Week 6 - Brain blood flow and exercise Flashcards

1
Q

Why is blood flow to and within the brain vital?

A

Its vital for survival and functional consequences such as performance, cognitive function, and preventing disease/conditions (stroke, dementia).

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2
Q

What % of body mass is the brain? What % of total cardiac output does it demand?

A

Brain only 2-3% of body mass, yet demands 20% of total cardiac output.

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3
Q

Why is habitual exercise important for brain blood flow?

A

Habitual exercise offsets the natural age-related decline in brain blood flow.

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4
Q

Two factors that reduce size of brain (and consequent blood flow)

A

1) Ageing
2) Inactivity

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5
Q

What does Near-Infrared Spectroscopy (NIRS) measure?

A

The balance of oxygen supply and oxygen demand directly at a capillary level in cerebral cortical tissue.
Gives us a measure of brain activation - neurovascular coupling.

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6
Q

What method of assessing the brain is suited to dynamic exercise?

A

Transcranial Doppler

  • measures blood velocity as an index of flow
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7
Q

5 factors that regulate blood flow.

A

1) Metabolism
2) Blood pressure
3) Neurogenic (Cerebral SNA)
4) Chemical (key factor - oxygen and carbon dioxide values in blood)
5) Cardiac output (key factor)

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8
Q

How can we explain why athletes faint after a long exercise bout or a maximal bout such as a deadlift?

A

During exercise, blood vessels are dilated to deliver blood to the muscles.
When exercise stops, we get a sudden drop in blood pressure but blood vessels are still dilated to the muscle, so we get a decline in BBF. This can result in fainting.

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9
Q

How does hyperventilation (during a deadlift) influence BBF?

A

It will decrease BBF because hyperventilating reduces arterial PCO2 - this can result in fainting.

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10
Q

What is the relationship between brain blood flow and arterial partial pressure of carbon dioxide (PaCO2)?

A

Brain blood flow increases as PaCO2 increases (not linear)

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11
Q

What is the relationship between brain blood flow and exercise intensity?

A

Inverted U response
- Once you go over the anaerobic threshold you start to hyperventilate (due to H+ production) so we reduce C02 which results in reduced BBF.

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12
Q

What happens to BBF when you hold PetCO2 (partial pressure of end-tidal carbon dioxide) constant as exercise intensity increases?

A

BBF continues to rise

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13
Q

Is the pattern of BBF the same for all exercise modalities?

A

NO - they appear to be different between exercise modes

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14
Q

What are exercise-induced changes in BBF dependent on?

A

1) The exercise modality (run vs cycle)
2) Exercise protocol used (HIIT/continuous)
3) Fitness level (fitter individuals get increase in BBF at higher intensities)

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15
Q

What acute events and chronic clinical conditions are associated with impaired BBF?

A

Acute events: faint, stroke

Chronic clinical conditions: hypertension, dementia, concussion

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16
Q

Name a technique used to measure brain perfusion and identify a strength and a limitation for its use in relation to studying the effects of exercise on brain blood flow.

A

Transcranial Doppler

Strength: we can measure BBF during exercise (can’t with MRI)
Limitation: