blood pressure (theme 3)

Question 1

what are the measurements and units of pressure?

Answer 1

• Mm
• Hg
• kPa

Question 2

what is a series capillary system? 3

Answer 2

• 2 paths in a row
• flow in both parts is the same
• pressure is higher in the 1st path than the 2nd as energy is lost as blood experiences resistance

Question 3

what is a parallel capillary system? 4

Answer 3

• branching paths
• flow is split between 2 paths
• pressure is the same at the start of both paths
• if paths have identical resistance they have the same pressure

Question 4

what are portal systems? 2

Answer 4

when a capillary bed reassembles to a blood vessel that splits again into another set of capillaries
-allows transport of chemicals from one tissue to another without being diluted by mixing with blood at the heart

Question 5

give an example of a portal system?

Answer 5

• hepatic portal system
• food absorbed in the capillaries of the gut, portal vein goes to the liver and breaks, liver sees nutrients in the blood at a high concentration

Question 6

what factors control blood pressure? 3

Answer 6

• cardiac output
• blood volume
• peripheral resistance

Question 7

how do you find blood pressure mean?

Answer 7

p(diastolic)+(p(systolic)-p(diastolic)/3

Question 8

what is stroke volume?

average level?

Answer 8

• volume of blood pumped out of a ventricle during one beat of the heart
• 70ml

Question 9

what is heart rate?

average level?

Answer 9

• measured in bpm
• reciprocal is the RR interval which is 60/HR
• 70 bpm
• 0.86 seconds

Question 10

what is cardiac output?

Answer 10

• volume of blood pumped out of the ventricle per minute

- 4.9L/min

Question 11

what is the equation for cardiac output?

Answer 11

HR x SV

Question 12

what does atrial systole add to the blood volume in the ventricles

Answer 12

• atrial systole adds final 20-25% to total to fill the ventricles

Question 13

what is end diastolic volume? 2

Answer 13

• volume of blood in a ventricle at the end of filling

- associated with preload, how stretched the muscle is

Question 14

what is end systolic volume?

average level?

Answer 14

• volume of blood remaining in a ventricle at the end of contraction
• 120ml

Question 15

what is the equation for systolic volume?

average level?

Answer 15

SV=EDV-ESV

50ml

Question 16

what is the ejection fraction?

average level?

Answer 16

percentage of filled ventricular volume pumped out during a heartbeat
58%

Question 17

what does vasoconstriction do to the resistance?

Answer 17

makes radius smaller, leads to higher resistance and lower flow rate

Question 18

what is the relationship between flow and radius? 2

Answer 18

• flow increases as the radius increases to the power of 4

- assuming the pressure stays the same

Question 19

what is the relationship between resistance and radius?

Answer 19

• resistance decreases as radius increases to the power of 4

Question 20

what causes the dilation and constriction of individual blood vessels? 4

Answer 20

• central regulation (CNS, autonomic, endocrine)
• local regulation of pressure
• immune
• haemostasis

Question 21

what happens to circulation during exercise? 3

Answer 21

• peripheral vasodilatation to muscles and skin
• vasoconstriction to splanchnic circulation
• increased systolic and decreased diastolic

Question 22

what happens to circulation when you stand up? 3

Answer 22

• likely a drop in blood pressure then a compensatory recovery (increase back to normal)
• peripheral vasoconstriction- arterial and venous and increased heart rate
• increased diastolic, no change to systolic

Question 23

explain the control of systemic blood pressure? 4

Answer 23

• local control–> endothelial cells release NO
• neurological–> the autonomic system- sympathetic-noradrenaline
• humoral–> renal/pituitary/adrenal
• the kidney is central to blood pressure

Question 24

explain local vasomotor control? 7

Answer 24

• endothelial cells release vasodilator compounds
• NO which causes smooth muscle relaxation and vasodilation
• controlled by local blood flow conditions
• hydrostatic pressure
• shear force
• made greater by laminar flow
• shear force is atheroprotective

Question 25

explain the autonomic control of blood pressure? 6

Answer 25

- increase in sympathetic - constrict blood vessels - increased peripheral resistance - increased pressure - increased heart rate - increased cardiac output

Question 26

what do baroreceptors do? 3

Answer 26

- detect pressure and feed back to the brain - located in the transverse aortic arch and the carotid sinuses of the left and right internal carotid arteries - decrease blood pressure

Question 27

what do chemoreceptors do? 2

Answer 27

- detect oxygen levels are too low and feedback to the brain | - located in the carotid bodies and aortic bodies

Question 28

what is the frank-starling mechanism? 2

Answer 28

- the stroke volume of the heart increases in response to an increase in the stretching of blood filling the heart (the end diastolic pressure) - as you put more blood into the ventricle, it pushes more blood out, meaning the ventricle can't overfill with blood

Question 29

what is venous return?

Answer 29

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

Question 30

what is preload? 2

Answer 30

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

Question 31

what is volume overload?

Answer 31

- results when preload becomes too large

Question 32

what factors increase preload? 7

Answer 32

- increasing atrial contractility - increases ventricular compliance - decreased venous compliance - increased thoracic venous blood volume - increased central venous pressure - increased aortic pressure - decreased heart rate

Question 33

what is afterload? 5

Answer 33

- the resistance that the chambers of the heart overcome in order to eject blood out of the heart - resistance during systole - increased by back pressure from aorta or pulmonary arteries - increases if the exit valve fails to open completely - pressure overload results from elevated afterload

Question 34

explain the thoracic pump? 5

Answer 34

- pulls blood towards the right atrium - during inspiration - intrathoracic pressure becomes more negative - abdominal pressure is positive (compression of abdominal organs by the diaphragm) - creates a pressure gradient

Question 35

explain the muscle pump? 4

Answer 35

- rhythmical contraction of limb muscles - as occurs during normal locomotor activity - squeezes blood out of nearby veins - venous valves ensure one-way flow to the heart

Question 36

describe pulmonary circulation? 8

Answer 36

- high capillary density - low vascular resistance - acts as a blood reservoir - endocrine control of BP(ACE) - acts as a filter - if oxygen is low in a region of the lung, the arterioles constrict - poor ventilation --> reduced perfusion - this minimises the amount of blood which is poorly oxygenated

Question 37

explain coronary circulation? 3

Answer 37

- cardiac muscle has high demand - most flow occurs during diastole - obtains blood almost before aorta

Question 38

what is hypertension? 6

Answer 38

- high blood pressure (especially high diastolic pressure) - often asymptomatic - may result in coronary heart disease - caused by a mismatch in blood volume and circulatory capacity - most cases are idiopathic (hormones) - can be secondary to kidney disease

Question 39

what is orthostatic hypotension? 5

Answer 39

-low BP on standing -decreased venous return - dizziness or syncope drugs -hypovolaemia (too little blood volume) -age

Question 40

what is cardiogenic shock? 7

Answer 40

- tachycardia - tachypnea (compensatory mechanisms) - low urine output - hypotension - confusion - syncope - acidosis (due to failure to compensate)