John Wiley and Sons, Inc. All rights reserved.
Chapter 10
Muscular
Tissue
Lecture slides prepared by Curtis DeFriez, Weber State University
Copyright © John Wiley and Sons, Inc. All rights reserved.
Excitation-Contraction CouplingWe will come back to the term excitation-
contraction coupling in a little bit
Before we can describe the
entire process, from
thinking of moving a
muscle to actual contraction
of sarcomeres, we must
first explore the processes
that occur at the ___________ junction
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___________-___________ coupling (___ coupling) involves events at the junction between a motor neuron and a skeletal muscle fiber
Neuromuscular Junction
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An enlarged view of the neuromuscular junctionThe presynaptic membrane is on the neuron while the postsynaptic membrane is the ___________plate on the muscle cell. The two membranes are separated by a space, or “cleft”
Neuromuscular Junction
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Conscious thought (to move a muscle) results in
activation of a motor neuron, and release of the
neurotransmitter ___________ (AcCh) at the NM
junction
The enzyme
_________________
breaks down AcCh
after a short period
of time
Neuromuscular Junction
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The plasma membrane on the “far side” of the NMJ
belongs to the muscle cell and is called the ___________
The motor end plate is rich in chemical (___________) -
gated sodium channels that respond to AcCh. Another
way to say this: The receptors for AcCh are on the
ligand-gated ______ channels on the motor end plate
Neuromuscular Junction
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The ___________ events at the NMJ transmit the electrical events of a neuronal action potential into the ___________ events of a muscle action potential
Neuromuscular Junction
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Neuromuscular JunctionInteractions Animation
Neuromuscular Junctions
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The muscle __ is propagated over the surface of
the muscle cell membrane (___________) via
voltage (___________)-gated Na+ and K+ channels
Muscle Action Potential
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By placing a micropipette inside a muscle cell,
and then measuring the electrical potential
across the cell membrane, the phases of an
_________________
(AP) can be
graphed (as in this
figure)
Muscle Action Potential
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The behavior of the _____
and ___ channels, at various
points in the AP, are seen
in this graphic
Na+ gates open during the
___________ phase
K+ gates open during the
___________ phase
Muscle Action Potential
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Generating An Action PotentialThe flow of ions through cell a membrane looks a lot
like a "piece" of electricity flowing through a wire
(but not as fast)
Generating an AP on the muscle membrane involves
the transfer of information from an ___________signal
(down the neuron), to a ___________signal (at the NMJ),
back to an ___________ signal (depolarization of the
sarcolemma)
This added complexity (changing from electrical to
chemical back to electrical signals) provides
necessary control of the process
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Excitation-Contraction Coupling
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Excitation-Contraction Coupling
EC coupling involves putting it all together
The thought process going on in the brain
The AP arriving at the neuromuscular junction
The regeneration of an AP on the muscle
membrane
Release of Ca2+ from the sarcoplasmic reticulum
Sliding of thick on thin filaments in sarcomeres
Generation of muscle tension (work)
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Excitation-Contraction Coupling
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The brain
The motor neuron
Acetylcholine (ACh)
Acetylcholinesterase
enzyme
Ach receptors on the
motor endplate
Na+-K+ channels on the
sarcolemma
Na+ flow
K+ flow
Regenerate AP
The T-tubules
The SR
Ca2+ release
Troponin/
Tropomyosin
ATP
Myosin binding
Filaments slide
Muscles contract
Role Players in E-C coupling
Excitation-Contraction Coupling
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Contraction of SarcomereInteractions Animation
Contraction of a Sarcomere
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Sources of Muscle EnergyStored ______
3 seconds
Energy transferred from stored
______________________
12 seconds
___________production
___________ glucose use
30-40 seconds
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Sources of Muscle Energy
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Sources of Muscle Energy
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Sources of Muscle Energy
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In a state of ___________, muscle use of O2
and nutrients is balanced by the production of
manageable levels of waste products like
_______
_______ - 70-80% of the energy used by
muscles is lost as heat - muscle activity is
important for maintaining body temperature
___________(anaerobic)
Skeletal Muscle Metabolism
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___________, or "Excess Post-Exercise Oxygen
Consumption" (EPOC) is the amount of
___________ required after exercise in skeletal
muscle to:
___________ ATP stores
___________ creatine phosphate and
myoglobin stores
___________ lactic acid back into pyruvate
so it can be used in the Krebs cycle to replenish
ATP
Skeletal Muscle Metabolism
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Skeletal Muscle Metabolism
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Muscle Metabolism
Muscle Metabolism
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Cardiac and Smooth Muscle Metabolism
In response to a single AP, cardiac muscle
contracts ____ times longer than skeletal muscle,
and must continue to do so, without ______, for
the _____ of the individual
To meet this constant demand, cardiac muscle
generally uses the rich supply of O2 delivered by
the extensive coronary circulation to generate
ATP through ___________ respiration
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Cardiac and Smooth Muscle Metabolism
Like cardiac muscle, smooth muscle (in your
deep organs) is ___________ and is not under
voluntary control (your heart beats and your
stomach digests without you thinking about it).
Unlike cardiac (and skeletal muscle) however,
smooth muscle has a low capacity for
generating ATP and does so only through
___________ (___________)
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___________ Unit is composed of a ___________
plus all of the muscle cells it innervates
_______ precision
• Fewer muscle fibers per neuron
• Laryngeal and extraocular muscles (2-20)
_______ precision
• Many muscle fibers per neuron
• Thigh muscles (2,000-3,000)
The Motor Unit
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Activities requiring extreme precision (like the subtle
and rapid movements of the eye) involve muscles
with ___________ motor units (1-4 muscle
fibers/neuron)
The Motor Unit
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___________ principle of muscle contraction
When an individual muscle fiber is stimulated to
depolarization, and an action potential is
propagated along its sarcolemma, it must
contract to it’s full force—it can’t ___________
contract
Also, when a single motor unit is recruited to
contract, all the muscle fibers in that motor unit
must all contract at the same time
The Motor Unit
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Skeletal muscle fibers are not all alike in appearance
or function. By appearance:
_____ muscle fibers (the dark meat in chicken legs)
have a high myoglobin content, more mitochondria,
more energy stores, and a greater blood supply
_______ muscle fibers (the white meat in chicken
breasts) have less myoglobin, mitochondria, and
blood supply
Skeletal Muscle Fiber Types
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Slow ___________ fibers (SO) are small, appear dark red, are
the least powerful type. They are very fatigue resistant
Used for endurance like running a marathon
Fast ______________________ fibers (FOG) are intermediate in
size, appear dark red, and are moderately resistant to fatigue.
Used for walking
Fast ___________ fibers (FG) are large, white, and powerful
Suited to intense anaerobic activity of short duration
Skeletal Muscle Fiber Types
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Skeletal Muscle Fiber Types
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Most skeletal muscles are a mixture of all three types
of skeletal muscle fibers; about half the fibers in a
typical skeletal muscle are slow oxidative (SO) fibers
Within a particular motor unit all the skeletal
muscle fibers are the _______ type
The different motor units in a muscle are
___________ in a specific order depending on the
task being performed (fast anaerobic activity for
maximal force, etc.)
Skeletal Muscle Fiber Types
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There is a brief delay called the ___________as the
AP sweeps over the sarcolemma and Ca2+ ions are
released from the sarcoplasmic reticulum (SR)
During the next phase the fiber is actively
___________
This is followed by ___________as the Ca2+ ions are
re-sequestered into the SR and myosin binding
sites are covered by tropomyosin
Temporary loss of excitability is call the
___________– All muscle fibers in a motor unit will
not respond to a stimulus during this short time
Tension in a Muscle
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A ___________ is recorded when a stimulus that results
in contraction (force) of a single muscle fiber is
measured over a very brief millisecond time frame
Tension in a Muscle
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Applying increased numbers of action potentials to a muscle fiber (or a ___________, a muscle, or a muscle group) results in fusion of contractions (___________) and the performance of useful work
Tension in a Muscle
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Two motor units, one in green, the other in purple, demonstrate the concept of progressive activation of a muscle known as ___________Recruitment allows a muscle to accomplish increasing gradations of contractile strength
Tension in a Muscle
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Muscle TensionInteractions Animation
Control of Muscle Tension
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Muscle Contraction___________ contractions results in
___________Concentric isotonic is a type of muscle
contraction in which the muscle shorten while
generating force
Eccentric isotonic is a contraction in which
muscle tension is less than the resistance (the
muscle lengthens)
___________ contractions results in ___________
Muscle force and resistance are equal
Supporting objects in a fixed position and
posture
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Muscle Contraction
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Exercise-induced muscle damage
After intense exercise electron micrographs
reveal considerable muscle damage including
torn sarcolemmas and disrupted Z-discs
Blood levels of proteins normally confined
only to muscle (including myoglobin and the
enzyme creatine kinase) increase as they are
released from damaged muscle
Imbalances of Homeostasis
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___________
A sudden involuntary contraction of a single
muscle within a large group of muscles – usually
painless
___________
Involuntary and often painful muscle contractions
Caused by inadequate blood flow to muscles (such
as in dehydration), overuse and injury, and
abnormal blood electrolyte levels
Imbalances of Homeostasis
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Disease States and Disorders
___________ (myofibrosis)
Replacement of muscle fibers by excessive
amounts of connective tissues (fibrous scar
tissue)
___________
Hardening of the muscle caused by calcification
Both myosclerosis and muscle fibrosis occur as a
result of trauma and various metabolic disorders
Imbalances of Homeostasis
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Aging
In part due to decreased levels of physical activity,
with aging humans undergo a _____, ___________ loss of
skeletal muscle mass that is replaced largely by fibrous
connective tissue and adipose tissue
Muscle strength at 85 is about _____ that at age 25
Compared to the other two fiber types, the relative
number of slow oxidative fibers appears to ___________
Imbalances of Homeostasis