Lecture 21 - Integration III Flashcards
What stimulates SV and HR increase during exercise?
Central command centre
What does central command do during steady exercise?
At steady exercise, central command stimulate parasympathetic system, parasympathetic neruons, and vagus nerve - release AcH which decelerates rate of sinus discharge,
What does central command do during increasing exercise intensity?
During exercise increase, central command stimulates sympathetic system to override parasympathetic system. Sympathetic nerves stimulate the AV node and SA node to beat faster. We also have sympathetic nerves going to ventricles to tell cardiac muscle to contract stronger
- Increase in HR and force of contraction of ventricles (increase in SV and CO)
What does central command do during anticipation?
Elevate HR, MAP, and respiratory rate in anticipation for exercise/movement
What is maximal HR based off?
Age not fitness
How is maximum heart rate defined?
The maximum HR is the highest HR value achieved in an all-out effect to the point of volitional fatigue.
What is steady state?
The plateau that heart rate reaches when exercise is held constant
How long does it take for HR to adjust to intensity increase in exercise?
2-3 mins
What phases BP increases most during elevated HR?
Systolic
Diastolic does not increase as much
What BP does the baroreceptor reflex respond to?
High blood pressure
Baroreceptor acts to reduce BP by decreasing sympathetic nervous activity
What does central command do to regulate BP during exercise?
Central command increases BP AND prevents a decrease in sympathetic nerve activity
How is blood flow distributed during exercise?
Increased blood flow to areas with greatest metabolic need (contracting skeletal muscle)
Sympathetic nerve activation leads to vasoconstriction & shunts blood away from less-active regions
What is local vasodilation triggered by during exercise?
Local vasodilation triggered by metabolic, endothelial products
What offsets sympathetic vasoconstriction in muscle during exercise?
Sympatholysis
What areas experience vasodilation during exercise?
Skeletal muscle and skin
What is the relative increase of ventilation from rest to exercise?
32X
What is the relative increase of tidal volume from rest to exercise?
8X
What is the relative increase of breath frequncy from rest to exercise?
4X
Why does Ve increase in exercise?
Increases because of increased tidal volume (and vital capacity) and increase in respiratory rate
Why does tidal volume increase during exercise?
Tidal volume increases because more muscles become engaged (abdominal, diaphragm, external intercostal muscles) - expiration becomes active process
What is the increase in Ve during exercise controlled by?
The increase in ventilation during exercise is controlled by both neural and humoral (chemical) pathways. Involves both mechanoreceptors in joints and muscles and chemoreceptors in carotid body and aortic body.
How does an increase in CO2 increase respiration rate?
Increase in CO2 leads to increase in respiration rate, via buffering of hydrogen bicarbonate and H+ sensing or chemoreceptors sensing increased CO2 in circulating blood.
