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Questions and Answers
What is the typical percentage of oxygen in the air at sea level?
What is the typical percentage of oxygen in the air at sea level?
The total atmospheric pressure at sea level is approximately 760 mm Hg.
The total atmospheric pressure at sea level is approximately 760 mm Hg.
True (A)
What is the value of the partial pressure of oxygen (PO2) at sea level?
What is the value of the partial pressure of oxygen (PO2) at sea level?
160 mm Hg
Air is primarily composed of nitrogen constituting _____% of the mixture.
Air is primarily composed of nitrogen constituting _____% of the mixture.
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Match the following terms with their correct descriptions:
Match the following terms with their correct descriptions:
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What is the primary gas that constitutes the atmosphere?
What is the primary gas that constitutes the atmosphere?
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Carbon dioxide diffuses from the alveoli into the capillaries during external respiration.
Carbon dioxide diffuses from the alveoli into the capillaries during external respiration.
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What role does surfactant play in the alveolar membrane?
What role does surfactant play in the alveolar membrane?
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Hemoglobin's oxygen binding is reduced by the presence of _______.
Hemoglobin's oxygen binding is reduced by the presence of _______.
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Match the following processes with their descriptions:
Match the following processes with their descriptions:
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What is the primary method of carbon dioxide transport in the body?
What is the primary method of carbon dioxide transport in the body?
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Bicarbonate ions are responsible for weakening the binding of oxygen to hemoglobin.
Bicarbonate ions are responsible for weakening the binding of oxygen to hemoglobin.
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What is the role of carbonic anhydrase in the transport of carbon dioxide?
What is the role of carbonic anhydrase in the transport of carbon dioxide?
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Carbon dioxide is mainly transported back to the lungs converted into __________.
Carbon dioxide is mainly transported back to the lungs converted into __________.
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Match the following respiratory functions with their descriptions:
Match the following respiratory functions with their descriptions:
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What is the primary role of receptor cells in the carotid arteries and aorta during respiration?
What is the primary role of receptor cells in the carotid arteries and aorta during respiration?
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Exhalation occurs when respiratory muscles contract.
Exhalation occurs when respiratory muscles contract.
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What maintains homeostasis of CO2, O2, and H+ in the blood?
What maintains homeostasis of CO2, O2, and H+ in the blood?
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PCO2 in arterial blood should be _____ mm Hg.
PCO2 in arterial blood should be _____ mm Hg.
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Match the following components of the respiratory regulation to their descriptions:
Match the following components of the respiratory regulation to their descriptions:
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Study Notes
Lecture 14: The Respiratory System-II
- Lecture presented by Dr. Nayantara Govindrajan, PhD (she/her)
- Course: BIOL305 Fall 2024
- Date: Monday, October 7th, 2024
Lecture Outcomes
- Students will learn about partial pressures
- Students will understand processes of external and internal respiration
- Students will understand neural regulation of the respiratory system
- Students will analyze links between respiration and respiratory disorders
Previous Lecture
- Covered components of the respiratory system and their functions
- Covered events during respiration
- Covered breathing/ventilation
Events of Respiration
- Breathing/Ventilation
- External Respiration
- Internal Respiration
- Cellular Respiration
Partial Pressure
-
Air exerts total pressure at sea level (atmospheric pressure)
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1 atmosphere (atm) = 760 mm Hg
-
Air is a mix of gases (78% nitrogen, 21% oxygen, trace amounts of carbon dioxide)
-
Pressure exerted by a gas in a mix is partial pressure
-
Partial pressure is proportional to its concentration in the gaseous mixture
-
Atmospheric pressure is 760 mm Hg.
-
Oxygen makes up 21% of air
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Partial pressure of oxygen (P02) = 0.21 x 760 mm Hg ≈ 160 mm Hg
Question Break 1
- Atmospheric pressure at the top of Mount Everest is 235 mm Hg
- Partial pressure of nitrogen at this altitude is 183 mm Hg
Partial Pressures
- Gases diffuse down a pressure gradient (from higher to lower partial pressure)
- Passive process (no energy required)
- Example: In the lungs, O2 moves from the alveoli (high partial pressure) into the blood (low partial pressure)
Partial Pressures and Diffusion
- Depends on:
- Partial pressure gradient between the membrane
- Membrane thickness (thinner is better)
- Membrane surface area (larger is better)
- Wet membranes facilitate gas diffusion
External Respiration
- Deoxygenated blood is pumped from the heart to the pulmonary arteries and capillaries
- Blood in capillaries comes into close contact with the air inside alveoli
- Oxygenated blood leaves capillaries via pulmonary vein and returns to the heart
- Oxygen from alveolar air (lungs) flows to the capillaries along a pressure gradient
- Carbon dioxide from capillaries flows to the alveoli along a pressure gradient
- Surfactant keeps alveolar membranes wet
Internal Respiration
- Oxygenated blood is collected and travels from pulmonary veins to the heart and then to body tissues
- Oxygen moves from capillaries to cells in tissues along a pressure gradient
- Carbon dioxide from cells in tissues moves into capillaries along a pressure gradient
- Exchange occurs via interstitial fluid
Events of Respiration
- Occurs by diffusion caused by partial pressure gradients
- Maintained by: breathing, blood transport and cellular respiration
Gaseous Transport- Oxygen
- Primarily transported by hemoglobin (Hb)
- Also dissolved in plasma as a small percent
- Partial pressure of oxygen in alveolar air > in blood
Gaseous Transport- Hemoglobin
-
Protein that binds and transports oxygen
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Has four iron-containing heme groups
-
Binds four oxygen molecules to form oxyhemoglobin (HbO2)
-
Reversible reaction (oxygen binds and detaches based on partial pressure)
-
Hemoglobin binds oxygen efficiently under neutral pH and cooler temperatures
Gaseous Transport - Carbon Dioxide
- Transported away from tissues to the lungs to be removed by the following:
- 70% converted to bicarbonate
- 20% binds to hemoglobin to form carbaminohemoglobin
- 10% is dissolved in plasma
Neural Regulation of Respiration
-
Organ systems work together in the body
-
Controls rate and depth of breathing via skeletal muscles (diaphragm and intercostal muscles)
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Maintains CO2, O2, and H⁺ homeostasis
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Limited conscious control over breathing
-
Chemical controls in the medulla oblongata and carotid and aortic bodies respond to changes in carbon dioxide, H+ and oxygen levels in the blood.
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Receptors near the respiratory center also detect changes in CO2
-
O2 receptors triggered only if P02 drops by at least 20%
-
Receptors near the center detect changes in H+
Respiratory Diseases- Emphysema
- Chronic disorder characterized by difficulty breathing and permanent damage to alveoli
- Primary cause: long-term exposure to airborne irritants (like cigarette smoke)
- Air pollution can worsen the condition
- Airways become less elastic, reducing surface area and gas exchange.
Respiratory Diseases- Asthma
- Spasmodic contractions of bronchi caused by allergens
- Episodic (not chronic)
Respiratory Diseases- Cystic Fibrosis
- Inherited disorder caused by mutation in the CFTR gene, causing thick mucus production.
- Impeded airflow and increased bacterial growth lead to frequent lung infections and blockages.
Review
- Partial pressure is the pressure exerted by a gas in a mixture
- External respiration: O2 moves from alveoli to capillaries; CO2 moves from capillaries to air
- Internal respiration: O2 moves from capillaries to cells; CO2 moves from cells to capillaries
- O2 is primarily transported by hemoglobin (98%)
- CO2 is primarily transported by conversion to bicarbonate (70%)
Practice Questions (Examples)
- Holding breath causes increased CO2 and H⁺ concentration.
- Acidic pH increases oxygen binding to hemoglobin.
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Description
In this lecture, students will delve deeper into the respiratory system, focusing on the concepts of partial pressures and the processes involved in external and internal respiration. The session also covers the neural regulation of respiration and the connections between respiration and various respiratory disorders.
