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Properties of Muscle
Tissue
• Contractility
• Excitability (Irritability)
• Extensibility
• Elasticity
Functions
•Movement
•Support
•Heat Production
•Stabilizing joints
• Take out a piece of paper
please. It’s time for a short
comprehension check!
Comprehension Check 07/12/16
• What are four properties of muscle tissue
listed in class?
• What are the four main functions of muscle
tissue?
• What is the difference between an origin and
an insertion, as related to a muscle?
• What is the difference between a synergist
and a fixator?
Origin and Insertion
•Origin - the point of
attachment to the more
stationary bone
•Insertion - the
attachment to the more
movable bone
Origin and Insertion
• Generally, as a muscle
shortens, its insertion
moves towards its origin
• Muscles can only pull – can
never push
Group Actions
• Group action - the
movement of more than
one muscle
–prime movers (agonists)provides the major force for
producing specific movement
–antagonists – opposes or
reverses a particular
movement
•relax during the action
Group Actions
–synergists - steady the
movement; aid the prime
mover
–fixators - stabilize the
origin of the prime mover
Naming Muscles
• Location
–Ex. Temporalis
• Shape
–Ex. Deltoid - triangular
–Ex. Trapezius - trapezoid
Naming Muscles
• Relative size
–Maximus – largest
–Minimus – smallest
–Longus – long
–Brevis - short
Naming Muscles
• Direction of muscle fibers
–In reference to some
imaginary line
–Rectus – runs parallel to axis
–Transverse – right angles to
axis
–Oblique – obliquely to axis
Naming Muscles
• Number of origins
–Biceps – 2
–Triceps – 3
–Quadriceps - 4
Naming Muscles
• Location of attachments
to origins (always 1st)
and insertions
–Ex. Sternocleidomastoid
•Origins: sternum and
clavicle
•Insertions: mastoid
process
Naming Muscles
• Action
–Flexor, extensor, adductor
•ex,. Adductor longus
Comprehension Check 08/12/16
• List five of the methods used for
naming muscles.
• What is the difference between a
prime mover and an antagonist?
• List four of the muscles of the skull.
Naming Muscles
• Often several criteria are
combined
–Ex. Extensor carpi radialis
longus
1. Temporalis
2. Orbicularis oculi
3. Zygomaticus
4. Orbicularis oris
5. Pectoralis major
6. Deltoid
7. Biceps brachii
8. Rectus abdominis
9. Transversus abdominis
10. Adductor group
11. Gracilis
12. Sartorius
13. Tibialis anterior
14. Frontalis
15. Masseter
16. Sternocleidomastoid
17. External oblique
18. Rectus femoris
19. Vastus lateralis
20. Vastus medialis
21. Fibularis longus
1. Gluteus maximus
2. Adductor muscles
3. Biceps femoris
4. Semitendinosus
5. Gastrocnemius
6. Trapezius
7. Deltoid
8. Triceps brachii
9. Latissimus dorsi
10. External oblique
11. Gluteus medius
12. Soleus
Connective Tissue of Muscle
• Fascia - a sheet or broad
band of dense connective
tissue
–Deep fascia
•surrounds a muscle
•serves as a support
•route for passage of blood
vessels & nerves
Connective Tissue of Muscle
(cont’d)
• Epimysium outermost
covering
– Surrounds
whole muscle
– Sometimes
blends with
deep fascia
Connective Tissue of Muscle
(cont’d)
• Perimysium thinner,
deeper layer
–Surrounds
muscle
fibers in
bundles
(fascicles)
Connective Tissue of Muscle
(cont’d)
• Endomysium deepest,
thinnest
–Surrounds
each muscle
fiber w/in
fascicle
Connective Tissue of Muscle
(cont’d)
• Tendon - thick
connective tissue
– Between
muscle and
bone
– Fibers of
tendons
converge onto
the periosteum
of the bone
Connective Tissue of Muscle
(cont’d)
• Areolar tissue
• Adipose tissue
• Both found superficial to the
epimysium
–support attachment to bones
or muscles
–provides energy storage
–cushions the muscle from
injury
Microscopic Structure of
Muscle
• “myo-” & “sarco-” refer
to muscle
Microscopic Structure of
Muscle (cont’d)
• Muscle fiber
(myofiber)single cell of
muscle tissue
– long, cylinder
shape
– typically the
length of the
muscle they
form
– contain many
nuclei
Microscopic Structure of
Muscle (cont’d)
–Sarcolemma - plasma
membrane
–Sarcoplasm – cytoplasm
•Contains some highly modified
organelles
–Myofibrils
–Sarcoplasmic Reticulum (SR)
–Transverse (T) Tubules
Microscopic Structure:
Myofibrils
• Myofibrils – contractile
elements of myofibers
–Cylindrical cords
–Lie parallel to one another
–Extend entire length of
cell
Microscopic Structure: Myofibrils
(cont’d)
– Thick filaments – myosin (dark
colored protein)
– Thin filaments – mostly actin (light
colored), troponin, tropomyosin
– Heads of myosin molecules form
cross bridges that intersect with
thin filaments
Microscopic Structure:
Myofibrils (cont’d)
– Striations –
repeating series
of dark A bands
and light I
bands
– A band - where
the thick and
thin filaments
overlap (entire
myosin length)
• Appear darker
Microscopic Structure:
Myofibrils (cont’d)
–I band where only
thin
filaments
occur
•Appear
light
Microscopic Structure:
Myofibrils (cont’d)
– Z line (disc)Thin strands of
protein
extending
perpendicular at
regular intervals
•Anchors thin
filaments &
connects each
myofibril to
the next
Microscopic Structure:
Myofibrils (cont’d)
–Sarcomere the segment
between 2 Z
lines
•Myofibrils
are chains
of
sarcomeres
Microscopic Structure:
Myofibrils (cont’d)
• H zone where no
overlapping
occurs - only
in center
– Only myosin
Microscopic Structure:
Sarcoplasmic Reticulum
(SR)
• SR – membranous tubules surround myofibrils
–stores and releases calcium
Microscopic Structure:
Transverse (T) Tubules
• T Tubules – help activate Ca
transport mechanism
Nerve Supply
• Resting membrane potential
- voltage difference inside &
outside the membrane
• Action potential - brief
reversal of charges
• Motor neurons - nerve cells
that carry action potential
to skeletal muscles
Nerve Supply (cont’d)
•Motor unit - motor
neuron & all the
muscle fibers it
stimulates
Motor Unit
Nerve Supply (cont’d)
• Motor end plate – troughlike part of the muscle
fiber’s sarcolemma that
helps form the
neuromuscular junction
Nerve Supply (cont’d)
• Neuromuscular
junction contains
terminal end of a
motor neuron, a
motor end plate,
& a narrow
space between
(synaptic cleft)
Nerve Supply (cont’d)
• At synaptic
cleft - the
sarcolemma is
repressed,
forming
pockets
–Acetylcholine
(ACh)
receptors
located here
Nerve Supply (cont’d)
• Synaptic
vesicles – tiny
sacs within
cytoplasm of
motor neuron.
– Contains ACh, a
neurotransmitter
(chemical that
carries a signal)
Nerve Supply (cont’d)
• As an action potential
reaches the neuron terminal
end, ACh is released .
• Diffuses across the synaptic
cleft until it contacts the
motor end plate.
• 1 neuron stimulates 25 3000 muscle fibers (avg.
150)
• Sliding filament mechanism
• Contractions achieved by
sliding action of thin
filaments inward toward
the H zones – sarcomere
shortens.
The Fiber at Rest
• Most available Ca ions
stored in SR
• ATP is bound to thick
filaments (myosin proteins)
• Thin filaments are intact w/
actin, troponin, &
tropomyosin
• Fibers are ready to contract
Role of a Stimulus
• Release of ACh begins
the events leading to
muscle contractions.
• ACh contacts the motor
end plate - action
potential is generated
Role of a Stimulus (cont’d)
• Runs along the sarcolemma,
down the T-tubule
membranes, thru the
membranes of the SR
• Ca ions - released into the
sarcoplasm & diffuse to the
myofibrils
Muscle Contractions
• Ca ions bind
to troponin
• Troponin
changes
shape,
removing
blocking
action of
tropomyosin,
and exposing
actin binding
sites
Muscle Contractions (cont’d)
• Cross
bridges bind
to them
forming
connections
between
thick and
thin
Muscle Contractions (cont’d)
• Ca ions activate the breakdown
of ATP that is bound to the
thick filaments
• Myosin catalyze the breakdown
of ATP to ADP + PO4 + energy
• Some energy used for moving
cross bridges
• Some released as heat
Muscle Contractions (cont’d)
• Movement of
cross bridges
cause the
filaments to
be drawn
toward the
center (cross
bridges tilt
inward).
Muscle Contractions (cont’d)
• When tilting
complete,
another ATP
molecule
binds to
myosin,
causing cross
bridges to
break from its
attachment
and return to
original angle
Muscle Contractions (cont’d)
• Rigor mortis
–When a person dies, ATP
becomes unavailable
–Cross bridge detachment
impossible
–Stiffness of muscle
Muscle Contractions (cont’d)
• Cross bridges reform their
attachment to binding site, but
closer to the sarcomere’s center
• Cycle of cross bridge formation,
movement, & release continues moves the filaments toward the
center of the sarcomere
Muscle Contractions (cont’d)
• Z lines draw closer and the
sarcomere shortens
• Each myosin cross bridge
must attach and detach
many times during a
contraction.
Return to Rest
• Action potential ends –
ACh release ends
• Stimulus does not end
until all ACh on motor
end plate is inactivated
Return to Rest (cont’d)
• Accomplished by AChE
(acetylcholinesterase)
–Destroys ACh
–Prevents continued muscle
fiber contractions in absence
of additional nerve stimulus
–Nerve gas – blocks action of
AChE
•Muscle spasms
Return to Rest (cont’d)
• ATP provides energy for
enzymes to return Ca ions
to the SR
• Causes the filaments to
return to their shape,
closing off binding sites
• Thin filaments slide back to
original position
Homeostatic Imbalances
• Myasthenia
Gravis
– Shortage of
ACh receptors
– Muscle
weakness,
droopy
eyelids
Homeostatic Imbalances
(cont’d)
• Curare
–Binds to ACh receptors
and blocks ACh
attachment
–Arrowhead poison
–Respiratory arrest
–Small amounts used in
surgery
Energy for contractions
• ATP – used up quickly
• Other long term sources
of energy:
–Glucose
–Creatine phosphate
–Glycogen
–Fat
Oxygen Debt
• Oxygen is needed to produce ATP
• Strenuous exercise uses too much
oxygen. Cannot meet demands for
oxygen.
–Anaerobic respiration produces
lactic acid (stored in muscle
fibers and liver)
–Lactic acid – soreness in muscles
• We breathe rapidly to restore
oxygen
Oxygen Debt (cont’d)
• Can lead to muscle
fatigue - muscles can’t
contract
• Once oxygen available,
lactic acid metabolized
within muscle cells
Cardiac Muscle
• Walls of heart
• Cylindrical, branching
• Striations
• Intercalated discs
• Intermediate contractions
• No oxygen debt
• Does not fatigue
• Contraction - autorhythmic
Smooth Muscle
•
•
•
•
•
•
Walls of hollow organs
Spindle shaped
No striations
No T Tubules
SR less developed
Contract more slowly with less
force
• Greatest ability to sustain
contraction
• No oxygen debt
Muscular Response
• All-or-None Response
–Pertains to single muscle
cell
–Weakest stimulus that can
initiate contractions –
threshold stimulus
–Muscles contract all the
way
Types of Muscle
Contractions
• Twitch
– Response to a
single, brief
threshold
stimulus
– A latent
period, a
period of
contraction,
and a period
of relaxation
Types of Muscle
Contractions (cont’d)
• Treppe
–Contraction
increases
slightly with
each
stimulus
Types of Muscle
Contractions (cont’d)
• Wave
Summation
– A muscle
receives a
second stimulus
before the first
is complete
– 2nd contraction
will be stronger
than 1st
Types of Muscle
Contractions (cont’d)
• Tetanus
–When successive stimuli
are received before
contractions are
completed
–Muscles reach maximum
contraction strength
–Sustained until stimuli
stops
Types of Muscle Contractions
(cont’d)
• Tetanus
(cont’d)
– If relaxation
occur
between
contractions
= incomplete
tetanus
– No relaxation
= complete
tetanus
Types of Muscle Contractions
(cont’d)
• Tetanus (cont’d)
–2 types of tetanic
contractions
Types of Muscle Contractions
(cont’d)
•Isotonic produce
movement
as the
muscle
pulls an
attached
structure
toward a
stationary
structure
until muscle
relaxes
Types of Muscle Contractions
(cont’d)
•Isometric
contraction produces
muscle tension
without
shortening
– No body
movement
results
» Ex. pushing
against an
immovable
object.
Exercise and Muscles
• Regular aerobic exercise:
–increased efficiency,
endurance, and resistance to
fatigue of skeletal muscles
–more efficient cardiovascular,
respiratory, and
neuromuscular functioning
Exercise and Muscles
(cont’d)
• Resistance exercise
causes skeletal muscle
hypertrophy and large
gains in skeletal muscle
strength
Exercise and Muscles
(cont’d)
• Complete immobilization
of muscles lead to
muscle weakness and
severe atrophy
Exercise and Muscles
(cont’d)
• Improper training and
excessive exercise result
in overuse injuries
–May be disabling
Truth About Anabolic
Steroids
• Synthetically produced
versions of testosterone
• Increase in weight or
muscle mass
• Addictive
• Behavioral changes,
aggression
• Permanent kidney damage
Truth About Anabolic
Steroids
• Increased cancer
incidence
• Sex drive reduced
• Shriveled testes –
infertility
• Changes in blood
cholesterol
Symptoms of Dependency
• More steroids often taken than
intended
• A desire to control or reduce
steroid use, which is not
realized
• A large amount of time spent
on steroid related activities
• Replacement of daily activities
by steroid use
Symptoms of Dependency
• Continued, prolonged use
despite recognition of problems
caused by steroids
• Tolerance of increasing doses
• Frequent feeling of anxiety or
intoxication when not using
steroids
• Use relieves anxiety symptoms