EP edit new

8/8/2019 EP edit new

http://slidepdf.com/reader/full/ep-edit-new 1/31





Explain the principle physiological functionof the pulmonary system

Outline the major anatomical componentsof the respiratory system

List major muscles involved in inspiration &expiration at rest & during exercise

Discuss the importance of matching bloodflow to alveolar ventilation in the lung

Explain how gases are transported acrossthe blood-gas interface in the lung



Discuss the major transportation modes

of O2 & CO2 in the blood

Discuss the effects of o temp, q pH, & olevels of 2,3 DPG on the oxygen-

hemoglobin dissociation curve

Describe the ventilatory response to

constant load, steady-state exercise



Ventilation/perfusion ratio¾ Indicates matching of blood flow to

ventilation¾ Ideal: ~1.0

Base¾ Overperfused (ratio <1.0)

Apex¾ Underperfused (ratio >1.0)



Fig 10.13



Approximately 99% of O2 is

transported in the blood bound to

hemoglobin (Hb)¾ Oxyhemoglobin: O2 bound to Hb

¾ Deoxyhemoglobin: O2 not bound to Hb

Amount of O2 that can be transported

per unit volume of blood independent on the concentration of

hemoglobin



Fig 10.14



Blood pH declinesduring heavy

exercise Results in a

´rightwardµ shift ofthe curve

¾ Bohr effect

¾ Favors ´offloadingµof O2 to the tissues

Fig 10.15



Increased bloodtemperature

results in aweaker Hb-O2

bond

Rightward shift

of curve¾ Easier ´offloadingµ ofO2 at tissues

Fig 10.16



RBC must rely on anaerobic glycolysis tomeet the cell·s energy demands

Aby-product is 2-3 DPG, which cancombine with hemoglobin and reduce

hemoglobin·s affinity of O2

2-3 DPG increase during exposure toaltitude

At sea level, right shift of of curve not tochanges in 2-3 DPG, but to degree ofacidosis and blood tempurature



Myoglobin (Mb) shuttles O2 from the cell

membrane to the mitochondria

Higher affinity for O2 than hemoglobin¾ Even at low PO2

¾ Allows Mb to store O2



Fig 10.17



Dissolved in plasma (10%)

Bound to Hb (20%)

Bicarbonate (70%)

¾ CO2 + H2Om H2CO3m H+ + HCO3-

¾ Also important for buffering H+



Fig 10.18



Fig 10.19



Initially,ventilation

increasesrapidly

¾ Then, a slower rise towardsteady-state

PO2 and PCO2

are maintained

Fig 10.20



During prolongedsubmaximal

exercise:¾ Ventilation tends

to drift upward

¾ Little change inPCO2

¾ Higher ventilationnot due toincreased PCO2

Fig 10.21



Linear increase in ventilation

¾ Up to ~50-75% VO2max

Exponential increase beyond this point

Ventilatory threshold (Tvent)

¾ Inflection point where VE increases

exponentially



In the trained runner

¾

Decrease in arterial PO2 near exhaustion¾ pH maintained at a higher work rate

¾ Tvent occurs at a higher work rateFig 10.22



Fig 10.22



1980·s: 40-50% of elite male enduranceathletes were capable of developing

1990·s: 25-51% of elite female enduranceathletes were also capable ofdeveloping

Causes:

¾ Ventilation-perfusion mismatch¾ Diffusion limitations due to reduce time of

RBC in pulmonary capillaries due to highcardiac outputs



Respiratorycontrol center ¾

Receives neuraland humoral input

x Feedback frommuscles

x CO2 level in the

blood¾ Regulates

respiratory rate

Fig 10.23



Humoral chemoreceptors¾ Central chemoreceptors

x Located in the medulla

x PCO2 and H+

concentration in cerebrospinalfluid

¾ Peripheral chemoreceptors

x Aortic and carotid bodies

x PO2, PCO

2, H+, and K+ in blood

Neural input¾ From motor cortex or skeletal muscle



Fig 10.24



Fig 10.25



Submaximal exercise

¾ Linear increase due to:

x Central commandx Humoral chemoreceptors

x Neural feedback

Heavy exercise

¾ Exponential rise above Tvent

x Increasing blood H+



Fig 10.26



Ventilation is lower at same work rate

following training

¾ May be due to lower blood lactic acid levels¾ Results in less feedback to stimulate

breathing



Fig 10.27



Low-to-moderate intensity exercise

¾ Pulmonary system not seen as a limitation

Maximal exercise¾ Not thought to be a limitation in healthy

individuals at sea level

¾ May be limiting in elite endurance athletes

¾ New evidence that respiratory musclefatigue does occur during high intensityexercise

Documents

EP edit new