5. Arranged in large sheet.
Haslow resistance bridges
(GapJunctions)between
individual muscles.
Function in a Syncitial
fashion & contract as a
single unit.
Has their own Rhythmic
contractility ( Myogenic
Tone)
6. Rate of contraction
determined by
Pacemakerregion &
Nervesupply only
Modulatesits activity.
Contraction is
stimulated by
Stretchinginvolved in
Autoregulationof blood
flow.
7. Made up of Multiple
units without
interconnecting
bridges-Non-Syncitial.
LocationâBlood
vessels, Epididymis, Vas
deference, Iris, Ciliary
body & Piloerector
muscle.
8. Multi-unit muscle each
innervated by single
nerve ending.
Contraction is
Neurogenic& each
stimuli causes
irregular Tetanic
contraction.
11. Post ganglionic fibres
branch extensively.
Neuronal network has
Beadedappearance
due to varicosities.
Varicosities contains
chemical
neurotransmitter
(Ach/NE)
12. Nerve fibres donotendin
MotorEndPlatebut releases
its neuro-transmitter in
interstitialfluid near muscle
fibre.
It then diffusesin muscle fibre
& causes activation.
So single stimuli will not cause
activation of entire muscle
MultipleStimuliare required.
13. Either depolarizing or
repolarizing responses
are recorded in
response to stimuli.
These potentials
Summatewith
repeated stimuli
EJP&IJPare local
responses.
14. Spindle shaped cells with
broad central part &
tapering ends.
Length & diameter varies
with organ
GITâ30-40 mm/5 mm
diameter.
Bloodvesselsâ15-20
mm/2-3 mm.
Uterusâ300 mm/10 mm
15. Plasmamembraneâsurrounded by Externa
Lamina.
Cell communicate through Gap Junction.
Sarcoplasm
NucleusâCentral/Oval
Contains Mitochondria, Golgi apparatus, Endoplasmic
Reticulum, Ribosomes.
Sarcoplasmicreticulumâsimilar to skeletal
muscle but not as developed.
16. t
Myofibrils-Sarcotubular
system & triad not well
developed.
Lessthick filaments &
Morethin filaments.
Zline not well developed.
ActinâTroponin is absen
Myosinâbind only if
phosphorylated.
17. Densebodies â
attached to thecell
membrane
Actin filaments are
attached to dense
bodies.
When muscle contracts
dense bodies are drawn
close to each other.
20. Rangebetween- -50mv to
-75mv
PeculiarityâUnstability â
keeps on oscillating between -55
to -35mv.
Oscillationsduetoâ
Superimposition by pacemaker
potential due to rhythmicchange
in Cachannelpermeability&
activity of Na-KPump.
21. When depolarization
reaches threshold action
potential begins &
transmitted to other muscle
cells through Gapjunctions.
3 types action potential
Spike potential
Spike potential over
pacemaker potential
Action potential with plateau.
22. Similartoskeletal
muscleexcept
Durationâ10 to 50 msec
Amplitudeâvery low
Donot reach Iso-electric
base.
Occur in response to
electrical stimulation,
hormone, neurotransmitter
& stretch of smooth muscle.
23. Slow wave rhythm called
Pacemakerwaves seen in
GIT
These cannot cause muscle
contraction but when
potential rises above -35mv
action potential develop.
Appear rhythmically &
causes contraction of muscle
fibre.
24. Seen in ureter, uterus &
vascular smooth muscle.
Like in skeletal muscle there
is rapid depolarization but
Repolarization is delayed
by 100-150msec.
This prolonged
depolarization is
responsible for sustained
contraction of certain
smooth muscle.
25. Depolarizationâdue to entry
of Carather thanNa.
This muscle has more voltage
gated Cachannels than Na
channels.
These open & close slowly &
responsible for prolonged
action.
Caalong with depolarization
alsocausescontraction of
smooth muscle.
27. Molecular mechanism is similarto skeletal muscle
but..
Smooth muscle donât contain Tropomyosin &
Troponin.
Light chain of Myosin acts as Tropomyosin & called
ď¨ Regulatorychain of Myosin.
Ca binding protein Calmodulinacts as Troponin.
28.
29. Cacombinewith Calmodulinâforms
complex âactivates enzymeMyosinLight
ChainKinase (MLCK)
Phosphorylation of the Myosin Regulatory
chain.
Myosin head acquires capability to bind with
actin & forms Cross-bridging.
30.
31. Powerstroke âformation of Actin-Myosin
ADPPi complex âconfirmational change in
myosin head- flex towards arm âgenerate
mechanical force i.e. Power Stroke.
Actin slide over myosin & causes contraction
Dense bodies are same as Zline.
RelaxationofsmoothmuscleâCapump
removes Cafrom ICFto ECFâreverse all stages
except Phosphorylation of Myosin.
36. CanReadjustits
resting length.
Thus it not follows
length tension
relationship that is valid
for striated muscle.
So length tension
relationship curve is
Jaggedline.
37. Mechanism by which
smooth muscle maintain
high tension without
actively contracting.
Allows long term
maintenance of Tone.
So muscle can not generate
active tension but Resists
passive stretching.
38. Since smooth muscle found
mainly in hollow viscera
that should resists
stretching.
CAUSEâBoth myosin
kinase & myosin
phosphatase enzyme
strongly activated, cycling
frequency of myosin head &
velocity of contraction
increases.
39. As this activation &
cycling frequency
decreases âlower
activation of enzymes
causes myosin head to
remain attached to actin
for longer time with less
energy expenditure as
ATP is required for
detachment.
40. Asmooth muscle can
contract more than 2/3rd
its stretched length
while skeletal muscle
contract up to 1/3rd.
This allows viscera to
change diameter from
largetoalmost zero.
43. Control movement of material through most
of hollow organs
Propel material in GIT
Control blood flow in arterioles.
Expell material from bladder.
Control Piloerection
Iris control.