blood pressure

Question 1

what is series blood flow?

Answer 1

• 2 paths in a row
• flow in both paths the same
• pressure is higher in the first path than the 2nd path because energy is lost as blood experiences friction/resistance

Question 2

what is parallel blood flow?

Answer 2

• branching paths
• flow is split between both paths
• if paths have identical resistance then same pressure

Question 3

what is a portal system?

Answer 3

when a capillary bed reassembles to a blood vessel that splits again into another capillary bed

Question 4

what is the function of a portal system?

Answer 4

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

Question 5

what is stroke volume?

Answer 5

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

Question 6

what is heart rate?

Answer 6

its reciprocal is the RR interval which is 60/HR

measured in beats per minute

Question 7

what is cardiac output?

Answer 7

volume of blood pumped out of a ventricle per minute

Question 8

what is the equation for cardiac output?

Answer 8

CO = HR x SV

Question 9

what is the end-diastolic volume?

Answer 9

volume of blood in a ventricle at the end of diastole. it is associated with preload, how stretched the muscle is

Question 10

what is the end-systolic volume?

Answer 10

volume of blood remaining in a ventricle at the end of systole

Question 11

what is the equation for stroke volume?

Answer 11

SV = end diastolic volume - end systolic volume

Question 12

what is the ejection fraction?

Answer 12

percentage of filled ventricular volume pumped out during a heart beat

Question 13

what is the equation for ejection fraction?

Answer 13

ejection fraction = SV/EDV

Question 14

what percentage of the total volume of the ventricles does arteriole systole add?

Answer 14

20-25%

Question 15

what are the effects of changes in radius?

Answer 15

• smaller radius = higher resistance
• smaller radius = lower flow rate
• flow increases as radius increases to the power of 4

Question 16

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

Answer 16

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

Question 17

what happens during exercise?

Answer 17

• peripheral vasodilation: muscle/skin
• vasoconstriction: splanchnic circulation
• BP systolic increases and diastolic decreases
• heart rate increases

Question 18

what happens during standing?

Answer 18

• initial drop in BP & then compensatory recovery
• peripheral vasoconstriction: arterial & venous & increased heart rate
• BP final: no change in systolic, increase in diastolic & increase in heart rate

Question 19

what vasodilator compounds do endothelial cells release and what does it do?

Answer 19

• nitric oxide

- causes smooth muscle to relax leading to vasodilation

Question 20

what conditions control local blood flow?

Answer 20

• hydrostatic pressure

- shear force made greater by laminar flow and shear force is atheroprotective

Question 21

what are baroreceptors?

Answer 21

receptors that detect pressure and feedback to the brain

Question 22

where are baroreceptors located?

Answer 22

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

Question 23

what does activity of the baroreceptors do to BP?

Answer 23

it decreases blood pressure

Question 24

what do chemoreceptors do?

Answer 24

detect when oxygen levels are low and feedback to the brain

Question 25

where are chemoreceptors found?

Answer 25

in the carotid bodies and aortic bodies

Question 26

what is the frank-starling mechanism?

Answer 26

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

Question 27

what is venous return?

Answer 27

the rate of blood flowing back to the heart through vein

Question 28

what is preload?

Answer 28

the initial stretching of the cardiac myocyte during diastole (prior to contraction) but it depends on venous return

Question 29

what causes volume overload?

Answer 29

results when preload becomes too large

Question 30

what causes pressure overload?

Answer 30

results from elevated afterload

Question 31

what is afterload?

Answer 31

the resistance that the chambers of the heart must overcome in order to eject blood out of the heart

Question 32

what increases afterload?

Answer 32

• back pressure from aorta or pulmonary arteries

- if the exit valve fails to completely open

Question 33

what are the 2 methods of venous return?

Answer 33

1) thoracic pump

2) muscle pump

Question 34

how does the thoracic pump work?

Answer 34

• ‘pulls’ the blood toward the right atrium
• during inspiration
• intrathoracic pressure is negative
• abdominal pressure is positive
• creates a pressure difference

Question 35

how does the muscle pump work?

Answer 35

• rhymical contraction of limb muscles
• as occurs during normal locomotor activity
• squeezes blood out of nearby veins
• venous valves assume one-way flow towards heart

Question 36

describe some features of pulmonary circulation

Answer 36

• high capillary density
• low vascular resistance
• acts as blood reservoir
• endocrine control of BP (ACE)
• acts as filter

Question 37

if carbon dioxide and H+ levels are high what happens?

Answer 37

vasoconstriction

Question 38

what does poor ventilation lead to?

Answer 38

reduced perfusion

Question 39

what process does most blood flow occur?

Answer 39

diastole

Question 40

what is hypertension?

Answer 40

high blood pressure (especially high diastolic pressure)

Question 41

describe some features of hypertension

Answer 41

• often asymptomatic
• may result in coronary artery disease & MI
• usually caused by mismatch between blood volume & circulatory capacity
• most causes are idiopathic
• secondary to kidney disease

Question 42

what can hypertension lead to?

Answer 42

kidney failure, heart failure, cardiac hypertrophy, aneurysm or stroke or MI

Question 43

what is orthostatic hypotension?

Answer 43

• low BP on standing

- dizziness or syncope

Question 44

what causes orthostatic hypotension?

Answer 44

drugs, hypovolemia and age

Question 45

what is cardiogenic shock?

Answer 45

• compensatory mechanism: tachycardia, tachypnoea
• failure to compensate: low urine output, hypotension, confusion, syncope
• acidosis