Lecture 15: Muscles of Ventilation

Lecture 15: Muscles of Ventilation

• Inspiration involves the diaphragm and accessory muscles like the sternocleidomastoid, scalenes, and external intercostals.
• Expiration is a passive process at rest, but during exercise uses internal intercostals, external/internal obliques, and transverse abdominis.
• Changes in lung pressure drive air flow.

Pulmonary Ventilation

• Pulmonary ventilation is the amount of air moved in or out of the lungs per minute.
• Resting tidal volume (Vt) is 500ml for men and 500ml for women.
• Resting breathing frequency (f) is 15 breaths/minute.
• Dead space ventilation (Vd) is the unused air in the conducting zone, not involved in gas exchange.

Measuring Lung Volume

• Spirometry measures lung volumes.

• Tidal volume (TV) is the volume of air inspired and expired per breath (600ml in men and 500ml in women).

• Inspiratory reserve volume (IRV) is the maximal volume that can be inhaled after a normal breath (3000ml in men and 1900ml in women).

• Expiratory reserve volume (ERV) is the maximal volume that can be exhaled after a normal breath (1200ml in men and 800ml in women).

• Residual lung volume (RLV) is the volume of air remaining in the lungs after maximum exhalation (1200ml in men and 1000ml in women).

• Total lung capacity (TLC) is the total volume of air the lungs can hold.

Lecture 16: Oxygen Transport

• Hemoglobin (Hb) carries approximately 99% of oxygen in the blood.
• Oxyhemoglobin is oxygen bound to Hb.
• Deoxyhemoglobin is oxygen unbound to Hb.
• Blood pH decreases during exercise, which results in a rightward shift on the oxygen-hemoglobin dissociation curve (Bohr effect). This facilitates unloading of oxygen to tissues.
• Myoglobin stores oxygen in muscle tissue.

Lecture 17: Altitude

• Altitude decreases partial pressure of oxygen (PO2).
• At high altitudes, there physiological adaptations to conserve oxygen.
• Breathing frequency and tidal volume increase at higher altitudes, this is due to decrease in arterial PO2.
• Physical adaptations include barrel-shaped chest, larger lung volume, larger hearts, increased capillary density, and greater red blood cell count.

Lecture 18: Thermoregulation (Heat)

• Body temperature regulation is maintained by a balance between heat production and heat loss.
• Voluntary heat production occurs during exercise, while involuntary heat production occurs through shivering and non-shivering thermogenesis.
• Heat loss occurs through radiation, conduction, convection, and evaporation.

Lecture 19: Thermoregulation (Cold)

• Cold stress can cause heat loss, if loss of body heat exceeds the rate of production, hypothermia occurs.
• Physiological changes are seen at high intensity in cold temperatures.
• Heart rate & oxygen consumption may increase during cold conditions to maintain body temperature.

Lecture 20: Ergogenic Aids

• Ergogenic aids are substances or phenomena that can improve physical performance.
• Steroids are illegal ergogenic aids used to increase muscle hypertrophy.
• Blood doping is another illegal ergogenic aid.

Lecture 21: Pregnancy and Exercise

• Exercise during pregnancy is appropriate and safe.
• Physiological adaptations in pregnancies are similar to adaptations to aerobic exercise, except no change in VO2 maximum.