Regulation of the blood is most imp chapter in anatomy and physiology

1. REGULATION OF BLOOD
PRESSURE
DR RASHMI MISHRA

2. Regulation of Blood Pressure
Arterial B.P. Is controlled by several
mechanism which under physiological
condition maintain the normal mean
arterial pressure which has a narrow
range 95-100 mm of Hg.

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REGULATION OF ARTERIAL
BLOOD PRESSURE
■ Immediate mechanism
■ Short term mechanism
■ Long term mechanism

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Short Term Regulatory
Mechanisms:
Neural mechanisms
1.1.Baroreceptor
reflexes
2.2. Chemo receptor
reflexes
3. Cerebral ischaemic
response

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BARORECEPTOR REFLEX

6. BARO RECEPTOR REFLEXES (MAREY’S REFLEXES)
BP

Stimulation of baroreceptors
(carotid sinus and aortic arch)

Tractus solitarius stimulation
Inhibition of VMC Stimulation of CIC
(nucleus ambiguous)
SNS Vagus
 Symp tone Vagal tone 
Blood Vessels Heart Rate Decreased
- Vasodilatation
- Venodilatation Bradycardia
BP

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Net effect
 Peripheral resistance
 Myocardial contractility
 Heart rate (Bradycardia)
 Fall in BP
BARORECEPTOR REFLEX

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 BP < 40 mm Hg (or)
 Intracranial
pressure
Cerebral ischaemia
Cerebral hypoxia
Direct effect on
VMC
SNS action 
Vasoconstriction
Cerebral Ischaemic Response
 BP with reflex
Cushing’s Reflex

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Delayed or Intermediate Mechanism
Capillary fluid shift phenomenon:
Whenever there is an increase in blood pressure
more fluid is filtered through the capillary wall
into the interstitial space.
Blood volume decreases and so BP itself decreases.
Reverse changes take place when BP falls.

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Stress Relaxation
Phenomenon:
BP Blood vessels are
stretched Stress relaxation
Increased capacity
Decreased effective
blood volume relaxation of
the vessel wall BP

13. REVERSE STRESS RELAXATION
 When the B.P. is low due to stress on the vessels walls and
tries to restore it back to normal.
 This mechanism can correct up to 15% change in blood
volume below normal.

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Long term Regulatory
Mechanisms:
All the
mechanisms
that tend to
alter the blood
volume
participate in
long term
regulatory
mechanisms

15. RENAL BODY FLUID SYSTEM FOR
ARTERIAL PRESSURE CONTROL
 The renal body fluid system corrects the B.P. by
causing appropriate changes in the Blood volume
through diuresis and natriuresis.
WHEN B.P RISES TOO HIGH- The kidney excrete
increased quantities of sodium and water because
of
pressure diuresis respectively.
 As a result of increased renal excretion.
The extracellular fluid volume and blood volume
both decrease until B.P return to normal and the
kidney excrete normal amount of sodium in water.

16. Increases B.P. (Large intake of Water & Salt)
Increased excretion of salt & water by Kidney
Decreased in Extracellular fluid & blood volume
Decreased venous return to Heart
Decreased Cardiac output
Decreases B.P.

17. WHEN THE B.P. FALLS TOO LOW
•The Kidney reduces the rate of sodium and water
excretion and over a period of hours
to day.
• If the person drinks enough water and eats enough
salt to increases blood volume the B.P. will return to
previous level.

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Renal –body fluid system:
• ECF or Blood
volume
• -  BP
•  GFR  urine output
• B.P is brought back to
the normal level
ECF or Blood volume
- BP
 GFR BP  urine output
B.P is slowly raised to
the normal level.

19. Indirect Mechanism
When B.P. & extracellular fluid decreases, Renin secreted from
kidney is increased it converts Angiotensinogen into
Angiotensin I , this is converted into Angiotensin II by
ACE(Angiotensin converting enzyme). Angiotensin II act in 2
ways to restore the B.P. :-
1) This causes constriction of arteriole in the body, so
the peripheral resistance is increased and B.P. raised,
in addition Angiotensin II causes constriction of
afferent arteriole in the kidneys so the the
glomerular filtrate reduces. This return in the
retention of water and salt, increase ECF volume to
normal volume, this in turn increases the BP to the
normal level.

20. 2) Simultaneously, Angiotensin II stimulate zona
glomerulosa of adrenal cortex to secrete aldosterone,
This hormone increases the reabsorption of Na+ from
renal tubules . Na+ is followed by water reabsorption
resulting in increased ECF volume and the blood
volume . It increases the B.P. to the normal level.

21. Decrease in B.P.
JG Apparatus
Renin
Angiotensinogen Angiotensin I
Angiotensin II
Angiotensin III
Angiotensin IV
Vasoconstriction
Adrenal Cortex
Increase in
Blood Volume
Increase in ECF
Volume
Reabsorption of
water and sodium
Kidney
Aldosterone
Normal B.P.
Stimulation
ACE (Lung)

22. Angiotensin III
It increases the BP and stimulate adrenal cortex to
secretes aldosterone. It has 100% Adrenal stimulating
activity. And 40% vassopresor activity of Angiotensin
II.
Angiotensin IV
It also has adrenal stimulating and vassopressor
activities

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HORMONAL REGULATIONS
Catecholamines
Mineralocorticocoid
Glucocorticoid
Thyroxine
ADH
Atrial Natriuretic Factor
Nitric Oxide
Histamine
Angiotensin
Serotonin

24. Local Mechanism for regulation of B.P.
 Instead of renal, nervous and hormonal regulation
some local substances regulates B.P. by
vasoconstrictor and vasodilation
Local Vasoconstrictors
They are derived from vascular endothelium.
These substances are called endothelium derived constricting
factors (EDCF).
Types of EDCF – ET1, ET2, ET3 are identified so far.
Local Vasodilators
Local vasodilators are of two types
1.Vasodilators of metabolic origin
(eg.-CO2, H+ ion, adenosine)
2.Vasodilator of endothelium
(eg.- NO(nitric oxide)

25. Hypertension
❖ Defined as an elevation of systolic
blood pressure
❖ Persistent hypertension very common
❖ 30% of people over 50 are
hypertensive
❖ Never diagnosed on one reading
❖ Indication of cardiovascular disease
❖ Trauma
❖ Side effect of medication

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 BP is called Hypertension
(Above 140/90 mm of Hg )
Primary (Essential
90%)
Secondary (10%)

27. Diseases Attributable to
Hypertension
Hypertension
Heart failure
Stroke
Coronary heart disease
Myocardial infarction
Left ventricular
hypertrophy
Aortic aneurysm
Retinopathy
Peripheral vascular disease
Hypertensive
encephalopathy
Chronic kidney failure
Cerebral hemorrhage
All
Vascular

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Hypertension
Predisposing factors:
■ Obesity
■ Hereditary
■ Alchoholism
■ Stress
■ Smoking
■ Sedentary life

29. Primary Hypertension : -
90% of patients suffer from primary
hypertension of which the cause is not known, But this is
the type of hypertension which is treatable but not
curable .
- it is treated by antihypertensive drugs.
Secondary Hypertension : -.
This is the type of hypertension which is
caused secondary to some disease .
Malignant Hypertension : -
This is chronic hypertension which shows
lesion in necrotic arterioles.
- This condition is associated with
Papilledema, Cerebral Manifestation & Renal Failure.
- it is treated by antihypertensive drugs.

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Secondary Hypertension
Causes:
■1.Renal-Acute & Chronic
Glomerulonephritis,Nephrotic syndrome
■2.Endocrine-
Cushings,Conns,Thyrotoxicosis,
Pheochromacytoma
■3.Vascular-Atherosclerosis
Arteriosclerosis

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Treatment of Hypertension
Modification of lifestyle:
■Cessation of smoking.
■Moderation in alcohol intake.
■Weight reduction.
■Programmed exercise.
■Reduction in Na+ intake.
■Diet high in K+.
■Relaxation technique – Yoga, TM

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Treatment of Hypertension
■ Medications:
■ Diuretics:
Increase urine volume.
■ Beta-blockers:
Decrease HR.
■ Calcium antagonists:
Block Ca2
+channels.
■ ACE inhibitors:
Inhibit conversion to angiotensin II.
Angiotension II-receptor antagonists:
Block receptors.

33. Prevention
■ Reduce the risk of developing High Blood
Pressure by making lifestyle changes…..
■ Eat a healthy , well balanced diet
■ Reduce salt and fat intake
■ Exercise regularly
■ Stop smoking
■ Reduce alcohol and caffeine consumption to
recommended levels
■ Reduce weight

34. Hypotension
❖ Defined in adults as a
systolic pressure below
100mm Hg
❖ Rarely treated in this
country

35.  HYPOTENSION
 A decrease in B.P. below the normal value of 90/60
mm of Hg.
 Types
1. Primary Hypotension :- It is low B.P. that
develops in the absence of any underlying
disease & develops due to unknown cause.
2. Secondary Hypotension :- It is the hypotension
that occurs due to some underlying disease
which cause hypotension-
a) Myocardial Infarction
b) Hypoactivity of pituitary gland
c) Hypoactivity of adrenal glands
d) Nervous disorders
e) Tuberculosis

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 BP is called Hypotension
(Below 90/60 mm of
Hg)
1. Hemorrhage
2.Dehydration
3.Vomiting
4.Diarrhea
5.Excessive sweating
6.Adissons disease
7.Hypothyroidism

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Treatment of Hypotension
Treat the cause
Blood transfusion
I.V. Fluids
Vasoconstrictors