• chielfly associated with inspiration
• responsible for basic rhythm in normal tidal breathing
  • pacemaker in rotral ventromedial medulla

Mechanism of action of dorsal medulla

• intrinsic rhythm
  • latent period several seconds
  • follwed by appearance of AP's
  • crescendo over few seconds

Function of ventral respiratory group in medulla

• mainly responsible for expiration
• active during forceful expiration (overdrive mechanism), but not needed during quit breading
• has some inspiratory neurons (increase inspiratory activity when demands for ventilation are high ie exercise)

apneustic (lower pons)

pneumotaxic (upper pons)

• promote inspiration by preventing inspiration neurons from being switched on
• impulses appear to have excitatory effect on DRG of medulla

Apneuses are prolonged, inspir. gasps

• inhibit innspiration by switching off inspiratory ramp
• regulate inspiratory volume and rate (regulate tidal volume(
• normal rhythm exists after ablation of this center (fine tuner)
• dominant over apneustic center

• breathin can be voluntary (cortex can overide brain stem)
  • voluntary hyperventilation can half PaCO2
  • voluntary hypoventilation (breath holdin) limited by rise in PaCO2 and PaO2

Sensors that can affect respiration

• irritant receptors in nose, upper airway
• irritant receptors in bronchi
• stretch receptors in airways
• J receptors in air-capillary membrane
• joint and muscle receptors
• gamma system in muscle spindles
• arterial baroR
• pain and temp.l

• lung stretch receptors
• irritant receptors
• J receptors
• joint and muscle receptors

• distension of lungs terminates inspiration and facilitates expiration
  • with lung inflation, lung stretch receptors send inhibitory signals to apneustic center that will terminate inspiration
  • stimulation of stretch receptors shorten inspiratory time as tidal volume increases, accelerating frequency of breathing
• deflation triggers next inspiration

Mechanism of action, location, clinical scenariors where seen, function of J receptors

• location- juxtacapillary receptors in alveolar wall
• mechanism of action
  • activated via changes in interstitial pressure or volume and travel via vagus N.
• function- cause rapid, shallow breathing (ex: left ventricular heart failure, interstitial lung disease)

• Mechanism of action- respond to mechanical and chemical stimuli (noxious gases, cold, particuloates)
• Effect- sneeze, nasal discharge, bronchoconstriction, hyperpnea

• location- muscle spindles in intercostals and diaphragm
• mechanism of action- sense elongation and influence strength of contraction

Affect of changes at arterial barorectpor

• increase bp cause reflex hypoventilation/ apnea
• decrease bp cause reflex hyperventilation

Effect of temperature stimuli warming of skin

central

peripheral

• location- brainstem (near CN 9, 10)
• mechanism of action
  • direct response in change to pH in CSF
  • indirect response to change in PaCO2

• location
  • carotid bodies at bifurcation of common carotid A's
  • aortic bodies above and below aortic arch
• responds to hydrogen, carbon dioxide, oxygen

• increase hydrogen ion stimulate ventilation
• decrease hydrogen ion inhibit ventilation

increase hyrogen ion concentration in CSF, leading to stimulation of ventilation

Mech. of action of chemoreceptors

• mainly response to decrease PaO2
• less potent response to increase PaCO2
• carotid body respond to decrease arterial pH
• response to decrease PaO2 enhanced by increased PaCO2 and decreased pH

• decrease in arterial PaO2 (below 60)
• increase in arterial PCO2
• decrease in arterial pH (chemoreceptors for H in carotid bodies)

Alteration in ventilatory response to PaCO2 in someone sleeping

causes the central chemoreceptors to reset itself, so it will not have as extreme of a ventilatory response to increased PaCO2 (curve shift to right with graph of PaCO2 on x axis and ventilation rate on y axis)

• definition- prolonged inspiratory gasps
• clinically seen in head trauma, neurological disorders

• definition- series of breaths of equal depth, irregularly alternating with periods of apnea
• clinically seen in meningitis

• gradual increase in depth and somtimes rate to maximum, followed by gradual decrease resulting in apnea (cycles 30 sec-1 min in length)
• clinically seen in severe hypoxemia, high altitude, brain damage, severe heart disease

define central sleep apnea and what associated with clinically

• definition- complete cessation of airflow with simultaneous cessation of respiratory muscle apnea
• assoc. with cardiac and neurologic disease

• def.- complete cessation of airflow with continued resp. musc. effort
• clinical findings
  • apneic episodes ends with brief arousal n noted in EEG
  • more than 10 episodes an hour abnormal