NPB101 lectures 38-41

What is the general function of respiration?

Obtain O2 for use by the body’s cells and to eliminate CO2 the body cells produce

What does respiraiton encompass?

External repsitation and internal (cellular) respiration

Why do we have 2 passages to breathe?

IN case one does not work or we cannot breathe through one

What encompasses the repsiratory system?

The airways leading to the lungs, lungs, and the structures of the thorax involved in producing movement of air though the airways into and out of the lungs

What are the respiratory airways?

Trachea and larger bronchi

Describe the trachea and bronchi.

Fairly rigid, non-muscular tubes composed of rings of cartilage to prevent collapse

Why is there smooth muscle surrounding the bronchi?

TO constrict and relax the airways

(T/F) The bronchioles contain cartilage to hold them open.

False, their walls contain smooth muscle innervated by autonomic nervous system

What does the autonomic nervous system do to the bronchiole’s walls.

Parasympathetic stim. constricts while sympathetic (weakly) relaxes

What do they type 2 alveolar cells produce?

Pulmonary surfactant that keeps the cell open

Why is the alveolus so much larger than the erythrocyte?

TO have efficient exchange of O2 and CO2

What are the alveoli?

Thin-walled inflatable sacs that function in gas exchange

What do the walls of the alveoli contian?

Single layer of flattened Type I alveolar cells

What do Type II alveolar cells secrete?

Pulmonary surfactant

What do alveolar macrophages do?

Guard the lumen

(T/F) pulmonary capillaries encircle each alveolus and they are all interconnected.

True

What does the surfactant produced by type II alveolar cells do?

Disrupts hydrogen bonding of water lining the alveolar wall and decreases siurface tension

Why is water dangerous in the alveolar wall?

Can cause collapse of the alveola

Why do the Type II alveolar cells need to decrease surface tension?

So large groups of small bubbles don’t collapse into a smaller number of larger ones

What induces the surfactant secreted by type II alveolar cells at birth?

Cortisol, just prior to birth

What do premature babies need to ensure they have proper lung function?

Synthetic glucocorticoid

What are the lungs suspended in?

A pleural sac that surrounds it

What is the pleural sac?

A double-walled, closed sac that separates each lung from the thoracic wall

What is the pleural cavity?

Interior of the pleural sac

What is the lubricant that is secreted by the surfaces of the pleura?

Intrapleural fluid

What is the purpose of the Intrapleural fluid?

To reduce friction from the lungs

What are the 3 important pressures for ventilation?

Atmospheric, intra-alveolar, and intrapleural pressure

What is atmospheric pressure (commonly)?

760 mm Hg

What is the intra-alveolar pressure?

760 mm Hg

What is the intrapleural pressure?

756 mm Hg

What produces the flow of air into and out of the lung?

Changes in intra-alveolar pressure

If intra-alveolar pressure is less than atmospheric, then air….

enters the lungs

If intra-alveolar pressure is greater than atmospheric pressure…

Air leaves the lungs

What pressure NEEDS to drop for air to enter?

intra-alveolar pressure

What NEEDS to increase for air to leave the lungs?

intra-alveolar pressure

What muscle help in bretahing?

Diaphragm and external intercostal muscle

(T/F) Lungs have elastic recoil

True

What other muscle is recruited when we are actively forcing air and in out of our lungs?

Abdominal muscles

Why do lungs have elastic recoil?

1. Highly elastic connective tissue in the lungs

2. Alveolar surface tension

What is tidal volume?

The average volume taken in when relaxed (~500mL)

What is the inspiratory reserve volume?

Air we can take in when needed (~3000mL)

What is the inspiratory capacity?

The max amount of air a person can take in (~3500mL)

What is residual volume?

The amount of air present in the lungs even after the max amount of air is forced out, present to prevent collapse (~1200mL)

What is the expiratory reserve volume?

The max amount of air a person can force out of their lungs (~1000mL)

What is the pulmonary ventilation (mL/min)?

The tidal volume (mL/breath) * respiratory rate (breath/min)

What is dead space?

The amount of “old” air that is in our lungs that has exchanges O2 and CO2

(T/F) Everyone has the same Tidal volume.

False, it changes from person to person, with larger lungs having more space

What is the: tidal volume, respiratory rate, dead space, pulmonary ventilation, and alveolar ventilation in Quiet breathing at rest?

TV: 500

RR: 12

Dead space: 150

Pulmonary ventilation: 6000

Alveolar ventilation: 4200

What is the: tidal volume, respiratory rate, dead space, pulmonary ventilation, and alveolar ventilation in Deep, slow breathing?

TV: 1200

RR: 5

Dead space: 150

Pulmonary ventilation: 6000

Alveolar ventilation: 5250

What is the: tidal volume, respiratory rate, dead space, pulmonary ventilation, and alveolar ventilation in Shallow, rapid breathing?

TV: 150

RR: 40

Dead space: 150

Pulmonary ventilation: 6000

Alveolar ventilation: 0

(T/F) Large blood flow helps balance small airflow, and vice versa.

True

What happens when there is small airflow and large blood flow?

1. Increase CO2, decrease O2

2. Relaxation of local airway smooth muscle, increase in constriction of pulmonary arteriolar smooth muscle

3. Dilation of local airways, constriction of blood vessels

4. Decrease airway resistance, increase vascular resistance

5. Increase airflow, decrease blood flow

What happens when there is large airflow and small blood flow?

1. decrease CO2, increase O2

2. Contraction of local airway smooth muscle, relaxation of pulmonary arteriolar smooth muscle

3. constriction of local airways, dilation of blood vessels

4. increase airway resistance, decrease vascular resistance

5. decrease airflow, increase blood flow

Why is the the diffusion constant of CO2 so high compared to O2?

Helps to offset the small partial pressure of CO2

(T/F) At pulmonary and tissue capillary levels, gas exchange involves simple diffusion.

True

What does the partial pressure exerted by each gas in a mixture equal to?

Total pressure * fractional composition of gas in mixture

Why is alveolar air composition different than atmospheric air?

1. Increased water vapor as air travels thru respiratory system

2. Dead space and residual volume not all air in alveoli is fresh, higher CO2 and lower O2\

3. O2 always being absorbed out and CO2 always being discharged in

How do O2 and CO2 exchange across the pulmonary and system capillaries?

Partial pressure gradients

How is most oxygen transported?

Bound to hemoglobin in erythrocytes (RBCs)

What is main factor determining the % of hemoglobin saturation?

Partial pressure of O2

The percent saturation (of heme) is high where the pO2 is _____. and vice versa.

high

The percent saturation(of heme) is _____ where pO2 is high and vice versa.

high

Where is the pO2 high?

lungs

Where is the pO2 low?

tissues

What does O2 do at the tissue cells?

Dissociate from hemeoglobin

When O2 binds to hemoglobin, the affinity for O2 goes (up/down).

up

Why does the steep part of the Oxygen-hemoglobin dissociation curve exist?

This is where hemoglobin unloads O2 to the tissue cells

What does the Bohr effect mean?

Increased CO2 and H+ at the tissue level shifts the dissociation curve (i.e. O2 is unloaded more readily at the same pO2)

WHat is the Haldane effect?

Reduced O2 in the tissues facilitates the loading of Hb with CO2 and H+ while increase O2 in the lungs promotes the dissociation of CO2 form Hb

What is the Chloride shift?

The inward shift of Cl- in exchange to the efflux of HCO3- from RBCs

What is primary form CO2 is moved as?

HCO3-

What does carbonic anhydrase do?

Facilitates the reaction of CO2 and H2O into HCO3- and H+, dependent on concentration

(T/F) In sickle cell anemia, only a single point mutation in the b-chain causes a defective Hb.

True

How does sickle cell anemia affect gas exchange?

Reduces it

What is the problem with hypoventilation?

Underventilation, increasing pCO2 and respiratory acidosis (increase pH)

What is the problem with hyperventilation?

INcreased pulmonary ventilation, decreased pCO2 and respiratory alkalosis

What are the nueral networks that control rhythmic firing of motor neurons to diaphragm?

1. Medullary respiratory centers

   1. Dorsal respiratory group (DRG)

   2. Ventral respiratory group (VRG)

2. Pons respiratory centers

   1. Modulate activity of medullary centers to promote smooth breathing rhythms

What is the dorsal respiratory group?

Inspiratory neurons that are active in normal, quiet breathing

What is the ventral respiratory group?

Inspiratory and expiratory neurons that are activated on demand (exercise)

What is the pro-botzinger complex?

A region rostral from the VRG where respiratory rhythm is generated

What is the Hering Breuer reflex?

Stretch receptors in smooth muscles of the bronchioles that prevents the over-inflation of the lungs

As CO2 increases, ventilation ______.

increases

As O2 increases, ventilation _______.

Decreases

(T/F) Low pH is initially beneficial, but can become dangerous.

True

Where are the carotid bodies located?

Carotid sinus

Where are the aortic bodies located?

Aortic arch

The carotid bodies and aortic bodies are ____-receptors.

Chemo

WHat happens if there is low pO2 in arterial blood (peripheral)?

Stimulates the carotid and aortic bodies when it has fallen to the point of being LIFE-THREATENING.

What happens if there is an increase in pCO2 in arterial blood (peripheral)?

Weakly stimulates carotid and aortic bodies.

What happens if there is an increase in the H+ in arterial blood (peripheral)?

Stimulates the carotid and aortic bodies, important in acid-base balance.

Why is hemoglobin always partially saturated?

High altitude and suffocation response

Explain what happens when there is a decrease in inspired pO2.

leads to: decrease in alveolar pO2, which leads to decreased arterial pO2, which increases the peripheral chemoreceptors firing, which increases contraction of respiratory muscles, which increases ventilation which returns the alveolar and arterial pO2 towards normal.

What are the peripheral chemoreceptors?

Carotid and aortic bodies

In the central chemoreceptors, what happens when there is a decrease in pO2 in arterial blood?

Directly depresses the central chemoreceptors and the respiratory center itself when lower than 60mmHg

In the central chemoreceptors, what happens when there is an increase in pCO2 in the arterial blood and increase in brain H+?

STRONGLY stimulates, dominant control of ventilation

In the central chemoreceptors, what happens when there is an increase in H+ in arterial blood?

Nothing, it cannot pass the blood-brain barrier

(T/F) There is NO H+ in the brain.

False, while arterial H+ cannot pass the blood-brain barrier, H+ can be present in the brain ECF if it is brain derived (i.e. from CO2 forming HCO3- and H+).

Why do the central chemoreceptors weakly stimulate the peripheral chemoreceptors?

Keeps the medullary respiratory center in check so it does NOT hypoventilate

Why is CO dangerous?

CO binds to hemoglobin irreversibly and with much more affinity

(T/F) The diaphragm is the main muscle we use during quiet (resting) inspiration.

True