•3/12/2016
•1
(Course Name and Number)







Describe the characteristics of muscle tissue
Compare the structures and functions of the
three forms of muscle tissue and give examples
of each.
List the components of a muscle cell.
Given a diagram of a sarcomere, label its
components.
Describe the sliding filament theory of
excitation- contraction coupling.
Describe the structure and function of the
neuromuscular junction.
Given a diagram, label the major muscles of the
body.
•3/12/2016
•2
(Course Name and Number)


Describe the functions of those muscles
directly involved with the cardiovascular
system.
Explain the role of muscle as it relates
to homeostasis.
•3/12/2016
•3







Characteristics of Muscle Tissue
Forms of Muscle Tissue
Muscle Cell
Organizational Structure of Skeletal
Muscle
Sarcomere
Action Potential
Neuromuscular Junction
•3/12/2016
•4






Sliding Filament Theory
Major Muscles of the Body
Cardiovascular System Muscle
Functions
Role of Muscles
Lab/Practical
Practical Test/Performance
Evaluation
•3/12/2016
•5
•3/12/2016
•6

Excitability
◦ A property of both muscle and nerve cells.
◦ Ability to respond to a certain stimuli by
producing electrical signals called action
potential (impulses)
◦ For muscle cells the stimulus that triggers
these action potentials are chemicals called
neurotransmitters

Conductivity
◦ Ability of a muscle cell to propagate or conduct
an action potential along the plasma
membrane
•3/12/2016
•7

Contractility
◦ Ability of the muscle to shorten and thicken
(contract) therefore generating the force to do
work.

Extensibility
◦ Muscle can be extended (stretched) without
damaging the tissue

Elasticity
◦ Muscle tends to return to its original shape
after contraction or extension
•3/12/2016
•8
•3/12/2016
•9

Three forms of muscle tissue:
◦ Skeletal muscle
o Striated
 Band-like appearance
 Multi–nucleated
‒ Voluntary tissue
 Under conscious control
 Function
‒ Movement of body parts
‒ 85% heat
‒ Provide posture for the body
•1
•3/12/2016
0
Three forms of muscle tissue (continued)
◦ Cardiac muscle
o Striated
o Involuntary
o Single nucleus per cell
o Not under conscious control
o Function
 Provide circulation of blood flow to and from all
body parts through cardiac contraction
◦ Smooth muscle
o Non-striated
 Shredded appearance
•1
•3/12/2016
1
‒ Smooth Muscle Tissue
o Involuntary
o Central single nucleus
o In hollow organs of body – blood vessels,
digestive tract, bladder or uterus
o Maintain lumen size of blood vessels
o Key in maintenance of blood pressure
o Aid in the expulsion of urine
o Rhythmic contractions of the uterus lead to
childbirth
•1
•3/12/2016
2
•1
•3/12/2016
3
•1
Source: Principles of Anatomy and Physiology, 12th Edition, Gerard J. Tortora and Bryan Dickerson, •3/12/2016
John Wiley and Sons, Figure 10.2
4

Sarcolemma
◦ Cell or plasma membrane

Sarcoplasm
◦ Cytoplasm of a muscle cell
◦ More abundant than most other cells

Sarcoplasmic reticulum
◦
◦
◦
◦
◦
Endoplasmic reticulum of muscle tissue
Intracellular transport
Support
Storage network
T-tubules
•1
•3/12/2016
5

Sarcoplasmic Reticulum cont
◦ T-Tubules
 Deep invaginations of the sarcolemma
 Provide for more rapid communication of
extracellular ions/electrolytes
 Storage and transport site for Ca++
 L-tubules
 Longitudinal tubules
 Encircle the myofibrils of the cell
 Contain dilated sacs (Terminal cisterns) that store
Ca++
 Not as abundant in skeletal muscle
•1
•3/12/2016
6

Triad
◦ The union of a T-tubule and two ends of the
L-tubules constitutes a triad.
 Storage site for Ca++
 Allows for the transference of substances from
one system to another
 Explains in part how electro/chemical stimulation
affects the entire cell at the same time
 Speeds conduction through the cell
 Affords contraction of the whole cell, vice a portion
at a time
•1
•3/12/2016
7

Nucleus
◦ Smooth muscle and cardiac muscle both have a
single centrally located nucleus.
◦ Skeletal muscle contains several peripherally
located nuclei.

Mitochondria
◦ Much larger in both size and number than in
any other cell
 Due to the high energy requirements
•1
•3/12/2016
8

Contractile elements
◦ Myofibrils
◦ Contraction of many muscle cells at the same
time
◦ Breakdown of a muscle to the contractile
elements
◦ Myofilaments
 Interconnecting proteins
 Actin
 Myosin
•1
•3/12/2016
9
◦ Sarcomeres
 Compartments of myofilaments
 Repeating units of contraction

Specialized Properties of Cardiac Muscle
tissue
◦ Intercalated discs
 Irregular thickening of sarcolemma
 Contains Desmosomes
 Provides enhanced strength needed for contraction
•2
•3/12/2016
0
(Intercalated discs continued)
 Constitutes the longitudinal boundaries of the
cardiac cell
 Offset itself at the level of one full sarcomere
 Provides for direct cell to cell communication
 Provides low-resistance bridges
 Efficient spread of excitation
 Speeds the conduction velocity of
cardiac tissue
•2
•3/12/2016
1
•2
•3/12/2016
2

Skeletal Muscle
◦ Fascicles: Consists of bundles of muscle fibers
surrounded by the perimysium (a type of
connective tissue)
◦ Muscle fibers (Myofibers)
 Long cylindrical bundles lying parallel
 Cells lie end to end, side by side and range from 10100 μm in diameter
 Cardiac muscle fibers may branch
 Contain many threadlike structures called myofibrils
•2
•3/12/2016
3
•2
•3/12/2016
4
◦ Myofibrils
Contractile elements of skeletal muscle
1-2 μm in diameter
Extend lengthwise within the muscle fiber
Prominent alternating light and dark bands called
cross striations
 Contains smaller structures called filaments
(myofilaments)




 Actin
 Myosin
•2
•3/12/2016
5
◦ Myofilaments
 Actin (thin filament) 8nm in diameter
 Myosin (thick filament) 16nm in diameter
 Can overlap each other depending on state of
muscle contraction
 These filaments do not extend the entire length
of a muscle fiber
 Arranged in compartments called sarcomeres
which are the basic functional units of striated
muscle tissue
•2
•3/12/2016
6
•2
•3/12/2016
7

Thick Myofilaments
◦ Composed of the protein myosin
◦ Occupies the center of the sarcomere
◦ Contains spine-like processes that extend out
toward the thin filaments actin
 Cross-bridges bind with receptor sites on Actin
filament during contraction
 Primary mechanism of muscle contraction
◦ Middle of myosin presents as a nodule
•2
•3/12/2016
8

M Line
◦ Thin Myofilaments
◦ Composed predominately of the protein actin
◦ Bound with a troponin-tropomyosin complex
which Inhibits the actin filament from
interacting with the myosin cross bridges in
the absence of intracellular calcium (relaxation)
◦ Contains receptor sites for myosin cross bridge
attachments
◦ There are six actin filaments surrounding each
myosin filament
◦ Each actin filament receives cross bridges from
three myosin filaments
•2
•3/12/2016
9
◦ Thin filaments originate from the Z lines (ZDisc).
 Extend toward center of the sarcomere
 Overlap partially with myosin filament when
relaxed
 When contraction takes place the actin filaments
may completely overlap one another

Z Line
◦ Transverse dense material where the thin
filaments originate
◦ Two Z lines (Z-Discs) in horizontal succession
constitute the limits of one sarcomere
•3
•3/12/2016
0

I band
◦ Area on both sides of the Z line
◦ Only thin myofilaments are found
•3
•3/12/2016
1
•3
Source: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=mcb&part=A5208&rendertype=figure&id=A5208
•3/12/2016
2

A band
◦ Center area of the sarcomere where thick and
thin myofilament overlap
◦ Encompasses the length of the myosin filament

H zone
◦ Center of the sarcomere where there are only
thick filaments (relaxed)
◦ Disappears during contraction as the Z lines
are drawn together
◦ Causes the sarcomere to become shorter
and fatter
•3
•3/12/2016
3
•3
•3/12/2016
4

Wave of negativity occurs along the
surface membrane of a cell causing a
rapid change in membrane potential,
which involves depolarization and repolarization.





Phase:
Phase:
Phase:
Phase:
Phase:
“0”
“1”
“2”
“3”
“4”

Phase 0
◦ Upon stimulation, acetycholine changes the
membrane permeability to Na+.
◦ The large influx of Na+ causes the cell to
depolarize.
◦ This is termed a “threshold”:
-70mV (nerve cell)
-60mV (“automatic” cardiac cell)
-90mV (“non-automatic” cardiac cell)
•Phase O starts
•here
•Phase 1

Phase 1
◦ “Overshoot” of Na+ causing the inside of the
cell to become momentarily positive.
◦ Termed “Depolarization”

Phase 2
 “Plateau Phase” cell undergoes a continuous
influx of Ca++
 From -50mV through phase 1 of the action
potential
 Allows for sustained contraction (or whatever that
cell’s particular function is)
•Phase 2

Phase 3
◦ Cessation of impulse stimulation,
◦ The beginning of acetylcholinestrase activity
(neuromuscular junction)
◦ The membrane undergoes increased
permeability to K+.

This causes an efflux of K+ from the
cell.
•Phase 3 area

Phase 4
◦ Restoring resting membrane state.
◦ Na+ / K+ pumps are powered by ATP and
easily restore the low concentration of Na+
inside the cell
•Phase 4
•aka.. Resting Potential
•4
•3/12/2016
6

The neuromuscular junction consists of:
◦ A muscle
◦ Terminal telodendria of a motor neuron

The terminal end of the nerve axon has
fine filament extensions called synaptic
end bulbs
◦ Lie in very close proximity with the
sarcolemma of the muscle cell
◦ Contain synaptic vesicles
•4
•3/12/2016
7

When a nerve stimulation reaches the
terminal axon
◦ Calcium activates the synaptic end bulbs to
release neurotransmitters by exocytosis

Neurotransmitter (Ach) is liberated from
the synaptic vesicles
◦ Travels into the synaptic gutter
◦ Located between the telodendria and the
muscle fiber
•4
•3/12/2016
8

Causes an action potential to occur on the
sarcolemma
◦ Changes membrane permeability
◦ Spreads the impulse
◦ Nearly simultaneous activation of acetylcholine
receptors and contraction of the muscle
•4
•3/12/2016
9
•5
•3/12/2016
0

A motor unit
◦ A motor neuron with all the muscle fibers it
stimulates
 May innervate from 1 up to 3000 muscle fibers
 All fibers within a motor unit contract or none do.
 When the nerve impulse reaches the terminal end
of the motor nerve
 Myoneural junction (Neuromuscular junction)
 Causes acetylcholine to be released
(neurotransmitter)
 Acetylcholine bridges the synaptic cleft and
stimulates the sarcolemma to undergo a change
•5
•3/12/2016
1

Upon stimulation of a muscle fiber by a
motor nerve there is a series of reactions
that sequentially takes place causing the
muscle cell to contract
◦ Ach causes the nerve impulses to spread
across the entire sarcolemma which changes
the membrane permeability to Na+ which
initiates an action potential (depolarization)

The action potential stimulates the
sarcoplasmic reticulum and releases the
calcium that is stored in the triads (Ttubules, L-tubules) to quickly enter the
sarcoplasm
•3/12/2016
•5
2

The released Calcium ions bind with the
troponin/tropomyosin complex
◦ Calcium shift the troponin/tropomyosin
complex off of the actin binding sites
◦ Allows myosin cross bridges to interact with
the actin filaments and perform “power stroke”
◦ Cross bridges interaction with the action
filaments pulls them toward the center of the
sarcomere

ATP is then utilized to break the bond
between the myosin head and the actin
site repowering the myosin cross bridge
for another power stroke if the binding
sites are still exposed
•3/12/2016
•5
3

Termination of contraction
◦ Acetylcholine is rapidly deactivated by the enzyme
acetylcholinesterase (Neuromuscular junction).
◦ Nerve impulse and stimulation ceases
◦ Calcium is pumped back out of the sarcoplasm by
active transport pumps on the Sarcoplasmic
Reticulum membrane into the SR (T & L Tubules).
 Troponin/tropomyosin complex shifts back over the
actin filament binding sites
•5
•3/12/2016
4

Cardiac excitation contraction coupling
◦ Cardiac muscle contracts and relaxes
continuously
 Rhythmically normally
 60 to 100 times a minute
 Major difference between cardiac and skeletal
muscle
o Cardiac muscle contracts without
outside stimulus
o Remains contracted longer
o Longer refractory period after each cell depolarizes
•5
•3/12/2016
5

Cardiac excitation contraction coupling
◦ Impulse propagates through the transverse
tubules to inside of cell
◦ Sliding-filament theory process takes place
as in the skeletal muscle
◦ The T-tubules are located at the Z lines
◦ Cardiac muscle fibers form two separate
networks
 Atria
 Ventricular

Each network contracts as a functional
unit and moves blood through the
heart
•3/12/2016
•5
6
•5
•3/12/2016
8

Muscles are named according to:
◦ Their anatomic location
◦ Their principle action
◦ Number of origin sites or number of tendons
of origin
◦ Description of the overall muscle mass in
comparison to another muscle
•5
•3/12/2016
9
•6
•3/12/2016
0
•6
•3/12/2016
1
•6
Source: Principles of Anatomy and Physiology, 12th Edition
•3/12/2016
2
•6
Source: Principles of Anatomy and Physiology, 12th Edition
•3/12/2016
3
•6
•3/12/2016
4

Diaphragm
◦ Forms floor of thoracic cavity
◦ Moves downward during inspiration
 Increasing vertical size of thoracic cavity

External intercostals
◦ Principle muscle of ventilation
 Lifts ribs up and out on inspiration
•6
•3/12/2016
5

Internal intercostals
◦ Pull ribs down and in on expiration

Rectus abdominus
◦ Accessory muscle of expiration
 Forced expiration (ex. Pulmonary function test)
•6
•3/12/2016
6

Smooth muscle of the vasculature
◦ Regional blood flow
◦ Blood pressure
◦ Very easily manipulated with medications

Skeletal muscles of the lower extremities
◦ Contraction aids in venous return


Heart
◦ Responsible for pumping blood throughout the
blood vessels by repeated, rhythmic
contractions
◦ Primary mechanism for maintaining cellular
perfusion through circulation of oxygenated
blood
◦ Cardiac Output:
 Determined by two factors
 HR (Chronotrope)
 Stroke Volume (amount of blood ejected from the
ventricles per beat)
•6
•3/12/2016
8
Source: Principles of Anatomy and Physiology, 12th Edition, Gerard J. Tortora and Bryan Dickerson, John Wiley and Sons, Figure 20.2
•6
•3/12/2016
9
•7
•3/12/2016
0
• Motion
◦ To produce movement of body parts in a
coordinated manner
 Running, walking

Moving Substances within the body
◦
◦
◦
◦
◦
Circulation
Ingestion
Digestion
Absorption
Respiration
•7
•3/12/2016
1

Heat production
◦ As Skeletal muscle contracts to perform work,
a by-product is heat
◦ Assist in the maintenance of normal body
temp.
◦ Generate approximately 85% of all body heat

Stabilizing body positions and organ
volume
◦ Partially contracted neck muscles to hold the
head upright
◦ Smooth muscle sphincters to prevent outflow
of contents within a hollow organ
•3/12/2016
•7
2

Worksheet Activity
Worksheet
Activity
Student Guide
•3/12/2016
•7
3










Characteristics of Muscle Tissue
Forms of Muscle Tissue
Muscle Cell
Organizational Structure of Skeletal
Muscle
Sarcomere
Action Potential
Neuromuscular Junction
Sliding Filament Theory
Major Muscles of the Body
Cardiovascular System Muscle
Functions
•3/12/2016
•7
4
Complete
Quick Check
Student
Guide
•7
•3/12/2016
5
•7
•3/12/2016
6