respiratory cycle. point in the volumes: 500 milliliters. for men. expiration, up to 1200 milliliters extra makes breathing Respiratory

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Emil Baldwin
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FUNCTION TESTS Respiratory volume is the term used

with the lungs at a given point in the respiratory

There are four major types of respiratory volumes:

normally enterss the lungs during quiet breathing,

Expiratory reserve volume (ERV) is the amount of

expiration, up to 1200 milliliters for men.

deep inhalation, pastt a tidal inspiration.

factors, and measuring the different types of

or more selectedd volumes, which further describes

In other words, capacities are mostly measurements

Total lung capacity (TLC) is the sum of all of the

represents the total amount of air a person can

TLC is about 6000 ml air for men, and about 4200

Vital capacity (VC) is the amount of air a person

the sum of all of the volumes except residual

1 10 II. RESPIRATORY VOLUMES, CAPACITIES & PULMONARY FUNCTION TESTS Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle. There are four major types of respiratory volumes: Tidal volume (TV) is the amount of air that normally enterss the lungs during quiet breathing, which is about 500 milliliters. Expiratory reserve volume (ERV) is the amount of air youu can forcefully exhale past a normal tidal expiration, up to 1200 milliliters for men. Inspiratory reserve volume ( IRV) is produced by a deep inhalation, pastt a tidal inspiration. This is the extra volume that can be brought into the lungs during a forced inspiration. Residual volume (RV) is the air left in the lungs if you exhale as much airr as possible. The residual volume makes breathing easier by preventing the alveoli from collapsing. Respiratory volume is dependent on a variety of factors, and measuring the different types of respiratory volumes can provide important clues about a person s respiratory health. Respiratory capacities are the combination of two or more selectedd volumes, which further describes the amount of air in the lungs during a given time. In other words, capacities are mostly measurements of elasticity and compliance. Total lung capacity (TLC) is the sum of all of the lung volumes (TV, ERV, IRV, and RV) ), which represents the total amount of air a person can hold in the lungs after a forceful inhalation. TLC is about 6000 ml air for men, and about 4200 ml for women. Vital capacity (VC) is the amount of air a person can movee into or out of his or her lungs, and is the sum of all of the volumes except residual volume (TV, ERV, and IRV), which is between 4000 and 5000 milliliters. These two graphs show (a) respiratory volumes and (b) the combination of volumes that resultss in respiratory capacity. Spirometry (meaning the measuring of breath) is the most common of the pulmonary function tests (PFTs), measuring lung function, specifically the amount (volume) and/or speed (flow) of air that can be inhaled and exhaled. The spirometry test is performed using a device called a spirometer, which comes in several different varieties.

PARTIAL PRESSURES - most gases are mixtures of

the individual component gases, each of which

(in other words, move into the liquid) in

their partial pressure gradients at different

is 79% Nitrogen gas (N2), 20% oxygen gas (O2),

= CO 2, water vapor, neon, helium, etc.).

all things being about equal, the solubility

to the partial pressure of the gas above the

2 III. GAS EXCHANGE IN THE BODY A) SOME GENERALITIES ABOUT GASES 11 1) DALTONS LAW OF PARTIAL PRESSURES - most gases are mixtures of gases. The pressure of the gas is therefore a summation of all thee individual pressures of the individual component gases, each of which has a PARTIAL PRESSURE: NOTE: Notice the partial pressures add up! 2) HENRY S LAW - gases dissolve in a liquid (in other words, move into the liquid) in proportion to their individual partial pressures. * In other words, gases willl diffuse down their partial pressure gradients at different rate or speed, depending on their pressure gradients. Air is a mixture of over 100 gases. EXAMPLE: AIR It is 79% Nitrogen gas (N2), 20% oxygen gas (O2), 2 and less than 1% is the rest (carbon dioxide = CO 2, water vapor, neon, helium, etc.). - Eventually, gases will reach equilibrium, and movement will stop. An equivalent way of stating the law is that, all things being about equal, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. * What has to be about equal? Recall hydrophobic versus hydrophilic substances. In this example, both gases (N 2 and O 2 ) have comparable solubility in water. NOTE: YOU CAN THINK OF PARTIAL PRESSURE GRADIENTS LIKE CONCENTRATIONN GRADIENTS! Particles move down own individual gradients! But do not think they are the same!

12 B) PARTIAL PRESSURES (PP) OF GASES IN ALVEOLI, BLOODSTREAM & TISSUESS - IN GENERAL: we maintain PP gradients for O 2 and CO 2 in order to keep things flowing the way we want them to flow!

* at the tissues, we want O 2 to move out of the blood stream (into the tissues) and CO 2 to move out of tissues and into the blood, so it can be transported to lungs and expired.

Why doesn t thee system go to equilibrium, thereby stopping the flow of respiratory gases? 1.

If it does, diffusion stops, CO 2 builds up in the cells, and they die. First to die are brain cells, because CO 2 is an acid (lowers ph; seee later). 2. Ventilation: New, oxygenated air is always being brought into the alveoli through inspiration, maintaining a PP gradient.

Hemoglobin: Both CO 2 and O 2 are attached to a carrierr molecule (red blood cell) as soon as they enter the blood plasma (not shown on image).

3 12 B) PARTIAL PRESSURES (PP) OF GASES IN ALVEOLI, BLOODSTREAM & TISSUESS - IN GENERAL: we maintain PP gradients for O 2 and CO 2 in order to keep things flowing the way we want them to flow! *at the lungs, we want O 2 to move into the blood stream so we can transport it to the tissues, and CO 2 to move out of blood into alveoli so it can be expired. * at the tissues, we want O 2 to move out of the blood stream (into the tissues) and CO 2 to move out of tissues and into the blood, so it can be transported to lungs and expired. - NOTE: all movement of RESPIRATORY GASES = passive movement! NEVER pump! - QUESTION: how are these gradients maintained? Why doesn t thee system go to equilibrium, thereby stopping the flow of respiratory gases? 1. Blood circulation: Blood is ALWAYS CIRCULATING - remember, I told you in the Blood Vessel chapter that it was important for blood flow to never stop--now you know why. If it does, diffusion stops, CO 2 builds up in the cells, and they die. First to die are brain cells, because CO 2 is an acid (lowers ph; seee later). 2. Ventilation: New, oxygenated air is always being brought into the alveoli through inspiration, maintaining a PP gradient. If you want to see how long it takes for diffusion to stop if new air isn t brought in, see how long you can hold your breath! 3. Hemoglobin: Both CO 2 and O 2 are attached to a carrierr molecule (red blood cell) as soon as they enter the blood plasma (not shown on image). Therefore, they are no longer CO 2 and O 2, which maintains the gradient. 4. Chemical Reactions: Cellular metabolism keeps the ppp O 2 low inside the cell. Another reaction keeps CO 2 low in the blood near the cell: Once in water (serum), CO 2 is immediately converted to bicarbonate (not shown on image see later). Therefore, it is no longer COO 2, and the gradient is maintained. - ANOTHER QUESTION: remember, I told you that air has a LOT more O 2 than CO 2. If that s the case, then the CO 2 gradient must be SMALLER than the O 2 gradient; so O 2 must diffuse must faster than CO 2. How does the system keep CO 2 from building up if it diffuses so slow? *ANSWER: the above statement is true; however, CO 2 is much more SOLUBLE IN WATER than O 2, (20 times more soluble!). This makes up for the lower PP gradient. This solubility of carbon dioxide will become very important later!

4 13 - NOTE ONE OTHER THING: the system depends on passive movement, which is why the RESPIRATORY MEMBRANE must be so thin. Anything that lowers the membrane s diffusion capability damages the system, and lets CO2 build up. * PNEUMONIA - tissue becomes edematous & takes in more fluid; lowers movement of gases, patient poisons himself. * EMPHYSEMA - walls between adjacent alveoli break down, causing alveoli to fuse together. Larger alveoli = less surface area; eventually, not enough to maintain diffusion rates of CO2. Patient poisons himself. C) TRANSPORT OF RESPIRATOR RY GASES IN BLOOD - We have seen how we get the gases in & out of the alveoli and cells passive transport by maintaining pp gradients. But, how do we transport these gases to the cells (O 2 ) and to the lungs (CO 2 ) in the first place? NOTE: I will discuss the transport of these 2 gases separately, even though we will see their transport is link to each other, and you can t really separate them! 1) TRANSPORT OF OXYGEN - Oxygen gas is carried to the cells for their use. Therefore, blood plasma must be able to carry it DESPITE THE FACT THAT IT IS NOT VERY SOLUBLE IN WATER! To combat this, we attach it to a carrierr molecule in the RBC - HEMOGLOBIN (Hb) * Also, we must not only be able to carry it, by the system has to have a way of letting it go once it has arrive at the tissues that need oxygen for cellular respiration:

5 14 ASSOCIATION & DISSOCIATION or LOADING & UNLOADING of O2 - SO, in order to deal with these 2 requirements, oxygen is transported in the plasma in 2 ways: 1. Directly dissolve in plasma - only about 1.5% 2. Attached to hemoglobin about 98.5% - RECALL FROM BLOOD CELL CHAPTER: Hemoglobin = 4 polypeptide chains, each with an iron-containing bonding group (= the HEME group). * iron in the heme group of hemoglobin - easily OXIDIZEDD (picks up an O 2 ) in the following reaction: - As 1 Hb picks up an O 2, Hb changes shape, and it becomes progressively easier for subsequent O 2 to attach. Therefore, Hb tends to FULLY SATURATE with oxygen. * Also, the UNLOADING of 1 molecule of O 2 makes it easier for subsequent O 2 s to unload. * IN OTHER WORDS, the AFFINITY for Hb to O 2 changes.

6 15 *** IMPORTANT POINT: since the affinity for Hb to O 2 changes, when blood is near tissues that are METABOLICAL LY ACTIVE (that is, have a very low P (O 2 ) there is a veryy high PP gradient, and the molecules let go of oxygen quicker, which then FACILITATES UNLOADING! In this way, the system assures that oxygen is only unloaded at tissues that really need it!!!!! Below is what is called the Oxygen-hemoglobin Dissociation Curve (under normal conditions), with an explanation to make it easier: - We are watching Hb s AFFINITY to oxygen change! - Variables that affect Hb s AFFINITY for O 2 : O 2 1. PP O 2 - more O 2 = more formation of HbO

7 2. ph = THE BOHR EFFECT: Acidity affects Hb saturation More acidic blood (low ph) releases O 2, while less acidic blood releases less O 2. Also see dissociation curve below! PP CO 2 - because it s an acid (= hydrogen donor!) Because it is an acid (Bohr Effect), and changes shape of Hb. 4. Temperaturee See dissociation curve below! The Effects of ph and Temperature to the Oxygen Dissociation Curve 5. A chemical called BPG, which is a natural by-product of metabolism. Some hormones (NE, epinephrine, GH, testosterone) increase production of BPG by the cells! ALL OF THESE ALLOW THE RBC TO GIVE UP OXYGEN WHERE IT IS MOST NEEDED. - HYPOXIA - any impairment to O 2 delivery at the cells. * CYANOTIC ( blue skin ) - first sign of hypoxia. Look at mucosae & nail beds. * ANEMIC HYPOXIA - low # RBC, or abnormal Hb. * ISCHEMIC HYPOXIA - blocked circulation. * HISTOXIC HYPOXIA - cells are unable to use O2, despitee the fact that delivery is normal. Usually caused by METABOLIC TOXINS (CYANIDE stops the Electron Transport Chain, etc.). * HYPOXEMIC HYPOXIA - reduced arterial pp O2; caused by a pulmonary disease or breathing air with low concentration of O2; e.g. DROWNING. CARBON MONOXIDE (CO) POISONING - Hb hass a 200 X greater affinity for CO than O2; soon, all heme groups are occupied by CO.

CHAPTER 3: The respiratory system

CHAPTER 3: The respiratory system Practice questions - text book pages 56-58 1) When the inspiratory muscles contract, which one of the following statements is true? a. the size of the thoracic cavity