Chapter 10
Respiration
During Exercise

EXERCISE PHYSIOLOGY

The Respiratory System

Provides a means of _________________________ between the ______________ and the body

Plays a role in the regulation of ______________ balance during exercise

Respiration Involves
Two Subdivisions

1. ______________ – Refers to:

Ventilation (breathing) and the exchange of gases (O₂ and CO₂) in the lungs

1. ______________ - Relates to:

O₂ utilization and CO₂ production by the tissues

This lecture is primarily concerned with ______________, and “respiration” will be used to designate this.

Function of the Lungs

Respiratory system involves:

Ventilation refers to the ______________  process of moving ­­­­­­_________ into and out of lungs

______________  is the random movement of molecules from an area of ______________  concentration to an area of ______________  concentration

Major Organs of the Respiratory System

Position of the Lungs, Diaphragm, and Pleura

Conducting and
Respiratory Zones

Conducting zone

Conducts air to respiratory zone

______________, ______________, and ______________  air

Components:

______________

______________

______________

Respiratory zone

Exchange of gases between air and blood

Components:

______________

______________  sacs

Conducting & Respiratory Zones

Pathway of Air to Alveoli

Mechanics of Breathing

Inspiration

Diaphragm pushes ______________  lowering intrapulmonary pressure

Expiration

Diaphragm ______________, raising intrapulmonary pressure

Resistance to airflow

Largely determined by airway ______________

Did you know that every few seconds you demonstrate ______________  Law? The human body is a large pressure chamber for breathing. Your diaphragm is like a large elastic cover to your rib cage. Your lungs are just large elastic bags, like balloons. When you inhale, your diaphragm lowers, creating a low pressure area in your lungs (greater volume). Because air moves to the area of least pressure (Bernoulli Principle), air goes into your lungs. When you exhale, the opposite happens. Your diaphragm raises, decreasing the volume of your lungs and creating a high pressure area. The air is then forced out of your lungs by the increased pressure.
You can create a model lung to help demonstrate this principle.

You need:

straw

clear plastic cup or similar container
two balloons
clear packaging tape

The Mechanics of
Inspiration and Expiration

Muscles of Respiration

Pulmonary Ventilation (V)

The ______________  of air moved in or out of the lungs per ______________

Product of tidal volume (V_T)  and breathing frequency (f)

Pulmonary Ventilation (V)

Dead-space ventilation (V_D)

“Unused” ventilation

________  ________  participate in gas exchange

Anatomical dead space: conducting zone

Physiological dead space:

Alveolar ventilation (V_A)

Volume of______________ gas that reaches the ______________  zone

Pulmonary Volumes
and Capacities

Measured by ______________

Vital capacity (VC)

Maximum amount of air that can be ______________  following a ______________  inspiration

Residual volume (RV)

Air ______________  in the lungs after a ______________  expiration

Total lung capacity (TLC)

Sum of VC and RV

Pulmonary Volumes
and Capacities

Spirogram showing lung volumes and capacity at rest

Partial Pressure of Gases
______________  Law

The total pressure of a gas mixture is equal to the ______________ ______________ ______________ independently

The partial pressure of oxygen (PO₂)

Air is ______________ % oxygen

Expressed as a fraction: 0.2093

Total pressure of air = 760 mmHg

Diffusion of Gases

______________ law of diffusion

The rate of gas transfer (V gas) is proportional to the tissue area, the diffusion coefficient of the gas, and the difference in the partial pressure of the gas on the two sides of the tissue, and inversely proportional to the thickness.

Summary of Ficks Law

Simple terms:

Rate of diffusion for any single gas increases when surface area of diffusion is large and “driving pressure” between two sides of tissue is high.

Surace Area > + Tissue Pressure > = > Diffusion Rate

Partial Pressure and
Gas Exchange

Blood Flow to the Lung

Pulmonary circuit

Same rate of flow as ______________  circuit

Lower pressure

This chart shows the pulmonary artery which receives venous blood from right side ventricle (mixed venous blood)

Blood is pushed to the pulmonary ______________  where gas exchange occurs.

Blood then moves to ______________  atrium (via ______________) and circulated throughout the body

Blood Flow to the Lung – 10.13

When standing, most of the blood flow is to the ______________  of the lung

Due to ______________  force

Ventilation-Perfusion Relationships

Ventilation/perfusion ratio

Indicates ______________  of blood flow to ______________

Ideal: ~1.0

Base

Overperfused (ratio <1.0)

Apex

Underperfused (ratio >1.0)

Ventilation/Perfusion Ratios

O₂ Transport in the Blood

Approximately ______________ of O₂ is transported in the blood bound to ______________  (Hb)

Oxyhemoglobin: O₂ bound to Hb

Deoxyhemoglobin: O₂ not bound to Hb

Amount of O₂ that can be transported per unit volume of blood in dependent on the ______________  of hemoglobin

Oxyhemoglobin
Dissociation Curve

O₂-Hb Dissociation Curve:
Effect of pH – 10.16

Blood ______________  declines during heavy exercise

Results in a “______________” shift of the curve

Bohr effect

Favors “______________” of O₂ to the tissues

O₂-Hb Dissociation Curve:
Effect of Temperature – 10.17

Increased blood ______________ results in a weaker Hb-O₂ bond

______________  shift of curve

Easier “______________” of O₂ at tissues

O₂-Hb Dissociation Curve:
2-3 ______________  (diphosphoglyceric acid)

RBC must rely on ______________  glycolysis to meet the cell’s energy demands

A by-product is ___-___DPG, which can combine with ______________  and reduce hemoglobin’s affinity of O₂

2-3 DPG ______________  during exposure to ______________

At sea level, right shift of curve not to changes in 2-3 DPG, but to degree of ______________  and blood temperature.

DPG’s are known to______________ during exposure to altitude and in anemic individuals (low blood hemoglobin).

O₂ Transport in Muscle

______________  is similar in structure to ______________, but about ______% of the weight

Myoglobin is an O2 binding ______________  found in ______________  muscle and ______________  muscle.

Myoglobin (Mb) shuttles O₂ from the cell ______________  to the ______________

______________  affinity for O₂ than hemoglobin

Even at low PO₂

Allows Mb to store O₂

Dissociation Curves for Myoglobin and Hemoglobin – Fig. 10.18

Question

CO₂ Transport in Blood
3 forms of transport
Fig. 10.19

Dissolved in plasma (___ %)

Bound to Hb (___%)

Bicarbonate (___%)

CO₂ + H₂O « H₂CO₃ « H⁺ + HCO₃^-

Also important for buffering H⁺

CO₂ Transport in Blood

Release of CO₂ From Blood

Rest-to-Work Transitions
10.21

Initially, ventilation ______________ rapidly

Then, a ______________ toward steady-state

PO₂ and PCO₂ are ______________

Exercise in a Hot Environment
Fig. 10.22

During prolonged submaximal exercise:

Ventilation tends to drift ______________

______________  change in PCO₂

______________  ventilation not due to increased PCO₂

Incremental Exercise

______________  increase in ventilation

Up to ~50-75% VO_2max

Exponential increase beyond this point

Ventilatory ______________  (T_vent)

Inflection point where V_E increases exponentially

Ventilatory Response to Exercise:
Trained vs. Untrained

In the trained runner,

______________  in arterial PO₂ near exhaustion

pH ______________  at a higher work rate

T_vent occurs at a ______________  work rate

See Figure 10.23 in textbook

Ventilatory Response to Exercise:
Trained vs. Untrained – Fig. 10.23

The drop in ______________  at high max work load parallels that drop in patients who have ______________
Exercise Induced______________ (diffusion limitation)

How prevalent is this condition in the trained athlete?

Exercise-Induced Hypoxemia

1980s: ______________ of elite male endurance athletes were capable of developing exercise induced hypoxemia.

1990s: ______________ of elite female endurance athletes were also capable of developing

 Causes:  Somewhat ______________ … Speculation:

Ventilation-perfusion mismatch

Diffusion limitations due to reduce time of RBC in pulmonary capillaries due to high cardiac outputs

Control of Ventilation
____________  ________________

Respiratory ______________ center

Receives neural and humoral input

Feedback from muscles

CO₂ level in the blood

Regulates ______________  rate

Effect of Arterial PCO₂
on Ventilation

Effect of Arterial PO₂
on Ventilation

Ventilatory Control
During Exercise

Submaximal exercise

Linear increase due to:

Central command

Humoral chemoreceptors

Neural feedback

Heavy exercise

Exponential rise above T_vent

Increasing blood H⁺

Ventilatory Control During Submaximal Exercise

Effect of Training on Ventilation

Ventilation is______________ at same work rate following training

May be due to lower blood ______________ levels

Results in less feedback to stimulate breathing

Effects of Endurance Training on Ventilation During Exercise

Do the Lungs Limit Exercise Performance?

Low-to-moderate intensity exercise

Pulmonary system ______________  seen as a limitation

Maximal exercise

Not thought to be a limitation in healthy individuals at sea level

May be limiting in ______________  ______________  athletes

New evidence that respiratory muscle fatigue ______________  occur during high ______________  exercise