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CVS > Special Circulations > Flashcards

Special Circulations Flashcards

1
Q

Compare the functions of the 2 circulations of the lungs

A

Bronchial circulation;

  • Meets the metabolic requirements of lung
  • Part of systemic circulation

Pulmonary circulation;

  • Blood supply to alveoli
  • Required for gas exchange
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2
Q

What are the mean pressures of the pulmonary vessels?

A

Mean Pulmonary Arterial Pressure: 12-15mmHg

Mean Pulmonary Capillary Pressure: 9-12mmHg

Mean Pulmonary Venous Pressure: 5mmHg

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3
Q

What is the Ventilation-Perfusion ratio

what is it represented as?
What is it optimally?

A

Represented as “ V/Q ratio”, Optimal=0.8

The matching of Ventilation of Alveoli to Perfusion of Alveoli

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4
Q

Name and explain the primary mechanism that regulates pulmonary vascular tone?

A

Hypoxia Pulmonary Vasoconstriction

Alveolar hypoxia results in vasoconstriction of pulmonary vessels

(Ensures that perfusion matches ventilation)

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5
Q

Explain 1 downside of Chronic Hypoxic Vasoconstriction

A

Chronic Hypoxia (Altitude/ lung disease)

  • Increase in vascular resistance-> Pulmonary hypertension
  • High aterload on RV-> RV heart failure
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6
Q

Compare the hydrostatic pressure of vessels in different parts of lung?

Explain the difference?

Thus, explain how they differ during inspiration?

A

Apex;

  • Low hydrostatic pressure (< Alveolar pressure)
  • Vessels collapse during inspiration

Level of Heart;

  • Higher H pressure (> Alveolar pressure)
  • Vessels continuously patent

Base;

  • Highest H pressure (> Alveolar pressure)
  • Vessels distended
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7
Q

How does exercise affect pulmonary blood flow and O2 uptake?

A
  • Increased cardiac output-> Small increase in arterial pressure
  • Opens apical capillaries-> increased O2 uptake
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8
Q

Explain the forces that determine tissue fluid formation

A

Starling forces

Hydrostatic pressure pushes fluid out of capillary
Oncotic pressure draws fluid into capillary

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9
Q

Is hydrostatic pressure affected more by arterial or venous pressure?

Using this knowledge, would hypertension usually cause oedema

A

Venous pressure

No, as hypertension is influenced by arterial pressure

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10
Q

Where do pulmonary oedemas form when upright and when lying down

Explain this

A

Upright: At base as hydrostatic pressure here is highest due to gravity

Lying down: Throughout lung

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11
Q

Compare the patient outcomes of blood flow to brain being reduced;

For a few seconds
3-4 minutes

Name 1 outcome of a small alteration to cerebral blood flow

A

Few seconds: Syncope (Fainting)
3-4 mins: (Permanent brain damage or death)

Headaches

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12
Q

How much of the cardiac output goes to brain

A

15%

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13
Q

What are 4 factors that allow the cerebral circulation to meet its high demand for O2

A
  • High capillary density
  • High basal flow rate
  • High O2 extraction
  • Secure O2 supply
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14
Q

What are 4 ways the secure blood supply to the brain is maintained

A

Structurally;
- Anastomoses between basilar and internal carotid arteries

Functionally;

  • Metabolic factors that control blood flow
  • Brainstem regulates other circulations
  • Myogenic autoregulation maintains perfusion during hypotension
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15
Q

Explain Myogenic Autoregulation in brain

Below what blood pressure, does this process fail?

A

Increase in BP-> Vasoconstriction to reduce blood flow to brain

Decrease in BP-> Vasodilation to increase blood flow to brain

50mmHg

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16
Q

Explain Metabolic Regulation in brain

What can panic ventilation cause? What does this present as

A

Hypercapnia: Vasodilation increases blood flow to brain

Hypocapnia: Vasoconstriction decreased blood flow to brain

(Hypercapnia= High partial pressure of CO2)

Panic hyperventilation can cause hypocapnia-> cerebral vasoconstriction, leading to dizziness and syncope

17
Q

How is blood flow affected in areas of brain with increased neuronal activity?

Name 1 substance that is a strong vasodilator of cerebral arterioles

A

Increased blood flow

Adenosine

18
Q

Describe Cushing’s Reflex

A
  • Cranium doesn’t allow for volume expansion
  • Increased intercranial pressure-> Impaired cerebral blood flow
  • Impaired flow to vasmotor control region of Brainstem increased sympathetic vasomotor activity-> Increased arterial BP
19
Q

Where to the right and left coronary arteries arise from

A

Right Coronary Artery- Right Aortic Sinus

Left Coronary Artery- Left Aortic Sinus

20
Q

Identify 3 features of Coronary circulation that improve blood flow+O2 supply

A
  • High capillary density
  • Short diffusion distance
  • Continuous production of NO by coronary endothelium (Vasodilator)
21
Q

Describe the relationship between Myocardial O2 demand and Coronary Blood Flow

What are coronary arteries prone to

A

Linear relationship until O2 demand is very high

Prone to atheroma

22
Q

Why is coronary blood flow mostly during diastole?

Explain why angina is more likely to occur during exercise

A

During systole, tension of ventricle walls compresses the coronary vessels

During exercise, less time spent in diastole, so less O2 supply

23
Q

How is the rate of flow through the myocardium controlled?

A

By the action of metabolites that cause vasodilation of coronary arterioles

(Adenosine, K+, Low pH)

24
Q

Name 1 important role of the skeletal muscle circulation

How does it do this?

A

Regulation of Arterial BP

Via resistance vessels innervated by sympathetic vasoconstrictor fibres

Pre-capillary sphincters are opened to allow perfusion of more capillaries

25
Q

In skeletal muscle, flow can be increased by vasodilation of capillaries.

What are 2 ways this can be done

A

Via metabolites;

  • K+
  • Inorganic phosphates
  • Adenosine
  • H+

Via nervous activity;

  • Adrenaline acts at arterioles
  • through B2 receptors
26
Q

What is the main role of cutaneous circulation

What is another role?

A

Temp. regulation

Maintaining blood pressure (Vasoconstriction to maintain BP)

27
Q

What are the specilaised structures in the skin that regulate temperature?

How are they controlled?

A

Artereovenous anastomose, under neuronal control via sympathetic vasoconstrictor fibres

28
Q

Outline how Artereovenous anastomoses regulate temperature in apical skin

A
  • Decreased core temp-> Increased sympathetic tone in AVAs-> Vasoconstriction of AVAs
  • Increased core temp-> reduced vasomotor drive-> Dilation of AVAs

CVS (15 decks)

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