1.2 The Circulatory System

The Regulatory Mechanism of Blood Pressure

Postural Hypotension

Blood pressure

force that the blood exerts on the wall of blood vessels

Measured in mm Hg

Accurate Measurement

Results

Category Systolic, mmHg Diastolic, mmHg Number of students

<90 <60

90 - 120 60 – 79

121 - 139 or 80 – 89

140 – 159 Or 90 - 99

160 - 179 Or 100 - 119

>180 Or > 120

Hypotension

Desirable

Prehypertension

Stage 1 Hypertension

Stage 2 Hypertension

Hypertensive Crisis

White Coat Syndrome

Regulation of Blood Pressure

BLOOD PRESSURE IS REGULATED BY:

Nervous system Kidney

Kidney

regulate blood pressure by controlling the amount of fluid in our blood

Kidney

If blood Pressure high :

kidneys remove water from the blood

less volume to pump lower the blood pressure

Nervous System

send impulses to speed up or to slow down the heart rate

Baroreceptors -group of nerve fibres within the walls of the carotid arteries & aorta

Regulation of High Blood Pressure

Tr.Rez@SB2014

Baroreceptors detect → send impulses to

cardiovascular centre medulla oblongata

Cardiovascular centre send impulses to heart & arterioles

Heart : REDUCE heart rate , LOWER cardiac

output

Arterioles : Vasodilation – reduce

resistance of blood flow

Reduced heart rate, lowered cardiac

output, vasodilation - ↓ BP

Regulation of low blood pressure

Baroreceptors detect → send impulses to

cardiovascular centre medulla oblongata

Cardiovascular centre send impulses to heart & arterioles

Heart : INCREASE heart rate , HIGHER

cardiac output

Arterioles : vasoconstriction –

INCREASE resistance of blood flow

Increased heart rate, higher cardiac output, vasocontriction - ↓ BP

LESSON SUMMARY

EXERCISE