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SA Cardiovascular system > special circulations > Flashcards

special circulations Flashcards

1
Q

special circulations

A
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2
Q

2 blood supplies to lungs

A
  • bronchial circulation

provide 02 to areas of lungs that cant reach 02 (systemic)

  • pulmonary circulation

blood supply to the alveoli

needed for gas exchange

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3
Q

pressure

A
  • works with low pressure

blood flows form low - high pressure but pressure should never exceed right atrial pressure

systolic

diastolic

left side of heart

aorta has elastic recoil so can maintain pressure

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4
Q

features of pulmonary circulation

A
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5
Q

adaptions for gas exchange

A
  • many alveoli
  • short diffusion distance
  • large surface area
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6
Q

ventilation perfusion ratio

A

V/Q ratio

  • need to match ventilation with perfusion
  • optimum = 0.8
  • ventilation = diffusion of gases
  • perfusion blood passing alveoli

if this ventilation/perfusion mismatch is occluded by thromus = VQ missmatch

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7
Q

hypoxic pulmonary circulation

A
  • diverts blood away from poorly ventilated alveoli
  • vasoconstriction of pulmonary vessels to move blood to better ventilated alveoli
  • perfusion = ventiliation
  • optimise gas exhange

BUT can cause hypertension of this is chronic

  • opposite effect in systemic (hypoxic = vasodialation)
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8
Q

chronic hypoxia

A

cronic vasoconstriction

= increase resistance

=hypertension

=harder for right ventricle to pump blood out

= right ventricular heart failure

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9
Q

gravities influence on pulmonary vessels

A

capillaries at apex = pressure is lower

capillaries at level of the heart are patent

capillaries at base = increase in hydrostatic pressure

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10
Q

effect of exercise on pulmonary blood flow

A
  • increase cardiac output
  • increase in arterial pressure
  • opens apical capillaries
  • increase 02 uptake in lungs
  • increase in blood flow = reduces capillary transit time
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11
Q

forming tissue fluid

A
  • relies on starling forces
  • hydrostatic pressure = push fluid out
  • osmotic = fluid in
  • pressure drops from artery to capillary
  • increase venous pressure = increase capillary pressure
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12
Q

what leads to pulmonary odema

A

increase in venous/ arterial pressure = pressure in capillaries increase

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13
Q

why might pressure in capillaries increase

A

left atrial pressure rises to 20-25mmHg

  • mitral valve stenosis (valve between left atria and ventricle = blood cant pass through = build up of pressure in atria = blood moves back to veins = increase in venous pressure)
  • left ventricular failure = (volume at end of systole is greater = hard for blood to pass from left atria to ventricle = increase in atrial pressure = increase in venous pressure)
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14
Q

pulmonary odema

A

impares gas exchange

  • odema more likley to be at the base of the lungs
  • when patient lies down = even capillary pressure = more blood to heart
  • treatment = diuretics
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15
Q

cerebral circulation

A

brain has high 02 demand = needs a strong supply of oxygen

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16
Q

how does cerebral circulation meet 02 demand

A
  • high capillary density (large SA, reduced diffusion distance)
  • high basal flow rate
  • high 02 extraction
17
Q

why is secure 02 important for brain

A
  • neurones sensitive to hypoxia
  • damage to neurones is irreversible
18
Q

how is a secure blood supply to brain ensured

A

structurally

-anastomoses (connection) between basilar and internal carotid arteries

functionally

  • myogenic autoregulation maintains perfusion during hypotension
  • metabolic factors control blood flow
  • brainstem regulates other circulations
19
Q

myogenic autoregulation

A

maintains cerebral blood flow

20
Q

metabolic regulation

A

cerebral vessels sensitive to P(co2)

  • panic = hypocapnia + cerebral vasoconstriction = dizziness/fainting
21
Q

what factors cause vasodialation in cerebral areas

A

high p(co2)

high K conc

high adenosine

low p(o2)

22
Q

cushings reflex

A

in response to a space occuping region in the brain

  • rigid cranium protects brain
  • increases in intercranial pressure = impair cerebral blood flow
  • impared blood flow increases sympathetic activity
  • increase arterial BP = bradycardia (activating stretch receptors) and hypertension = red flag
23
Q

coronary circulation

A
  • must be able to deliver 02 at basal rate
  • must meet increased demand
  • coronary blood flow proportional to myocardial demand due to metabolic hyperaemia (vasodialation)
24
Q

comparison between cardiac musccle and skeletal muscle circulation

A
25
Q

when does most of the blood flow to the coronary arteries occur

A

during diastole

especially in the left coronory artery

26
Q

problems arising with coronary arteries

A
  • prone to atheromas (degenration in walls of artery due to build up of scar tissue and fatty deposits)
  • narrowed arteries = angina on exercise (blood flows mainly during diastole)
  • stress and cold = sympathetic coronary constriction and angina
  • obstruction via thrombus = MI

angina = chest pain due to lack of 02

27
Q

skeletal muscle circulation

A
  • must increase 02 + nutrient delivery + remove metabolites
  • regulates arterial blood pressure
  • baroreceptor relex maintains blood pressure

- at any one time only half the capillaries are being used

28
Q

metabolic hyperaemia

A

vasodialators

  • increase K
  • increase osmolarity
  • inorganic phosphates
  • adenosine
  • increased H

adrenaline - B2 receptors

29
Q

cinditions related to skeletal muscle

A
  • atheroma formation
  • intermittent claudication (pain that occurs during exercise and stops at rest)
30
Q

cutaneous circulation

A
  • vasoconstriction helps maintain blood pressure (along with skeletal muscle)
  • regulates blood flow to skin to help control heat loss
  • regulate body temp around 37
31
Q

arterovenous anastomoses (AVAs)

A

apical skin (top layer, palm, nose, ear) has high SA:vol

  • AVA under neural control (sympathetic vasoconstrictor fibres)
  • have vasoconstrictor control on them
  • lose heat = AVAs open up = diverts blood to veins near surface of skin
32
Q

how does non apical skin control body temp

A

sympathetic cholinergic fibres activate sweat glands = release vasodialators like bradykinin

33
Q

conditions with cutaneous circulation

A
  • decreased blood flow due to pressure = pressure ulcers
  • raynauds = exessive vasoconstriction
  • postural hypotension = excessive vasodialation

SA Cardiovascular system (16 decks)

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