Ch.37 Respiration

Essential knowledge 4.B.2: Cooperative interactions within organisms promote efficiency in the use of energy and matter. a. Organisms have areas or compartments that perform a subset of functions related to energy and matter, and these parts contribute to the whole.

Essential knowledge 4.A.4: Organisms exhibit complex properties due to interactions between their constituent parts. a. Interactions and coordination between organs provide essential biological activities. b. Interactions and coordination between systems provide essential biological activities.

Essential knowledge 2.D.2: Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. a. Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions. b. Organisms have various mechanisms for obtaining nutrients and eliminating wastes. c. Homeostatic control systems in species of microbes, plants and animals support common ancestry.

Essential knowledge 2.A.3: Organisms must exchange matter with the environment to grow, reproduce and maintain organization. a. Molecules and atoms from the environment are necessary to build new molecules. b. Surface area-to-volume ratios affect a biological system’s ability to obtain necessary resources or eliminate waste products.

Ch.37 Gas Exchange Respiration involves three events External respiration - gas exchange occurs between air and blood (O2 from air to blood; CO2 from blood into air) within the lungs and oxygen is carried to other parts of the body by circulatory system Internal respiration - gas exchange occurs between blood and tissue fluid (O2 from blood to tissue fluid; CO2 from tissue fluid into blood). Bodies’ cells exchange gases (O2 taken in; CO2 released) with tissue fluid. Blood carries carbon dioxide from cell to lungs

Gas exchange occurs across specialized respiratory surfaces Gas exchange supplies oxygen for cellular respiration and disposes of carbon dioxide

Animals require large, thin, moist respiratory surfaces for the adequate diffusion of respiratory gases between their cells and the respiratory medium, either air or water (1)This means that respiratory surfaces must be kept moist for oxygen and carbon dioxide to diffuse through the cell’s plasma membrane

(2)Respiratory surfaces must be extensive enough (large surface area) to take up enough oxygen and get rid of carbon dioxide for the entire body (3)These delicate moist tissues of respiratory surfaces need to be protected

Gas Exchange Hydras and planarians Small animals with large surface area Most of their cells exchange gases directly with the environment

Types of respiratory systems Skin Gills Tracheal system Lungs

Skin Skin - animals such as earthworms have no specialized gas exchange surfaces Oxygen diffuses into capillaries beneath the skin They must live in damp places or in water to keep respiratory surfaces moist

Gills in Aquatic Animals Gills are featherlike outfoldings (evaginations) of the outer or inner body surface specialized for gas exchange, and occur in aquatic animals Gills have finely subdivided surfaces to provide adequate surface area and contain a rich blood supply for transport (vascularization)

The feathery gills projecting from a salmon Are an example of a specialized exchange system found in animals

In some invertebrates The gills have a simple shape and are distributed over much of the body

Many segmented worms have flaplike gills That extend from each segment of their body

The gills of clams, crayfish, and many other animals Are restricted to a local body region

Oxygen makes up 0.45% of seawater, but 21% of air This means that aquatic animals have a greater problem obtaining enough oxygen than do terrestrial animals and expend much more energy doing so (25% compared to1-2% of their energy) Diffusion is also 1000X slower in water than in air (water is 1000X more dense than air)

The effectiveness of gas exchange in some gills, including those of fishes is increased by ventilation and countercurrent flow of blood and water

Counter-current exchange This maintains a favorable gradient between blood and the water at every point of exchange, this maximizes the amount of oxygen the blood removes from the water

Respiratory systems Land animals have two advantages: air contains more oxygen than an equal volume of water and air is lighter and easier to move. Terrestrial animals expend much less energy than an aquatic animal in gas exchange

Most terrestrial animals have respiratory surfaces that are infoldings (invaginations) of the body surface This protects the respiratory surface and keeps it moist

Land Environments: Tracheae Insects and other terrestrial arthropods A respiratory system consists of branched tracheae Tracheae branch until end in tracheoles (surface area) that are in direct contact with body cells so they do not require circulatory system to transport gases

The tracheal tubes supply O2 directly to body cells and are filled with fluid for gas exchange

Lungs Spiders, land snails, and most terrestrial vertebrates have internal lungs Lungs are invaginated Lungs are restricted to one part of the body, so a circulatory system is needed to transport gases from lungs to the rest of the body

Land Environments: Lungs of Vertebrates Terrestrial vertebrates have evolved lungs Lungs of amphibians Possess a short tracheae which divides into two bronchi that open into lungs Many also breathe to some extent through skin Reptiles Inner lining of lungs is more finely divided in reptiles than in amphibians Lungs of birds and mammals are elaborately subdivided All terrestrial vertebrates, except birds, use a tidal ventilation system

How an Amphibian Breathes An amphibian such as a frog Ventilates its lungs by positive pressure breathing, which forces air down the trachea

How a Mammal Breathes Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs

Ventilation in Terrestrial Vertebrates Inspiration (inhalation) in mammals Create negative pressure in lungs The rib cage is elevated (rib muscles contract) The diaphragm lowers (contracts) Thoracic pressure decreases (volume increases) to less than atmospheric pressure

Ventilation in Terrestrial Vertebrates Expiration (exhalation) in mammals Create positive pressure in lungs The rib cage is lowered The diaphragm rises Thoracic pressure increases,(thoracic cavity volume decreases) to more than atmospheric pressure

Besides lungs, bird have eight or nine air sacs How a Bird Breathes Besides lungs, bird have eight or nine air sacs That function as bellows that keep air flowing through the lungs

Every exhalation completely renews the air in the lungs Lungs do not have alveoli, but contain tiny parallel tubes called parabronchi Air flows one direction and blood flows in the opposite direction acting as counter-current exchange

Human Respiratory System As air moves through upper respiratory system It is filtered to free it of debris Warmed, and Humidified When air reaches lungs It is at body temperature, and

Human Respiratory System Air passes from pharynx through glottis Larynx and trachea Permanently held open by cartilage rings Facilitates movement of air When food is swallowed The larynx rises, and The glottis is closed by the epiglottis

Human Respiratory System Trachea divides Forms two primary bronchi Bronchi enter the right and left lungs Bronchi branch until there are a great number of tiny bronchioles Each bronchiole terminates in an elongated space enclosed by alveoli which greatly increase the surface area of the respiratory surface Alveoli are air sacs lined with a thin layer of epithelial cells which form the respiratory surface

Humans breathe using a tidal mechanism Ventilation Humans breathe using a tidal mechanism Volume of thoracic cavity and lungs is increased by muscle contractions that lower the diaphragm and raise the ribs

Control of Breathing in Humans The main breathing control centers Are located in two regions of the brain, the medulla oblongata and the pons

The centers in the medulla regulate the rate and depth of breathing in response to pH changes (H+) in the blood and cerebrospinal fluid The medulla adjusts breathing rate and depth to match metabolic demands CO2 reacts with H2O to form carbonic acid, which lowers the pH of the blood

By monitoring pH, the medulla regulates CO2 levels in the blood

Sensors in the aorta and carotid arteries Monitor O2 and CO2 concentrations in the blood

Respiratory Pigments Respiratory pigments are proteins that transport oxygen and greatly increase the amount of oxygen that blood can carry O2 is not very soluble in water, so blood transports very little dissolved O2

Hemoglobin is composed of four polypeptide chains, each polypeptide chain contains a heme group which contains an iron atom.

Like all respiratory pigments Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body

Gas Exchange and Transport Oxygen diffuses into pulmonary capillaries Most combines with hemoglobin in red blood cells to form oxyhemoglobin CO2 diffuses out of pulmonary capillaries Most carbon dioxide is transported in the form of bicarbonate ion

Loading and unloading of O2 Depend on cooperation between the subunits of the hemoglobin molecule

Carbon Dioxide Transport Hemoglobin also helps transport CO2 and assists in buffering the pH of the blood

Carbon dioxide from respiring cells Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs

CO2 transport Some CO2 dissolves in the plasma, but most enters the red blood cells Some CO2 binds to hemoglobin, but most reacts with H2O to form carbonic acid (H2CO3) Carbonic acid forms more easily in RBC’s with the help of the enzyme carbonic anhydrase H2CO3 dissociates to become (H+) hydrogen ion and (HCO3-) bicarbonate ion

Bicarbonate ions buffer the blood pH by combining with H+ ions and removing them from the blood, or by releasing H+ ions when needed

Respiration and Health Upper Respiratory Tract Infections Strep Throat Streptococcus pyogenes Sinusitis Infection of sinuses Tonsillitis Infection of tonsils Laryngitis Infection of larynx

Respiration and Health Lower Respiratory Tract Infections Acute bronchitis Infection of primary and secondary bronchi Pneumonia Viral or bacterial infection of the lungs where bronchi and alveoli fill with fluid Pulmonary tuberculosis

Disorders Pulmonary fibrosis Chronic bronchitis Emphysema Fibrous connective tissue builds up in the lungs Chronic bronchitis Airways inflamed and filled with mucus Emphysema

Disorders Asthma Lung Cancer Airways are unusually sensitive to specific irritants When exposed to the irritants, the smooth muscles in the bronchioles undergo spasms Lung Cancer