Pulmonary/Respiratory pt.2

Question 1

lungs are composed of __________

Answer 1

elastic and inelastic properties

Question 2

how do the elastic components of the lungs play a role in its function

Answer 2

the stretch(inspiration) and recoil(expiration) of these components play a role in lung compliance

Question 3

explain the significance of the surface tension of water in the fluid lining the alveoli

Answer 3

the surface tension of water in the fluid lining the alveoli plays a major role in lung compliance with the strong attraction of water molecules to each other tending to pull alveoli shut

Question 4

surfactant

Answer 4

a compound which aids in the prevention of lung collapse as a result of water tension

• > composed of the phospholipid dipalmitoylphosphatidylcholine (DPPC)
• > surfactant prevents the total colapse of lungs by decreasing the surface tension of water

Question 5

pressures within the lung are ALWAYS compared to __________

Answer 5

atmospheric pressure (P_atm)

= 760 mmHg

• > calculated as ΔP

Question 6

intrapulmonary pressure

Answer 6

P_pul

P_pul at rest = atmospheric pressure so ΔP = 0 mmHg

• > however, P_pul varies during respiration such that P_pul is less than P_atm during inspiration and greater than P_atm during expiration

Question 7

describe the pressures inside the alveoli as lung volumes increases and decreases

Answer 7

as lung volume increases (alveoli open/stretch), pressures within the alveoli decrease

as lung volume decreases (alveoli recoil), pressures within the alveoli increase

Question 8

transpulmonary pressure; what happens when this increases

Answer 8

measure of distending force across the lungs

• > an increase in Transpulmonary P = greater distending P across the lungs and the alveoli expand

Question 9

intrapleural pressure at rest

Answer 9

P_ip

at rest = -4 mmHg

P_ip does vary during respiration but is always negative during normal breathing; postive reading can indicate a collapsed lung

Question 10

describe lung volume during inspiration and what happening as it occurs

Answer 10

• > increased V occurs duing inspiration
• > elevation of ribs by the external intercostals = increasing anterior-posterior diameter of the chest
• > downward movement of the diaphragm (contraction) = lengthening of the chest cavity

Question 11

describe pressure within the lungs during inspiration

Answer 11

• > as lung volumes increase, pressure within the lungs (P_pul) decreases and is now less than P_atm by -1 mmHg
• > this creates a “vacuum” effect due to a pressure gradient (higher pressures outside the lungs than inside)
• > therefore, air moves from an area of high pressure (outside) to and area of low pressure (inside) filling the lungs with air until the outside P = inside P

Question 12

describe lung volume during expiration

Answer 12

a decrease in V occurs during expiration

• > relaxation of external intercostals + upward movement of the diaphragm + elasetic recoil properties of the lungs decreases lung volume snd thorasic cage volume

* relaxation of the respiratory muscles stop the physical pull on the alveoli, causing the walls of the alveoli to recoild and “close” the alveoli

Question 13

describe pressure during expiration

Answer 13

as lung volumes decrease, pressure within the lungs increases (increased Ppul) and is now greater than Patm by +1 mmHg

• > pressure gradient is now from inside to outside and air flows from inside the lungs to outside the lungs until the pressure within the lungs = atmospheric pressure

Question 14

what is Daltons law

Answer 14

each gas contributes to total atmospheric pressure in direct proportion to its relative concentration

• > therefore in a mixture of gases, the pressure exerted by each gas is independent of the pressure exerted by others

Question 15

explain the ambient conc. of O2 and PAO2 and PaO2

Answer 15

the O₂ we breath in only makes up 21% of total atmospheric pressure, and 21% of 760 mmHg = 160 mmHg (ambient air concentration of O₂)

• > but inside the alveolus, changes occur such that the partial pressure (PAO2) of O2 decreases to around 104 mmHg

- > arterial partial pressure (PaO2) of oxygen is usually around 100 mmHg while tissue PO2 can be as low as 40 mmHg in the resting state

Question 16

changes to the partial pressure of O₂ within the alveolus can be caused by what

Answer 16

1. temperature
2. humidity
3. CO₂ mixing with incoming air

Question 17

ventilation

Answer 17

= frequency (RR) x depth of breathing

• > around 10-20 breaths/min

RR = respiratory rate

Question 18

total ventilation (at rest)

Answer 18

V_T

= amount inspired/breath x RR

= tidal volume (TV) x RR

TV = 6000 cc/min

Question 19

dead space ventilation

Answer 19

V_D

amount of each TV that remains in the non-gas-exchanging portions of the airways

dead space minute ventilation = 150 cc/breath x 12 breaths/min

• > = 1800 cc/min (amount of each ventilatory intake that is lost in the non gas exchaning portions of the lungs)

Question 20

Alveolar Ventilation

Answer 20

V_A = V_T - V_D

• > provides the 104 mmHg of P_O2 for the alveoli and the 100 mmHg of P_O2 for the arteries

= 6000cc/min - 1800cc/min = 2400cc/min

Question 21

normal at rest value of V_A, V_T, V_D and the ratio of dead space minute ventilation to total ventilation

Answer 21

total ventilation/min = 6000cc

dead space ventilation/min = 1800cc

alveolar ventilation/min = 4200cc

dead space minute ventilation to total ventilation = 1800/6000 = 0.3

Question 22

IRV vs ERV

Answer 22

Inspiratory reserve volume

• > the max volume of air that can be increased above tidal volume

Expiratory reserve volume

• > the expiration of a volume of air after resting tidal volume has been expired

Question 23

what is RV and why is it useful

Answer 23

residual volume

• > volume of air remaining in the lugs after maximal expiration
• > helps hold alveoli open and prevent lung colapse
• > an increased RV can indicate loss of elastic tissue which leads to decreased recoil of the lungs

Question 24

FVC

Answer 24

forced vital capacity

• > maximal volume of air a person can expire after maximal inspiration
• > IRV + TV+ ERV

Question 25

FEV₁

Answer 25

forced expiratory volume in 1 second - \> maximal volume of air that can be exhaled in 1 sec following maximal inspiration

Question 26

FER

Answer 26

**forced expiratory ratio = FEV₁ /FVC** - \> healthy individuals with good lung function can expire around 80% of their vital capacity in 1 sec - \> the FEV₁ /FVE ratio is used to help determine the level of functional loss in an individual

Question 27

Medullary respiratory centre

Answer 27

controls both inspiration and expiration and contains the **dorsal respiratory group (DRG)** neurons and the **ventral respiratory group (VRG)** neurons

Question 28

respiration

Answer 28

respiration = reflex activity

Question 29

describe the DRG neurons during resting/quiet breathing

Answer 29

- \> neurons of the DRG appear to integrate information from the peripheral stretch receptors and chemoreceptors and communicates that information to the VRG

Question 30

describe the VRG during resting/quiet breathing

Answer 30

- \> the VRG contains inspiratory neurons that excite the diaphragm and external intercostals resulting in the V and P chnages for inspiration to occur - \> within the VRG is a rhythm generator composed of pacemaker cells that set basal/quiet breathing rates

Question 31

what happens during resting/quiet breathing once inspiratory muscle contration and inspiration have occured

Answer 31

signals to the spinal motor neurons cease and the external intercostals and diaphragm relax = passive expiration

Question 32

eupnea

Answer 32

normal, unlaboured breathing - \> around 2 seconds in inspiration and around 3 seconds in expiration (12-15 breaths/min)

Question 33

describe active/increased ventilation

Answer 33

- \> with increased ventilation, the VRG expiratory neurons send signals to the expiratory muscles (internal intercostals, external abdominal obliques and the rectus abdominus) resulting in contraction of these muscles and increased release of air from the lungs - \> the inspiratory and expiratory muscles in active breathin are activated alternately

Question 34

explains the pons control of the medullary inspiratory neurons

Answer 34

- \> the pontine respiratory centres found within the pons, modify the activity of the medula - \> impulses from the pontine centres to the VRG influences the transition between inspiration and expiration \* some ventilation is under voluntary control (i.e. coughing, singing) and controled by the centres in the thalamus and cerebral cortex (brain) of the CNS which sends input to the pontine respiratory centres

Question 35

which processes set/determine respiration rhythm

Answer 35

it's set by several processes 1. specialized inspiratory neurons that act as pacemaker neurons - \> although such neurons have be found, loss of these pacemakers doesn't stop respiration 2. reciprocal inhibition of the interconnected neuronal networks in the medula - \> most likely there are 2 sets of pacemaker neurons that inhibit each other and cycle that inhibition to set te rhythm

Question 36

how is inspiration depth alterned

Answer 36

inspiration depth is altered by how actively (frequency of stimulus) the respiratory centre stimulates the motor neurons serving the respiratory muscles - \> increased depth of each breath gives you increased ventilation

Question 37

what is RR

Answer 37

rate of respiration - \> how long the inspiratory centre is active or how quickly it is switched off/ moves to expiration

Question 38

different ways RR can be suppressed and what happens when it is completely suppressed

Answer 38

suppression of the inspiratory centre can occur with... - \> sleeping pills, morphine, alcohol, polio complete suppression of inspiration results in **cessation of breathing (apnea)**

Question 39

respiratory centres require input from which receptors to monitor blood chemistry

Answer 39

1. Central chemoreceptors 2. peripheral chemoreceptors 3. pulmonary receptors

Question 40

what are central chemoreceptors and how do they react to change

Answer 40

- \> respond to changes (CO₂ levels) in brain extracellulaar fluid (ECF) - \> **stimulated by an increase in blood CO2 above the normal 40mmHg** via increased blood H⁺ levels - \> the increased free H+ = decreased blood pH which **stimulates the central chemoreceptors to send information to the respiratory regulatory centres** - \> this **stimulation results in increased ventilation** (increased depth and rate) which will result in **increased release of CO₂** from the body (causes decreased [H⁺])

Question 41

what are peripheral chemoreceptors and how do they react to change

Answer 41

- \> peripheral chemoreceptors help maintain ventilation when the central chemoreceptors (brain centres) have become hypoxic and unable to function **carotid body chemoreceptor** - \> monitor arterial PO₂ (normal PO2 of arteria blood is 100mmHg) and a decrease of PO2 below 60mmHg will trigger increased ventilation **aortic body chemoreceptors** - \> monitor the O2 rich blood released from the LV

Question 42

hypercapnia

Answer 42

increased blood CO₂ levels

Question 43

major terms we should know (respiratory)

Answer 43

Question 44

pulmonary receptors

Answer 44

- \> receptors in the lungs that respond to a variety of irritating factors (i.e. smoke, pollutants, excess mucus) - \> these communicate with the respiratory centres - **inititate coughing**

Question 45

Cheyne - Strokes Breathing

Answer 45

periodic breathing with rise and fall patterns separated by periods of apnea = result of impaired central feedback mechanisms (need to accumulate large accumulate large arterial concentrations of CO2 to trigger expiration)