Theme 3: Lecture 2 - Blood pressure Flashcards by Anna Rogerson

Units of BP

mmHg (or kPa)

How well did you know this?

Not at all

Perfectly

What is a portal system

2 capillary beds in series (When a capillary bed reassembles to a blood vessel that splits again into another capillary bed)

How well did you know this?

Not at all

Perfectly

What does a capillary system allow

transport of chemicals from one tissue to another without being diluted by mixing with blood at the heart.

How well did you know this?

Not at all

Perfectly

Give an example of a portal system

Hepatic portal system

How well did you know this?

Not at all

Perfectly

An increase in what things will cause an increase in BP

Peripheral resistance
Cardiac output
Blood volume

How well did you know this?

Not at all

Perfectly

Why is there not one measurement of BP

The arterial pressure changes due to systole and diastole

How well did you know this?

Not at all

Perfectly

Equation for mean arterial pressure

P mean = P diastole + (P systole - P diastole)/3

How well did you know this?

Not at all

Perfectly

Stroke volume

Volume of blood pumped out of a ventricle during one beat of the heart

How well did you know this?

Not at all

Perfectly

Heart rate

measured in beats per minute. Its reciprocal is the RR interval, which is 60 ÷ HR.

How well did you know this?

Not at all

Perfectly

RR interval

Time elapsed between 2 heart beats (reciprocal of heart rate)

How well did you know this?

Not at all

Perfectly

Cardiac output

Volume of blood pumped out of a ventricle per minute

How well did you know this?

Not at all

Perfectly

Cardiac output equation

CO = HR x SV

How well did you know this?

Not at all

Perfectly

Normal stroke volume

70mL

How well did you know this?

Not at all

Perfectly

Normal heart rate

70 bpm

How well did you know this?

Not at all

Perfectly

Normal RR interval

0.86 s

How well did you know this?

Not at all

Perfectly

Normal cardiac output

4.9 L/min

How well did you know this?

Not at all

Perfectly

End diastolic volume

Volume of blood in a ventricle at the end of filling (diastole). EDV is associated with “pre-load”, how stretched the muscle is.

How well did you know this?

Not at all

Perfectly

End systolic volume

Volume of blood remaining in a ventricle at the end of contraction (systole). So: SV = EDV – ESV

How well did you know this?

Not at all

Perfectly

Ejection fraction

Percentage of filled ventricular volume pumped out during a heart beat: SV / EDV

How well did you know this?

Not at all

Perfectly

How much does atrial systole add to total fill of ventricles

20-25%

How well did you know this?

Not at all

Perfectly

Normal end diastolic volume

120mL

How well did you know this?

Not at all

Perfectly

Normal end systolic volume

50mL

How well did you know this?

Not at all

Perfectly

Normal ejection fraction

58% (50-70%)

How well did you know this?

Not at all

Perfectly

Vasomotor

actions on a blood vessel that alter its diameter

How well did you know this?

Not at all

Perfectly

What does vasoconstriction lead to

a smaller radius which leads to a higher resistance which leads to a lower flow rate

What causes dilation on constriction of individual blood vessels

- Central regulation (CNS, autonomic, endocrine) - Local regulation of pressure - Immune - Haemostasis

What happens to blood vessels during exercise

- Peripheral vasodilation (skin/muscle) | - Vasoconstriction of splanchnic circulation

What happens to blood pressure and heart rate in exercise

- Increased systolic BP - Decreased diastolic BP - Increased heart rate

What happens initially when you stand

-Initially a drop in BP then compensatory recovery (ie increase back to normal)

What happens to the blood vessels and heart rate during standing

- peripheral vasoconstriction (arterial + venous) | - increased HR

What happens to blood pressure and heart rate after standing up

- no change in systolic BP - increased in diastolic BP - increased heart rate

How is blood pressure controlled systemically

- Local (Endothelial, Nitric Oxide (NO)) - Neurological – the autonomic system - Humoral – renal / pituitary / adrenal

What does nitric oxide do

causes smooth muscle relaxation leading to vasodilatation

What is nitric oxide released by

endothelial cells

What are the local blood flow conditions that would cause vasodilatation

- increased hydrostatic pressure | - increased shear force

What is shear force protective for

it's atherogenic (protective against atherosclerosis)

What is shear force increased by

laminar flow (smooth, opposite to turbulent flow)

What does increased sympathetic stimulation cause in relation to BP and cardiac output

- Constricts blood vessels - increase in peripheral resistance - increase in pressure - increase in heart rate - increase in cardiac output

What do baroreceptors do

- Detect pressure and feed back to the brain | - Activity leads to a decrease in BP

Where are baroreceptors located

- transverse aortic arch | - carotid sinuses of the left and right internal carotid arteries

What do chemoreceptors do

Detect when CO2 levels are low and feed back to the brain

Where are chemoreceptors located

- carotid bodies | - aortic bodies

How does the heart pump the right amount of blood as the volume of blood entering the heart must equal the volume of blood leaving the heart

Due to the Frank Starling mechanism

Frank Starling law

the stroke volume of the heart increases in response to an increase in the stretching of blood filling the heart (the end diastolic pressure)

Venous return

the rate of blood flowing back to the heart through the veins

Preload

the initial stretching of the cardiac myocytes during diastole (prior to contraction). Depends on venous return

Volume overload

Results when preload becomes too large

5 factors that cause an increase in preload

- decrease in heart rate - increase in aortic pressure - increase in atrial contractility - increase in ventricular compliance - increase in central venous pressure

2 factors that cause an increase in central venous pressure

- decrease in venous compliance | - increase in thoracic venous blood volume

Afterload

the resistance that the chambers of the heart must overcome in order to eject blood out of the heart (resistance during systole)

What is afterload increased by

- back pressure from aorta or pulmonary arteries | - if the exit valve fails to open completely

Pressure overload

- results from elevated afterload | - a pathological state

What is the thoracic pump for venous return

- "pulls" the blood (from below) towards the right atrium. - during inspiration intrathoracic pressure is negative and abdominal pressure is positive (compression of abdominal organs by diaphragm). - Creates a pressure gradient

What is the muscle pump in venous return

- Rhythmical contraction of limb muscles as occurs during normal locomotor activity - Squeezes blood out of nearby veins - Venous valves assure one-way flow toward heart

Describe the pulmonary circulation

- High Capillary Density - Low Vascular Resistance - Acts as Blood Reservoir - Acts as Filter

What controls the BP of the pulmonary circulation

endocrine control via ACE

What happens to arterioles if O2 is low in a region of the lung

they constrict

What happens to arterioles if CO2 or H+ are high in an area of the lung

they constrict

What does poor ventilation in the lung lead to

- reduced perfusion | - this minimises the amount of blood that is poorly oxygenated

Describe the coronary circulation

- Cardiac Muscle has High Demand - Most Flow occurs during Diastole (unusual) - Obtains blood almost before aorta

What is hypertension

high blood pressure (esp high diastolic pressure)

What may chronic hypertension result in (7 things listed)

- Coronary artery disease - MI - Aneurysm - Stroke - Kidney failure - Heart failure - Cardiac hypertrophy

Symptoms of hypertension

often asymptomatic

What is hypertension caused by

- mismatch in blood volume and circulatory capacity - most cases are idiopathic - often secondary to kidney disease

What is orthostatic hypotension

low BP on standing up due to decreased venous return

Symptoms of orthostatic hypotension

- dizziness | - syncope

hypovolaemia

too little blood volume

Causes of orthostatic hypotension

- drugs - hypovolaemia - age

What is cardiogenic shock

shock due to heart not pumping enough blood to meet body's demands

Signs and symptoms of cardiogenic shock (7 things listed)

- tachycardia - tachypnoea - low urine output - hypotension - confusion - syncope - acidosis

Compensatory mechanisms of cardiogenic shock

- tachycardia | - tachypnoea

Things seen when the body fails to compensate cardiogenic shock

- low urine output - hypotension - confusion - syncope