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Cardiovascular System > Lecture 8.1: Special Circulations > Flashcards

Lecture 8.1: Special Circulations Flashcards

1
Q

What are the 2 Main Circulatory Systems in the Body?

A

1) Pulmonary
2) Systemic

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2
Q

Pulmonary Circulation

A
  • ‘Managed’ by the right side of the heart
  • Deals with the oxygenation of venous blood
  • Delivery of ‘good to go’ arterial blood to the left
    side of the heart
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3
Q

Systemic Circulation

A
  • Managed by the left side of the heart
  • Delivers oxygenated arterial blood to the body * Returns it via the venous system back to the
    right side of the heart
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4
Q

Pulmonary Artery Pressure

A
  • Low Pressure
  • Low Resistance
  • 15-30mmg/4-12mmHg
  • Short, wide vessels
  • Lots of capillaries (in parallel)
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5
Q

Local Hypoxia effect on Pulmonary & Systemic Circulation

A
  • Causes vasodilation in the systemic circulation
  • Causes vasoconstriction in the pulmonary
    circulation
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6
Q

What can happen if pulmonary capillary pressure increases?

A
  • Pulmonary oedema can form
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7
Q

Why is Pulmonary Oedema bad? What relieves the systems?

A
  • Pulmonary oedema impairs gas exchange
  • Mainly at base when upright
  • Throughout lung when lying down
  • Diuretics relieves the symptoms
  • But treat the cause
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8
Q

Consequences of Failure of Cerebral Circulation (4)

A
  • Neurons very sensitive to hypoxia
  • Loss of consciousness after a few seconds of
    ischaemia
  • Irreversible Damage in ~ 4 minutes
  • Strokes/Cardiac Events
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9
Q

Blood supply to brain is via…? (carotid…..to penetrating arteries)

A
  • Internal Carotid Arteries
  • Vertebral Arteries (from which the basilar artery
    originates)
  • Carotids and basilar anastomose to form a
    circle around the optic chiasm (circle of Willis)
  • Anterior, middle and posterior cerebral arteries
    arise from the circle of Willis
  • The cerebral arteries divide to form the pial
    arteries that run over the surface of the brain
  • From pial arteries, smaller arteries are formed
    that penetrate
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10
Q

What is an anastomose?

A

A surgical connection between two structures

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11
Q

Why are Anastomoses important in younger people?

A
  • In younger people, the anastomoses ensure
    cerebral perfusion if a carotid fails
  • In older individuals, this process is less
    effective
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12
Q

What is Autoregulation?

A

The intrinsic ability of an organ to maintain blood flow at a nearly constant rate despite changes in arterial perfusion pressure

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13
Q

Do Cerebral Arteries show Autoregulation?

A
  • Cerebral vessels show considerable
    autoregulation to maintain proper flow
  • If BP drops and perfusion is threatened,
    cerebral resistance vessels dilate
  • The brain is extremely selfish, brainstem
    responses can interrupt flow to other vascular
    beds to preserve itself!
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14
Q

What does local hypoxia results in cerebral arteries?

A

Local hypoxia results in cerebral vasodilation via adenosine

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15
Q

What is the Cushings Reflex/Cushings Response?

A
  • It is a physiological nervous system response
    to acute elevations of intracranial pressure
    (ICP)

Results in Cushing’s Triad of:
* Widened pulse pressure (increasing systolic,
decreasing diastolic)
* Bradycardia
* Irregular Respirations

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16
Q

What problems space occupying lesions cause in terms of the cerebrum?

A
  • Impaired CSF drainage
  • Raises intracranial pressure with displacement
    of brainstem down into foramen magnum
  • Compression of brainstem produces activation
    of vasomotor centres
  • Cushing’s Reflex is caused
  • Also evoke bradycardia mediated via.
    baroreceptor reflex
17
Q

What substances can move through the Blood Brain Barrier?

A
  • Lipid soluble substances able to move freely
    from blood to brain
  • Lipid insoluble eg salts do not
18
Q

Brain capillaries have specialised tight junctions, what are they made of?

A
  • Made of cadherin-10, claudin-1 and occluding
    amongst others
  • Unbroken seal between cells
  • Aided by feet of astrocytes
19
Q

In what places is the BBB defective?

A
  • Circumventricular Organs (allows Na+/Cl- to
    access osmoreceptors)
  • Area Postrema (medulla) (allows emetics to
    access vomiting centre)
20
Q

Coronary Circulation

A
  • Right and left coronary arteries arise in the
    aorta from dilatations called the sinuses of
    Valsalva
  • Left coronary artery (left ventricle and
    interventricular septum)
  • Right coronary artery (right ventricle)
  • Venous drainage primarily to the right atrium via
    the coronary sinus
21
Q

When does most coronary blood flow occur?

A
  • ~80% of coronary blood flow occurs during
    diastole
  • Many vessels are compressed during systole
22
Q

What does continuous production of NO by endothelium do?

A
  • Maintains a high basal flow
  • Flow reduced by NO synthase inhibitors
23
Q

Additional demand of exercise met by metabolic..?

A
  • Additional demand of exercise met by metabolic
    hyperaemia
  • Adenosine prime contender
24
Q

What is Hyperaemia?

A

It is the process by which the body adjusts blood flow to meet the metabolic needs of its different tissues in health and disease

25
Q

What are the 3 Ways Heat is Lost?

A
  • Radiation
  • Conduction/convection (air next to skin warmed
    up and moved on)
  • Evaporation
26
Q

What is the Importance of Cutaneous Circulation?

A
  • Important role in temperature regulation
  • Cutaneous heat loss matched to core heat
    production
  • Cutaneous blood flow is the principal factor in
    regulating heat loss by the aforementioned
    mechanisms
27
Q

The skin itself is Poikilothermic, what does this mean?

A

It has variable temperature/temperature changes

28
Q

What does Homeothermic mean?

A

Having a relatively uniform body temperature maintained nearly independent of the environmental temperature

29
Q

What are Arteriovenous Anastomoses (AVAs)? Where are they found?

A
  • They are specialised structures that are direct
    connections between small arteries and small
    veins
  • Acral (Apical) Skin
  • Fingers/toes/lips/nose/ie exposed regions
30
Q

What part of the nervous system are AVAs controlled by?

A
  • Show little basal tone
  • Controlled almost exclusively by SANS
    influenced by hypothalamic temperature
    regulating centre
31
Q

What happens when core temp increases to encourage heat loss?

A
  • Sympathetic drive is reduced
  • Leads to vasodilation
  • Blood flows into skin increasing blood flow and
    heat delivery = heat loss

Cardiovascular System (19 decks)

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