EFFECT OF EFFECT OF LOCAL TISSUE LOCAL TISSUE

FACTORSFACTORSHORMONES TO CAUSE HORMONES TO CAUSE

SMOOTH MUSCLE SMOOTH MUSCLE CONTRACTION WITHOUT CONTRACTION WITHOUT

ACTION POTENTIALACTION POTENTIAL

SMOOTH MUSCLE CONTRACTION SMOOTH MUSCLE CONTRACTION IN RESPONSE TO LOCAL TISSUE IN RESPONSE TO LOCAL TISSUE

CHEMICAL FACTORSCHEMICAL FACTORS Initiation of smooth muscle Initiation of smooth muscle

contraction by stimulatory factorscontraction by stimulatory factors Without action potentialWithout action potential Non-nervous stimulatory factorsNon-nervous stimulatory factors

1.Local tissue factors1.Local tissue factors 2.Various hormones2.Various hormones

SMOOTH MUSCLE CONTRACTION SMOOTH MUSCLE CONTRACTION IN RESPONSE TO LOCAL TISSUE IN RESPONSE TO LOCAL TISSUE

CHEMICAL FACTORSCHEMICAL FACTORS Smallest vessels have absence of nervous Smallest vessels have absence of nervous

supplysupply Responding rapidly to changes in local Responding rapidly to changes in local

chemical condition in the surrounding chemical condition in the surrounding interstitial fluidinterstitial fluid

In normal resting state contraction of blood In normal resting state contraction of blood vessels occurvessels occur

Extra blood is needed by tissueExtra blood is needed by tissue Relaxation of vessel by multiple factorsRelaxation of vessel by multiple factors Allowing for increased flow Allowing for increased flow

CONTROL SYSTEMSCONTROL SYSTEMS Local feedback control systemLocal feedback control system Control blood flow to local tissue areaControl blood flow to local tissue area Lack of oxygen in the local tissueLack of oxygen in the local tissue It causes smooth muscle relaxation and It causes smooth muscle relaxation and

vasodilationvasodilation Excess carbon dioxide causes Excess carbon dioxide causes

vasodilationvasodilation Increased hydrogen ion concentration Increased hydrogen ion concentration

causes vasodilationcauses vasodilation

CONTROL FACTORS CONTROL FACTORS CAUSING VASODILATIONCAUSING VASODILATION

AdenosineAdenosine Lactic acidLactic acid Increased potassium ionsIncreased potassium ions Low calcium ion concentrationLow calcium ion concentration High body temperatureHigh body temperature

EFFECT OF HORMONES ON EFFECT OF HORMONES ON SMOOTH MUSCLE CONTRACTIONSMOOTH MUSCLE CONTRACTION EpinephrineEpinephrine Nor-epinephrineNor-epinephrine AcetylcholineAcetylcholine AngiotensinAngiotensin EndothelinEndothelin VasopressinVasopressin OxytocinOxytocin

EFFECT OF HORMONES ON EFFECT OF HORMONES ON SMOOTH MUSCLE CONTRACTIONSMOOTH MUSCLE CONTRACTION SerotoninSerotonin HistamineHistamine Hormone-gated excitatory receptorHormone-gated excitatory receptor Hormone-gated excitatory receptorHormone-gated excitatory receptor

MECHANISM OF SMOOTH MUSCLE MECHANISM OF SMOOTH MUSCLE EXCITATION OR INHIBITION BY EXCITATION OR INHIBITION BY HORMONES OR LOCAL TISSUE HORMONES OR LOCAL TISSUE

FACTORSFACTORS MECHANISM OF SMOOTH MUSCLE MECHANISM OF SMOOTH MUSCLE

EXCITATION EXCITATION Nerve stimulationNerve stimulation Hormone receptor in membraneHormone receptor in membrane Open sodium and calcium channelsOpen sodium and calcium channels DepolariztionDepolariztion Enhancement of action potential Enhancement of action potential

alreadty occuringalreadty occuring

MECHANISM OF SMOOTH MECHANISM OF SMOOTH MUSCLE EXCITATIONMUSCLE EXCITATION

In other casesIn other cases No action potentialNo action potential Depolarization occursDepolarization occurs Allows Ca influxAllows Ca influx Promotes contractionPromotes contraction

MECHANISM OF SMOOTH MECHANISM OF SMOOTH MUSCLE INHIBITIONMUSCLE INHIBITION

Hormone or tissue factors closes sodium Hormone or tissue factors closes sodium and calcium channelsand calcium channels

Entry is non-permissibleEntry is non-permissible Normally closed potassium channels are Normally closed potassium channels are

openedopened Allowing positive ions to diffuse out of the Allowing positive ions to diffuse out of the

cellcell Increase of negativityIncrease of negativity HyperpolarizationHyperpolarization Cessation of contractionCessation of contraction

MECHANISM OF SMOOTH MECHANISM OF SMOOTH MUSCLE EXCITATION BY MUSCLE EXCITATION BY

HORMONESHORMONES No change in membrane potentialNo change in membrane potential Hormone activate a membrane receptorHormone activate a membrane receptor No ion channel openingNo ion channel opening Cause an internal change in muscle cellCause an internal change in muscle cell Release of calcium ions from Release of calcium ions from

intracellular sarcoplasmic reticulumintracellular sarcoplasmic reticulum ContractionContraction

MECHANISM OF SMOOTH MUSCLE MECHANISM OF SMOOTH MUSCLE INHIBITION BY RECEPTOR INHIBITION BY RECEPTOR

MECHANISMSMECHANISMS Activation of enzyme adenylate cyclase Activation of enzyme adenylate cyclase

or guanylate cyclaseor guanylate cyclase Present in cell membranePresent in cell membrane Portions of receptor protrude in cellPortions of receptor protrude in cell Receptors are coupled with the enzymesReceptors are coupled with the enzymes Formation of cyclic adenosine Formation of cyclic adenosine

monophosphatemonophosphate Second messengerSecond messenger

SECOND MESSENGERSECOND MESSENGER They are molecules that relay signals from They are molecules that relay signals from

receptor on the cell surface to target receptor on the cell surface to target molecules inside the cellmolecules inside the cell

cAMP system, phosphoinositol, arachidonic cAMP system, phosphoinositol, arachidonic systemsystem

The binding of ligands (first messenger) to The binding of ligands (first messenger) to many cell surface receptors leads to a short many cell surface receptors leads to a short lived increase or decrease in concentration of lived increase or decrease in concentration of certain low molecular weight intracellular certain low molecular weight intracellular signalling molecules termed second messengersignalling molecules termed second messenger

EFFECTS OF SECONFD EFFECTS OF SECONFD MESSENGERMESSENGER

To change the degree of To change the degree of phosphorylation of enzymes phosphorylation of enzymes inhibiting contractioninhibiting contraction

Acivation of sarco pumpAcivation of sarco pump Acivation of cell membrane pumpAcivation of cell membrane pump Reduction of calcium ion Reduction of calcium ion

concentration in cellconcentration in cell Cessation of contractionCessation of contraction

EFFECTS OF EFFECTS OF SUBSTANCESSUBSTANCES

Same substance cause contraction Same substance cause contraction and relaxation in different locationsand relaxation in different locations

Nor-epinephrine inhibits contraction Nor-epinephrine inhibits contraction in intestinein intestine

Stimulates contraction in blood Stimulates contraction in blood vesselsvessels

SMOOTH MUSCLE SMOOTH MUSCLE CONTRACTIONCONTRACTION

SOURCE OF CALCIUM IONSSOURCE OF CALCIUM IONS Sarcoplasmic reticulum is slightly Sarcoplasmic reticulum is slightly

developeddeveloped Entry of calcium ions from extracellular Entry of calcium ions from extracellular

fluidfluid Concentration of calcium ions in Concentration of calcium ions in

extracellular fluid is greaterextracellular fluid is greater 10-3 molar inside smooth muscle10-3 molar inside smooth muscle Calcium pores openingCalcium pores opening Rapid diffusionRapid diffusion

SMOOTH MUSCLE SMOOTH MUSCLE CONTRACTIONCONTRACTION

200-300ms200-300ms Latent periodLatent period 50times great as compared to 50times great as compared to

skeletal musclesskeletal muscles

ROLE OF SMOOTH ROLE OF SMOOTH MUSCLE SARCOPLASMIC MUSCLE SARCOPLASMIC

RETICULUMRETICULUM Slightly developed sarcoplasmic reticulumSlightly developed sarcoplasmic reticulum CaveolaeCaveolae Small invaginations of cell membraneSmall invaginations of cell membrane Present to near to tubulesPresent to near to tubules Rudimentary analog of transverse tubule Rudimentary analog of transverse tubule

systemsystem Action potential reaches at caveloaeAction potential reaches at caveloae Transmission through sarco-tubulesTransmission through sarco-tubules Release of calcium ionsRelease of calcium ions

EFFECT OF SMOOTH MUSCLE CONTRACTION EFFECT OF SMOOTH MUSCLE CONTRACTION CAUSED BY CHANGING OF EXTRACELLULAR CAUSED BY CHANGING OF EXTRACELLULAR

CALCIUM ION CONCENTRATIONCALCIUM ION CONCENTRATION

Changing in extracellular calcium Changing in extracellular calcium ion concentration in skeletal musclesion concentration in skeletal muscles

Opposite effect for smooth musclesOpposite effect for smooth muscles Calcium ion concentration falls from Calcium ion concentration falls from

1/3 to 1/101/3 to 1/10 Contraction is inhibitedContraction is inhibited

CALCIUM PUMPCALCIUM PUMP Calcium ions must be removed from Calcium ions must be removed from

intracellular enviromentintracellular enviroment Pumps calcium back to extracellular Pumps calcium back to extracellular

fluid or sacroplasmic reticulumfluid or sacroplasmic reticulum Slow actingSlow acting Comparison to skeletal musclesComparison to skeletal muscles Prolonged contractionProlonged contraction