Blood pressure

Cardiovascular System

2. •Bloodpressureistheforceorpressureof
thebloodagainstthewallsoftheblood
vessels.
•Arterialbloodpressureisameasureofthe
pressureexertedbythebloodasitflows
throughthearteries.Itistheresultofthe
ejectionofbloodfromtheleftventricleinto
theaorta.

3. •Bloodpressureismentionedintermsof
systolicbloodpressureoverdiastolicblood
pressure.
•Systolicbloodpressureisthehighest
pressureattainedinarteriesduringsystole
anddiastolicbloodpressureisthelowest
arterialpressureduringdiastole

5. •Thesystolicpressureisthepressureasa
resultofcontractionoftheventricles.When
theleftventriclecontractsandpushesblood
intotheaortathepressureproducedwithin
thearterialsystemiscalledthesystolic
bloodpressure.
•Inadultsitisabout120mmHg.

6. •Thediastolicpressureisthepressurewhen
theventriclesareatrest.
•Whencompletecardiacrelaxationoccurs
andtheheartisrestingaftertheejectionof
blood,thepressurewithinthearteriesis
calleddiastolicbloodpressure.
•Inanadultitisabout80mmHg.

7. •Arterialbloodpressureis
measuredwithasphygmomanometer.
•Bloodpressureisrecordedasafraction:
systolicpressureoverthediastolicpressure,
andexpressedinmillimetersofmercury
(mmHg).
•Atypicalbloodpressureforahealthyadultis
120/80mmHg.

8. Pulse pressure
•Thedifferencebetweensystolicanddiastolic
bloodpressuresisthepulsepressure.
•Anormalpulsepressureisabout40mmHg.

9. Factors Affecting Blood Pressure
•Age:Thepressureriseswithage,reachingapeakat
theonsetofpuberty,andthentendstodecline.
•Exercise:Physicalactivityincreasesthecardiac
outputandhencethebloodpressure.
•Stress:Stimulationofthesympatheticnervous
systemincreasescardiacoutputand
vasoconstrictionofthearterioles,thusincreasing
thebloodpressure.
•Race:AfricanAmericanstendtohavehigherblood
pressuresthanEuropeanAmericans.Theexact
reasonsareunclear.

10. •Sex:Femaleshavelowerbloodpressuresthan
malesduetohormonalvariations.After
menopause,womenhavehigherblood
pressures.
•Medications:Manymedications,including
caffeine,mayincreaseordecreasetheblood
pressure.
•Obesity:Predisposetohypertension.
•Positions:Sitting,standingorlyingdown
positioncauseslightvariationinBP.
•Diurnalvariations(timeofday):Pressureis
lowestearlyinthemorning,whenthe
metabolicrateislowest,thenrisesthroughout
thedayandpeaksinthelateafternoonor
evening.

11. •Medicalconditions:Anyconditionaffecting
thecardiacoutput,bloodvolume,blood
viscosity,and/orcomplianceofthearterieshas
adirecteffectonthebloodpressure.
•Temperature:Becauseofincreasedmetabolic
rate,fevercanincreasebloodpressure.
However,externalheatcausesvasodilationand
decreasedbloodpressure.Coldcauses
vasoconstrictionandelevatesbloodpressure.

12. Regulation of blood pressure
1.Regulation by cardio vascular center
2.Neural regulation
3.Hormonal regulation
4.Auto regulation

13. 1.Regulation by cardiovascular center
Thecardiovascular(CV)centerinthemedulla
oblongatacontrolsneural,hormonal,andlocalnegative
feedbacksystemsthatregulatebloodpressure.
GroupsofneuronswithintheCVcenterregulate
heartrate,contractility(forceofcontraction)ofthe
ventricles,andbloodvesseldiameter.Someneurons
stimulatetheheart(cardiostimulatorycenter);others
inhibittheheart(cardioinhibitorycenter).
Someneuronscontrolbloodvesseldiameterby
causingconstriction(vasoconstrictorcenter)ordilation
(vasodilatorcenter)whichisreferredasthevasomotor
center. AllgroupofneuronsintheCVcenterneurons
communicateoneanotherandfunctiontogether.

15. •Thecardiovascularcenterreceivesinput
bothfromhigherbrainregionsandfrom
sensory receptors(proprioceptors,
baroreceptors,andchemoreceptors).
•Outputfromthecardiovascularcenterflows
alongsympatheticandparasympathetic
neuronsoftheANS.
Sympath
etic
impulse
via cardiac
accelerator
nerves
Reach
heart
Sympatheti
c
stimulation
Increases
heart
rate and
contractil
ity
Increases
BP

16. •Thecardiovascularcenteralsosends
impulsestosmoothmuscleinbloodvessel
wallsviavasomotornerves.Thisproduce
sympatheticstimulationandresultsin
vasoconstriction.ThusincreasesBP.
Para
sympathe
tic
impulse
Via
vagus
nerve
Reach
heart
Inhibitory
action
Decrease
heart
rate
Decrease
BP

17. 2.Neural regulation
•ThenervoussystemregulationofBPisanegative
feedbackmechanismviabaroreceptorreflexesand
chemoreceptorreflexes.
i.Baroreceptorreflexes
Baroreceptorsarepressure-sensitivesensory
receptors,locatedintheaorta,internalcarotidarteries
andotherlargearteriesintheneckandchest.They
sendimpulsestothecardiovascularcentertohelp
regulatebloodpressure.
Thetwomostimportantbaroreceptorreflexes
arethecarotidsinusreflexandtheaorticreflex.

18. •Baroreceptorsinthewallofthecarotid
sinusesinitiatethecarotidsinusreflex
helpstoregulatebloodpressureinthe
brain.Nerveimpulsesfromthecarotidsinus
reachthecardiovascularcentervia
glossopharyngealnerves.
•Baroreceptorsinthewalloftheaorta
initiatetheaorticreflex,whichregulates
systemicbloodpressure.Nerveimpulses
fromaorticbaroreceptorsreachthe
cardiovascularcenterviavagus(X)nerves.

19. Decrease BP
impulses from baroreceptors to CV center
parasympathetic stimulation
sympathetic stimulation
secretion of epinephrine and norepinephrine
by the adrenal medulla
Increased heart rate vasoconstriction
Increased CO systemic vascular resistance
Increase BP negative feed back

20. ii.Chemoreceptor Reflexes
Chemoreceptorsaresensory receptors that
monitor the chemical composition of blood
located close to the baroreceptors of the carotid
sinus and arch of the aorta. Chemoreceptors
detect changes in blood level of O
2, CO
2, and H
+
.
Hypoxia (lowered O
2availability), acidosis
(an increase in H
+
concentration) or hypercapnia
(excess CO
2) stimulates the chemoreceptors to
send impulses to the cardiovascular center.
In response, the CV center increases
sympathetic stimulation to arterioles and veins,
producing vasoconstriction and increases blood
pressure.

21. 3.Hormonal regulation
Hormonal regulation of BP is done by
i.Renin–angiotensin–aldosterone system
ii.Epinephrine and norepinephrine
iii.Antidiuretic hormone (ADH)
iv.Atrial natriuretic peptide

22. i.Renin–angiotensin–aldosterone system
Renal blood flow
Blood volume
Blood pressure
Secretion of renin by kidneys
Angiotensinogen Angiotensin 1
by ACE
Angiotensin2
Secretion of aldosterone Vasoconstriction
Increases blood pressure

23. Whenrenalbloodflowisreducedor
bloodvolumedecreasesorBPdropsthe
enzymereninissecretedbykidneycells.
Reninconvertstheplasmaprotein
angiotensinogen,producedbytheliver,to
angiotensin1.Angiotensinconvertingenzyme
(ACE)convertsangiotensin1toangiotensin2.
Angiotensin2causesvasoconstrictionand
increasesbloodpressure.Alsoangiotensin2
stimulatessecretionofaldosteronewhich
causesvasoconstrictionandincreasesblood
pressure.

24. ii.Epinephrine and norepinephrine
Inresponsetosympatheticstimulation,the
adrenalmedullareleasesepinephrineand
norepinephrine.Thesehormonesincrease
cardiacoutputbyincreasingtherateandforceof
heartcontractions.ThusincreasesBP.
Sympathetic stimulation
Release of epinephrine and norepinephrine
Increase heart rate and contractions
Increase CO
Increase BP

25. iii.Antidiuretic hormone (ADH)
Decreased blood volume
ADH released from the posterior pituitary
Vasoconstriction ADH promotes movement of
water from kidney tubules into
bloodstream
blood volume and urine
output
Increases CO
Increases blood pressure

26. iv.Atrialnatriureticpeptide
Atrialnatriureticpeptide(ANP)is
releasedbycellsintheatriaoftheheart.ANP
lowersbloodpressurebycausingvasodilation
andbypromotingthelossofsaltandwaterin
theurine,whichreducesbloodvolume.

27. 4.Auto regulation
•Theabilityofatissuetoautomaticallyadjust
itsbloodflowtomatchitsmetabolicdemands
iscalledautoregulation.
•Inheartautoregulationisanimportant
contributortoincreasedbloodflowthrough
thetissue.
•Stimulithatcauseautoregulatorychangesin
bloodfloware;
–Physicalchanges:Warmingpromotesvasodilation,
andcoolingcausesvasoconstriction.
–Vasodilatingandvasoconstrictingchemicals

28. THANK YOU