HK 368 Exam #3 respiratory response to exercise

When does ventilation increase in relation to exercise?

almost instantly because of the central command

What are respiratory centers?

clusters of nuerons that are responsible for firing of the nerves that control respiration, found in the brain stem (medulla oblongata and pons), seperate center for inspiration and expiration, these will self depolarize and cause neurons to fire, establish rate and depth of breathing via signals to respiratory muscles

Can respiratory centers be override?

yes the cortex can override them if necessary

What are the two peripheral mechanisms of regulation?

central and peripheral chemoreceptors

Central chemorecpetors?

stimulated by increased CO2 in spinal fluid, increased rate and depth of breathing to remove excess CO2 from the body

Peripheral chemoreceptors?

are found in the aortic bodies and carotid bodies, sensitive to blood PO2, PCO2, and H+, the blood itself

How do afferent fibers get feedback from exercise?

they are found in the tissue and sense stretch, pH changes, etc. monitor metabolic and mechanical conditions, send these signals upstream to cardiorespiatory centers, working limbs contributes to this neural feedback

What is the first phase respiatory response to exercise?

immediate increase in ventilation, even before muscle contractions, is an anticipatory response coming from the central command

Explain the second phase of respiratpry respnse to exercise?

gradual second phase increase of ventilation, this is driven by chemorecptors in arterial blood, and right atrial stretch receptors, more of a fine tuned process than the first phase

How does ventilation increase in comparison to metabolic needs?

it is proportional, at low exercise intensities there is only a tidal volume increase for high intensity exercise the rate will also increase

What regulates recovery after exercise?

it will take several minutes and depends on blood pH, PCO2, and temperature

What is the shape of the graph that shows the relationship between pulmonary ventilation and runing at increasing velocities?

the graph is V shaped, ventilation is linear until the break point where the slope increases creating a v shape, something causes a greater drive to breathe at about 50-60% VO2 max, fibers are progessively being more challenged

What is led to beleive to be the cause of the slope increase of ventilation during increasing exercise?

it was beleived that the lactate threshold accurred at about the same time as the ventilation slope increased but was later found that lacate had nothing to do with it

What happens if lactic acid is not quickly converted to pyruvate?

it dissociates into hydrogen and lactate and rops muscle pH and blood pH, bicarbonate forms to cope with acidosis, which then creates increase of CO2 this will signal the chemoreceptors to increase ventilation

Is it possible for a muscle to have anoxia (not enough oxygen)?

no muscles is constantly being fed oxygen, lactate builds up producing more CO2 faster than O2 can be consumed

What other mechanisms mediate the extra drive to breathe?

increased K+, body temperature, blood catecholamines all also stimulate breathing

What is required the more a locomotor muscle fatgues?

more central command must be generated to maintain locomotor muscle force

What is the gas exchange threshold?

the point where CO2 during exercise increases more than O2 consumption

is ventilation ever the limiting factor?

no ventiliation is not a limiting facotr unless you have a limiting disease, these muscles are very fatigue resistant

What is the stealing phenomenom?

respiratory muscle are stealing blood and cardiac output away from the locomotive muscles to sustain ventilatory demand, this will cause an early terminatioon of exercise to keep up with the demand

Can you train respiratoy muscles so they dont steal as much blood from the active muscles?

yes it can provide a couple more seconds of maintaing the ventilation demand

What is arterial hypoxemia?

it is mostly found within elite female athletes, when arterial oxyhemoglobin desaturates, unable to maintain saturation of hemoglobin, not enough oxygen is being captured for this level of exercise