Biol 1215 Chapter 39/42: Gas Exchange and Circulation

Questions and Answers

All animals need to have a way to acquire _ from their environment and eliminate _ from their body.

O2, CO2

Most gas exchange involves five steps: 1. Ventilation – movement of air or water through a specialised gas exchange organ (e.g., lung or gill, involves the ____________________________)

movement of air or water

Diffusion at the respiratory surface – O2 moves from air or water into circulatory fluid, CO2 moves from circulatory fluid into air or water (also called external respiration, involves the ____________________________)

respiratory surface

Circulation – transport of dissolved O2 and CO2 throughout the body (involves the ____________________________)

circulatory system Signup and view all the answers

Diffusion at the body tissues – O2 moves from circulatory fluid into tissues, CO2 moves from tissues into circulatory fluid (involves the ____________________________)

body tissues Signup and view all the answers

Gases diffuse from regions of partial pressure to regions of partial pressure.

high, low Signup and view all the answers

Partial pressure is the pressure exerted by a given gas in a mixture of gases; it is to concentration (# of molecules/unit volume), but also impacted by .

proportional, temperature Signup and view all the answers

What factors impact the rate of diffusion in gas exchange?

Solubility of the gas, temperature, surface area available for diffusion, partial pressure gradient, thickness of the barrier to diffusion. Signup and view all the answers

O2 has very low solubility in water in general, and it varies based on two factors: 1. Temperature – as temperature , solubility of O2 and other gases .

increases, decreases Signup and view all the answers

As an animal gets larger, increases more rapidly than does.

volume, surface area Signup and view all the answers

Give three examples of adaptations that increase surface area of a transport surface in animals.

Folds, branched structures, and projections. Signup and view all the answers

Obtaining O2 from water requires greater efficiency than obtaining O2 from air: Per unit volume, air has about __________________ more O2 than water.

Breathing air requires less energy, but animals must have a way of preventing ____________________________ across their gas exchange surfaces.

water loss Signup and view all the answers

Gills are extensions of the body surface made of a thin layer of epithelium, flattened, and may have several levels of ____________________________.

folding Signup and view all the answers

List two ways in which the structure of gills matches their function, with respect to maximising rate of gas diffusion.

Thin epithelial layers and large surface area due to folding. Signup and view all the answers

Briefly describe how countercurrent flow maintains a concentration gradient of O2 so that blood oxygenation is maximised.

Countercurrent flow ensures that blood and water flow in opposite directions, maintaining a gradient for oxygen diffusion. Signup and view all the answers

Describe the exchange of gases in the lungs and in tissues for mammals.

In mammals, gas exchange occurs in the alveoli of the lungs, where oxygen is absorbed into the bloodstream and carbon dioxide is released for exhalation. In tissues, oxygen is delivered from the blood to cells, and carbon dioxide produced by metabolism is transported back to the lungs for removal. Signup and view all the answers

What is the importance of respiratory pigments?

Respiratory pigments, like hemoglobin, bind oxygen in the lungs and transport it to tissues, ensuring efficient oxygen delivery necessary for cellular respiration and energy production. Signup and view all the answers

Leukocytes (white blood cells) – diverse set of cells that act as part of the immune system by ____________________________.

protecting the body against infections Signup and view all the answers

What is cooperative binding and how does it impact the shape of the oxygen dissociation curve?

Cooperative binding refers to the phenomenon where the binding of oxygen to one subunit of hemoglobin increases the affinity of the remaining subunits for oxygen. This results in a sigmoidal shape of the oxygen dissociation curve, indicating a more efficient oxygen uptake and release. Signup and view all the answers

How do heat and pH impact hemoglobin to ensure more oxygen is unloaded to tissues with the greatest need?

Increased heat and lower pH (higher acidity) enhance the unloading of oxygen from hemoglobin, a phenomenon known as the Bohr effect. This ensures that active tissues receive more oxygen during increased metabolic activity. Signup and view all the answers

Respiratory pigments are ____________________________ that bind to O2, greatly increasing the amount of O2 that the circulatory fluid can carry.

proteins Signup and view all the answers

Arthropods and many have hemocyanin, which contains as the O2-binding component.

mollusks; copper Signup and view all the answers

Compare and contrast open and closed circulatory systems.

Open circulatory systems have blood that bathes organs directly and is not confined to vessels, whereas closed circulatory systems keep blood confined within vessels, allowing for more efficient transport and regulation of blood flow. Signup and view all the answers

Compare and contrast the circulatory systems of the major groups of vertebrates.

The circulatory systems of vertebrates can be categorized into 2, 3, or 4 chambered hearts. Fish have a single circuit with a 2-chambered heart, amphibians and reptiles usually have a 3-chambered heart with partial separation of oxygenated and deoxygenated blood, while birds and mammals have a 4-chambered heart that completely separates these blood types for optimal efficiency. Signup and view all the answers

Most vertebrates and some invertebrates have hemoglobin, which contains ____________________________ as the O2-binding component.

iron Signup and view all the answers

Each hemoglobin molecule is composed of ____________________________ and can carry four O2 molecules.

four subunits Signup and view all the answers

Distinguish between pulmonary and systemic circuits and explain the function of each.

The pulmonary circuit transports deoxygenated blood from the heart to the lungs for oxygenation and returns oxygenated blood to the heart. The systemic circuit carries oxygenated blood from the heart to the rest of the body and returns deoxygenated blood to the heart. Signup and view all the answers

The O2 dissociation curve shows of hemoglobin at different levels.

affinity; oxygen Signup and view all the answers

Define homeostasis and explain the importance of homeostatic mechanisms in animals.

Homeostasis is the maintenance of a stable internal environment in an organism despite external changes. Homeostatic mechanisms are crucial for sustaining life, as they regulate vital parameters like temperature, pH, and electrolytes. Signup and view all the answers

Explain how each part of the O2 dissociation curve is related to the cooperative binding/unbinding of hemoglobin and O2: Cooperative binding results in exercising tissues ____________________________ than resting tissues.

having a higher affinity for O2 Signup and view all the answers

Identify the sensor, integrator, and effector(s) in negative feedback mechanisms.

The sensor detects changes in the internal environment, the integrator processes this information and determines the response, and the effector carries out the response to restore balance. Signup and view all the answers

Without cooperative binding hemoglobin would be less likely to reach ____________________________ at the respiratory surface.

saturation Signup and view all the answers

Briefly describe the negative feedback mechanisms involved in maintaining homeostasis of ventilation and blood pressure in humans.

In ventilation, sensors in the brain monitor carbon dioxide levels and adjust breathing rates accordingly. For blood pressure, baroreceptors detect changes in blood pressure, and the integrator (medulla oblongata) activates the heart and vessels to restore normal pressure. Signup and view all the answers

Two limitations of open circulatory systems include and .

lower blood pressure; less efficient delivery of oxygen Signup and view all the answers

Closed circulatory systems are found in animals that are typically ____________________________.

large and highly mobile Signup and view all the answers

Vertebrates have closed circulatory systems with three types of vessels: 1. Arteries are tough, thick-walled vessels that take blood ____________________________.

away from the heart Signup and view all the answers

Vertebrate hearts contain two or more chambers; at least one thin-walled atrium, which receives blood from ____________________________.

the body Signup and view all the answers

Amphibians have a three-chambered heart (two atria, one ventricle) and double circulation; O2-poor blood flows through the pulmocutaneous circuit to pick up O2 from ____________________________.

the lungs and skin Signup and view all the answers

Why might mixing of blood in the ventricle decrease gas exchange efficiency?

It reduces the oxygenation of blood Signup and view all the answers

Both mammals and birds have a four-chambered heart with two atria and two ventricles; the ____________________________ of the heart pumps and receives only O2-rich blood.

left side Signup and view all the answers

Homeostasis is the stability in ____________________________ conditions within a cell, tissue, or organ.

internal Signup and view all the answers

Different organisms regulate different conditions to different degrees; for example, a dog spends energy either ____________________________ to maintain a consistent body temperature.

regulating Signup and view all the answers

Most animals achieve homeostasis via regulatory systems that _________________________ internal conditions.

monitor and control Signup and view all the answers

An animal needs to maintain appropriate levels of blood PO2 and PCO2 in order for ____________________________ during both rest and high levels of activity.

cellular respiration Signup and view all the answers

If blood pressure increases or decreases too much, baroreceptors in the walls of the ____________________________ sense the change.

blood vessels Signup and view all the answers

Explain how the impact of pH and temperature on hemoglobin's affinity for O2 ensures that more O2 is delivered to tissues that need it the most.

Lower pH and higher temperatures decrease hemoglobin's affinity for O2, allowing more O2 to be released to active tissues. Signup and view all the answers

Study Notes

Impact of the Environment on Gas Exchange

Gas Exchange in Animals

Mechanisms for acquiring O2 and eliminating CO2 are crucial for all animals, called gas exchange.
Involves five steps:
- Ventilation, diffusion at the respiratory surface, circulation, diffusion at body tissues, and cellular respiration.

Movement of Gases by Diffusion

Gases move from areas of higher to lower partial pressure.
Partial pressure is influenced by concentration and temperature.
Tissues generally have lower PO2 and higher PCO2 compared to their environment; thus, O2 moves into tissues while CO2 exits.

Rate of Diffusion

Influenced by gas solubility in the liquid layer, temperature, surface area for diffusion, partial pressure gradient, and barrier thickness.
Increasing surface area or decreasing thickness improves diffusion efficiency.

Diffusion of Gases in Air and Water

Diffusion of Gases in Air

Determined by the gas's proportion in the atmosphere and total air pressure.
The typical composition of air: 76% N2, 21% O2, and 0.04% CO2.

Diffusion of Gases in Water

O2 solubility is low and varies with temperature (higher temperatures reduce solubility) and solute presence (more solutes reduce gas solubility).
Photosynthetic organisms, respiration by decomposers, water mixing, and the surface area of water bodies affect O2 availability.

Adaptations for Gas Exchange

Relationship Between Form and Function

Gas exchange challenges vary with the animal's size and physiology, affecting adaptations.
Natural selection influences anatomical changes, which in turn affect physiological functions.

Surface Area to Volume Ratio

The surface area allows for substance exchange, while volume dictates substance use efficiency.
As animal size increases, the surface area to volume ratio decreases, impacting O2 use and CO2 production.

Gas Exchange via Diffusion

Small animals (like flatworms) may utilize diffusion directly, relying on a moist environment for gas exchange.
Such organisms’ gas exchange surfaces are more vulnerable to water loss due to their necessity for moisture.

Gas Exchange in Air vs. Water

Air contains significantly more O2 than water (about 20 times more), and water is denser, making ventilation energetically costly.
Strategies must be in place in aquatic species to prevent water loss while maintaining efficient gas exchange.

Gills of Aquatic Animals

Gills are extensions of body surfaces and vary in structure and placement among aquatic species.
Internal gills are protected, requiring specialized structures to drive water over them.

Gills of Bony Fishes

Composed of gill arches, filaments, and lamellae, which maximize surface area for gas exchange.
Fish ventilate by opening and closing their mouths or through ram ventilation while swimming.

Countercurrent Flow in Bony Fish Gills

Water flows in the opposite direction of blood in capillaries, maximizing O2 uptake and CO2 removal through sustained concentration gradients.

Tracheal Systems in Insects

Insects breathe via tracheae, minimizing water loss with spiracles that can close.
Gas exchange happens directly with body tissues, relying on diffusion and muscle contractions for ventilation.

Lungs

Lungs are infoldings of the body surface used for gas exchange in terrestrial animals.
Lung structures correlate with an animal's size, utilized in various vertebrates and certain invertebrates.

Lung Ventilation in Amphibians

Amphibians utilize positive pressure ventilation to assist in breathing, involving specific muscular actions to push air into lungs.

Lung Ventilation in Mammals

Mammals employ negative pressure ventilation through rib and diaphragm actions, creating pressure differences to draw air into the lungs.

Lung Ventilation in Birds

Birds have an efficient lung system with air sacs, allowing for continuous gas exchange even during exhalation.
Air moves through a sequence of sacs, ensuring a constant flow and gas exchange efficiency.

Circulation and Gas Exchange with Body Tissues

Blood Composition

Blood consists of plasma (mostly water) and formed elements, including platelets, leukocytes, and erythrocytes.

Respiratory Pigments

Respiratory pigments, like hemocyanin in some arthropods and hemoglobin in vertebrates, enhance O2 transport efficiency.
Hemoglobin can bind up to four O2 molecules due to its cooperative binding mechanism.

Hemoglobin’s Affinity for O2

Cooperative binding of hemoglobin enables a more significant release of O2 when tissues require it and enhances O2 uptake under higher demand situations.
O2 dissociation curve indicates how hemoglobin's affinity for O2 changes across varying partial pressures.

O2 Dissociation Curve and Hemoglobin

Cooperative binding of O2 enhances delivery to exercising tissues compared to resting tissues.
Without cooperative binding, hemoglobin's ability to saturate with O2 at the respiratory surface diminishes.
The O2 delivery discrepancy between resting and exercising tissues would be diminished without this cooperation.
The shape of the O2 dissociation curve without cooperative binding suggests a hyperbolic relationship instead of the sigmoid curve typical of cooperative binding.

Impact of pH and Temperature on Hemoglobin

A decrease in pH (Bohr shift) lowers hemoglobin's affinity for O2, facilitating greater O2 release to tissues.
Increasing temperature also results in reduced hemoglobin affinity for O2, enhancing O2 delivery during heightened activity.

Types of Circulatory Systems

Circulatory systems consist of a circulatory fluid, a heart or hearts, and blood vessels facilitating fluid flow.
Open circulatory systems have hemolymph, which is not confined strictly to vessels and acts as both circulatory and interstitial fluid.
Closed circulatory systems have blood, which is distinct from interstitial fluid and remains confined within vessels.

Open Circulatory Systems

Common in arthropods and some mollusks, allowing hemolymph to circulate through a limited set of vessels.
Hemolymph exchanges with body tissues to transport gases, nutrients, wastes, and other substances.
Hemolymph is pumped into vessels by heart contractions, drawing it back when the heart relaxes.

Limitations of Open Circulatory Systems

Lower oxygen and nutrient transport efficiency due to slow hemolymph flow.
Limited ability to regulate blood distribution to active tissues.

Closed Circulatory Systems

Found in larger, more active animals, such as vertebrates and cephalopods, allowing for efficient circulation.
Blood pressure is maintained at higher levels than in open systems, enabling targeted blood flow response to tissue needs.

Vertebrate Circulatory Systems: Vessels

Arteries carry blood away from the heart; small arteries are referred to as arterioles.
Capillaries enable gas and substance exchange due to their thin walls.
Veins return blood to the heart; small veins are termed venules.

Vertebrate Hearts

Formed with two or more chambers: at least one atrium and one ventricle.
Mammalian hearts have both atria and ventricles for efficient blood circulation.
Right ventricle pumps to the lungs, while the left ventricle pumps to the body.

Circulatory Systems in Different Vertebrates

Fish possess a two-chambered heart and single circulation; they face blood pressure drops through capillary beds.
Amphibians have a three-chambered heart and double circulation; potential mixing of O2-rich and poor blood occurs.
Non-avian reptiles have a partially divided three-chambered heart for improved gas exchange.
Birds and mammals feature a fully divided four-chambered heart, ensuring complete separation of O2-rich and poor blood.

Homeostasis in Gas Exchange and Circulation

Homeostasis maintains stable internal conditions essential for optimal organism function.
Organisms possess mechanisms to regulate internal conditions, minimizing fluctuations.
Regulation vs. conformation: dogs regulate temperature while reptiles conform to environmental temperatures.

Negative Feedback Loops

Negative feedback systems involve sensors, integrators, and effectors to counteract changes from set points.
Sensors detect deviations, integrators compare them to set points, and effectors enact corrective measures.

Homeostatic Control of Ventilation

Ventilation maintains appropriate blood gas levels for rest and activity.
Breathing rate is regulated by the medullary respiratory center and increases during exercise due to heightened oxygen demand.

Homeostatic Control of Blood Pressure

Necessary to maintain blood transport efficacy and prevent hypertension or hypotension.
Baroreceptors detect blood pressure changes, signaling the brain which initiates responses via various effectors.

Learning Outcomes

Characterization of efficient gas exchange conditions and the advantages/disadvantages of respiratory media.
Analysis of surface area/volume ratio implications on size and gas exchange structures.
Understanding of circulatory system comparisons and homeostatic mechanisms regarding ventilation and blood pressure.

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Description

This quiz covers the concepts from Chapters 39 and 42 of Biology 1215, focusing on gas exchange in animals and the impact of the environment on this process. Test your understanding of how different organisms adapt their gas exchange methods to their surroundings.