Respiratory System Flashcards

Question

Expiration Expiration (exhalation) is the movement of air out of the lungs. Exhalation occurs when alveolar pressure is h......... than atm............ pressure. Relaxation of the diaphragm and external intercostal muscles results in elastic re........of the chest wall and lungs, which increases intr......... pressure, decreases lung volume, and increases al......... pressure so that air moves from the lungs to the atmosphere. There is also an inward pull of surface tension due to the film of alveolar fluid. Exhalation becomes active during labored breathing and when air movement out of the lungs is impeded. Forced expiration employs contraction of the internal intercostals and abdominal muscles.

Answer 1

Expiration Expiration (exhalation) is the movement of air out of the lungs. Exhalation occurs when alveolar pressure is higher than atmospheric pressure. Relaxation of the diaphragm and external intercostal muscles results in elastic recoil of the chest wall and lungs, which increases intrapleural pressure, decreases lung volume, and increases alveolar pressure so that air moves from the lungs to the atmosphere. There is also an inward pull of surface tension due to the film of alveolar fluid. Exhalation becomes active during labored breathing and when air movement out of the lungs is impeded. Forced expiration employs contraction of the internal intercostals and abdominal muscles.

Answer 2

Quiet Expiration Passive process with no muscle action Elastic recoil & surface tension in alveoli pulls inward Alveolar pressure increases & air is pushed out

Answer 3

Labored Breathing Forced expiration abdominal muscle movements force diaphragm up internal intercostals depress ribs Forced inspiration sternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air

Answer 4

Alveolar pressure decreases & air rushes in | Alveolar pressure increases & air rushes out

Answer 5

Compliance of the Lungs Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension Some diseases reduce compliance tuberculosis forms scar tissue pulmonary oedema --- fluid in lungs & reduced surfactant paralysis

Answer 6

Airway Resistance ``` Resistance to airflow depends upon airway size increase size of chest airways increase in diameter contract smooth muscles in airways decreases in diameter ```

Answer 7

Breathing Patterns Eupnea is normal variation in breathing rate and depth. Apnea refers to breath holding e.g. sleep apnea Dyspnea relates to painful or difficult breathing. Tachypnea involves rapid breathing rate. Costal breathing requires combinations of various patterns of intercostal and extracostal muscles, usually during need for increased ventilation, as with exercise. Diaphragmatic breathing is the usual mode of operation to move air by contracting and relaxing the diaphragm to change the lung volume. Modified respiratory movements are used to express emotions and to clear air passageways.

Answer 8

LUNG VOLUMES AND CAPACITIES Air volumes exchanged during breathing and rate of ventilation are measured with a spiromometer, or respirometer, and the record is called a spirogram. Among the pulmonary air volumes exchanged in ventilation are tidal (500 mL), inspiratory reserve (3100 mL), expiratory reserve (1200 mL), residual (1200 mL) and minimal volumes. Only about 350 ml of the tidal volume actually reaches the alveoli, the other 150 mL remains in the airways as anatomic dead space. Pulmonary lung capacities, the sum of two or more volumes, include inspiratory (3600 mL), functional residual (2400 mL), vital (4800 mL), and total lung (6000 mL) capacities. The minute volume of respiration is the total volume of air taken in during one minute (tidal volume x 12 respirations per minute = 6000 mL/min).

Answer 9

Lung Volumes and Capacities Tidal volume = amount air moved during quiet breathing MVR= minute ventilation is amount of air moved in a minute Reserve volumes ---- amount you can breathe either in or out above that amount of tidal volume Residual volume = 1200 mL permanently trapped air in system Vital capacity & total lung capacity are sums of the other volumes

Answer 10

Air = 21% O2, 79% N2 and .04% CO2 Alveolar air = 14% O2, 79% N2 and 5.2% CO2 Expired air = 16% O2, 79% N2 and 4.5% CO2 Observations alveolar air has less O2 since absorbed by blood Anatomical dead space = 150 mL of 500 mL of tidal volume

Answer 11

Henry’s Law Quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient explains why you can breathe compressed air while scuba diving despite 79% Nitrogen N2 has very low solubility unlike CO2 (soda cans) dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis) decompression sickness if come back to surface too fast or stay deep too long Breathing O2 under pressure dissolves more O2 in blood

Answer 12

Hyperbaric Oxygenation A major clinical application of Henry’s law is hyperbaric oxygenation. Use of pressure to dissolve more O2 in the blood treatment for patients with anaerobic bacterial infections (tetanus and gangrene) anaerobic bacteria die in the presence of O2 Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that tissues absorb more O2 Used to treat heart disorders, carbon monoxide poisoning, cerebral edema, bone infections, gas embolisms & crush injuries

Answer 13

External Respiration O2 and CO2 diffuse from areas of their higher partial pressures to areas of their lower partial pressures Diffusion depends on partial pressure differences Compare gas movements in pulmonary capillaries to tissue capillaries

Answer 14

Rate of Diffusion of Gases Depends upon partial pressure of gases in air p O2 at sea level is 160 mm Hg 10,000 feet is 110 mm Hg / 50,000 feet is 18 mm Hg Large surface area of our alveoli Diffusion distance (membrane thickness) is very small Solubility & molecular weight of gases O2 smaller molecule diffuses somewhat faster CO2 dissolves 24X more easily in water so net outward diffusion of CO2 is much faster disease produces hypoxia before hypercapnia lack of O2 before too much CO2

Answer 15

Haemoglobin and Oxygen Partial Pressure The most important factor that determines how much oxygen combines with haemoglobin is PO2. The relationship between the percent saturation of haemoglobin and PO2 is illustrated the oxygen-hemoglobin dissociation curve. The greater the PO2, the more oxygen will combine with haemoglobin, until the available haemoglobin molecules are saturated.

Answer 16

Hemoglobin and Oxygen Partial Pressure Blood is almost fully saturated at pO2 of 60mmHg people OK at high altitudes & with some disease Between 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle

Answer 17

Oxygen Transport in the Blood Oxyhemoglobin contains 98.5% chemically combined oxygen and haemoglobin inside red blood cells Does not dissolve easily in water only 1.5% transported dissolved in blood Only the dissolved O2 can diffuse into tissues Factors affecting dissociation of O2 from haemoglobin are important Oxygen dissociation curve shows levels of saturation and oxygen partial pressures

Answer 18

Other Factors Affecting Haemoglobin Affinity for Oxygen In an acid (low pH) environment, O2 splits more readily from haemoglobin. This is referred to as the Bohr effect. Low blood pH (acidic conditions) results from high PCO2. Within limits, as temperature increases, so does the amount of oxygen released from hemoglobin. Active cells require more oxygen, and active cells (such as contracting muscle cells) liberate more acid and heat. The acid and heat, in turn, stimulate the oxyhaemoglobin to release its oxygen. BPG (2, 3-biphosphoglycerate) is a substance formed in red blood cells during glycolysis. The greater the level of BPG, the more oxygen is released from haemoglobin

Answer 19

Acidity & Oxygen Affinity for Hb As acidity increases, O2 affinity for Hb decreases Bohr effect H+ binds to haemoglobin & alters it O2 left behind in needy tissues

Answer 20

pCO2 & Oxygen Release As pCO2 rises with exercise, O2 is released more easily CO2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH.

Answer 21

Temperature & Oxygen Release ``` As temperature increases, more O2 is released Metabolic activity & heat More BPG, more O2 released RBC activity hormones like thyroxine & growth hormone ```

Answer 22

Oxygen Affinity & Fetal Haemoglobin Differs from adult in structure & affinity for O2 When pO2 is low, can carry more O2 Maternal blood in placenta has less O2

Answer 23

Foetal Haemoglobin Foetal haemoglobin has a higher affinity for oxygen because it binds BPG less strongly and can carry more oxygen to offset the low oxygen saturation in maternal blood in the placenta. Because of the strong attraction of carbon monoxide (CO) to haemoglobin, even small concentrations of CO will reduce the oxygen carrying capacity leading to hypoxia and carbon monoxide poisoning (Clinical Application).

Answer 24

Carbon Monoxide Poisoning CO from car exhaust & tobacco smoke Binds to Hb haeme group more successfully than O2 CO poisoning Treat by administering pure O2

Answer 25

Control of Ventilation: The Respiratory Center The area of the brain from which nerve impulses are sent to respiratory muscles is located bilaterally in the reticular formation of the brain stem. This respiratory center consists of a medullary rhythmicity area (inspiratory and expiratory areas), pneumotaxic area, and apneustic area.

Answer 26

Role of the Respiratory Center ``` Respiratory mm. controlled by neurons in pons & medulla 3 groups of neurons medullary rhythmicity pneumotaxic apneustic centers ```

Answer 27

Medullary Rhythmicity Area The function of the medullary rhythmicity area is to control the basic rhythm of respiration. The inspiratory area has an intrinsic excitability of autorhythmic neurons that sets the basic rhythm of respiration. The expiratory area neurons remain inactive during most quiet respiration but are probably activated during high levels of ventilation to cause contraction of muscles used in forced (labored) expiration.

Answer 28

Medullary Rhythmicity Area Controls basic rhythm of respiration Inspiration for 2 seconds, expiration for 3 Autorhythmic cells active for 2 seconds then inactive Expiratory neurons inactive during most quiet breathing only active during high ventilation rates

Answer 29

Pneumotaxic Area The pneumotaxic area in the upper pons helps coordinate the transition between inspiration and expiration. The apneustic area sends impulses to the inspiratory area that activate it and prolong inspiration, inhibiting expiration.

Answer 30

Pneumotaxic Area The pneumotaxic area in the upper pons helps coordinate the transition between inspiration and expiration. The apneustic area sends impulses to the inspiratory area that activate it and prolong inspiration, inhibiting expiration.

Answer 31

Regulation of Respiratory Center Cortical Influences voluntarily alter breathing patterns Cortical influences allow conscious control of respiration that may be needed to avoid inhaling noxious gasses or water. Voluntary breath holding is limited by the overriding stimuli of increased [H+] and [CO2]. inspiratory center is stimulated by increase in either if you hold breathe until you faint----breathing will resume

Answer 32

A slight increase in PCO2 (and thus H+), a condition called hypercapnia, stimulates central chemoreceptors. As a response to increased PCO2, increased H+ and decreased PO2, the inspiratory area is activated and hyperventilation, rapid and deep breathing, occurs. If arterial PCO2 is lower than 40 mm Hg, a condition called hypocapnia, the chemoreceptors are not stimulated and the inspiratory area sets its own pace until CO2 accumulates and PCO2 rises to 40 mm Hg. Severe deficiency of O2 depresses activity of the central chemoreceptors and respiratory center

Answer 33

Chemical Regulation of Respiration ``` Central chemoreceptors in medulla respond to changes in H+ or pCO2 hypercapnia = slight increase in pCO2 is noticed Peripheral chemoreceptors respond to changes in H+ , pO2 or PCO2 aortic body---in wall of aorta nerves join vagus carotid bodies--in walls of common carotid arteries nerves join glossopharyngeal nerve ```

Answer 34

Negative Feedback Regulation of Breathing ``` Negative feedback control of breathing Increase in arterial pCO2 Stimulates receptors Inspiratory center Muscles of respiration contract more frequently & forcefully pCO2 Decreases ```

Answer 35

Control of Respiratory Rate ``` Proprioceptors of joints and muscles activate the inspiratory center to increase ventilation prior to exercise induced oxygen need. The inflation (Hering-Breuer) reflex detects lung expansion with stretch receptors and limits it depending on ventilatory need and prevention of damage. Other influences include blood pressure, limbic system, temperature, pain, stretching the anal sphincter, and irritation to the respiratory mucosa. ```

Answer 36

Hypoxia Hypoxia refers to oxygen deficiency at the tissue level and is classified in several ways (Clinical Application). Hypoxic hypoxia is caused by a low PO2 in arterial blood (high altitude, airway obstruction, fluid in lungs). In anaemic hypoxia, there is too little functioning hemoglobin in the blood (hemorrhage, anemia, carbon monoxide poisoning). Stagnant hypoxia results from the inability of blood to carry oxygen to tissues fast enough to sustain their needs (heart failure, circulatory shock). In histotoxic hypoxia, the blood delivers adequate oxygen to the tissues, but the tissues are unable to use it properly (cyanide poisoning).

Answer 37

EXERCISE AND THE RESPIRATORY SYSTEM The respiratory system works with the cardiovascular system to make appropriate adjustments for different exercise intensities and durations. As blood flow increases with a lower O2 and higher CO2 content, the amount passing through the lung (pulmonary perfusion) increases and is matched by increased ventilation and oxygen diffusion capacity as more pulmonary capillaries open. Ventilatory modifications can increase 30 times above resting levels, in an initial rapid rate due to neural influences and then more gradually due to chemical stimulation from changes in cell metabolism. A similar, but reversed, effect occurs with cessation of exercise. Smokers have difficulty breathing for a number of reasons, including nicotine, mucous, irritants, and that fact that scar tissue replaces elastic fibers.

Answer 38

Smokers Lowered Respiratory Efficiency Smoker is easily “winded” with moderate exercise nicotine constricts terminal bronchioles carbon monoxide in smoke binds to hemoglobin irritants in smoke cause excess mucus secretion irritants inhibit movements of cilia in time destroys elastic fibers in lungs & leads to emphysema trapping of air in alveoli & reduced gas exchange

Answer 39

Hyperbaric pressure As water is incompressible the tissues of the body are reasonably protected from external pressures Air-filled spaces e.g. lungs, respiratory passages, middle ear and other sinuses will be affected by pressure changes At a depth of 30m and deeper the volume of air in the lungs becomes so small that the chest begins to collapse under the forces of ambient pressure This is also true for the eardrum (middle ear) and other air filled spaces. Fluid and blood will move into the vacuum created.

Answer 40

Nitrogen narcosis A diver must breathe air or other gases at increased pressure to equalise the increased pressure on the chest wall and abdomen CO2 is routinely removed to prevent its accumulation 100% O2 at an increased pressure causes CNS symptoms of O2 toxicity (therefore reduced to 20% or less) If a diver breathes compressed air the increased PN2 can cause nitrogen narcosis or ‘rapture of the deep’ At 4-5 atm (30-40m) 80% N2 produces a definite euphoria At greater pressures, the symptoms resemble alcohol intoxification This problem can be avoided by breathing mixtures of O2 and helium…however, this can cause high pressure neurological syndrome, HPNS, during a deep dive (drowsiness, tremors and impaired manual dexterity).

Answer 41

Decompression sickness When a diver breathing 80% N2 ascends from a dive, alveolar PN2 falls and N2 diffuses from the tissues into the blood and then into the lungs If decompression is gradual no harmful effects are observed However, in a rapid ascent N2 escapes from solution i.e. it ‘bubbles’ to cause the bends (severe pains in the joints, paresthesia and itching, obstruction of arteries in the brain leading to paralysis and respiratory failure) Treatment involves prompt recompression followed by slow decompression

Answer 42

Air embolism A diver breathing from a tank at increased pressure holds his breath and rises to the surface The gas in the lungs expands and drives the air into the blood vessels (air embolism) This can occur during a rapid ascent from as shallow a depth as 5m This can also occur as a result of rapid expansion of gas in the lungs when external pressure is suddenly reduced from atmospheric to sub-atmospheric i.e. when the wall of a pressurised cabin of an airplane at altitude is breached.

Answer 43

Hypobaric pressure As altitude increases the partial pressure of the constituent gases ↓ (although the relative amount of gases remains the same) ↑ altitude is also accompanied by a ↓ in air density, temperature and relative humidity A ↓ PO2 has implications for the loading of respiratory pigments

Answer 44

Responses to altitude Hyperventilation (short-term) – sensory receptors detect a ↓ in oxygen levels in the blood and stimulate an increase in tidal volume (↑ arterial PO2 but ↓ PCO2) Alkalosis (long-term) – hyperventilation causes a respiratory alkalosis Increased excretion of HCO3- in the kidney (long-term) – helps control any alkalosis

Answer 45

Acute Mountain Sickness A rapid ascent to high altitude brings about AMS Characterised by nausea, tachycardia, insomnia, dyspnea, muscle weakness, oedema in legs/feet, anorexia, dizziness Treatment involves rest, aspirin, fluid replacement…also acetazolamide (diamox) is effective in reducing the incidence/severity of AMS (it ↑ blood CO2 and ↓ blood pH) or use of the Gamow bag