Good Copy Week 11

What are the two primary systems that cooperate to load O2 and offload CO2

The respiratory and cardiovascular systems.

Besides gas exchange, what is a primary homeostatic function of the respiratory system performed in cooperation with the kidneys?

Regulation of H+(pH) concentration.

The process of forming speech sounds is known as _____.

Phonation

How does the respiratory system protect against systemic blood clots?

It traps and dissolves blood clots arising from systemic veins.

Definition: Respiratory Cycle

The combination of one inspiration (inhalation) and one expiration (exhalation).

Approximately how much fresh air enters and leaves the alveoli per minute at rest?

4 L

What are the two functional zones the airways are divided into below the larynx?

The conducting zone and the respiratory zone.

Which specific structure in the conducting zone is surrounded by smooth muscle to regulate airflow?

Bronchioles

What is the principal functional component of the respiratory system where gas exchange occurs?

Alveoli

Approximately how many alveoli are found in a typical adult human?

300 million

The total surface area of the human alveoli is approximately equal to the size of a _____.

Tennis court (75 $m^{2}$)

What is the approximate distance separating the air in the alveoli from the blood in the capillaries?

0.2 um

Which blood vessels deliver deoxygenated blood from the right ventricle to the alveoli?

Pulmonary arteries

Which blood vessels deliver oxygenated blood from the alveoli to the left atrium?

Pulmonary veins

What is the primary function of Type II alveolar cells?

To produce surfactant, which prevents alveolar collapse.

Which type of alveolar cells form the single-cell thick layer of the alveolar wall?

Type I alveolar cells

The lungs are located in the _____ and each is surrounded by a pleural sac.

Thorax (chest)

Concept: External Respiration

The exchange of $O_{2}$ and $CO_{2}$ between an organism and its environment.

Concept: Internal (Cellular) Respiration

The utilization of $O_{2}$ in the metabolism of organic molecules by cells.

Formula: Ohm's Law for Air Flow

Air Flow = Delta Pressure / Resistance

Inspiration occurs when alveolar pressure is _____ than atmospheric pressure.

Lower (less)

Expiration occurs when alveolar pressure is _____ than atmospheric pressure.

Higher (greater)

Concept: Boyle's Law

The inverse relationship between the pressure exerted by a gas and the volume of its container.

According to Boyle's Law, an increase in lung volume leads to a(n) _____ in gas pressure.

Decrease

Concept: Transpulmonary Pressure ($P_{tp}$)

The difference in pressure between the inside of the alveoli ($P_{alv}$) and the intrapleural space ($P_{ip}$).

Formula: Transpulmonary Pressure

P tp = P alv - P ip

• inside minus outside

Why is transpulmonary pressure always a positive value under normal conditions?

Because the intrapleural pressure ($P_{ip}$) is negative (a vacuum).

What are the two factors that create the negative pressure (vacuum) in the intrapleural space?

The lungs' tendency to recoil inward and the chest wall's tendency to expand outward.

Which nerve innervates the diaphragm?

The phrenic nerve.

During inspiration, which way does the diaphragm move upon contraction?

Downward into the abdomen.

Inspiration sequence: Increased thoracic volume leads to _____ intrapleural pressure.

Decreased (more negative)

How does a decrease in intrapleural pressure during inspiration affect transpulmonary pressure?

It increases transpulmonary pressure, creating a greater outward driving force on the lungs.

During normal resting expiration, what causes the chest wall and diaphragm to recoil?

Relaxation of the diaphragm and external intercostal muscles.

Definition: Tidal Volume ($TV$)

The volume of air inspired and expired during a single resting respiratory cycle (~500 mL).

Definition: Inspiratory Reserve Volume ($IRV$)

The additional volume of air that can be inspired after a normal inspiration (~3,000 mL).

Definition: Expiratory Reserve Volume ($ERV$)

The additional volume of air that can be expired after a normal expiration (~1,000 mL).

Definition: Residual Volume ($RV$)

The volume of air remaining in the lungs even after maximal expiration (~1,200 mL).

What is the approximate total lung capacity in a healthy adult?

5,700 mL

Formula: Minute Ventilation (total ventilation per min)

Pulmonary Ventilation (mL/min) = tidal volume (mL) x respiratory rate aka breaths/minute

At rest, what is the typical minute ventilation ($V_{E}$) calculation?

6,000 mL/min (500 mL $\times$ 12 breaths/min).

Concept: Anatomical Dead Space

The volume of inspired air that remains in the conducting airways and does not participate in gas exchange (~150 mL).

Formula: Alveolar Ventilation ($Alveolar\ V_{E}$)

Alveolar Ventilation = (tidal vol - dead space) x resp. rate

Why does increasing tidal volume have a greater effect on alveolar ventilation than increasing respiratory rate?

Because anatomical dead space is a fixed volume, so larger tidal volumes increase the proportion of air reaching the alveoli.

In the lungs, $O_{2}$ diffuses from the _____ to the pulmonary capillaries.

Alveoli

At the systemic tissues, $CO_{2}$ diffuses from the _____ to the capillaries.

Cells (tissues)

Concept: Dalton's Law

The total pressure of a gas mixture is the sum of the individual partial pressures of each gas.

Formula: Partial Pressure of a Gas

Partial pressure of a gas = % concentration X total pressure of gas mixture

What is the standard barometric pressure at sea level?

760 mmHg

Calculate the partial pressure of Oxygen ($P_{O2}$) in the atmosphere at sea level (21% $O_{2}$).

160 mmHg

Concept: Henry's Law

The amount of gas dissolved in a liquid is proportional to the partial pressure of that gas in the surrounding environment.

What is the partial pressure of Oxygen ($P_{O2}$) in the alveoli at rest?

105 mmHg

Why is alveolar $P_{O2}$ (105 mmHg) lower than atmospheric $P_{O2}$ (160 mmHg)?

Because oxygen constantly leaves the alveoli to enter the pulmonary capillaries.

What is the partial pressure of Carbon Dioxide ($P_{CO2}$) in the alveoli at rest?

40 mmHg

What is the $P_{O2}$ of deoxygenated blood entering the pulmonary capillaries?

40 mmHg

What is the $P_{CO2}$ of deoxygenated blood entering the pulmonary capillaries?

46 mmHg

Net diffusion of a gas always occurs from a region of _____ partial pressure to a region of _____ partial pressure.

High; Low

When does the diffusion of $O_{2}$ and $CO_{2}$ between the capillaries and alveoli stop?

When the partial pressures in the blood and alveoli reach equilibrium (become approximately equal).

What is the typical $P_{O2}$ within systemic tissue cells?

$<$ 40 mmHg

Which two forms is oxygen transported in the blood? (Name the % for each)

Dissolved in plasma (1.5%) and bound to hemoglobin (98.5%).

How many oxygen molecules can a single hemoglobin molecule bind?

Four

Which specific component within the hemoglobin subunit contains the iron atom that binds $O_{2}$?

The heme group.

What is the term for hemoglobin that is bound to oxygen?

Oxyhemoglobin

Definition: Hemoglobin Saturation

The ratio of $O_{2}$ bound to Hb divided by the maximal capacity of Hb to bind $O_{2}$, expressed as a percentage.

What is the primary factor that determines the percentage of hemoglobin saturation?

Blood PO2 (the partial pressure of oxygen in the blood)

Why is the flat portion of the oxygen-hemoglobin dissociation curve (70-100 mmHg) considered a safety backup?

It allows $P_{O2}$ to drop significantly with only a minimal decrease in hemoglobin saturation.

• The flat part is a safety backup because oxygen levels can fall without greatly affecting how much oxygen your blood carries

• Even if oxygen drops a bit, hemoglobin still holds onto most of it

The steep portion of the oxygen-hemoglobin dissociation curve ($<$ 60 mmHg) facilitates oxygen _____ in the tissues.

Offloading (unloading)

• In low-oxygen tissues, hemoglobin unloads a lot of oxygen quickly, so cells get what they need.

• As a little oxygen leaves hemoglobin, it triggers a lot more to be released

• Small drop in oxygen → big release from hemoglobin

• Like a steep hill:

  • A small push → things roll down fast and a lot

Does oxygen bound to hemoglobin contribute to the $P_{O2}$ of the blood?

No, only dissolved oxygen in the plasma contributes to $P_{O2}$.

How does hemoglobin maintain the diffusion gradient for $O_{2}$ at the lungs?

By binding dissolved oxygen, it keeps the plasma $P_{O2}$ lower than alveolar $P_{O2}$ until the Hb is fully saturated (until it can’t bind any more O2)

Which way does the oxygen-hemoglobin dissociation curve shift when blood temperature or acidity increases?

Rightwards

What is the physiological benefit of a rightward shift in the oxygen-hemoglobin dissociation curve during exercise?

It allows hemoglobin to release oxygen more easily to the working muscles.

What are the three fates of $CO_{2}$ produced by tissues? (Name % for each)

Dissolved in plasma (10%), bound to hemoglobin (25-30%), and converted to bicarbonate (60-65%).

Definition: Carbaminohemoglobin

Hemoglobin that is bound to carbon dioxide.

Which enzyme catalyzes the conversion of $CO_{2}$ and water into carbonic acid within red blood cells?

Carbonic anhydrase

In the systemic tissues, bicarbonate ($HCO_{3}^{-}$) is moved out of the erythrocyte and into the _____.

Plasma

How does deoxygenated hemoglobin help manage acidity in systemic capillaries?

It has a high affinity for $H^{+}$ and binds it, reducing the amount of free $H^{+}$ in the blood.

Where is the primary respiratory center that contains neurons controlling the motor neurons of respiratory muscles

The medulla (brainstem).

Which two locations house peripheral chemoreceptors?

The carotid sinuses (carotid bodies) and the aortic arch (aortic bodies).

Which specific chemical change do central chemoreceptors primarily detect?

$H^{+}$ ion concentration (pH) in the medulla.

Peripheral chemoreceptors detect changes in which three variables?

$P_{O2}$, $P_{CO2}$, and $H^{+}$ concentration.

At what arterial $P_{O2}$ threshold does ventilation begin to increase strongly?

$<$ 60 mmHg

Why do small increases in arterial $P_{CO2}$ lead to large increases in ventilation?

Because of the sensitive effect of $H^{+}$ (derived from $CO_{2}$) on both central and peripheral chemoreceptors.

When hemoglobin is at the lung where PO2 levels are rising, it…

Takes up a lot of oxygen

Higher PO2​​ = more oxygen around = hemoglobin fills up

When hemoglobin is at the tissue (e.g., muscle) where PO2 levels are falling, it…

Releases oxygen

• Hemoglobin releases oxygen where it’s needed most—in low PO2 areas like active muscles

Why does CO₂ move from tissues into the blood?

Because PCO₂ is higher in cells than in blood, so CO₂ diffuses into capillaries.

What is the main form CO₂ is transported in blood?

Bicarbonate (HCO₃⁻)

What happens to bicarbonate after it is formed in RBCs?

It leaves the RBC and dissolves in plasma

Why does CO₂ move from blood into the alveoli?

Because PCO₂ is higher in blood than in alveoli

What happens to CO₂ bound to hemoglobin in the lungs?

It unbinds from hemoglobin and diffuses into alveoli

What happens to bicarbonate in the lungs?

It combines with H⁺ → forms carbonic acid → becomes CO₂ + H₂O

What happens to H⁺ in systemic capillaries?

H⁺ is produced and binds to deoxygenated hemoglobin

• Hemoglobin binds H⁺ in tissues to control pH and help carry CO₂ back to the lungs and reduce free H+

Why does hemoglobin bind H⁺ in tissues?

To reduce free H⁺ and help maintain pH

What happens to H⁺ in the lungs?

Oxygen binding to Hb causes Hb to release H⁺

What happens after H⁺ is released in the lungs?

H⁺ + bicarbonate → carbonic acid → CO₂ + H₂O

What happens to the CO₂ formed in the lungs?

It diffuses into the alveoli and is exhaled

What is the relationship between oxygen binding and H⁺ release?

When O₂ binds to hemoglobin, H⁺ is released

What is the overall goal of CO₂ and H⁺ transport?

• Move CO₂ from tissues → lungs (to remove it, since it is waste and removing it also helps balance pH)

• Maintain blood pH balance

What happens to ventilation when arterial PO2 decreases?

Ventilation increases via arterial chemoreceptors.

How do arterial chemoreceptors increase breathing?

They stimulate medullary inspiratory neurons

What happens when arterial PCO2 increases?

Ventilation increases

• ↑ CO₂ → ↑ acidity → body detects it → ↑ breathing to remove CO₂ → pH returns to normal