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Medicine 2 Weeks 1 - 6 > Regional Circulation > Flashcards

Regional Circulation Flashcards

1
Q

Discuss the effect of pressure on blood flow in the brain

A

A constant flow over a wide range of pressure

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2
Q

Neural control of blood in the brain

A

Relatively minor neural control as there are relatively few alpha1 adrenoceptors

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3
Q

Importance of hormones in blood flow to the brain

A

Minor importance

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4
Q

Local regulation of blood flow in brain

A

Good autoregulation

Important metabolic control during mental activity - (H+, K+, Adenoside, Hypercapni, hypoxia cause vasodilation)

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5
Q

Endothelin

A

Important vasoconstrictor released in pathological states - e.g. subarrachnoid haemmorage to limit blood loss

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6
Q

Mechanical control of brain circulation

A

Constrained in rigid cranium influenced by CSF pressure

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7
Q

Special feature of brain circulation

A

Brain can sometimes steal blood from other regions due to its extreme importance

medullary ischaemic reflex
Ischaemia in medulla, brain detects this and sends signals to other body parts to send driving force to brain

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8
Q

Coronary sympathetic innervation

A

Not much innervation, but the effect of the innervation is chronotropy and inotropy, increasing metabolic activity in heart, releasing vasodilators (e.g. CO2, adenosine) and thus blood flow

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9
Q

Mechanical control of cardiac circulation

A

Major influence on flow during cardiac cycle - peak flow in early diastole; zero or negative flow at onset of systole

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10
Q

Why is the heart usually slowed in heart conditions

A

Heart spends longer in diastole so increased time for blood to be delivered

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11
Q

Special feature of cardiac circulation

A

Parallelism between metabolism and flow

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12
Q

AV anastomoses

A

Direct connections between arterioles and venules without having to go through capillaries

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13
Q

Neural control of skin vessels

A

Arterioles have relatively weak innervation, A-V anastomoses have a dense innervation though

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14
Q

What happens to arterioles and AV anastomoses as core temperature

A

Vasoconstriction in order to decrease skin blood flow and limit heat loss

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15
Q

Local control of skin circulation

A

Arterioles show some degree of myogenic autoregulation; endothelin may be involved in pathological states like raynauds

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16
Q

Hormones involved in skin circulation

A

Angiotensin, Vasopressin, Noradrenaline, Adrenaline all cause vasoconstriction

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17
Q

Special features of skin circulation

A

The primary funtion is thermoregulation

Sweat glands have sympathetic cholinergic innervation which may cause vasodilatation via release of e.g. bradykinin

18
Q

Neural control of skeletal muscle circulation

A

Rest - important alpha vasoconstriction, some beta vasodilation

Exercise - Very little neural incluence, some beta vasodilation via mostly adrenaline, not nerve

19
Q

Hyperaemia

A

Increased blood flow

20
Q

Local control of skeletal muscle circulation

A

Rest - neural control over-ride autoregulatory mechanisms

Exercise - Local metabolites have major influence (K+, adenosine, lactate, etc.) all causing vasodilation

21
Q

Hormones involved in skeletal muscle circulation

A

Adrenaline at low concentrations will vasodilate (beta adrenoceptors)

22
Q

Special features of skeletal muscle circulation

A

Capacity to increase flow in exercise (20-fold) - active hyperaemia

Large increase in flow post-occlusion - reactive hyperaemia
(Increase above normal in blood flow if supply is temporarily cut off)

23
Q

Describe the blood that reaches the liver

A

70% of blood in the liver is deoxygenated as it has passed through the digestive organs and is filtered before entering blood stream

30% enters as oxygenated via the hepatic artery

24
Q

Neural control of intestinal circulation

A

Moderate alpha vasoconstriction

25
Q

Neural control of hepatic circulation

A

Important venoconstriction

26
Q

Local control of GI circulation

A

Poor autoregulation but importantly influenced by local peptides

27
Q

Local control of hepatic circulation

A

Portal vein - No autoregulation

Hepatic artery - Good autoregulation

28
Q

Hormones involved in GI circulation

A

GI hormones (gastrin, cholecystokinin) vasodilate, vasopressin, angiotensin constrict potently

29
Q

Neural control of GI circulation

A

Minimal influence

30
Q

Mechanical control of hepatic circulation

A

Minimal influence

31
Q

Why is there pain sometimes if you exercise immediately after eating

A

There may be competition for blood supply between the GI tract and muscles

32
Q

Special features of GI tract

A

Intestinal circulation exhibits functional hyperaemia following feeding; intense vasoconstriction can lead to damage and toxin release

33
Q

Neural control of renal circulation

A

Important alpha vasoconstriction, some beta vasodilation

34
Q

Discuss innervation of renin secreting cells

A

They have an important sympathetic innervation of beta adrenoceptors

35
Q

Local control of renal circulation

A

Good autoregulation of flow over wide pressure range

36
Q

Hormones involved in renal circulation

A

Noradrenaline, adrenaline, angoitensin can cause constriction

Vasopressin may cause vasodilation via PGI2/NO release

Dopamine causes vasodilation

37
Q

Special features of renal circulation

A

Efferent constriction causes increase in BP upstream of that; thus the glomerulus

38
Q

Neural control of pulmonary circulation

A

Relatively minor (alpha vasoconstriction)

39
Q

Local control of pulmonary circulation

A

Unlike elsewhere, hypoxia causes vasoconstriction, augmented by hypercapnia (possibly mediated by endothelin)

NO causes vasodilation and may be therapeutic

40
Q

Mechanical control of pulmonary circulation

A

Flow is affected by changes in aveolar pressure and lung volume; increase in flow (cardiac output) associated with recruitment and distentsion of mucrovessels and decrease in vascular resistance

41
Q

When alveolar pressure > intravascular pressure

A

Flow is reduced
Lung inflation reduces resistance in extra-alveolar vessles (traction) and increases resistance in intra-alveolar vessels (compression)

42
Q

Special feature of pulmonary circulation

A

Thin walled vessels with low resistance & low vasoconstrictor capacity
Hydrostatic pressure < colloid osmotic pressure which favours reabsorption

Medicine 2 Weeks 1 - 6 (54 decks)

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