CIRCULATORY SYSTEM FOR NURSES CLASS 5

1. BP,PULSE

11. BLOOD PRESSURE
• CAUSED BY VENTRICULAR SYSTOLE
• HYDROSTATIC PRESSURE EXERTED ON THE
BLOOD VESSEL WALL BY BLOOD
• HIGHEST IN BIG ARTERIES
• SYSTOLIC BP ABOUT 110 mmHg & 35mmHg IN
ARTERIOLES
• DIASTOLIC BP ABOUT 70 mmHg & 16mmHg IN
CAPILLARIES
• 0 mmHg IN RIGHT VENTRICLE

12. MAP
• MAP = DBP + 1/3 (SBP-DBP)
• Ex. BP 110 / 70; MAP = 70 + 1/3 (110-70
= 70 + 1/3 (40)
= 83.33 mmHg
• CO = MAP / R ( RESISTANCE)
• So, MAP = CO x R
• IF CO INCREASES, MAP INCREASES IF THE
RESISTANCE IS THE SAME.
• BP ALSO DEPENDS ON BLOOD VOLUME

13. RESISTANCE
• PERIPHERAL RESISTANCE IS THE OPPOSITION TO
BLOOD FLOW DUE TO FRICTION ON THE WALL.
• DEPENDS ON SIZE OF THE LUMEN
• SMALLER THE SIZE, GREATER THE RESISTANCE
• IF THE LUMEN DIAMETER OF THE VESSEL
DECREASES BY HALF, THE RESISTANCE INCREASES
16 TIMES.
• IF ARTERIOLES DILATE, RESISTANCE DECREASES
AND BP FALLS

14. RESISTANCE
• BLOOD VISCOSITY DEPENDS ON THE RATIO OF
BLOOD CELLS TO PLASMA VOLUME
• THE HIGHER THE VISCOSITY, THE HIGHER THE
RESISTANCE
• DEHYDRATION, POLYCYTHEMIA INCREASES
VISCOSITY AND BP
• LOSS OF PLASMA PROTEIN OR RBC DECREASES
VISCOSITY AND BP

15. RESISTANCE
• TOTAL BLOOD VESSEL LENGTH - RESISTANCE IS
DIRECTLY PROPORTIONAL TO THE BLOOD
VESSEL LENGTH
• THE LONGER THE VESSEL THE GREATER THE
RESISTANCE
• OBESE PEOPLE HAVE HYPERTENSION AS THEY
NEED ADDITIONAL BLOOD VESSEL TO SUPPLY
THE FAT

16. RESISTANCE
• SYSTEMIC VASCULAR RESISTANCE IS ALL THE
VASCULAR RESISTANCE OFFERED BY THE BLOOD
VESSEL
• DEPENDS ON DIAMETER, LENGTH OF BLOOD
VESSEL.
• SMALLEST VESSELS – ARTERIOLES, CAPILLARIES
AND VENULES CONTRIBUTE THE MAXIMUM
RESISTANCE
• THE CENTRE FOR REGULATION IS THE
VASOMOTOR CENTRE IN THE BRAIN STEM

19. VENOUS RETURN
• THE VOLUME OF BLOOD FLOWING BACK TO
THE HEART THROUGH THE SYSTEMIC VEINS
• PRESSURE IN THE RIGHT ATRIUM IS MINUS
WHICH IS SUFFICIENT FOR VENOUS RETURN
• IF RIGHT ATRIAL PRESSURE INCREASES,
VENOUS RETURN WILL DECREASE.
• SKELETAL MUSCLE PUMP
• RESPIRATORY PUMP

21. VELOCITY OF BLOOD FLOW
• VELOCITY IS INVERSELY PROPORTIONAL TO CROSS
SECTIONAL AREA
• WHEN A VESSEL BRANCHES, THE CROSS SECTIONAL
AREA IS GREATER THAN THAT OF THE ORIGINAL VESSEL
– SO BLOOD FLOW BECOMES SLOWER AS BLOOD
MOVES AWAY FROM THE HEART.
• CIRCULATION TIME – THE TIME REQUIRED FOR A DROP
OF BLOOD TO PASS FROM THE RIGHT ATRIUM
THROUGH THE PULMONARY CIRCULATION BACK TO
LEFT ATRIUM THROUGH SYSTEMIC CIRCULATION BACK
TO THE RIGHT ATRIUM.
• NORMAL TIME IS ABOUT 1 MINUTE

24. CONTROL OF BLOOD PRESSURE
• CARDIOVASCULAR CENTRE IN MEDULLA
REGULATES HEART RATE AND STROKE
VOLUME.
• CONTROLS – NEURAL, HORMONAL AND
LOCAL NEGATIVE FEEDBACK SYSTEM
• INPUT FROM HIGHER CENTRES AND SENSORY
RECEPTORS
• THROUGH LIMBIC SYSTEM AND
HYPOTHALAMUS

25. CONTROL OF BLOOD PRESSURE
• OUTPUT FROM CARDIOVASCULAR CENTRE TO
AUTONOMIC SYSTEM
• SYMPATHETIC IMPULSES VIA CARDIAC
ACCELERATOR NERVES
• INCREASES HEART RATE AND CONTRACTILITY
• PARASYMPATHETIC NERVOUS SYSTEM THROUGH
VAGUS NERVE HAS THE OPPOSITE EFFECT
• VASOMOTOR NERVES CONTROL THE BLOOD
VESSEL TONE

27. NEURAL REGULATION OF BP
• BARORECEPTOR REFLEX
• PRESSURE SENSITIVE SENSORY RECEPTORS IN
THE AORTA AND CAROTID ARTERIES SEND
IMPULSES TO CARDIOVASCULAR CENTRE.
• THROUGH THE GLOSSOPHARYNGEAL NERVE
AND VAGUS NERVE
• IF BP FALLS, BARORECEPTORS ARE STRETCHED
LESS AND PARASYMPATHETIC ACTIVITY
DECREASES

29. CHEMORECEPTOR REFLEX
• CHEMORECEPETORS MONITOR THE
CHEMICAL COMPOSITION OF BLOOD
• LOCATED NEAR CAROTID AND AORTIC BODIES
• MEASURE OXYGEN, CO2, H+ ETC
• CONTROL IS VIA RESPIRATORY CENTRE IN THE
BRAIN

31. HORMONAL CONTROL OF BP
• RAA SYSTEM
• EPINEPHRINE & NOR EPINEPHRINE
• ADH
• ANP LOWERS BLOOD PRESSURE BY CAUSING
VASODILATATION AND PROMOTING LOSS OF
SALT AND WATER IN URINE

32. AUTOREGULATION
• THE ABILITY OF TISSUE TO AUTOMATICALLY
ADJUST ITS BLOOD FLOW TO ITS NEEDS
• Ex. DURING MUSCULAR ACTIVITY, BLOOD FLOW
INCREASES
• WHEN YOU ARE TALKING BLOOD FLOW TO THE
BRAIN INCREASES
• MYOGENIC RESPONSE – WARMING INCREASES
VASODILATATION, STRETCHING CAUSES
CONTRACTION
• CHEMICALS – ELECTROLYTES, VASODILATORS, NO,
CONSTRICTORS, THROMBOXANE

34. PULSE
• THE ALTERNATE EXPANSION AND RECOIL OF
ELASTIC ARTERIES WITH LEFT VENTRICULAR
SYSTOLE CREATES A PRESSURE WAVE CALLED
PULSE
• STRONGEST IN ARTERIES CLOSE TO THE HEART
AND DISAPPEARS IN CAPILLARIES

35. HYPERTENSION
• BP > 140 /90 mmHg
• ESSENTIAL HYPERTENSION
• MALIGNANT HYPERTENSION – RAPID,
AGGRESSIVE ACCELERATION OF HYPERTENSION
DBP > 120 mmHg CAUSING HEMMORAGE IN
RETINA PAPILLOEDEMA, ENCEPHALOPATHY AND
CCF
• SECONDARY HYPERTENSION RENAL, ENDOCRINE,
AORTIC STRICTURE, DRUG INDUCED

36. COMPLICATIONS OF HT
• HEART - LVH, RVF, IHD
• BRAIN – STROKE DUE TO HEMMORRAGE
• KIDNEYS- FAILURE DUE TO RAA
• BLOOD VESSEL – WALLS BECOME HARD,
ATHEROMA, CAPILLARY HEMMORRAGE

37. PULMONARY HYPERTENSION
• DUE TO LVF
• LUNG DISEASE – EMPHYSEMA
• PRIMARY PULMONARY HYPERTENSION