Medical Physiology Block 5 Week 1

Question 1

Define diffusion. Is energy expended?

Answer 1

movement of molecules from regions of high concentration to low concentration (driving force is concentration gradient); No

Question 2

Define convection. What are the two convection systems of the human body?

Answer 2

bulk fluid movement that enhances diffusion by producing steeper gradients across the diffusion barrier; circulation and air pump (conducting airways)

Question 3

Why is surface area important for the respiratory system? which portion of the respiratory system contributes the most surface area?

Answer 3

surface area amplification enhances diffusion; alveolar air space

Question 4

What is the role of respiratory pigments? What is the pigment utilized in the human respiratory system?

Answer 4

increase the carrying capacity of the blood for oxygen and carbon dioxide; hemoglobin

Question 5

What describes external respiration? internal respiration?

Answer 5

tissue and organs used for breathing; mitochondrial respiration (including transporters and oxidizers)

Question 6

Describe the differences between the early conducting airways (bronchi) and late conducting airways (bronchioles). How many generations are considered conducting airways?

Answer 6

bronchi contain cartilage, cilia, mucus secreting glands, and submucosal glands (G0-10); bronchioles do not contain cartilage and as generation decreases the number of cilia, mucus secreting glands, and submucosal glands decreases (G11-G16)

Question 7

Describe how velocity and shape of the airways changes in subsequent bifurcations from G0-G16.

Answer 7

diameter (and radius) decrease; increase in aggregate surface area; decrease in velocity

Question 8

Describe alveolar airways.

Answer 8

Respiratory bronchioles, alveolar ducts, alveolar sacs; type I epithelial cell (thin; majority); type II epithelial cell (secretes and produces surfactant; following injury shows metaplastic growth)

Question 9

What are the non-respiratory roles of the respiratory system?

Answer 9

olfaction; humidifier (warms and moisturizes); macrophages attack foreign substances; filter small emboli; site of biochemical reactions

Question 10

Describe the different lung volumes. Which lung volume cannot be measured by a spirometer?

Answer 10

tidal volume is the volume inspired or expired with each normal breath; inspiratory reserve volume is the volume that can be inspired over and above the tidal volume; expiratory reserve volume is the volume that can be expired after the expiration of a tidal volume; residual volume is the volume that remains in the lungs after a maximal expiration; RESIDUAL VOLUME

Question 11

Describe the different lung capacities

Answer 11

inspiratory capacity is the sum of tidal volume and IRV; functional residual capacity is the volume remaining in the lungs after a tidal volume is expired (ERV + RV); forced vital capacity is is the volume of air that can be forcibly expired after a maximal inspiration (IR + ERV + TV); total lung capacity = TV + IRV + ERV + RV

Question 12

What is forced expiratory volume?

Answer 12

FEV1 is the volume of air that can be expired in the first second of a forced maximal
expiration (normally 80% of forced vital capacity)

Question 13

Describe negative pressure breathing.

Answer 13

thoracic volume increases due to the muscles of inspiration (diaphragm lowers elevating lower ribs, intercostals elevate ribs); expiration results from elastic recoil of the lung (no primary muscles)

Question 14

What are the accessory muscles for inspiration? expiration?

Answer 14

sternocleidomastoids (elevates sternum) and scalenes (elevate upper ribs); intercostals (pull ribs down) and abdominals (pull ribs down and raise diaphragm)

Question 15

Describe the compliance of the lung.

Answer 15

static property of the alveoli and decreases as lung volume increases

Question 16

What is the equation for work done during inspiration and expiration?

Answer 16

intrapleural pressure = - transpulmonary pressure + alveolar pressure; transpulmonary pressure is static and defines lung volume (compliance); alveolar pressure is dynamic and is positive during expiration (resistance)

Question 17

What is surface tension?

Answer 17

Net force pulls the surface molecules away from the air-water interface toward the bulk water phase also creates a tension parallel to the surface

Question 18

What are the roles of surfactant?

Answer 18

reduces surface tension increasing compliance; minimizes fluid accumulation in the alveoli; helps to keep alveolar size relatively uniform during the respiratory cycle; helps alveoli dynamically adjust their rates of inflation and deflation- making ventilation more uniform

Question 19

What is the equation for transmural pressure?

Answer 19

negative transmural pressure = pressure in the airway minus intrapleural pressure

Question 20

What changes airway resistance?

Answer 20

vagal stimulation (constricts); epinephrine (dilates); histamine (constricts); increased lung volume (decreases resistance); COPD

Question 21

What is the equation for airflow?

Answer 21

Airflow = (difference between atmospheric pressure and alveolar pressure)/airway resistance

Question 22

Does a small alveoli or large alveoli have a higher collapsing pressure (surface tension)?

Answer 22

small; P = 2T/r

Question 23

What is the Henderson-Hasselbalch equation?

Answer 23

pH = pK + log [HCO3-]/(s x PCO2) or pH = 6.1 + log (kidney/lung)

Question 24

What is buffering power?

Answer 24

Buffering power = the amount of strong base (concentration) to raise the pH of solution by 1 (10 fold decrease in proton concentration); The buffering power of a weak base or weak acid is strongest when pH is at the pK of the weak acid or base (bell-shaped curved for pH and buffering power)

Question 25

Does the blood buffering power of non-bicarbonate buffers changes at different pHs?

Answer 25

No

Question 26

What is the body’s response to a respiratory acidosis?

Answer 26

metabolic alkalosis (increased secretion of protons and production of bicarbonate); pH change never completely reverses

Question 27

How do acid/base transporters regulate intracellular pH?

Answer 27

Injecting protons or hydroxide into the cell interrupts the balance between acid extruders and acid loaders (normally at equilibrium)

Question 28

What is an example of an acid loader? acid extruder?

Answer 28

AE3 (chloride into the cell and bicarbonate out of the cell); NBCn1 (sodium and bicarbonate into the cell; increases pH)

Question 29

How do extracellular acid/base disturbances (respiratory acidosis) effect intracellular pH?

Answer 29

A patient with respiratory acidosis, has acidosis in cells; the kidney responds by compensating with metabolic alkalosis; cells in the body will slowly experience an increase in pH

Question 30

What is the pH of blood at 37 degrees Celsius?

Answer 30

7.4

Question 31

What is the effect of doubling proton concentration of pH?

Answer 31

lower pH by 0.3 (log10 2 = 0.3)

Question 32

What is the definition of an acid?

Answer 32

can donate (or generate) a proton

Question 33

What is the pK for the reaction (two reactions with carbonic acid initially produced, the rate limiting step) of carbon dioxide and water to yield a proton and bicarbonate?

Answer 33

6.1

Question 34

Describe the dynamic compliance of the alveoli.

Answer 34

Over a wide range of breathing frequencies, the change in lung volume (tidal volume) is largely unchanged; only when respiratory frequency approaches extremely high values does total lung capacity begin to fall off; a patient with COPD achieves well below normal total lung capacity at low breathing frequencies (worse with hyperventilation)

Question 35

What is true of negative transpulmonary pressure and intrapleural pressure whenever the lungs are under static conditions?

Answer 35

intrapleural pressure is the same as negative transpulmonary pressure

Question 36

what happens to alveolar pressure during inspiration? is this the same as airflow?

Answer 36

During inspiration, Pa rapidly becomes negative but then relaxes to 0 by the end of inspiration. The opposite is true during expiration; yes if we assume that airway resistance does not change with lung volume

Question 37

What is the effect of the negative shift of intrapleural pressure on inspiration?

Answer 37

The body invests some of the energy represented by δP IP into transiently making Pa more negative (dynamic component). The result is that air flows into the lungs and V L increases; but this investment in Pa is only transient. Throughout inspiration, the body invests an increasingly greater fraction of its energy in making P TP more positive (static component). The result is that the body maintains the new, higher V L . By the end of inspiration, the body invests all of the energy represented by δP IP in maintaining V L and none in further expansion.

Question 38

Describe how to calculate lung volume through volume of distribution methodology.

Answer 38

volume in spirometer x ((initial concentration of helium/final concentration of helium) -1); or nitrogen; for maximal expiration the calculation is residual volume and for normal expiration the calculation is FRC

Question 39

Describe how to calculate lung volume using a plethysmograph and Boyle’s law.

Answer 39

lung volume = change in volume of the system x ((atmospheric pressure-change in pressure)/change in pressure)