Physiology Chapter 18

What are the two main types of gas exchange that occur in the lungs?

O2 from lung air to blood and CO2 from blood to lung air.

What are the two main types of gas exchange that occur at the systemic tissues?

CO2 from tissues to blood and O2 from blood to tissues

What is the most important factor affecting gas exchange via diffusion?

The concentration gradient of the gases involved.

What are the constant factors affecting gas diffusion?

Surface area, membrane thickness, permeability, diffusion distance, and solubility in the medium.

What is important to recognize?

Where the concentrations are high or low and where (and in which direction) concentration gradients exist

What can cause low alveolar PO2?

Low oxygen content in inspired air, inadequate alveolar ventilation, decreased lung compliance, increased airway resistance, and CNS depression.

Emphysema does what to the alveoli?

Creates less surface area for gas exchange

What does fibrotic lung disease do to the alveoli

Thicken the alveolar membrane, slows gas exchange, and loss of lung compliance

What does Pulmonary Edema do to the alveoli?

Fluid in the interstitial space increases the diffusion distance

What does asthma do to the alveoli?

Constrict the bronchioles leading to the alveoli, increasing airway resistance

What must gases diffuse across in the lungs?

Alveolar epithelia and capillary endothelium

What must gases diffuse across at systemic tissues?

Capillary endothelium and cell membranes

What is the solubility difference between oxygen and carbon dioxide in the body?

Carbon dioxide is 20 times more soluble in aqueous solutions than oxygen.

How is most oxygen transported in the blood?

98% of oxygen is bound to hemoglobin.

How many molecules of O2 can Hb transport?

4 molecules

If all 4 binding sites are occupied on Hb what is it called?

Saturated

The availability of oxygen determines what?

The oxygen saturation of Hb

What is the oxygen-carrying capacity of hemoglobin?

Each gram of hemoglobin can transport 1.34 ml of O2 when fully saturated.

At the lungs what is the oxygen saturation of Hb?

98%

Is hemoglobin saturated or not at the systemic tissues?

It is less saturated

Arterial hemoglobin arrives at the systemic tissues filled with oxygen, and does what?

releases its oxygen to systemic tissues

Hemoglobin is sensitive to what?

Temperature

What happens when tissue becomes active and heats up?

Hemoglobin detects the heat and gives up more oxygen to the active tissues.

What happens to hemoglobin saturation at high altitudes?

Hemoglobin saturation with oxygen decreases due to lower atmospheric oxygen levels.

Active tissues tend to...

Be more acidic → ↓ pH- Be warmer → ↑ temperature- Generate more waste gas → ↑ PCO2- Perform more glycolysis → ↑ [2,3-DPG]

What is the effect of temperature on hemoglobin's affinity for oxygen?

Higher temperatures decrease hemoglobin's affinity for oxygen, promoting oxygen release.

What happens to hemoglobin in active tissues?

Hemoglobin releases more oxygen due to lower pH, higher temperature, and increased PCO2.

How does fetal hemoglobin differ from maternal hemoglobin?

Fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin.

What percentage of carbon dioxide is transported as bicarbonate in the blood?

70%

Where is much of CO2 picked up, and what does it do?

Venous blood at active tissue, it's converted to bicarbonate, leading to a drop in pH, causing Hb to give up more of its oxygen.

What is the role of chemoreceptors in regulating ventilation?

Monitor oxygen, carbon dioxide, and pH levels to adjust ventilation.

Where are peripheral chemoreceptors located?

In the carotid and aortic arteries.

What reflexes protect the lungs from irritants?

Bronchoconstriction, sneezing, coughing, and the inflation reflex.

What is the primary function of the medulla in respiration?

The medulla controls the rate and depth of ventilation.

Arterial blood holds?

Relatively little CO2 and contains Hb that is near-fully saturated with O2

Venous blood holds?

Plentiful CO2 and contains Hb that is now only partially saturated with O2

What is the significance of the oxygen-hemoglobin dissociation curve?

It illustrates how hemoglobin saturation changes with varying oxygen levels.

What is the impact of increased H+ concentration on hemoglobin?

(lower pH) promotes oxygen release from hemoglobin.

What is the effect of exercise on oxygen delivery to tissues?

Exercise increases oxygen demand, leading to enhanced oxygen release from hemoglobin.

What happens to bicarbonate at the lungs?

Bicarbonate is converted back into CO2 for expulsion during gas exchange.

What is the normal range of hemoglobin levels in blood?

12-17 g Hb/dL.

How does the body respond to hypoxia?

By increasing respiratory rate and depth to enhance oxygen intake.

What is hypoxia

too little O2

What is the role of the pons in respiration?

The pons integrates sensory information and influences medullary neurons for ventilation control.

What can cause a decrease in alveolar surface area?

Pathological conditions such as lung diseases can reduce alveolar surface area.

What is the relationship between gas exchange and diffusion distance?

Increased diffusion distance decreases the efficiency of gas exchange.

What is the primary method of CO2 transport in the blood?

As bicarbonate ions (70%), dissolved in plasma (7%), and bound to hemoglobin (23%).

What is hypercania

Too much CO2

Peripheral chemoreceptors

Located in carotid and aortic bodies. sense changes in PO2, pH, PCO2

Central Chemoreceptors

Respond to changes in CO2 via pH sensing