40. Circulatory System

Gas Exchange

The Bohr Effect ~ For A-level & Up Revision

Partial Pressure and the Diffusion of Gases in Blood

 It allows diving seals to store twice as much oxygen in their blood as the average human of similar size. 

 No. It's true that Weddell seals can store much more oxygen in their blood than the average human can, but this is not due to myoglobin. 

 It allows diving seals to store a considerable amount of oxygenated blood in their spleens. 

 No. Weddell seals do store a considerable amount of oxygenated blood in their spleens, but this is not due to myoglobin. 

 It allows seals to switch from cellular respiration to fermentation after the oxygen in muscle cells has been depleted. 

 No. Myoglobin stores oxygen in muscle tissue that is used for cellular respiration during long dives. 

 None of the listed responses is correct. 

 No. One of the listed responses is correct. 

 It allows diving seals to store a considerable amount of oxygen in their muscles. 

Consider the prefix "myo-."

How does myoglobin aid diving mammals such as the Weddell seal?

Oxygen Dissociation Curve Explained - Bohr Effect

 No. These are found in insects, and insects are mostly terrestrial organisms. 

 No. Animals with lungs generally live on land. Some exceptions are whales, dolphins, manatees, sea snakes, and lungfish. 

 No. Alveoli are the microscopic sacs in the lung where gas exchange occurs. 

 No. Animals such as frogs, salamanders, and caecilians respire through their skin, but these are amphibians and live in water only part of the time, if at all. 

This respiratory organ would collapse in a terrestrial environment

Which respiratory organ is most often found only in fully aquatic animals?

 No. Vocal cords are within the conducting portion of the airway; no gas exchange occurs within this region. 

 No. Bronchioles are within the conducting portion of the airway; no gas exchange occurs within this region. 

 No. The trachea is within the conducting portion of the airway; no gas exchange occurs within this region. 

 No. The diaphragm alters the dimensions of the thorax, but it does not directly participate in gas exchange. 

Consider the function of gills.

Which structure in a human is most similar in function to the gill lamellae of a fish?

A decrease in pH and an increase in the PO2

No. Oxygen diffuses into regions with a lower PO2.

An increase in pH and an increase in the PO2

No. Oxygen diffuses fastest at a lower pH and a lower PO2.

An increase in pH and a decrease in the PO2

 No. Oxygen diffuses fastest at a lower pH. 

A decrease in pH and a decrease in the PO2

These are conditions found in a very active muscle.

Which of the following would increase the release of oxygen from red blood cells?

Biology  Carbon Dioxide Transport

No. Exercise increases cellular respiration, which produces CO2.

No. Cellular respiration always results in increased concentrations of CO2.

 All of the listed responses are correct. 

Consider which of these does not stimulate you to increase your respiratory rate.

What causes CO2 in the blood to decrease?

Diffusion of Gases

Inhaling and Exhaling - How breathing works

Respiratory System, Part 2: Crash Course Anatomy & Physiology #32

 both the diaphragm and rib muscles contract 

 the rib muscles contract and the air pressure in the alveoli becomes lower than atmospheric pressure 

 No. Pressure in the alveoli does decrease when the rib muscles contract, but the result of this is inhalation. 

 the volume of the chest cavity increases 

 No. This decreases thoracic pressure and results in inhalation. 

 the diaphragm relaxes and the lungs expand 

 No. When the diaphragm relaxes the lungs will deflate, not expand.  

 both the diaphragm and the rib muscles relax 

Consider the events leading to pressure-volume changes during ventilation.

When you exhale, __________.

Gas Exchange and Breathing

Mechanism of Breathing, Animation

Air Movement and Partial Pressure

 No. Cells do not expend energy to move these gases across alveoli. 

 No. Pinocytosis occurs when a cell engulfs a liquid and its dissolved solutes. 

 No. Osmosis is the diffusion of water across a selectively permeable membrane. 

This process also allows you to know if someone is cooking something in a kitchen.

In the alveoli and lung capillaries, carbon dioxide and oxygen are exchanged by means of __________.

 No. This does not decrease the pH of cerebrospinal fluid. 

 No. This would increase the pH of cerebrospinal fluid. 

 No. One of the other choices is correct. 

Consider which of these decreases the pH of cerebrospinal fluid.

When you hold your breath, which of the following blood gas changes leads initially to the urge to breathe again?

No. Increased CO2 is a result of cellular respiration. When the CO2 level increases in the blood, the pH decreases.

The pH of the cerebrospinal fluid also increases and is detected by O2 sensors in arteries near the heart.

No. The pH of the cerebrospinal fluid decreases when the CO2 level increases. When the CO2 level increases, O2 concurrently decreases and this lowered level of oxygen is detected by arterial O2 sensors, which signal the breathing control centers, which then stimulate an increase in the respiratory rate.

The O2 level automatically increases.

No. The nervous system and muscles associated with the respiratory system must be stimulated before more rapid breathing removes the excess CO2 and brings in more O2.

The medulla, moderated by the pons, signals the heart muscle to beat harder, bringing in more O2.

No. The medulla, moderated by the pons, signals the breathing control center (not the heart) to increase the breathing rate and depth, eliminating CO2, allowing the blood pH to increase, and bringing in more O2.

 A decrease in the pH of the cerebrospinal fluid triggers the brain's breathing control centers, which stimulate diaphragm and rib muscle contractions. 

Consider the effect on blood chemistry.

What happens when the CO2 level from cellular respiration increases in the blood?

Blood Gases (O2, CO2 and ABG)

Respiratory System, Part 1: Crash Course Anatomy & Physiology #31

Oxygen Dissociation Curve and the Bohr Shift

 speeds up the flow of water through the gills 

No. Countercurrent exchange results from opposite flow of blood within the gills and water over the gills.

 enables blood oxygenation in fish regardless of the direction of water flow relative to blood flow 

 No. If the flow of water across a fish's gills were reversed, there would be no countercurrent system. 

 means that blood and water flow in the same direction 

 No. This describes concurrent flow. It is called "countercurrent" because the water crosses the gill in the opposite direction that blood moves within it. 

 interferes with the efficient absorption of oxygen 

 No. The countercurrent systems seen in bony fish allow very efficient absorption of oxygen. 

 maintains a gradient that enhances diffusion 

Gas exchange occurs across gills.

Countercurrent flow in the gills of a fish __________.

When you hold your breath, which of the following blood gas changes first leads to the urge to breathe?
a. rising O2
b. falling O2
c. rising CO2
c, falling CO2

 No. The trachea has a ciliated surface. 

 No. All but the smallest bronchioles have ciliated surfaces. 

 No. Large bronchioles have ciliated surfaces. 

Consider where the actual exchange of gases occurs.

Which of the following components of the mammalian gas exchange system has a surface covered by a thin film of fluid without cilia?

 Gills are not as efficient as lungs in picking up oxygen. 

 No. The countercurrent exchange in fish gills is actually more efficient at removing available oxygen from water than the "tidal" breathing mechanisms of mammal lungs. 

 Gills are too small to provide oxygen for a mammal. 

 No. There are many fish that are much larger than most mammals. 

 Air has higher oxygen content than water, so gills were no longer necessary. 

 No. Gills are an impediment to life on land because they cannot function for very long without being immersed in water. The lungfish lineage was the one to move onto land. 

 Gills work only in aquatic animals; lungs work only in terrestrial animals. 

 No. Some land snails have gills; whales, dolphins, and manatees all have lungs. 

 Protecting gas-exchange surfaces from desiccation is difficult in terrestrial environments. 

Think about environmental conditions and the structure of gills.

What is the major reason that land-dwelling mammals evolved lungs rather than gills as a primary respiratory organ?

AS Biology - Oxygen dissociation curve (OCR A Chapter 8.4)

Gas Exchange Principles in Respiration | Gas diffusion | Respiratory Physiology

 Nasal cavity, pharynx, larynx, bronchiole, bronchus, trachea, alveolus 

 No. The trachea is larger than bronchi. 

 Nasal cavity, larynx, pharynx, trachea, bronchus, bronchiole, alveolus 

 No. Air flows through the pharynx before it reaches the larynx. 

 Nasal cavity, pharynx, larynx, trachea, bronchiole, bronchus, alveolus 

 No. Bronchioles are smaller than bronchi. 

 Nasal cavity, pharynx, trachea, larynx, bronchus, bronchiole, alveolus 

 No. During inhalation, air flows through the larynx before it reaches the trachea. 

 Nasal cavity, pharynx, larynx, trachea, bronchus, bronchiole, alveolus 

The respiratory system is organized like an inverted tree.

What is the correct order of structures through which air passes as it is inhaled by a typical mammal?

 No. This describes the vertebrate skin. Vertebrates do not respire across their skin. 

 No. You have the moist part right, but some glandular secretions can impede diffusion. 

 No. Respiratory surfaces must be moist, but diffusion is much more efficient over short distances. 

 No. This is true of most terrestrial animals, but the main respiratory surface of an amphibian is its skin. 

Consider the conditions that promote diffusion.

For a body surface to be a respiratory surface, it must __________.

Gas exchange

Easy Concepts - The Bohr Effect

Compared with the interstitial fluid that bathes active muscle cells, blood reaching these cells in arterioles has a
a. higher PO2.
b. higher PCO2.
c. greater bicarbonate concentration.
d. lower pH.

 No. Fish do not have tracheal systems; they use gills for respiration. 

 No. This is the way in which mammals ventilate their lungs. Bony fish use countercurrent flow to maximize gas exchange. 

 No. Alveoli are structures in lungs; most fish have gills for respiration rather than lungs. 

 No. This is the way in which amphibians ventilate their lungs. Bony fish use countercurrent flow in the gills to maximize gas exchange. 

Consider the pattern of blood flow through the gills.

Gas exchange in the gills of a bony fish is maximized by which of the following?

Mechanism of Breathing in Human-Beings | Human Respiratory System | Biology | Letstute

The Respiratory System

Basic Breathing Mechanics

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