Arterial Blood Pressure ( Cardiovascular Physiology )

1. Arterial BP
Dr. Mohammed AL-Mojtaba A. Awad

2. Objectives
• Definition
• Components & Calculated Pressures
+Systolic
+Diastolic
+Pulse pressure
+MAP
• Determinants .
• Regulation of Arterial BP .
• Methods of Measurement of BP .

3. Definition :
• Defined as the lateral pressure exerted by the
column of blood on wall of arteries.
• The pressure is exerted when blood flows
through the arteries.
• Generally, the term ‘blood pressure’ refers to
arterial blood pressure.

4. Components
• It is Expressed by
+Systolic Pressure :
The Maximum pressure that is exerted by blood on
arterial wall when the Ventricles are Contracted .
+Diastolic Pressure :
The Minimum pressure that is exerted by the blood
on arterial wall when the Ventricles are relaxed .

5. +Calculated Pressures
#Pulse Pressure
It is the difference between Systolic & Diastolic
Blood pressure .
#MAP (Mean Arterial Pressure)
It represents the Average Blood pressure
Calculated by
MAP = Diastolic BP + 1/3 PUSLE Pressure

6. Normal Ranges of BP
• Systolic BP = 100 – 139 mmHg
• Diastolic BP = 60 – 89 mmHg
• Pulse pressure = depend on Systolic &
Diastolic BP ,, IF Systolic is 120 & Diastolic is 80
,, the Pulse Pressure = 40 mmhg
• MAP = Diastolic BP ,, WITH the same Numbers
it equals = 80 + 1/3 x 40 = 93 mmhg

7. • Systolic BP indicates the Force of
Contraction
• Diastolic BP indicates the Peripheral
Resistance
• Pulse Pressure indicates Stroke Volume
• MAP indicates the Average Pressure .

8. Determinants :
BP = COP X PVR
• COP (Cardiac Output) :
Which is also determined by
+Stroke Volume
+Heart Rate
• PVR (Peripheral Vascular Resistance) : which is
further determined by :
+Viscosity of the Blood
+Diameter of Arterioles

9. • So any Factor affects
Stroke Volume
, Heart Rate
, Viscosity of the Blood
OR Diameter of the Arterioles
will Directly affects Arterial Blood Pressure

10. Regulation of Arterial BP :
• Classified into :
+Short-term ,
+Intermediate &
+Long term Mechanisms

11. • Short-term Mechanisms
Chemical - Neural
• Intermediate Mechanisms
ADH & Thirst Mechanism - ANP
• Long-term Mechanisms
RAAS
Renal Body Fluid Mechanism

12. • Chemical Regulation :
+Vasoconstrictors
+Vasodilators
• Neural Regulation :
+Barroreceptor Mechanism
+Chemoreceptor Mechanism
+CNS Ischemic Response

14. Barroreceptor Reflex
• Barroreceptors are Mechano-Senesitive .
• They are Strech Receptor
• They are continuously Firing
• IX & X th Cranial Nerves are called as Buffer
Nerves ( Buffer the Changes of BP )
• Located in :
Carotids (INTERNAL) = firing range 60-
180 mmhg
Aortic (Arch) = 90-210 mmhg

15. • These receptors are continuously firing , when
blood flow decreases , pressure decreases &
then impulses decreases >> sending signals
into Vasomotor Centre that changes
Vasomotor TONE

16. Chemoreceptor Reflex
• Receptors located in Carotid Body in Common
Carotid Artery
• They are Chemosensitive Cells (Glomus Cells)
>> Sensitive to Hypoxia
• BP from 60-30 controlled by Chemoreceptors

17. • BP up to 80 mmhg is Controlled by
Barroreceptor Reflex
• 60-30 mmhg Controlled by Chemoreceptors
• Less than 30 mmhg Controlled by CNS
Ischemic Response

18. CNS Ischemic Response
• At such low BP , blood flow to Vasomotor
Center is decreased & CO2 accumulates
around Vasomotor Center & Stimulates
Vasoconstrictor Center & BP rises immediately
• Cushing Reflex :
increase in in intracranial pressure >>result in
reduction in Cerebral Perfusion Pressure > as a
response Cushing triads occurs

19. • Cushing triads :
+Wide pulse pressure ( increasing Systolic
, Decreasing Diastolic )
+Bradycardia
+Irregular respiration

20. Intermediate Mechanisms
• ADH & THIRST Mechanisms as response to
reduction of Blood Volume
• ANP (Atrial Natriuretic Peptide) >> they are
released from the atria because of increased
Venous Return , they act on the Kidneys >>
they induces Natriuresis & Diuresis .

21. Long-term Mechanisms
• Renal Body Fluid Mechanism :
Urine output adjusted according the renal Blood
Flow that is affected by the Blood Volume
• RAAS (Renin Angiotensin Aldosterone
System):
+Reduction in renal Blood Flow will result in
Activation of ProRenin into Renin
+Renin will activates Angiotensinogen (produced
by the Liver) into Angitensin I

22. +Angiotensin I will be Converted in the Lungs BY
the action of ANGIOTENSIN CONVERTING
ENZYME (ACE) into Angiotensis II
+Which will
-It is potent Vasocontrictor
-Activates Thirst Center
-Release ADH (AntiDiuretic Hormone from
posterior pituitary)
-activates Release of ALDOSTERONE from
adrenal CORTEX
-Activates release of Catecholamines from
adrenal Medulla

23. Measurement of BP
By the use of Sphygmomanometer three
methods may be used :
1. Palpatory method
2. Auscultatory method(the most accurate)
3. Oscillatory method.

24. THANQ