Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

CVS * > S8 Special Circulations > Flashcards

S8 Special Circulations Flashcards

(61 cards)

Start Studying
1
Q

List 5 of the special circulations.

A
  1. Pulmonary
  2. Coronary
  3. Cerebral
  4. Skeletal
  5. Cutaneous
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two circulations in the lungs?

A
  • bronchial circulation

* pulmonary circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the bronchial circulation?

A
  • part of the systemic circulation

* meets the metabolic requirements of the lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the pulmonary circulation?

A
  • supplies blood to the alveoli

* required for gas exchange

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What must the pulmonary circulation accept the whole of?

A

Whole cardiac output

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is normal CO at rest? What is the maximum CO of a non-athlete?

A
  • 5L/min

* 20-25L/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Is the pulmonary circulation low or high pressure and resistance?

A
  • low pressure

* low resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is diastole in the right ventricle the same/lower than diastole in the right atrium?

A

If it was higher than the right atrial diastolic pressure then blood wouldn’t flow as wouldn’t be down a concentration gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why is the pressure in the atria only diastolic pressure?

A

The atria don’t undergo systole like the ventricles do

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is low resistance maintained in the pulmonary circulation?

A
  • short, wide vessels
  • lots of capillaries
  • arterioles with little smooth muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the mean arterial, capillary and venous pressures in the pulmonary circulation?

A

Arterial - 12-15mmHg
Capillary - 9-12mmHg
Venous - 5mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is efficient gas exchange promotes in the pulmonary circulation?

A
  • high density of capillaries in alveolar wall - large SA
  • short diffusion distance

Means high oxygen and carbon dioxide transport capacity produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the optimal ventilation-perfusion ratio (V/Q)?

A

0.8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is needed for efficient oxygenation in terms of V/Q ratio? How is this maintained? When might this happen?

A

Need to match ventilation of alveoli with perfusion of alveoli

Maintained by diverting blood away from alveoli that aren’t well ventilated

Hypoxia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is hypoxic pulmonary vasoconstriction?

A

Important mechanism in regulating pulmonary vascular tone.
When alveolar hypoxia occurs, vasoconstriction of pulmonary vessels occurs to ensure perfusion matches ventilation (poorly ventilated alveoli are less well perfumed) - to optimise gas exchange

This is the opposite to what happens in systemic circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is a disadvantage of hypoxic vasoconstriction?

A

Can lead to right ventricular heart failure

  • chronic hypoxia can occur at altitude or in diseases like hypoxia
  • the chronic increase in vascular resistance leads to chronic pulmonary hypertension
  • a high afterload on the right ventricle (due to pulmonary hypertension) leads to right ventricular heart failure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the low pressure pulmonary vessels strongly influenced by?

A

Gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does gravity effect the pulmonary vessels?

A

In the upright position (orthostasis) there’s increase hydrostatic pressure on the blood vessels in the lower part of the lung

  • at the apex - vessels collapse during diastole
  • at the level of heart - vessels are continuously open
  • at the base - vessels are ‘swollen’/distended
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the effect of exercise on pulmonary blood flow?

A
  • increases CO
  • there’s a small increase in pulmonary arterial pressure
  • this open apical capillaries (improves the V/Q ratio)
  • there’s increased oxygen uptake by lungs
  • as blood flow increases, capillary transit time decreases (can fall to 0.3s from 1s without compromising gas exchange)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How is tissue fluid formed?

A

Due to Starling forces

  • hydrostatic pressure of blood in capillaries - pushes fluid out
  • oncotic pressure - draws fluid in
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

In systemic circulation, does arterial or venous pressure influence capillary hydrostatic pressure more?

A

Venous pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How is lung lymph formation kept to a minimum?

A

Due to the low capillary pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Is oncotic pressure of tissue fluid higher in the lungs or periphery?

A

Lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Is capillary hydrostatic pressure higher in the lungs or systemic capillaries?

A

Systemic capillaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Is plasma oncotic pressure higher in lungs or systemic circulation?
Equal
26
What does increased capillary pressure cause?
Causes more fluid to filter out and this leads to oedema
27
What prevents pulmonary oedema?
Low capillary pressure
28
When can you get pulmonary oedema?
When capillary pressure increases e.g. if left atrial pressure rises to 20-25mmHg * mitral valve stenosis * left ventricular failure
29
What does pulmonary oedema impair? What is it affected by?
Impairs gas exchange Affected by posture (changes in hydrostatic pressure due to gravity) - when upright, oedema forms at base of lungs and when lying down, oedema forms throughout lungs
30
How do you manage/treat pulmonary oedema?
* use diuretics to relieve symptoms | * treat the underlying cause e.g. mitral valve stenosis, left ventricular heart failure
31
How much of the CO does the brain receive?
15%
32
How does the cerebral circulation meet the high demand for oxygen?
* high capillary density (large SA and reduced diffusion distance) * high basal flow rate * high oxygen extraction
33
What are neurones sensitive to, why is a secure oxygen supply to the brain needed?
Sensitive to hypoxia Leads to loss of consciousness within few seconds of cerebral ishcaemia and damage is irreversible after 4 mins
34
How is a secure blood supply to the brain ensured?
* anastomoses between basilar and internal carotid arteries (so even if one blokes, can still get blood to brain) * myotonic autoregulation (maintains perfusion during hypotension) * metabolic factors control blood flow * the brainstem regulates other circulations
35
What is myogenic autoregulation?
Maintains cerebral blood flow when blood pressure changes (but fails if BP falls below 50mmHg) * if BP increases, vasoconstriction occurs * if BP decreases, vasodilation occurs
36
How is cerebral circulation controlled by metabolic regulation?
Cerebral vessels are very sensitive to changes in arterial carbon dioxide pressure * hypercapnia (increased carbon dioxide) leads to vasodilation * hypocapnia (decreased carbon dioxide) leads to vasoconstriction
37
What can panic hyperventilation cause?
Hypocapnia and so cerebral vasoconstriction which leads to dizziness and fainting
38
What does regional activity in the brain (neuronal activity) lead to?
Increased local blood flow
39
Which aspects/molecules of neuronal activity lead to vasodilation?
* increased carbon dioxide pressure * increased K+ concentration * increased adenosine - important vasodilator of cerebral arteries * decreased oxygen pressure
40
What is Cushing’s Reflex?
* a rigid cranium protects the brain and doesn’t allow for volume expansion * so increases in intracranial pressure (cerebral tumour/haemorrhage) impair cerebral blood flow * this impaired blood flow to vasomotor control regions of brainstem leads to increased vasomotor activity (bradycardia occurs) * arterial BP increases - this helps maintain arterial flow But need to relieve this pressure, or will die
41
Where do the right and left coronary arteries arise from?
Arise from right and left aortic sinuses
42
When does most of the flow to the left coronary artery occur, during systole or diastole? What is a disadvantage of this?
Diastole If HR increases, diastole is shortened, this mean less blood is able to flow to the L coronary artery. Becomes a problem when narrowing of coronary arteries occurs.
43
How is efficient oxygen delivery to heart facilitated?
* high capillary density and they are constantly perfused * short diffusion distance * a continuous production of NO by the coronary endothelium meant aims a high basal flow - NO causes vasodilation, decreased vascular resistance and inhibition of platelet aggregation
44
How does coronary blood flow increase with myocardial oxygen demand?
* extra oxygen is required if workload is high * this is supplied by increased blood flow - vasodilation occurs due to hyperaemia * almost linear relationship until v high oxygen demand
45
What are some vasodilators involved in increased blood flow for coronary circulation?
* adenosine * increased K+ concentration * decreased pH
46
What are coronary arteries prone to due to having few arterio-arterial anastomoses (having many end arteries)?
Atheromas
47
What ‘symptom’ do narrowed coronary arteries lead to on exercise? What conditions also lead to sympathetic vasoconstriction and this symptom?
Angina * due to the increased oxygen demand * diastole is reduced as HR increases, but most of blood flow in L coronary artery is during diastole Stress and cold
48
Sudden obstruction of a coronary artery by a thrombus leads to what?
Myocardial infarction
49
When must oxygen and nutrient delivery and removal of metabolites increase in skeletal muscle circulation?
During exercise
50
What do skeletal muscle play an important role in regulating?
Arterial blood pressure
51
What does capillary density in the skeletal muscle circulation depend on?
Depends on muscle type
52
Some vessels in the skeletal muscle circulation are innervated by the sympathetic nervous system. What happens in these vessels, vasoconstriction or vasodilation? What maintains the blood pressure?
Vasoconstriction which increases resistance Baroreceptors
53
What does the high vascular tone of skeletal muscle vessels permit?
Permits lots of vasodilation so flow can increased massively in active muscles
54
At rest, how many of the skeletal muscle capillaries are perfused? What is the advantage of this?
About half Means when need perfusion of capillaries due to contraction/metabolic demand/etc the effect is bigger (increased recruitment)
55
What opens to allow more capillaries to be perfused in the skeletal muscle circulation?
Precapillary sphincters
56
What agents act as vasodilators?
* increased K+ concentration * increased osmolarity * inorganic phosphates * adenosine * increased H+ concentration
57
What does adrenaline act as at arterioles in skeletal muscle? What is the opposite effect?
Acts as a vasodilator * acts through beta-2 adrenoreceptors Noradrenaline acting on alpha-1 adrenoreceptors causes vasoconstriction
58
What does cutaneous circulation have a role in regulating?
Temperature (and blood pressure - via vasoconstriction)
59
What structures does the apical/acral skin have? What is their role in temperature regulation in terms of the cutaneous circulation?
Artereovenous anastomoses (AVAs) They direct blood flow to superficial/deep vessels dependent on whether wanting to lower or increase body temperature
60
What type of control are AVAs under?
Neural control - sympathetic vasoconstrictor fibres
61
When are AVAs opened? When are they closed?
When there’s an increase in core temperature (decreased sympathetic tone) leads to dilation of AVAs and so diverts blood to superficial veins Opposite if decreased core temperature - increased sympathetic done so vasocontraction and blood diverted to deep veins

CVS * (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions