Systolic pressure, diastolic pressure, mean arterial pressure and pulse pressure

What generates systemic blood pressure?

The pumping action of the heart

What does blood pressure do?

Drives blood flow through the circulatory system

How does blood flow move?

Down a pressure gradient from high to low pressure

What opposes blood flow?

Resistance within blood vessels

How does blood pressure change with distance from the heart?

It decreases as blood travels farther from the heart

Where is blood pressure highest?

In the aorta

Where is blood pressure lowest?

In the venae cavae (near 0 mmHg)

Where does the steepest drop in pressure occur?

In the arterioles (resistance vessels)

Why does pressure decline throughout the system?

Energy is lost as blood overcomes resistance to maintain flow

What is the direction of blood flow?

From high pressure to low pressure (down the pressure gradient)

What is the relationship between pressure and resistance?

Pressure must overcome resistance to maintain blood flow

What two factors determine arterial pressure?

Compliance and stroke volume

What is compliance?

The ability of elastic arteries to stretch when blood is forced into them

What is stroke volume?

The volume of blood ejected by the ventricle into the arteries during contraction

How does increased stroke volume affect pressure?

It increases pressure because more blood enters the arteries and pushes on their walls

Why is blood pressure in elastic arteries pulsatile?

Because the heart’s pumping action causes alternating high and low pressures

What are the two extremes of arterial pressure?

Systolic pressure and diastolic pressure

What is systolic pressure?

The peak pressure in large arteries when the ventricles contract

What is the average systolic pressure in a healthy young adult?

Approximately 120 mmHg

What is the normal range for systolic pressure?

90–120 mmHg

What happens to systolic pressure when compliance decreases?

It increases (greater afterload)

What is diastolic pressure?

The pressure in large arteries during ventricular relaxation

What is the average diastolic pressure in a healthy young adult?

Approximately 80 mmHg

What is the normal range for diastolic pressure?

60–80 mmHg

What causes diastolic pressure?

Elastic recoil of the arteries maintaining blood flow during relaxation

What is pulse pressure?

The difference between systolic and diastolic pressure

How is pulse pressure calculated?

Pulse pressure = systolic pressure – diastolic pressure

What is the normal pulse pressure value?

Approximately 40 mmHg (120 – 80 = 40 mmHg)

What does pulse pressure represent?

The force generated by each ventricular contraction

How is pulse pressure felt?

As a throbbing pulsation in an artery (a pulse)

Where can pulse points be felt?

At superficial arteries overlying bone (e.g., radial, carotid, temporal)

How does pulse pressure change with distance from the heart?

It declines as distance increases

What is mean arterial pressure (MAP)?

The pressure that propels blood through the vessels

How is MAP calculated?

MAP = diastolic pressure + (1/3 × pulse pressure)

What is the normal MAP value?

Approximately 93 mmHg (80 + 1/3 × 40)

Why is MAP not halfway between systolic and diastolic pressure?

Because diastole lasts longer than systole

How does MAP change with distance from the heart?

It declines as blood travels farther from the heart

Why is MAP clinically important?

It reflects the average effective pressure driving blood to tissues

What is mean arterial pressure (MAP)?

The average pressure that drives blood through the circulatory system

How is MAP calculated from systolic and diastolic pressure?

MAP = diastolic pressure + 1/3 × pulse pressure

Why is MAP closer to diastolic pressure than systolic pressure?

Because the heart spends more time in diastole than systole

What is the example calculation for MAP?

MAP = 90 + (120 – 90)/3 = 100 mmHg

Why is MAP important?

It is the driving force for blood flow through tissues

How can MAP also be calculated using cardiac output and resistance?

MAP = CO × R

What is the relationship between blood flow, pressure, and resistance?

Blood flow (F) = pressure (P) / resistance (R)

How does vasoconstriction affect MAP?

Increases resistance → increases blood pressure

How does vasoconstriction affect venous return?

Increases venous return → increases cardiac output → increases MAP

How does increased cardiac output affect MAP?

Higher heart rate or stroke volume → increased MAP

What happens when either cardiac output or resistance increases?

Blood pressure increases

What happens when either cardiac output or resistance decreases?

Blood pressure decreases

What are the main factors that influence MAP?

Cardiac output and peripheral resistance

What is hypotension?

Abnormally low blood pressure with systolic pressure below 90 mmHg

What are symptoms of hypotension?

Dizziness and fainting due to inadequate blood flow to the brain

What is hypertension?

Abnormally high blood pressure

What can cause transient hypertension?

Exercise, illness, or emotional stress

What is chronic hypertension?

Sustained systolic pressure above 140 mmHg

What are the major health risks of chronic hypertension?

Heart failure, vascular disease, and stroke

What are common risk factors for hypertension?

Smoking, stress, poor diet, obesity, age, and general health

What is the normal range of capillary blood pressure?

35 mmHg at the arterial end to 15 mmHg at the venous end

Why is capillary pressure low?

To prevent damage to thin-walled capillaries and allow proper exchange

Why would high capillary pressure be harmful?

It could rupture fragile capillary walls

Why is low pressure adequate in capillaries?

Capillaries are highly permeable, allowing efficient fluid exchange even at low pressure

What happens to pressure across a capillary bed?

It decreases from the arterial end to the venous end

What is the average venous blood pressure?

Approximately 15 mmHg

Does venous pressure change with the cardiac cycle?

No, it remains fairly constant

Why is venous pressure low?

Because the pressure gradient is small and insufficient alone to return blood to the heart

How does blood return to the heart despite low pressure?

Through mechanisms that assist venous return

What is the function of venous valves?

They compartmentalise blood flow, prevent backflow, and help move blood in small volumes toward the heart

What is the muscular pump?

Skeletal muscle contraction that squeezes veins and pushes blood toward the heart

What is the respiratory pump?

Pressure changes during breathing that move blood toward the heart by compressing abdominal veins and expanding thoracic veins

How do nearby arteries assist venous return?

Their pulsations help push blood through adjacent veins

What is venoconstriction?

Constriction of the tunica media under sympathetic control to help propel blood toward the heart

Why are valves important in veins?

They prevent backflow and ensure one-way movement of blood toward the heart

What happens to venous return during exercise?

It increases due to enhanced muscle and respiratory pump activity