L23 Brain Blood Flow

Question 1

why is effective regulation of brain blood flow important?

Answer 1

blood tot he brain is vital. It is only 2-3% of the body’s mass but needs 15-20 % of the total cardiac output.
The brain is the central command for everything in the body so it needs a constant supply of blood so that it gets all the nutrients it needs.

Too little and you faint or have a stroke. Too much and hypertension, diabetes, dementia occurs

Question 2

List the key regulators of brain blood flow and explain how exercise effects these

Answer 2

1. Metabolic - nerve cell activity
2. Autoregulatory - perfusion pressure
3. Neurogenic - sympathetic nerve activity
4. Chemical - oxygen and carbon dioxide
5. Systemic - cardiac output

Question 3

Describe the techniques available to measure brain perfusion and discuss their strengths and limitations

Answer 3

MRi –> shows structure and function but is expensive and time consuming.

Transcranial Doppler –> Measures the blood flow velocity in the brain, can measure global flow. It is good for functional analysis and exercise. Good as it shows high temporal resolution.

near-infrared spectroscopy (NIRS) –> measures the balance of oxygen supply and the O2 demand directly at a capillary level in the cerebral cortical tissue. Gives us a measure of brain activation.

No limitations on the lecture slides?

Question 4

Explain how exercise influences brain blood flow, with specific reference to the effect of exercise intensity and modality

Answer 4

Above 65% of VO2 max, we reach anaerobic threshold, CO2 is decreased and brain blood flow mirrors that.
When you hold partial pressure of end tidal CO2 constant brain blood flow continues to rise as exercise intensity increases.

Question 5

Discuss the links between fitness, brain blood flow and brain health

Answer 5

As we age our brain function decreases. Exercise has big effects on executive function.

With school kids there is a positive relationship between how fit you are and brain performance

Habitual exercise appears to off set the natural age-related decline - can be by about 10 years

Frequent physical activity improves cerebral blood flow regulation, which in turn improves cognitive inhibitory control

Aerobic conditioning improves resting brain blood flow and responsiveness with 12 weeks of aerobic training in disease-free sedentary poopulation