Respiratory System

Question 1

The medullary respiratory center

Answer 1

• generates the rhythm for quiet/regular, conscious breathing
• composed of 2 collections of neurons (dorsal and ventral respiratory groups)

Question 2

The pontine respiratory group

Answer 2

• is within the pons
• modifies the rhythm set by the medullary
• smooths out transitions between inhale and exhale

Question 3

The most important factors influencing breathing rate and depth are

Answer 3

Levels of CO2, O2, and H in the arterial blood (sensed by chemoreceptors)

Question 4

Central chemoreceptors are located

Answer 4

throughout brainstem (including medulla)

Question 5

Peripheral chemoreceptors are located

Answer 5

in aortic arch & carotid sinus (like baroreceptors for BP)

Question 6

The main trigger for regulation of breathing is

Answer 6

Arterial blood CO2 pressure

Question 7

Hypercapnia occurs when

Answer 7

• Blood CO2 pressure increases causing CO2 to accumulate in the brain, leading to increased acidity
• ventilation increases to flush out excess CO2

Question 8

Hypocapnia occurs when

Answer 8

• Blood CO2 pressure is too low
• respiration is inhibited and slows

Question 9

Hyperventilation is

Answer 9

An increased depth & rate of breathing that exceeds body’s need to remove CO2
- this leads to a decrease in blood CO2 levels (hypocapnia)

Question 10

Indirect effect on ventilation of peripheral chemoreceptors being sensitive to arterial O2 pressure:

Answer 10

Low O2 pressure enhances peripheral chemoreceptors sensitivity to CO2 pressure

Question 11

Direct effect on ventilation of peripheral chemoreceptors being sensitive to arterial O2 pressure:

Answer 11

Substantial drop in arterial O2 pressure is necessary to increase ventilation directly
- Due to the large reserves of O2 carried on Hb

Question 12

Changes in arterial blood pH can modify respiration via

Answer 12

peripheral chemoreceptors
- H does not cross the blood brain barrier

Question 13

↑ blood H + may be in response to

Answer 13

• ↑ blood CO2 pressure
• Metabolites causing acidification of the blood (lactic acid, ketone bodies)

Question 14

The Hypothalamus & limbic system

Answer 14

• Signals respiratory centers to modify respiratory
  rate & depth
• is in response to strong emotions & pain (i.e gasping in pain)

Question 15

The Cerebral cortex

Answer 15

• Can exert conscious control over ventilation
  behavior
• Bypasses the medullary centers & directly
  stimulates respiratory muscles (i.e holding your breath)

Question 16

Pulmonary irritant reflexes

Answer 16

• Respond to inhaled irritants in nasal passages or
  trachea
• Cause reflexive bronchoconstriction in respiratory airways

Question 17

Inflation (Hering-Breuer) reflex

Answer 17

• is activated by stretch receptors in visceral pleurae
  & conducting airways
• Protects lungs from overexpansion by inhibiting
  inspiration

Question 18

Hyperapnea is

Answer 18

increased ventilation in response to metabolic needs
- occurs during vigorous exercise to ensure that tissue O2 demands are met
- Unlike hyperventilation, does not cause large
changes in blood CO2 pressure

Question 19

3 neural factors that contribute to change in respiration:

Answer 19

• Psychological stimuli (anticipation of exercise)
• Simultaneous cortical motor stimulation of
  skeletal muscles & respiratory centers
• Excitatory impulses to the respiratory areas from
  proprioceptors in muscles, tendons, & joints

Question 20

Atmospheric pressure and O2 pressure are

Answer 20

Lower at high elevations

Question 21

Acute mountain sickness (AMS)

Answer 21

• May result from a rapid transition from sea level to altitudes above 8000 feet
• symptoms are headaches, shortness of breath, nausea, dizziness

Question 22

long-term change from sea level to high altitudes results in acclimatization of the body via

Answer 22

◦ Increase in ventilation rate
◦ Lower than normal Hb saturation
◦ Increased production of erythropoietin