heart physiology (Cardiovascular physiology) physiology of blood vessels

1. Regulation of Arterial
Pressure-II
Prof. Dr. Rashid Mahmood
Surah: 3 Aal-e-ImranSurah: 3 Aal-e-Imran

2. Intermediate
mechanisms of
arterial pressure
control
Prof. Dr. Rashid Mahmood 2

3. Blood
pressure
control
systems
Prof. Dr. Rashid Mahmood 3

4. Intermediate mechanisms of
BP control
•Vasopressin mechanism
•Atrial natriuretic mechanism
•Stress-relaxation response
•Capillary Fluid shift mechanism
•Renin angiotensin mechanism
Prof. Dr. Rashid Mahmood 4

5. Intermediate mechanisms of
BP control
Vasopressin mechanism
Causes increased reabsorption of
water from the kidney tubules

6. Intermediate mechanisms of
BP control
Atrial natriuretic mechanism (ANP)
♦ released from the cardiac muscle when atrial
blood pressure increases (Atrial stretch)
♦ Effects:
• Decreased reabsorption of Na in the kidney
tubules
• Stimulates an increase in urine production
• Decreases blood volume and blood pressure

7. Intermediate mechanisms of
BP control
Stress-relaxation response
Adjustment of smooth muscles of blood vessels
↓ blood volume → reverse stress relaxation
(contraction) of the blood vessels → ↑ blood
pressure

8. Intermediate mechanisms of
BP control
♦ Capillary fluid shift mechanism
Movement of fluid from and into the
interstitial spaces from the capillaries

9. Q.1
•Name any Intermediate mechanism
of BP control
Prof. Dr. Rashid Mahmood 9

10. Intermediate mechanisms of
BP control
Renin angiotensin mechanism
Renin is released from the kidney in
response to low blood pressure
Renin promotes the production of
angiotensin II

11. Renin angiotensin system
Juxtaglomerular apparatus
Prof. Dr. Rashid Mahmood 11

12. Sequential events by which increased
salt intake increases the arterial
pressure.
Increased salt intake
Increased extracellular volume
Increased arterial pressure
Decreased renin and angiotensin
Decreased renal retention of salt and water
Return of extracellular volume almost to
normal
Return of arterial pressure almost to normal

13. Renin angiotensin systemRenin angiotensin system
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1313

14. ADH & ThirstADH & Thirst
↑↑ HH22O Reabsorption &O Reabsorption &
↓↓ Urine outputUrine output →→ ↑↑ B.PB.P
ACEACE
BPBP
BPBP
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1414

15. Renin Angiotensin systemRenin Angiotensin system
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1515

16. Q.2Q.2
Write any two functions ofWrite any two functions of
Angiotensin IIAngiotensin II
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17. Long-termLong-term
control of BPcontrol of BP
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1717

18. Blood
pressure
control
systems
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1818

19. Renal- Body Fluid systemRenal- Body Fluid system
forfor
Arterial Pressure controlArterial Pressure control
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 1919

20. Long term regulation of BloodLong term regulation of Blood
PressurePressure
Body fluid controlBody fluid control
Balance between intake and out putBalance between intake and out put
fluid and saltsfluid and salts
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2020

21. Renal body fluid systemRenal body fluid system
↑↑ECF → ↑blood volume → ↑Blood pressureECF → ↑blood volume → ↑Blood pressure
→ ↑Urinary out put of salt and water→ ↑Urinary out put of salt and water
(Kidneys simply excrete extra volume of
blood responsible for ↑Blood pressure )
↓↓ECF → ↓blood volume → ↓Blood pressureECF → ↓blood volume → ↓Blood pressure
→ ↓ urinary out put of salt and water→ ↓ urinary out put of salt and water
(Retention of salt and water)
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2121

22. Renal body fluid systemRenal body fluid system
A few mm Hg rise in arterial pressureA few mm Hg rise in arterial pressure
• → ↑→ ↑ Urinary water loss- (Urinary water loss- (Pressure diuresisPressure diuresis))
• → ↑→ ↑ Urinary NaUrinary Na++
– (– (Pressure natriuresisPressure natriuresis))
Fall in arterial pressureFall in arterial pressure
• → ↓→ ↓ urinary water and Naurinary water and Na++
excretionexcretion
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2222

23. Pressure Diuresis (Renal out curve ROC)Pressure Diuresis (Renal out curve ROC)
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2323

24. Q.3Q.3
Define pressure diuresisDefine pressure diuresis
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2424

25. Renal body fluid mechanism ofRenal body fluid mechanism of
controlcontrol
150 mm Hg150 mm Hg
• More loss of waterMore loss of water
and salts thanand salts than
intakeintake
• Till equilibriumTill equilibrium
80 mm Hg80 mm Hg
• Intake of salt andIntake of salt and
water more thanwater more than
out putout put
• Till equilibriumTill equilibrium
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2525

26. PR and long term Arterial PressurePR and long term Arterial Pressure
BP = COP x PRBP = COP x PR
Long term increase in PR withoutLong term increase in PR without
changing ROC and/or salt & water intakechanging ROC and/or salt & water intake
does not maintain elevated pressuredoes not maintain elevated pressure
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2626

27. RelationshipRelationship
between PR,between PR,
COP andCOP and
ArterialArterial
pressure inpressure in
differentdifferent
clinicalclinical
conditionsconditions
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28. Increased ECF Volume CausesIncreased ECF Volume Causes
increased Arterial pressureincreased Arterial pressure
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2828

29. Excess pure water intake does not maintainExcess pure water intake does not maintain
elevated pressureelevated pressure
• It is very quickly excreted in the urineIt is very quickly excreted in the urine
• ADH mechanismADH mechanism
Excess salt intake is more important for longExcess salt intake is more important for long
term elevation of arterial pressureterm elevation of arterial pressure
• Thirst mechanismThirst mechanism
• ADH mechanismADH mechanism
• Osmotic retentionOsmotic retention
ImportantImportant
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2929

30. Chronic HypertensionChronic Hypertension
MAPMAP > 110 mm Hg> 110 mm Hg
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 3030

31. Take Home Points (1/2)Take Home Points (1/2)
IIntermediatentermediate mechanisms of BP controlmechanisms of BP control
includeinclude
1.1. Vasopressin (ADH) mechanism:Vasopressin (ADH) mechanism: causescauses ↑↑
reabsorption of waterreabsorption of water from kidneysfrom kidneys
2.2. Atrial natriuretic mechanism:Atrial natriuretic mechanism: causes ↓causes ↓
reabsorption of Nareabsorption of Na in the kidneyin the kidney
3.3. Stress-relaxation response:Stress-relaxation response: adjustment ofadjustment of
smooth musclesmooth muscle of blood vesselsof blood vessels
4.4. Capillary Fluid shift mechanism:Capillary Fluid shift mechanism: movement ofmovement of
fluid fromfluid from capillaries to interstitial spacescapillaries to interstitial spaces
5.5. Renin angiotensin mechanismRenin angiotensin mechanism
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 3131

32. Take Home Points (2/2)Take Home Points (2/2)
Renin angiotensin mechanismRenin angiotensin mechanism: ↓ blood pressure: ↓ blood pressure
causes secretion ofcauses secretion of reninrenin from kidneys. Reninfrom kidneys. Renin
convertsconverts AngiotensinogenAngiotensinogen intointo Angiotensin-IAngiotensin-I,,
which is then converted towhich is then converted to Angiotensin-IIAngiotensin-II byby
converting enzymeconverting enzyme in the lungsin the lungs
Angiotensin-II is a strongAngiotensin-II is a strong vasoconstrictorvasoconstrictor. It. It
causescauses ↑ reabsorption of Na from kidneys↑ reabsorption of Na from kidneys by aby a
direct actiondirect action and by stimulating secretion ofand by stimulating secretion of
aldosteronealdosterone..
Angiotensin-II also causesAngiotensin-II also causes ↑ secretion of ADH↑ secretion of ADH
and stimulates thirstand stimulates thirst
Long acting arterial pressure control is byLong acting arterial pressure control is by renal-renal-
body fluid systembody fluid system that acts inthat acts in hours to dayshours to days 3232

33. Q.4Q.4
Name the Long acting arterialName the Long acting arterial
pressure control systempressure control system
Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 3333

34. Questions ?Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 3434