Respiratory System Flashcards
The medullary respiratory center
- generates the rhythm for quiet/regular, conscious breathing
- composed of 2 collections of neurons (dorsal and ventral respiratory groups)
The pontine respiratory group
- is within the pons
- modifies the rhythm set by the medullary
- smooths out transitions between inhale and exhale
The most important factors influencing breathing rate and depth are
Levels of CO2, O2, and H in the arterial blood (sensed by chemoreceptors)
Central chemoreceptors are located
throughout brainstem (including medulla)
Peripheral chemoreceptors are located
in aortic arch & carotid sinus (like baroreceptors for BP)
The main trigger for regulation of breathing is
Arterial blood CO2 pressure
Hypercapnia occurs when
- Blood CO2 pressure increases causing CO2 to accumulate in the brain, leading to increased acidity
- ventilation increases to flush out excess CO2
Hypocapnia occurs when
- Blood CO2 pressure is too low
- respiration is inhibited and slows
Hyperventilation is
An increased depth & rate of breathing that exceeds body’s need to remove CO2
- this leads to a decrease in blood CO2 levels (hypocapnia)
Indirect effect on ventilation of peripheral chemoreceptors being sensitive to arterial O2 pressure:
Low O2 pressure enhances peripheral chemoreceptors sensitivity to CO2 pressure
Direct effect on ventilation of peripheral chemoreceptors being sensitive to arterial O2 pressure:
Substantial drop in arterial O2 pressure is necessary to increase ventilation directly
- Due to the large reserves of O2 carried on Hb
Changes in arterial blood pH can modify respiration via
peripheral chemoreceptors
- H does not cross the blood brain barrier
↑ blood H + may be in response to
- ↑ blood CO2 pressure
- Metabolites causing acidification of the blood (lactic acid, ketone bodies)
The Hypothalamus & limbic system
- Signals respiratory centers to modify respiratory
rate & depth - is in response to strong emotions & pain (i.e gasping in pain)
The Cerebral cortex
- Can exert conscious control over ventilation
behavior - Bypasses the medullary centers & directly
stimulates respiratory muscles (i.e holding your breath)
Pulmonary irritant reflexes
- Respond to inhaled irritants in nasal passages or
trachea - Cause reflexive bronchoconstriction in respiratory airways
Inflation (Hering-Breuer) reflex
- is activated by stretch receptors in visceral pleurae
& conducting airways - Protects lungs from overexpansion by inhibiting
inspiration
Hyperapnea is
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
3 neural factors that contribute to change in respiration:
- 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
Atmospheric pressure and O2 pressure are
Lower at high elevations
Acute mountain sickness (AMS)
- May result from a rapid transition from sea level to altitudes above 8000 feet
- symptoms are headaches, shortness of breath, nausea, dizziness
long-term change from sea level to high altitudes results in acclimatization of the body via
◦ Increase in ventilation rate
◦ Lower than normal Hb saturation
◦ Increased production of erythropoietin
