1. Cardiovascular system 2
Physiology
232 BMS

2. Arterial blood pressure
Is the force per unit area exerted on the vessel wall by blood If the amount of blood entering & leaving the elastic arteries in a given period were equal arterial pressure will be constant

3. Types of arterial blood pressure
1.Systolic pressure
As the left ventricle contracts & expels blood into aorta ….. This will lead to stretching the elastic aorta ….. The pressure inside the aorta will reach to its peak, this pressure peak is called: Systolic pressure
(Average 120mmHg in healthy adults)
2.Diastolic pressure
After that blood will move from aorta to the other blood vessels (Because blood pressure in aorta is higher than in other blood vessels)
Aortic valve will close, preventing blood from flowing back into the heart & the walls of aorta will recoil, to keep the blood flowing forward into the other blood vessels
During this, aortic pressure will drop to its lowest level called: Diastolic pressure
(Average 70 – 80 mmHg in healthy adults)

4. Types of arterial blood pressure
3.Pulse pressure The difference between systolic & diastolic blood pressure 4.Mean arterial pressure (MAP) The pressure that propels the blood to the tissues pulse pressure MAP = diastolic pressure + ______________ 3

5. Factors affecting arterial blood pressure
Cardiac output
Resistance
Blood volume
Cardiac output increases …… Blood pressure increases
Resistance increases …….. Blood pressure increases
Blood volume increases ……. Blood pressure increases

6. Control of arterial blood pressure
Short term control Long term control
By changing the Resistance By changing the Blood volume
( ↑ R ….. ↑ BP) ( ↑ BV ….. ↑ BP)
Short term control
1. Neural control
2. Hormonal control

7. Control of arterial blood pressure (ABP)
1. Neural control:
Baroreceptor reflex action Vasomotor center: Center in the brain
Chemoreceptors that controls the changes in the diameter
of blood vessels (Cause blood vessels
to be in moderate constriction)
Baroreceptor: Pressure sensitive
receptors
If ABP rises …… Baroreceptors
Will feel change in blood pressure …… And then will send impulse to the vasomotor center ….. This impulse will inhibit the vasomotor center causing vasodilatation ….. And so decrease in blood pressure

9. Control of arterial blood pressure (ABP)
Chemoreceptors
When the oxygen content of the blood drops, or the carbon-dioxide levels rise ……. Chemoreceptors will send impulses to the cardio-acceleratory center ………. Which will increases the cardiac output ….. And so blood pressure will increase …. And will increase blood return to heart & lungs

10. Control of arterial blood pressure (ABP)
2. Hormonal control: A. Adrenal hormones During periods of stress, the adrenal gland releases nor- epinephrine ….. That enhances the sympathetic response ….. Causing vasoconstriction & increase in blood pressure B. Atrial natriuretic peptide (ANP) The atria of the heart produce the hormone ANP ….. Which decreases blood volume & blood pressure C. Angiotensin II If blood pressure decreases ….. The kidneys will secrete the hormone Renin …. Which leads to the production of Angiotensin II …. Which causes vasoconstriction & increase in blood pressure

11. Control of arterial blood pressure (ABP)
Long term control: It is performed by the kidneys (Direct & Indirect ways) Direct way If blood pressure decreases ….. Kidneys will keep the fluids & return them to the blood stream …. So increases blood volume & blood pressure Indirect way (Renin – Angiotensin mechanism) If blood pressure decreases ….. Kidneys will secrete Renin …… Leads to secretion of Angiotensin II 1. Vasoconstriction …… So increases blood pressure 2. Stimulates secretion of Aldosterone hormone …… ↑ water & salt re-absorption …… So increases blood volume & blood pressure 3. Stimulates secretion of Anti-diuretic hormone (ADH – Vasopressin) from pituitary gland …. ↑ water & salt re-absorption … So increases BP

13. Alterations in blood pressure
1. Hypotension: Is systolic blood pressure below 100 mmHg Orthostatic hypotension Is a temporary low blood pressure when the person rises suddenly from a sitting position

14. Alterations in blood pressure
2. Hypertension:
Is arterial blood pressure of 140/90 or higher
Chronic hypertension is common & dangerous disease, that is called(Silent killer) as it is usually asymptomatic for the first 10 – 20 years
It is the main cause of atherosclerosis & cardiovascular diseases
Types
Primary Secondary
With no reason Is due to certain diseases
as: kidney diseases

15. Alterations in blood pressure
Primary hypertension Causes which may be involved: 1. Diet: High intake of sodium 6. Stress 2. Obesity 7. Smoking 3. Age: Usually appears after age of Diabetes mellitus 5. Hereditary

16. Gas exchange
Gas exchange occurs between: Lungs & Blood And then between: Blood & Tissues (By a process called Diffusion which depends on the movement along a concentration gradient ….. Each substance moves from an area of its higher concentration to an area of its lower concentration) (Oxygen & nutrients pass from the blood, where their concentration is high to the cells – Carbon dioxide & waste products pass from cells, where their concentration is high to the blood)
Diffusion
The capillary walls consist of semi-permeable membrane that allow small molecules to pass into tissues, & retain large molecules in blood
Diffusable substances include: Oxygen, Carbon dioxide, Fatty acids

17. Gas exchange
Hydrostatic pressure: Is the pressure exerted by a fluid against a wall In capillaries: HP is the pressure exerted by the blood on the capillary walls (Capillary hydrostatic pressure HPC ) …. Force fluids to pass from capillaries to outside HPC is opposed by interstitial fluid hydrostatic pressure (Hpif ) acting outside the capillaries & pushing the fluid from outside to inside the capillaries And so Net hydrostatic pressure acting on capillaries = HPC - HPif HPif is usually Zero & so Net hydrostatic pressure = HPc

18. Gas exchange
Osmotic pressure: The force opposing hydrostatic pressure, is created by the presence of large non-diffusible molecules (Such as: Plasma proteins) that are unable to cross the capillary wall (Against hydrostatic pressure, it pulls fluid back to the capillaries) The presence of plasma proteins in the capillaries will produce (Capillary osmotic pressure OPC = 26 mmHg) Interstitial fluid contains small amount of proteins & so it has (Interstitial fluid osmotic pressure OPif ….. But it is low = 1mmHg) And so Net osmotic pressure that pulls fluid back into the capillaries = OPc – OPif = 26 – 1 = 25 mmHg (The same in arterial & venous ends)

19. Gas exchange
And so to determine whether fluid will pass into the capillaries or away from the capillaries we must calculate Net filtration pressure (NFP) NFP = (HPc - Hpif ) – (OPc – OPif ) At arterial end of the capillaries: = (35 – 0) – (26 – 1) = (35 – 25) HP > OP & so fluid passes = 10 mmHg from capillaries into the tissues At venous end of the capillaries: = (17 – 0) – (26 – 1) = (17 – 25) HP < OP & so fluid passes from = -8 mmHg the tissues into the capillaries

20. Arterial end of capillaries Venous end of capillaries
Gas exchange
Arterial end of capillaries
Venous end of capillaries
At the arterial end of the capillaries:
Hydrostatic pressure = 35 mmHg
Osmotic pressure = 25 mmHg
& so HP > OP inside the vessel
This causes the movement of blood (Carrying Oxygen) & some solutes from the capillaries into tissues
At the venous end of the capillaries:
Hydrostatic pressure = 17 mmHg
& so HP < OP inside the vessel
This causes the movement of blood (Carrying Carbon-dioxide) & some waste products from tissues into capillaries
Not all waste products return to the capillaries ….. The excess is drained away from tissues into lymph capillaries (Similar to blood capillaries but more permeable) & then pass into the blood

24. Some heart diseases
Tachycardia: Abnormally fast heart rate (More than 100 beats/min)
Bradycardia: Abnormally slow heart rate (Less than 60 beats/min)
Congestive heart failure: COP is below the normal level (And so the circulating blood is not sufficient or the tissue needs)
Coronary atherosclerosis: The coronary arteries are blocked by fatty materials, which impairs blood & oxygen delivery to the cardiac cells, & so the heart begins to contract insufficiently
Multiple myocardial infarctions: Pumping ability of the heart ↓, as the dead heart cells are replaced by non-contractile fibrous tissue

25. Some heart diseases
Pulmonary congestion: If the left side of the heart fails …. The right side continues to give blood to the lungs …. But the left side fails to eject blood into the circulation …. So pressure in the lungs will increase causing pulmonary edema
Peripheral congestion: If the right side of the heart fails …. Blood will stay in body organs & will not return to the heart …. This will cause edema

26. Some heart diseases
Hypertrophic cardiomyopathy (HCM): Enlargement of cardiac muscle cells & thickening of the heart wall …. This will cause the heart to pump strongly but doesn’t relax well during diastole Ventricular tachycardia: Rapid ventricular contractions Myocarditis: Inflammation of the cardiac muscle

27. Summary
Arterial blood pressure: Is the force per unit area exerted on the vessel wall by blood
Types of arterial blood pressure:
Systolic pressure: During contraction
Diastolic pressure: During relaxation
Pulse pressure: Difference between systolic & diastolic pressures
Mean arterial pressure (MAP): The pressure that propels the blood to the tissues
Factors affecting ABP:
Cardiac output: COP ↑ ……. ABP ↑
Resistance: Resistance ↑ …… ABP ↑
Blood volume: Blood volume ↑ …….. ABP ↑

28. Summary Control of ABP: 1. Short term control: By changing resistance
Neural control:
Baroreceptor reflex action
Chemoreceptors
Hormonal control:
Adrenal hormones
Atrial natriuretic peptide
Angiotensin II
2. Long term control: By changing blood volume
Direct way
Indirect way (Renin – Angiotensin mechanism)

29. Summary Alterations in ABP:
1. Hypotension: Is systolic blood pressure below 100 mmHg
2. Hypertension: Is arterial blood pressure of 140/90 or higher
Types:
Primary: With no reason
Secondary: Is due to certain diseases as: kidney diseases
Gas exchange:
Hydrostatic pressure: Is the pressure exerted by a fluid against a wall
Osmotic pressure: The force opposing hydrostatic pressure
To determine whether fluid will pass into the capillaries or away from the capillaries we must calculate Net filtration pressure (NFP)
NFP = (HPc - Hpif ) – (OPc – OPif )

30. Summary At arterial end of the capillaries:
HP > OP & so fluid passes from capillaries into the tissues
At venous end of the capillaries:
HP < OP & so fluid passes from the tissues into the capillaries
Some heart diseases:
Tachycardia: Abnormally fast heart rate (More than 100 beats/min)
Bradycardia: Abnormally slow heart rate (Less than 60 beats/min)
Congestive heart failure: COP is below the normal level
Coronary atherosclerosis: The coronary arteries are blocked by fatty materials, which impairs blood & oxygen delivery to the cardiac cells, & so the heart begins to contract insufficiently
Multiple myocardial infarctions: Pumping ability of the heart ↓
Pulmonary congestion: If the left side of the heart fails …. The right side continues to give blood to the lungs …. But the left side fails to eject blood into the circulation …. So pressure in the lungs will increase causing pulmonary edema

31. Summary
Peripheral congestion: If the right side of the heart fails …. Blood will stay in body organs & will not return to the heart …. This will cause edema
Hypertrophic cardiomyopathy (HCM): Enlargement of cardiac muscle cells & thickening of the heart wall …. This will cause the heart to pump strongly but doesn’t relax well during diastole
Ventricular tachycardia: Rapid ventricular contractions
Myocarditis: Inflammation of the cardiac muscle