Week 6 - Cardiac Output Regulation

Question 1

What factors promote hyperaemia
(Greater blood flow to tissues and organs)

Answer 1

Tissue hypoxia
CO2 increase
pH decrease
Lactate production
Breakdown products of ATP
Potassium
Osmolality

Question 2

How is blood flow redistributed during exercise

Answer 2

Increase blood flow to working skeletal muscle
At rest, 15-20% of cardiac output to muscle. 80-85% during maximal exercise

Decrease blood flow to less active organs.
Liver, kidneys, GI tract

Question 3

How is local blood flow regulated during exercise

Answer 3

1. Skeletal muscle vasodilation (decrease vascular resistance).
2. Increased blood flow to meet metabolic demands, changes in local factors (Nitric oxide, ATP, adenosine)
3. Vasodilation magnitude is proportional to size of recruited muscle

Vasoconstriction to visceral organs and inactive tissues

Question 4

What occurs during the redistribution of cardiac output during exercise

Answer 4

Skeletal muscle can take up to 90% of cardiac output at maximal exercise
Skin and coronary circulation also major users

Question 5

What happens during splanchnic circulation during exercise

Answer 5

Blood flow decreases through sympathetic vasoconstriction and circulating catecholamines
Oxygen extraction increases to compensate
20-25% of total blood volume is in splanchnic region

Question 6

What sympathetic neutral control occurs in the splanchnic region during exercise

Answer 6

Constriction in the splanchnic circulation can add blood volume into the circulation back to the heart, increasing venous return

Question 7

How does skin circulation controlled under neural control during exercise

Answer 7

Sympathetic neural control of skin blood vessels
Vasoconstriction from adrenergic vasoconstrictor (noradrenaline release from SNS) to maintain BP and redistribute blood to active muscle.
Vasodilation from cholinergic vasodilator (acetylcholine release from ANS) to dissipate heat generated from exercise

Adrenergic vasoconstrictor (non-hairy skin)
Cholinergic vasodilator (hairy skin)

Question 8

How does skin circulation regulate thermoregulation

Answer 8

Vasoconstriction occurs from an increased sympathetic constrictor activity
Vasodilation occurs from decrease sympathetic constrictor activity and increased dilator activity

Question 9

How does temperature affect skin thermoregulation

Answer 9

Cold stress leads to vasoconstriction
Heat stress leads to vasodilation

Question 10

What are the neurotransmitters for adrenergic and cholinergic control of skin circulation under neural control

Answer 10

Adrenergic = noradrenaline (SNS)
Cholinergic = acetylcholine (ANS)

Question 11

What occurs in skin circulation during exercise

Answer 11

Vasoconstriction at onset with sympathetic activation
Active vasodilation occurs at a threshold core temperature to lose heat
Vasoconstriction during prolonged exercise to maintain central blood volume and venous return

Question 12

How does regular exercise affect brain blood flow

Answer 12

Regular exercise offsets age-related declines in brain blood flow

Question 13

What are the key regulators of brain blood flow

Answer 13

SNS & ANS activity
Arterial blood pressure
Cardiac output
Cerebral neural activity
Metabolism of metabolites (CO2, NO, O2)

Question 14

What are some ways in measuring brain blood flow

Answer 14

MRI
Transcranial Doppler
Near-infrared Spectroscopy

Question 15

How does skin circulation change throughout exercise

Answer 15

Vasoconstriction at onset from exercise from sympathetic activation
Active vasodilation at threshold occurs decrease core body temperature
Vasoconstriction occurs again to maintain blood pressure and venous return

Question 16

What are the factors that affect brain blood flow

Answer 16

Increases in these factors increases Cerebral blood flow:
1. Nerve cell activity
2. Perfusion pressure
3. Arterial PCO2
4. Cardiac Output
& decrease in Cerebral SNA

Question 17

What effect does continuous aerobic fitness have on brain blood flow

Answer 17

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

Question 18

What are some acute and chronic outcomes from impaired cerebral blood flow

Answer 18

Acute: Stroke or faint
Chronic: Hypertension, Dementia, Concussion

Question 19

How is brain blood flow impacted by exercise intensity and modality

Answer 19

Brain blood flow increase as exercise intensity increases due to increased PaCO2 concentration. Modes of exercise that produce high amounts of CO2 in body could affect brain blood flow