Physiology Ch.8

What is the purpose of the respiratory system?

to carry O2 to body tissues and expel the CO2 produced from all body tissues

What is pulmonary ventilation?

process of moving air into and out of lungs

What is the tract of pulmonary ventilation?

nose/mouth - nasal cavity - pharynx - larynx - trachea - bronchial tree - alveoli 

How are the lungs suspended in pulmonary ventilation?

suspended by pleural sacs

What is the anatomy of pulmonary ventilation?

consists of lung, pleural sacs, diaphragm, rib cage. The anatomy determines the airflow in and out of lungs. Through inspiration and expiration.

What is inspiration? 

an active process and involves multiple muscles. It expands thoracic cavity in 3 dimensions, thus expanding volume of thoracic cavity and lungs. Air passively rushes in due to pressure difference.

What are the muscles used in inspiration?

diaphragm flattens toward abdomen. External intercostals move rib cage (bucket handle) and sternum (pump handle) up and out.

What is pump handle action?

elevation of ribs leads to increase in antero-posterior diameter of thoracic cavity. Consists of your sternum moving up and down.

What is bucket handle action? 

Elevation of ribs leads to increase in lateral diameter of thoracic cavity. Consists of your lungs moving up and down. 

Lung volume in inspiration?

Lung volume increases and intrpulmonary pressure decreases. Boyle’s law regarding pressure vs. volume. Pressure and volume inversely proportional.

How does forced breathing affect the muscle in inspiration? 

typically muscles of chest and neck. Consists of scalenes, sternocleidomastoid, and pectorals. AKA all the stuff tha feels stiff and tight when youre stressed. Ribs raised even farther. 

What is expiration?

usually a passive process. Contains inspiratory muscles relax, lung volume decrease, intrapulmonary pressure increase, and air is forced out of lungs.

What is expiration forced breathing?

Active process. Internal intercostals pull ribs down. Forced generally recruits more muscles with major attachments below or on lower aspects of ribs or sternum. Latissimus dorsi, quadratus lumborum, abdominal muscles force diaphragm back up.

What is the process of inspiration and expiration? 

• Resting positions of the diaphragm and the thoracic cage, or thorax. Note the size of the rib cage at rest. 

• The dimensions of the lungs and the thoracic cage increase during inspiration, forming a negative pressure that draws air into lungs. 

• during expiration, the lung’s volume decrease, thereby forcing air out of the lungs.

What is work of breathing?

energy required to overcome elastic resistance of lungs, move chest wall/abdomen. At rest, use <5% of resting VO2. Intense exercise 30% of VO2, increased rate and depth of breathing.

Work of breathing for swimming vs. land-exercising?

Greater work of breathing in swimming. Hydrostatic pressure. Altered ventilatory mechanics.

What is the regulation of pulmonary ventilation? 

Body must maintain homeostatic balance between blood oxygen (O2), carbon dioxide (CO2), pH. requires coordination between respiratory, muscular, and cardiovascular systems. Coordination occurs via involuntary regualtion of pulmonary ventilation. 

What are respiratory centers for central mechanisms of regulation?

inspiratory, expiratory. In brain stem (medulla oblongata, pons). Establish rate and depth of breathing via signals to respiratory muscles. Cortex overrides signals if necessary.

Central chemoreceptors for central mechanisms of regulation? 

Stimulated by increased H+ in cerebrospinal fluid. Increased rate and depth of breathing and remove excess CO2 from body. 

Peripheral chemoreceptors for peripheral mechanisms of regulation?

In aortic bodies, carotid bodies. Sensitive to blood PO2, PCO2, and H+

Mechanoreceptors for peripheral mechanisms of regulation?

In pleurae, bronchioles, alveoli. Excessive stretch leads to reduced depth of breathing. Hering-Breuer reflex.

What are other mechanisms of regulation? 

Exercising Limbs. Neural feedback from working limbs contributes to the fast initiation of the drive to breathe at the beginning of exercise. Proportional to the frequency of limb movement. 

Exercise training and respiratory function for healthy individuals?

Aerobic training has little influence on the respiratory system. Land exercising vs. swimming. Decrease in resting breathing frequency. Increased tidal volume. Increased Maximal Ve. Ex: horse vs. humans.

Exercise training and respiratory function for compromised function?

Aging, asthma, and pneumonia.

Aging for compromised function? 

Impaired recruiment and distension of pulmonary capillaries during exercise. Not limited in highly fit older adults. 

Asthma for compromised function?

Habitual aerobic exercise is beneficial.

Pneumonia for compromised function?

Habitual aerobic exercise is beneficial. Greater exercise energy expenditure is associated with lower disease risk.

What is pulmonary diffusion? 

How blood gases (oxygen and carbon dioxide) are transported in and out of the lungs.

Gas exchange between alveoli and cappilaries?

Blood path: RV - pulmonary trunk - pulmonary arteries - pulmonary capillaries. Alveoli are surrounded by capillaries.

Blood flow to the lungs at rest for pulmonary diffusion?

at rest: ~4 to 6 L blood/min. RV cardiac output = LV cardiac output. Lung blood flow = systemic blood flow.

Low pressure circulation for blood flow to the lungs at rest? 

lung MAP (mean arterial pressure) = 15 mmHg vs. aortic MAP = 95 mmHg. Resistance much lower due to thinner vessel walls. 

What is the respiratory membrane in pulmonary diffusion?

Also called alveolar-capillary membrane. Surface across which gases are exchanged. Large surface area: 300 million alveoli. Very thin: 0.5 to 4 um. Maximization of gas exchange.

Speed of exchange in pulmonary diffusion depends on?

Available surface area, thickness of respiratory membranes, partial (P) gradient, and diffusion constant of gas.

What is available surface area? 

aka more alveoli interacting with more capillaries

What is thickness of respiratory membranes?

thinner = quicker, thicker = slower

What is partial pressure (P) gradient?

increased difference between amount of oxygen in alveoli vs. capillary will increase speed of transfer.

What is diffusion constant of gas? 

carbon dioxide diffuses much easier than oxygen and therefore can move across membrane very quickly with relatively small pressure gradient. 

Why is partial (P) gradient important?

Most important factor for determining gas exchange. Partial P gradient drives gas diffusion. Without gradient, gases are in equilibrium-no diffusion.

Partial pressure (P) gradients in oxygen exchange for gas exchange in the alveoli?

Atmospheric PO2 = 159 mmHG. Alveolar PO2 - 105 mmHg. pulmonary artery PO2 = 40 mmHg.

PO2 gradient across respiratory membrane for oxygen exchange for gas exchange in the alveoli? 

65 mmHg (105 mmHg - 40mmHg). Result: pulmonary vein PO2 ~ 100 mmHg. 

Maximal exercise increase for oxygen exchange for gas exchange in the alveoli?

maximal exercise increases O2 diffusion capacity. Venous O2 decrease leads to PO2 bigger gradient. Diffusion capacity increase by three times resting rate.

How does max exercise impact the other factors that modify gas exchange?

available surface area

Gas exchange in the alveoli for oxygen exchange at rest?

O2 diffusion capacity limited, incomplete lung perfusion. Only bottom 1/3 of lung perfused with blood. Top 2/3 lung surface area has poor gas exchange.

Gas exchange in the Alveoli for oxygen exchange during exercise?

O2 diffusion capacity is increased, more even lung perfusion. Systematic blood pressure increase opens the top 2/3 perfusion. Gas exchange over full lung surface area. Lungs fill from the “bottom up” relative to gravity. 

Gas exchange in the alveoli, carbon dioxide exchange?

Pulmonary artery PCO2 ~46 mmHg. Alveolar PCO2~40 mmHg. Diffusion permitted by 6mmHg PCO2 gradient. (CO2 diffusion constant 20 times greater than O2. Diffusion allowed despite lower gradient)

• dependent of the diffusion constant of gas.

What is oxygen cascade?

Step by step dropping of partial pressures of oxygen as it works its way from the air (atmospheric partial pressure )2) to alveoli to cappilaries to exercising tissues and mitochondria.

What is disruption for oxygen cascade? 

Disruption of gradient at ANY of these steps can lead to loss of oxygen (hypoxia) and severe illness or death 

What is hemoglobin saturation?

> 98% oxygen is bound to hemoglobin (Hb) in red blood cells as oxygen is carried from lungs to working tissues.

What is high hemoglobin saturation?

High PO2 (in lungs). Small change in Hb saturation/mmHg with relatively large change in PO2. Results in almost complete Hb saturation.

What is low hemoglobin saturation? 

Low PO2 (in body tissues). Large change in Hb saturation/mmHg change in PO2 

What is the loading portion for hemoglobin and oxygen saturation?

sticky part of hemoglobin. The saturation stays high even with large changes in PO2

What does PO2 stand for?

The partial pressure of oxygen in a gas phase in equilibrium with the blood.

What is the unloading portion for hemoglobin and oxygen saturation? 

Saturation changes quickly with even small changes in PO2, allowing oxygen unloading to tissues.

What are the factors affecting hemoglobin saturation?

blood pH, blood temperature, and carbon monoxide poisoning

How does blood pH affect hemoglobin saturation?

More acidic leads to a O2-Hb curve shifted to right. More O2 unloaded at acidic exercising muscle.

How does blood temperature affect hemoglobin saturation? 

warmer leads to a O2-Hb curve shifted right. More tissue O2 unloading during exercise. 

How does carbon monoxide poisoning affect hemoglobin saturation?

creates excessively high strength of bonding between Hb and O2. No oxygen is able to be released to tissues due to strength of affinity —> suffocation.

What is the max amount of O2 blood can carry?

Based on Hb content (12-18 g Hb/100 mL blood). Hb 98% to 99% saturated at rest (0.75 s transit time). Lower saturation with exercise (shorter transit time).

What is blood oxygen-carrying capacity dependent on? 

1 g Hb binds 1.34 mL O2. Blood capacity is 16 to 24 mL )/100 mL blood. Anemia leads to decreased Hb content which leads to decreased O2 capacity

What is blood doping?

the misuse of certain techniques or substances to increase the number of circulating red blood cells and hemoglobin mass in the bloodstream. This illicit practice enhances athletic performance, particularly in endurance sports, by allowing the body to transport more oxygen to working muscles, thereby improving stamina, speed, and recovery.

What are blood transfusions for blood doping?

this involves withdrawing, storing, and later re-infusing red blood cells.

What are erythropoietin (EPO) or other Erythropoiesis-stimulating agents (ESAs) injections for blood doping? 

EPO is a hormone naturally produced by the kidneys that stimulates red blood cell production. Synthetic EPO can be injected to artificially increase the red blood cell count beyond normal levels. 

What is the primary danger of blood doping?

is that increasing the red blood cell count thickens the blood, making it harder for the heart to pump. This can lead to serious and potentially fatal health consequences.

What is altitude training?

increases RBC production by exposing the body to lower oxygen levels, which stimulates the release of EPO, a hormone that prompts the bone marrow to create more RBC’s. This adaptation enhances oxygen transport to muscles, improving endurance and performance upon returning to sea level.

What is carbon dioxide transport? 

released as water from cells. Carried in blood in three ways. 

What are the three ways carbon dioxide is carried in the blood?

As bicarbonate ions (60-70%). Dissolved in plasma (7-10%). Bound to Hb (carbaminohemoglobin) (20-33%) - does not compete with )2-Hb binding. Deoxyhemoglobin binds CO2 more easily than oxyhemoglobin does.

What is gas exchange at the muscles: arterial-venous oxygen difference?

difference in concentration of oxygen in venous vs. arterial blood. Reflects O2 extraction from tissues.

What is oxygen transport in muscle by myoglobin? 

O2 transported within muscle by myoglobin. Similar structure to hemoglobin. Higher afinity for O2. 

What is oxygen transport in muscle O2-myoglobin?

O2-myoglobin dissociated curve shaped differently. At PO2 0 to 20 mmHg: slope very steep. Loading portion at PO2 = 20 mmHg. Releasing portion at PO2 = 1 to 2 mmHg.

What are the factors influencing oxygen delivery and uptake?

O2 content of blood, blood flow, and local conditions (pH, temperature)

What is O2 content of blood for oxygen delivery and uptake? 

represented by PO2, Hb percent saturation. Creates arterial PO2 gradient for tissue exchange. 

What is blood flow for oxygen delivery and uptake?

decreased blood flow = decreased opportunity to deliver O2 to tissue. Exercise increases blood flow to muscle.

What are local conditions for oxygen delivery and uptake? 

pH and temperature. Shift O2-Hb dissociation curve. Decreased pH, increased temp promote unloading in tissue (shift curve to the right)

What is carbon dioxide removal for gas exchange at muscles?

CO2 exits cells by simple diffusion. Exit is driven by PCO2 gradient.

• tissue (muscle) PCO2 high, blood PCO2 low