Muscle
Thick filaments: Myosin, rodlike tail terminates in
Contraction:
potential
energy
stored
in
high-energy
Skeletal
(striated,
voluntary),
cardiac
(striated,
invSarcolemma
(plasma
membrane),
sarcoplasm
(cytEvents
during
contraction:
Nerve
impulse
(afferent
Contraction
of
skeletal
muscle
(sliding
theory):
two globular
heads,
tail
consists
of heavy
meromysin
configuration
is used
to pivot myosin
head (myosin
oluntary),
smooth
(non-striated,
involuntary).
oplasm
of muscle
cells),
myofibrils
(contractile
signal)
from
motor
neuron
generates
AP inconsists
nerve
Thin
filaments
slide
past
thick
ones,
overlap
to a
(polypeptide
chains
(2)
interwoven),
head
Individual
fibers
surrounded
by
endomysium
2+
head
bends
as itstate:
pulls
on actin,
ADP
and inorganic
During
relaxed
Ca
conc.
in(fibers),
sarcoplasm
is
Common
features:
elongated
cells
myofilaMicrofilaments
(myofilaments)
with
in and
bands
elements
ofheavy
skm),
A-band
(dark
band):
anisotropic
cell,
AP of
propagated
along
sarcolemma
down T
greater
degree.
Prior
to contraction
cross
bridges
of
ends
meromysin
+ light
meromysin,
(areolar
connective
tissue),
multiple
fibers
bundled
phosphate
are
released
from myosin),
newcomplex
ATP
low
(stored
in SR),
troponin-tropomyosin
ments
(actin&myosin),
comprised
of:
fibers,
CT,
Thick
filaments
(myosin):
entire
length
of
A-band,
(polarize
light),
I-band
(light
band):
Isotropic(nontubules,
myosin
ATPase
activated
(ATP
splits
to
are
disengaged
&
all
bands
distinct.
Nerve
impulse
during
contraction
heads
(cross
bridges)
interact
as
fascicles,
fascicles
bound
by
collagen
sheath
attach
to to
myosin
head
(cross
simultaneously
attached
actin
filament
(tobridge
block
myosin
binding
blood
vessels
&
nervous
tissue.
Terminology:
myo
thin
filaments
(actin):
across
I-bandengage,
&
part
of
A- in
polarizing),
H-band
(within
A-band):
visible
only
high
energy
myosin-ADP
complex),
AP
causes
initiates
cross
bridges
ATP
with
thincontraction,
myofilaments,
thin
myofilaments:
actin,
(perimysium),
epimysium
surrounds
all
fascicles,
detach),
following
death
no ATP
(muscle
sites
on actin
filament),
ATP
andmaintain
inactivecannot
ATPase
2+
&
sacro.
Functions:
movement,
posture,
band,
Z-disc
(protein
sheet
connecting
myofibrils)
relaxed
muscle,
M-line
(bisects
H-band),
Z-disc
release
of
from
SR,
binds
to
splits,
energy
used
for
swinging
oftroponin,
cross
bridges,
consists
ofCa
Gbinds
(globular)
actin,
double
stranded
helix
deep
fascia
muscles
into
functional
groups
2+
relax:
rigor
mortis),
if no
new
impulse;
Ca is
bound
tojoints
myosin
head
(low
energy
configuration,
stabilize
&
temperature
homeostasis.
(membrane):
midline
in
I-band,
Sarcomere
(region
molecular
shape
of troponin
changes
(tropomyosin
actin
filaments
pulled
together,
H-zone
and
Z-disc
regulatory
proteins:
tropomyosin,
sprial
around
pumped
back
into
relaxation occurs, if Ca2+
binding to
actin
not(SR),
possible)
between
two
successive
Z-discs):
functional
unit
is
removed
from
binding
site
of mysosin
on the
smaller
or
lost,
I-band
reduced,
cross
actin,
block
myosin
head
binding
sites:bridges
relaxation,
present from additional impulse; cycle repeats
2+ (TnC),
actin
filament),
myosincomplex),
attaches
to
actin.
disengage
& filaments
return
to original
troponin
(polypeptide
binds
Caposition.
(myosin head “steps” to next binding site on actin)
binds
Exit tropomyosin (TnT) & binds actin (TnI) Home
BASIM ZWAIN LECTURE NOTES
Muscle
Comparison
Regulation
Motor
Cardiac
Smooth
unit
muscle
Muscle
ofofContraction
skeletal, cardiac & smooth muscle
Characteristic
Skeletal
Cardiac
Smooth
Characteristic
Characteristic
Skeletal
Cardiac
Smooth
Isotonic
Muscle
Metabolism
and
Isometric
ATP
contractions
is
sole
source
of
energy
for
Transduction
Red
muscles
contain
events:
higher
%
of
red
fibers
with
mV interdigitated,
Small,
spindle-shaped,
sheets
of
opposing
fibers,
Branched,
syncytium,
intercalated
Gap
Junctions
None
Intercalated
In
single-unit
Muscle
twitch:
response
of
muscle
to
single
supraLocation
Attached
to
Walls
of
heart
Single-unit:
visceral
organs
Pacemakers
None
Present
In
single-unit
Prepotentials
N
o
r
m
a
l
r
h
y
t
h
m
Tetanus:
At
high
frequencies,
no
relaxation
occurs,
Tension
contraction,
is
force
little
of
ATP
contracting
is
stored,
muscle
regenerated
on
an
object,
Synapse
is
site
of
communication
between
neuron
1.
few
Nerve
white
impulse,
fibers.
They
2.
ACh
respond
released
slowly,
from
long
presynaptic
latency,
Could
be
small
in
size
(few
collaterals
arise
from
discs
bones,
fascia
and
Multi-unit:
Internal
eye
Property
of
stress-relaxation
(plasticity)
,
gradual
Pacemaker
potential:
Cardiac
muscle
contraction
generally
two
sheetsmuscle:
(longitudinal
&phase
circular):
discs,
gap
junctions,
RMP
=Function
-85
mV,
AP
slow,
Nervous
System
Excitation
Excitation
or
Excitation
or
inhibition
+20
threshold
Single-unit
stimulus,
smooth
3
Phases:
latent
as
syncytium,
(few
ms),
contractions
fuse,
smooth
sustained
contraction
+
Neuromuscular
Present
None
In
multiunit
load
(recycled)
is
reciprocal
rapidly:
force
direct
exerted
phosphorylation
by
object,
to
of
move
ADP
1
skinposture
muscles,
large
airways
and
and
muscle
(neuron
to
neuron
in
nervous
system):
Neuromuscular
junction
is
connection
between
specialized
neuron,
for
3.
Binds
maintenance,
to
receptors,
Na
contain
channels
more
motor
nerve
to
supply
few
muscle
fibers)
or
large
in
increase
in
stretch;
tension
increase
then
decrease
Treppe
force
of
contraction
ncrz
during
response
to
myogenic,
(originated
in
muscle)
not
neurogenic
Affects
inhibition
plateau,
peristalsis,
AP
lacks
phases
highly
are:
structured
Phase
0:
Depolarization:
NMJ,
lower
2
2 contraction
found
mainly
in
the
wall
of
hollow
viscera.
contraction
phase
(
10-100
ms),
relaxation(
10-100
ms)
Junctions
Velocity
duration
of
l
as
load
ncrz,
0and
arteries
Force
of
Contraction
more
motor
units
recruited;
Motor
unit
summation
(response
to
ncrz
stimulus
object;
by
creatine
tension
phosphate,
must
be
anaerobic
greater
than
glycolysis
load.
(in
the
2+
Contact
is
not
direct,
physical
separation,
synaptic
somatic
nervous
system
and
muscles:
motor
neuron
open,
blood
depolarizing
capillaries,
mitochondria
current,
AP,
ACh
and
myoglobin,
destroyed
size
(so
numerous
collaterals
and
muscle
fibers).
+
+,
Speed
of
Varies:
slow
to
Slow
Very
slow
even
below
its
initial
level,
uterus
to
adapt
increase
Regulation
of
Somatic
NS;
Autonomic
NS,
Autonomic
NS,
hormones,
local
stimuli
at
the
same
strength,
result
ofinon-striated,
ncrz
Ca
(initiated
by
nerve),
nerve
isrNo
regulatory:
presence
myosin
to
actin
ratio
than
skm
(1:13
vs.
1:2),
lacks
ms,
activation
of
all
Na
channels,
influx
of
Na
Appearance
Single,
long,
Branching
Single,
uninucleate
Graded
Multi-unit
responses
smooth
depend
muscle:
on
stimulation
gap
junctions,
frequency
each
velocity
and
duration
decrease,
muscle
fiber
type
0
B
a
d
y
c
a
r
d
a
greater
force,
greater
cross
sectional
area;
greater
Fatty
acids
are
the
major
source
of
energy
at
rest
intensity):
primary
mechanism
for
ncrz
force
of 5.
Isotonic
absence
of
contraction
O
,
glycolytic
(change
products
in
length):
“pyruvic
concentric
acid”
Contraction
voluntary
intrinsic
regulation,
response
to
stretch
Contraction
fast
cleft,
requires
signal,
transduced
to
chemical
signal
axons
bifurcate
to
form
multiple
endings:
separate
(ACE),
resistant
4.
to
AP
fatigue,
propagated,
sensitive
sarcolemma,
to
hypoxia.
T
White
tubules,
cylindrical,
chains
of
cells,
Three
types
of
muscle
fibers:
Slow
oxidative
fibers
2
3
in
fetal
size,
urinary
bladder
to
adapt
increase
in
availability,
heat
created
during
contraction
ncrz
of
specialized
conductive
tissue
in
heart,
pacemaker
troponin
complex
and
sarcomeres.
Gap
junctions
Phase
1:
Initial
rapid
repolarization,
inactivation
of
&
muscle
strength.
works
Temporal
individually,
(wave)
found
summation:
in
the
iris
strength
of
eye,
(slow
or
fast),
pathway
for
ATP
formation
(aerobic
(pacemaker),
tension,
optimum
resting
length
is
the
length
at
striated,
uninucleate,
contraction,
multiple
motor
unit
2+
2+
2+
Rhythmic
None
Yes
Insummation
single-unit
(muscle
are
metabolized
shortens
to
and
lactic
does
acid
work),
producing
eccentric
additional
(muscle
85
4by
(NT,
ACh
is
NT
at
NMJ)
endings
synapse
with
individual
mfs
(mf
synapses
Ca
muscles
released
contain
from
higher
SR,
%
6.
Ca
of
white
removed
fibers,
few
Ca
red
(slow
red),
fast
oxidative
fibers
(fast
red)
which
is
+
urine
volume.
Sm
in
continuous
partial
contraction
efficiency
of
enzymes
(warming,
athletic
activity)
tissue,
unstable
low
potential,
prepotential,
declines
Na
make
channels,
entire
sheet
Phase
responds
2:
Plateau:
to
a
single
200
ms,
stimulus,
opening
of
hormones,
multinucleate
striated
vas
deferens,
epididymus,
large
pulmonary
airways
of
contraction
increases
with
successive
stimuli,
or
anaerobic
glycolysis)
Contraction
which
maximum
force
can
be
generated
(recruitment),
at
threshold;
first
contraction,
as
contracts
small
quantities
as
it
lengthens),
of
ATP,
aerobic
concentric
respiration:
and
eccentric
95%
Motor
end
plate
is
physical
modification
of
sarcowith
single
motor
neuron,
motor
neurons
synapse
+
pumps,
fibers,
respond
contraction
quickly,
ceases,
short
7.
At
latency,
individual
specialized
muscle
involuntary
very
rare
in
human,
fast
glycolytic
fibers
(fast
2+
2+,
2+
Connective
Epimysium,
Endomysium
Endomysium
(tone),
nerve
supply
&
multiple
NT
to
modify
tone,
&
depolarizes
continuously:
decrease
in
K
efflux,
Ca
some
channels,
has
pacemaker,
influx
of
some
Ca
self-excitatory,
Phase
3:
Late
Ca
rapid
Response
to
Strength
of
Strength
of
Stress-relaxation
response
2+ thatblood
T
a
c
h
y
c
a
r
d
i
a
and
large
vessels.
They
have
many
functional
fibers
are
already
contracted,
contract
further
0 same
Time
>200
msactivated,
Ca
Source
SR
SR,
extracellular
SR,
extracellular
fluid
stimulus
intensity
ncrz;
additional
units
Tissue
perimysium,
can
of
ATP
occur
during
at
the
light
exercise,
time,
eccentric
in
presence
put
of
muscle
O
,
to
lemma
where
neuron
synapses
with
fiber,
ACh
with
multiple
mf)
fibers
for
fine
(cells);
skilled
contraction
movements,
is
less
all
or
blood
nothing,
capillaries,
in
white).
Skeletal
muscle
is
a
mixture
of
these
types
2+
2
also
affected
by
chemicals,
pH,channels,
temperature,
CO
2+,over
spreads
impulses
all
heart.
Steeper
prepotentStretch
contraction
contraction
(plasticity)
interacts
with
regulatory
molecules:
calmodulin,
repolarization,
closure
of
Ca
Phase
4:2,
fluid
with
similarities
additional
to
skeletal
Ca
if
muscles
stimulation
but
irregularly
is
delivered
and
endomysium
maximal
stimulus:
strongest,
causes
ncrz
contractconcentric,
products
of
isometric
glycolysis
contraction
broken
down
(tension
entirely,
ncrz
with
but
2+to
receptors
located
on
motor
end
plate
response
mitochondria
threshold
and
myoglobin,
stimuli,
APs
less
sensitive
are
generated
to
in
of
fibers,
so
there
are
red
and
white
muscles
increases
increases
Role
of
Ca
Via
Via
Via
calmodulin/myosin
O
....etc,
Two
types
of
sm:
Single-unit
&
Multi-unit
ials:
tachycardia,
lower
prepotentials:
bradycardia.
Sarcomere
Present
Present
None
Base
slow,
line
sustained
(RMP)
&
resistant
to
fatigue.
It
contracts
2
involuntarily
contract
with
prolonged
duration.
prior
to
relaxation,
contractions
are
summed
ion,
accomplished
by
ncrz
neural
activation
length
generation
constant):
oftroponin/actin
large
amounts
greater
ofthan
ATP,
glycogen
(maintenis the
troponin/actin
interaction
Aerobic
oreach
Aerobic
Primarily
anaerobic
TRespiration
Tubules
Present
atload
Present
at one
Noneforce
ainnon-graded
hypoxia,
easily
fashion,
fatigued.
8.
When
Refractory
nerve
period
to
slow
cells
fiber
response tointeractions
stretch.
interactions
end
end aerobic involve
anaerobic
Home
Exit
ance
source
of
of
posture,
glucose
most
for
both
movements
&
anaerobic
both
must re-polarize
replaced
by
nerve
before
to
fast
another
fiber;
slow
AP
becomes
fast!
BASIM ZWAIN LECTURE NOTES
_
Muscle
Lever systems
Muscle Mechanics
Exit
BASIM ZWAIN LECTURE NOTES
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