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Y1 Cardiology > Physiology > Flashcards

Physiology Flashcards

1
Q

Right and left coronary arteries arise from…

A

the base of the aorta

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2
Q

Coronary venous blood drains via…

A

the coronary sinus into the right atrium

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3
Q

Special adaptations of the CORONARY circulation

A

High capillary density
High basal blood flow
High oxygen extraction at rest

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4
Q

How does oxygen extraction differ in the coronary circulation in comparison to the rest of the body?

A

~75% in comparison to a 25% body average

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5
Q

INTRINSIC mechanisms of coronary blood flow control

A 
Reduced PO2 = vasodilatation 
Metabolic Hyperaemia (match flow)
Adenosine = vasodilatation
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6
Q

EXTRINSIC mechanisms of coronary blood flow control

A

Metabolic Hyperaemia overrides sympathetic vasoconstrictor nerves = vasodilation (functional sympatholysis)

adrenaline = B2 adrenergic receptor activation = vasodilatation

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7
Q

Where in the cardiac cycle does most coronary blood flow and myocardial perfusion take place?

A

During Diastole (peak left flow), as subendothelial vessels from the left coronary artery are compressed during systole.

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8
Q

What effect does tachycardia have on coronary blood flow?

A

reduction of coronary blood flow occurs due to shortening of diastole.

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9
Q

What vessels supply the brain?

A

Internal Carotids and Vertebral arteries (cerebral flow)

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10
Q

Grey matter is sensitive to hypoxia- what does this cause?

A

Unconsciousness after only a few seconds

Irreversible cell damage within 3 mins

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11
Q

Special Adaptations of CEREBRAL blood flow

A

Circle of Willis
Autoregulation
Little effect of sympathetic stimulation
Negligible participation in baroreceptor reflex

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12
Q

Circle of Willis =

A

Basilar + Carotid (anastomosis)

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13
Q

How is cerebral perfusion maintained when one carotid artery is blocked?

A

Circle of Willis

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14
Q

Obstruction of branch of main carotid artery would…

A

deprive a certain area of the brain of oxygen

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15
Q

Two types of Stroke are…

A

Ischaemic (clotting) and Haemorrhagic (bleeding)

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16
Q

What is the function of autoregulation of cerebral blood flow?

A

To preserves the cerebral blood flow against changes in MABP.

17
Q

What range does autoregulation of cerebral blood flow occur within?

A

60-160 mmHg

18
Q

What occurs as a result of MABP dropping below 50 mmHg (cerebral flow)?

A

confusion, fainting, brain damage if not quickly corrected.

19
Q

Effects of PCO2 on cerebral blood flow

A

Increased PCO2 = vasodilatation
Decreased PCO2 = vasoconstriction

(this is why hyperventilation can lead to fainting)

20
Q

Regional Hyperaemia

A

Blood flow increases to active parts of the brain.

Mechanism unknown- suspected to be associated with potassium efflux.

21
Q

Hypercapnia

A

AKA hypercarbia, carbon dioxide retention.

Abnormal elevated levels of CO2 in the blood.

22
Q

Normal Intracranial Pressure

A

8-13 mmHg

23
Q

Cerebral Perfusion Pressure (CPP) =…

A

MABP - ICP

24
Q

What effect does increased ICP have on CPP?

A

Increased ICP decreases CPP and therefore cerebral blood flow

25
Q

Examples of causes of ICP

A

head trauma

brain tumour

26
Q

What forms the blood brain barrier?

A

Cerebral capillaries tight intercellular junctions

27
Q

Permeability of BBB

A

Highly permeable to O2 and CO2
Glucose passes via facilitated diffusion
Impermeable to hydrophilic molecules to protect brain neurones.

28
Q

How does glucose spread across the BBB?

A

Via facilitated diffusion using specific carrier molecules- the brain has requirement for glucose.

29
Q

Metabolic needs of the airways are met by…

A

the systemic bronchial circulation

30
Q

Pulmonary Artery BP =

A

(20-25)/(6-12) mmHg

31
Q

Special adaptations of the Pulmonary Circulation

A 
Low pressure (8-11mmHg) 
Absorptive forces exceed filtration (protect against PO) 
Hypoxia causes vasoconstriction (note- opposite to systemic) to divert blood away where lungs poorly ventilated
32
Q

Why is the resting blood flow in skeletal muscle circulation low?

A

underlying sympathetic vasoconstrictor tone

33
Q

Why does skeletal muscle circulation flow increase many folds with exercise?

A

Local metabolic hyperaemia overcomes sympathetic vasoconstrictor tone
Circulating adrenaline activates B2 adrenergic receptors
CO increases

34
Q

What aids venous return from the limbs in the skeletal muscle circulation?

A

Veins lie between skeletal muscles in the limbs- contraction aids VR
One way venous valves

35
Q

Blood pools in the lower limb veins when venous valves are impaired =

A

varicose veins

36
Q

Why do varicose veins not reduce CO?

A

chronic compensatory increase in blood volume

Y1 Cardiology (9 decks)

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