BIO 300 Lecture15.IntroToRespiratory.PhysiologyReview.pptx

BIO 300 Pathophysiology

Respiration Physiology Overview.

Respiration.

• Provides cells with oxygen & removes CO₂.

• 4 processes:.

1. Pulmonary ventilation (aka breathing) (moves air in and out of lungs).

2. Pulmonary gas exchange (moves gases between lungs & blood).

**aka external respiration.

3. Gas transport in the blood (moves gases through blood).

4. Tissue gas exchange (moves gases b/w blood & tissues).

**aka internal respiration.

Pulmonary Ventilation.

• the movement of air between the atmosphere and the alveoli.

• 2 phases:.

1. Inspiration (inhalation).

2. Expiration (exhalation).

(respiratory cycle = 1 inspiration & 1 expiration).

• made possible by changes in the intrathoracic volume.

**the lungs have no skeletal muscle, so they can’t change volume on their own**.

• Inspiration.

• lungs depend on the inspiratory muscles = increase size of thoracic cavity.

• Diaphragm increases vertical diameter of thoracic cavity (~75% of air entering).

• External intercostals elevate the ribs (~25% of air entering).

• Expiration.

• occurs because the muscles relax!

• A passive process (no muscle contraction required!).

1. At rest (diaphragm relaxed).

2. During inhalation (diaphragm contracting).

Notice pressure ↓ so air goes in.

During quiet inhalation, diaphragm descends about 1 cm.

3. During exhalation (diaphragm relaxing).

Notice pressure ↑ so air goes out.

Summary of pulmonary Ventilation (Quiet and Forced).

Thoracic cavity increases in size and volume of lungs expands.

Alveolar pressure decreases to 758 mmHg.

(a) Inhalation.

During normal quiet exhalation, exhalation, diaphragm and external intercostals relax. During forceful exhalation, abdominal and internal intercostal muscles contract.

(b) Exhalation.

Thoracic cavity decreases in size and lungs recoil.

Alveolar pressure increases to 762 mmHg.

During normal quiet inhalation, the diaphragm and external intercostals contract. During labored inhalation, sternocleidomastoid, scalenes, and pectoralis minor also contract.

Atmospheric pressure is about 760 mmHg at sea level.

Thoracic cavity increases in size and volume of lungs expands.

Sternocleidomastoid.

Scalenes.

Can be used in deep, forceful inhalation.

Internal intercostals.

External oblique.

Can contract during forced exhalation.

Factors that Influence Ventilation.

• Airway resistance.

• Anything that impedes air flow through the respiratory tract.

• Varies slightly during inhalation & exhalation -nothing significant.

• Diameter of bronchioles controlled by smooth muscles.

• Bronchodilation = relaxation = less resistance = more air to alveoli (triggered during exercise, emergencies, stress).

• Bronchoconstriction = contraction = more air resistance = less air to alveoli (triggered by irritants, disease such as asthma & bronchitis).

• Pulmonary compliance.

• Ability of lungs & chest wall to stretch.

• Determined by elasticity & surface tension in alveoli.

• Disease & injury can weaken it (pneumonia, emphysema, broken ribs, scar tissue on lungs [TB], low surfactant).

• Surface Tension in alveoli.

• Water is a main component of alveolar environment.

• Water molecules would stick together if nothing to counteract the attraction between them.

• Surfactant produced by type 2 alveolar cells interacts with the water = reduces the surface tension = alveoli remain partially open during expiration.

Respiration Overview.

Respiration.

• Provides cells with oxygen & removes CO₂.

• 4 processes:.

1. Pulmonary ventilation (aka breathing) (moves air in and out of lungs).

2. Pulmonary gas exchange (moves gases between lungs & blood).

**aka external respiration.

3. Gas transport in the blood (moves gases through blood).

4. Tissue gas exchange (moves gases between blood & tissues).

**aka internal respiration.

Pulmonary Gas Exchange (aka external respiration).

• External Respiration.

• Exchange of gases between the alveoli and the blood.

• O₂ goes from air in alveoli into blood in the pulmonary capillaries.

• Thebloodthen goes to the left atrium via pulmonary veins.

• CO₂ goes in opposite direction.

• Mechanisms behind it same as pulmonary (pressure gradient).

Alveolus Lungs.

Pulmonary capillary.

Recall capillaries are the sites of gas exchange!

Respiration Overview.

Respiration.

• Provides cells with oxygen & removes CO₂.

• 4 processes:.

1. Pulmonary ventilation (aka breathing) (moves air in and out of lungs).

2. Pulmonary gas exchange (moves gases b/w lungs & blood).

**aka external respiration.

3. Gas transport in the blood (moves gases through blood).

4. Tissue gas exchange (moves gases b/w blood & tissues).

**aka internal respiration.

Tissue Gas Exchange (aka internal respiration).

• Internal Respiration.

• Exchange of O₂ and CO₂ between the blood and the tissues.

• O₂ goes from blood in the systemic capillaries into the tissues.

• CO₂ moves opposite direction.

• Mechanisms behind it same as pulmonary (pressure gradient).

**note: this is happening in tissues throughout the body**.

Partial pressure of O₂ is low in tissue cells because they are using it to make ATP.

Respiration Overview.

Respiration.

• Provides cells with oxygen & removes CO₂.

• 4 processes:.

1. Pulmonary ventilation (aka breathing) (moves air in and out of lungs).

2. Pulmonary gas exchange (moves gases b/w lungs & blood).

**aka external respiration.

3. Gas transport in the blood (moves gases through blood).

4. Tissue gas exchange (moves gases b/w blood & tissues).

**aka internal respiration.

Gas Transport through the Blood.

• O₂ has limited solubility in water.

• about 1.5% of O2 is dissolved in the plasma.

• not enough to stay alive.

• How does the body solve this problem?

**Hemoglobin (Hb)**.

• about 98.5% is carried attached to Hb.

• Oxygenated Hb is called oxyhemoglobin.

• Factors that affect Hb’s ability to unload the O2 to the tissues:.

• Temperature.

• H⁺ ions (aka pH).

• PCO₂.

• BPG (2, 3 bisphosphoglycerate).

• produced during glycolysis.

When these things ↑ in concentration, Hb’s affinity for O₂ decreases, & it releases more O₂ to the tissues.

• PO₂.

When it is low, Hb’s affinity for O₂ decreases, & it releases more O₂ to the tissues.

Gas Transport through the Blood.

CO2 is transported in the blood in three different forms:.

7% - 10% is dissolved in the plasma.

70% is converted into carbonic acid through the action of an enzyme called carbonic anhydrase (CA).

• CO₂ + H₂O H₂CO₃ H⁺ + HCO₃-.

20% - 23% is attached to Hb (but not at the same binding sites as oxygen – attaches on the polypeptide chain) = carbaminohemoglobin.

Notice the CO₂.

- some dissolves in plasma.

- some binds with water to produce H₂CO₃.

- some binds to Hb.

Notice the oxygen diffuse into the cells.

Notice the small amount of oxygen that dissolves in plasma.

Notice the bulk of the oxygen attaches to Hb to form oxyhemoglobin.

• the H that is released aids in the process to remove CO₂ to the lungs.

The binding of CO₂ to Hb actually causes the O₂ to dissociate from Hb

Other Important Functions of the Respiratory System.

• Production of speech/vocal sounds.

• Laryngeal structures...

• Detects odors.

• Olfactory epithelium in nasal cavity.

• Maintain homeostasis.

• Acid-base balance with the bicarbonate-buffer system.

• Fluid/blood pressure homeostasis (RAAS system).

Regulation of aldosterone secretion by the renin - angiotensin - aldosterone (RAA) pathway.

Aldosterone helps regulate blood volume, blood pressure, and levels of Na⁺, K⁺, and H⁺ in the blood.

1. Dehydration, Na⁺ deficiency, or hemorrhage.

2. Decrease in blood volume.

3. Decrease in blood pressure.

4. Juxtaglomerular cells of kidneys.

5. Increased renin.

Liver.

6. Angiotensinogen.

7. Increased angiotensin I.

8. ACE.

Lungs (ACE = Angiotensin Converting Enzyme).

9. Increased angiotensin II.

10. Adrenal cortex.

11. Increased aldosterone.

12. In kidneys, increased Na⁺ and water reabsorption and increased secretion of K⁺ and H⁺ into urine.

13. Increased blood volume.

14. Blood pressure increases until it returns to normal.

15. Vasoconstriction of arterioles.

16. Increased K⁺ in extracellular fluid.