1) The document discusses several factors that influence blood flow and pressure, including the formula relating flow, pressure difference, and resistance. The three main determinants of resistance are also discussed. 2) Circulation time and factors that can increase or decrease it are outlined. Various cardiovascular regulatory mechanisms are described, including neural, humoral, local, and systemic regulatory systems. 3) Determinants of arterial blood pressure are examined, including cardiac output, peripheral resistance, arterial blood volume, and vessel compliance. The generation of blood pressure via ventricular contraction is also briefly explained.

1. Dr. Kamla Choudhary

2. 1) State the formula relating flow, pressure
difference, and resistance.
2) What are the three determinants of resistance?
3) Which determinant of resistance is varied
physiologically to alter blood flow?
4) How does variation in hematocrit influence the
hemodynamic of blood flow?

3. Circulation Time
- Time taken by blood to travel through whole circulatory system
Substances used to measure – histamine, ether, florescence dye,
radioactive substance etc.
Conditions which alter the circulation time
Increase
(Due to blood flow sluggish)
1.- Myxedema
2.- Polycythemia
3.- Cardiac failure
Decrease
1.- Exercise
2.- Hyperthyrodism
3.- Anemia
4.- Decrease PR

4. Cardiovascular regulatory Mechanisms
Circulatory adjustments affected by altering
Output from Heart (by pumping)
Changing diameter of blood vessels
 Altering the amount of blood in Capacitance vessels
All these factors finally control the blood flow
Blood flow is regulated by Various regulatory mechanism-
A.Neural Regulatory Mechanism
B. Humoral Regulatory mechanism
Local Regulatory mechanism
Systemic Regulatory mechanism

5. A. Neural Regulatory Mechanism
 Vasoconstriction
 sympathetic innervations (noradernergic)
 basal vessel tone is present
 Vasodilatation
 Parasympathetic innervations
 Decrease vascular resistance

6. B.-Humoral Regulatory Mechanism
 Local Regulatory mechanism  Systemic Regulatory mechanism
Autoregulation
Myogenic theory
Metabolic theory
Vasodilator
Bradykinin
Kaliden
VIP
ANP
Vasoconstriction
ADH
Angiotension II
Epinephrine and Norepineprine

8. Arterial Blood Pressure
• Pressure is force on an area
• If there is a fluid in a container
we measure the pressure
on the surface area of the container.
• That pressure is related to
the number of particles that crash into
that surface area per unit time

9. ORIGINS OF PRESSURE IN
THE CIRCULATION
Four factors help generate pressure in the
circulation:
gravity,
compliance of the vessels,
viscous resistance,
and inertia.

10. 1- Gravity causes a hydrostatic pressure difference
when there is a difference in height
Because gravity produces a hydrostatic pressure difference between two
points whenever there is a difference in height one must always express
pressures relative to some reference h level. In cardiovascular
physiology, this reference—zero height—is the level of the heart.

11. 2- Compliance Of The Vessels,
Low compliance of a vessel causes the transmural pressure
to increase when the vessel blood volume is increased
Compliance: changes in pressure with vessels of different compliances.

12. of blood causes an axial pressure difference when
there is flow
3- The viscous resistance
of the blood and vessels causes pressure to decrease
when the velocity of blood flow increases
4- The inertia

13. For the most part, we have been assuming that the flow of blood as
well as its mean linear velocity is steady,
But , blood flow in the circulation is not
steady; the heart imparts its energy in a
pulsatile manner, with each heartbeat
Therefore,
v– in the aorta increases and reaches a maximum during systole and
falls off during diastole.
These changes in velocity lead to compensatory changes in
intravascular pressure.

14. The relation between velocity and pressure reflects
the conversion between two forms of energy
“fluids flow from a higher to a lower pressure”
it is more accurate to say that fluids flow from a higher to a lower
total energy.
Potential Energy And The Kinetic Energy
The impact of the interconversion between these two forms of energy is
manifested by the familiar Bernoulli effect.
In a tube or a blood vessel the total energy—the sum of the kinetic energy
of flow and the potential energy—is constant (Bernoulli's principle).

15. A1
A2
v1 v2
A1
v1
Low speed
Low KE
High pressure
high speed
high KE
low pressure
Low speed
Low KE
High pressure
As fluid flows along a horizontal tube with a narrow central region, which has
half the diameter of the two ends, the pressure in the central region is actually
lower than the pressure at the distal end of the tube

16. How can the fluid paradoxically flow against the
pressure gradient from the lower pressure central to the
higher pressure distal region of the tube?
F low
= Area X Velocity
Because the flow is the
same in both portions of
the tube
but the cross-sectional
area in the center is
lower by a factor of 4
the velocity in the
central region must
be 4-fold higher

17. • There are two types of pressure:
• Static Pressure
– Pressure from the blood distending the
vessel against the vascular smooth muscle
– LaPlace: T=Pr (tension, pressure, radius)
 Dynamic Pressure
 Pressure from the movement of particles along the blood
stream
 P=ρv2
/2 (density, velocity)

18. v small v smallv large
p large p large
p small
According to the principle, the greater the velocity of flow in a vessel,
the lower the lateral pressure distending its walls.
When a vessel is narrowed, the velocity of flow in the
narrowed portion increases and in the distending pressure
decreases

19. Therefore, when a vessel is narrowed by a
pathologic process such as an atherosclerotic
plaque, the lateral pressure at the constriction is
decreased and the narrowing tends to maintain
itself.

20. Bernoulli Pressure Lowering
The linear drop in fluid pressure is according to Poiseuille's
law,
but the constriction produces an extra drop in pressure
according to the BernoulliPrinciple

21. The liquid column height is a measure of the fluid
pressure at that point in the flow tube
The vertical tubes act as manometers.
The manometers show that the pressure is lowered
at the constriction relative to what it would have been in
a uniform tube.
The pressure that drives the fluid through the tube is
the static fluid pressure at the bottom of the reservoir.
The resistance to flow represented by the tube
causes a drop in pressure as you proceed along the
tube.

22. Blood Pressure
The Total Pressure is the sum of the static and
dynamic pressures.
This is much like Total Energy is the sum of the
kinetic and potential energies.

23. Blood Pressure
From a practical standpoint…
THE blood pressure is what we measure if we stick a
catheter into the lumen of a vessel and measure the
outflow pressure.

24. If a cannula is inserted into an artery, the arterial
pressure can be measured directly with a mercury
manometer

25. Arterial Blood Pressure (BP)
= The lateral pressure force generated by the pumping
action of the heart on the wall of aorta & arterial blood
vessels per unit area.
■ Measured in (mmHg), & sometimes in (cmH2O),
where 1 mmHg = 1.36 cmH2O.
■ Of 2 main components:
systolic … (= max press reached) = 110-130 mmHg. (C.O&
compliance of arteries)
diastolic … (= min press reached) = 70-90 mmHg.
(peripheral resistance)
In normal adult ≈ 120/80 mmHg.

26. Arterial Blood Pressure(continued)
■ Diastolic pressure is more important, because diastolic
period is longer than the systolic period in the cardiac
cycle.
Other components:-
■ Pulse pressure = Systolic BP – Diastolic BP. (20-50 mmHg)
■ Mean arterial pressure = Diastolic BP + 1/3 Pulse press.
In normal adult ≈ 120/80 mmHg.

28. DETERMINANTS OF ARTERIAL BLOOD
PRESSURE
Physical – Arterial Blood volume and compliance of system
Physiological-
 Cardiac output (H.R X S.V)
 Peripheral Resistance

29. Blood Pressure:Blood Pressure:
Generated by Ventricular ContractionGenerated by Ventricular Contraction

30. Formation of the blood pressure:
Elasticity of Windkessel vessel
 ① diastolic blood pressure
 ② continuous blood flow in diastole
 ③ buffering blood pressure