Lecture 24: Brain Blood Flow and Exercise

Question 1

Why is efficient brain blood flow important?

Answer 1

Acute: too much or too little blood flow can cause a stroke or fainting
Chronic: blood flow problems can result in hypertension; diabetes and dementia

Question 2

What influence can age have on disease related to brain blood flow?

Answer 2

Increases the likelihood of chronic brain disease

Question 3

What are the three methods of measuring brain blood flow?

Answer 3

MRI
Transcranial Doppler
NIRS

Question 4

What does the MRI measure?

Answer 4

Velocity of blood flow
Structures
Deep mapping of the brain
Can’t be carried out during exercise

Question 5

What does the transcranial doppler measure?

Answer 5

Blood flow and oxygenation of brain tissues

Question 6

What does NIRS measure?

Answer 6

Specifically at the cerebral cortex
A form of Doppler
Can be done during exercise
Blood flow of capillaries (tissues)

Question 7

How does blood flow in the brain differ to that of the coronary system?

Answer 7

Blood flow in the brain increases during systole and decreases during diastole

Question 8

What are the 5 ways the brain can be regulated?

Answer 8

Metabolically 
Systemically
Neurogenically 
Chemically 
Autoregulatory

Question 9

What is the most important regulatory mechanism for brain blood flow?

Answer 9

Chemical

Question 10

What does high/low nerve cell activity cause in the brain?

Answer 10

Low nerve cell activity = coma

High nerve cell activity = seizure

Question 11

What is the effect of high CO2 (hyperventilation) on brain blood flow?

Answer 11

Increased blood flow (flush out metabolites)

Question 12

What is the effect of increased oxygen in the brain?

Answer 12

Lowered blood flow

Don’t require as much blood flow as haemoglobin is saturated with more oxygen

Question 13

How does autoregulation of brain blood flow work?

Answer 13

Autonomic nervous system detects drop in blood pressure
This causes a myogenic response: contraction of systemic arteries and a systemic response: baroreflex of increased heart rate
This increases brain blood flow

Question 14

How are strokes caused?

Answer 14

When there is a drop in cerebral blood flow due to decreased CO2

Question 15

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

Answer 15

CBF increases to about 40% of maximal intensity.
Then begins to decrease.
This is due to the anaerobic threshold being met (lactate produced faster than it’s cleared) which causes loss of CO2.
This causes blood flow to the brain to decrease.

Question 16

What occurs if petCO2 is held constant?

Answer 16

Brain blood flow increases as you increase exercise intensity

Question 17

Can maintenance of petCO2 improve exercise performance?

Answer 17

No.

Question 18

How can brain blood flow affect brain cognition?

Answer 18

Increased academic performance
Increased CBF with higher VO2max scores
More brain blood flow is required for more complex tasks (greater o2 extraction)

Question 19

What is the relationship between age and brain blood flow?

Answer 19

Increased age decreases brain blood flow

More blood flow required than young people for complex tasks

Question 20

How can brain blood flow be improved?

Answer 20

Regular aerobic training (causes improved sensitivity to CO2)

Question 21

How does Alzheimer’s disease affect CBF?

Answer 21

Reduced CBF

Question 22

What are the 5 ways brain blood flow can be regulated|?

Answer 22

Metabolically 
Neurogenically 
Systemically 
Autoregulation 
Chemically