Respiratory System Flashcards

Gas Exchange & Transport

• Covers gas exchange and transport mechanisms, focusing on the movement of oxygen and carbon dioxide between the lungs, blood, and tissues.

Control of Ventilation

• Focuses on the control mechanisms of ventilation, detailing the neural and chemical regulation of breathing rate and depth.

Learning Outcomes

• Describe the exchange of oxygen (O2) and carbon dioxide (CO2) during internal and external respiration, including the factors that influence gas exchange efficiency.

• Describe how O2 and CO2 are transported within the blood, specifying the roles of hemoglobin, plasma, and bicarbonate ions.

External Respiration

• External respiration is the exchange of oxygen and carbon dioxide between the air in the alveoli and the blood in the pulmonary capillaries. This process allows oxygen to enter the bloodstream and carbon dioxide to be removed.

Internal Respiration

• Internal respiration is the exchange of oxygen and carbon dioxide between the blood in systemic capillaries and the tissues. This process supplies oxygen to cells for metabolism and removes carbon dioxide, a waste product.

Exchange of Respiratory Gases - Dependencies

• Depends on differences in the partial pressures of a gas, where gases move from areas of high pressure to low pressure.

• Depends on the thickness of the membrane through which the gas must pass; a thinner membrane facilitates faster diffusion.

• Depends on the total surface area available for gas exchange; a larger surface area allows more gas exchange to occur.

Features Aiding Gas Exchange

• The alveolar surface is moist to allow the respiratory gases to dissolve, which is essential for diffusion across the respiratory membrane.

• The respiratory membrane is thin to speed up diffusion, consisting of a single layer of cells from the alveolus and capillary.

• The alveoli provide a very large surface area for gas exchange, maximizing the efficiency of oxygen and carbon dioxide exchange.

• Each alveolus is surrounded by many capillaries, ensuring close proximity between air and blood for effective gas exchange.

Oxygen Transport in Blood

• Almost all oxygen (98.5%) is chemically combined with hemoglobin (Hb), which greatly increases the blood's oxygen-carrying capacity.

• Very little oxygen (1.5%) is dissolved in plasma, as oxygen is not very soluble in water.

Carbon Dioxide Transport in Blood

• Most CO2 (78%) is transported as bicarbonate ions in plasma. The reaction is represented as: CO2 + H2O
  ightharpoons H2CO3
  ightharpoons HCO3^- + H^+ This process is crucial for maintaining blood pH.

• Some CO2 (13%) is transported combined with hemoglobin, forming carbaminohemoglobin.

• A little CO2 (9%) is dissolved in plasma.

Control of Respiration: Role of the Respiratory Centre

• The respiratory center controls the basic rhythm of breathing, ensuring a consistent and appropriate respiratory rate.

• Located in the medulla oblongata and pons, this center integrates various inputs to regulate ventilation.

• The respiratory center can alter the rate and depth of breathing in response to various inputs, such as changes in blood gas levels and physical activity.

Modification of the Basic Rhythm

1. Cortical influences (conscious thought): Voluntary control over breathing, such as holding one's breath or hyperventilating.

2. The inflation reflex prevents over inflation of the lungs, protecting the lungs from damage due to excessive stretching.

3. Chemical stimuli:

   • Changes in pCO2 levels: Increased pCO2 is the most potent stimulus for breathing.

   • Changes in H+ concentration: Increased H+ concentration (decreased pH) stimulates breathing.

   • Large decreases in pO2: Significant drops in pO2 can stimulate breathing, but this is a less sensitive mechanism than pCO2 or H+ levels.

Learning Outcomes (Revisited)

• Describe the exchange of oxygen (O2) and carbon dioxide (CO2) during internal and external respiration.

• Describe how O2 and CO2 are transported within the blood.

• Explain how breathing is controlled by the nervous system, detailing the roles of the medulla oblongata, pons, and various receptors.

• Name other factors influencing the rate and depth of breathing, including temperature, pain, and emotional stimuli.