Respiratory Control Flashcards
Basic elements of the control system
Chemoreceptors (central and peripheal) and vagal bronchopulmonary receptors (stretch, irritant, J)…input to pontine and medullary centers…output to motor neurons of respiratory muscel
Respiratory centers
Specific groups o neruons i nthe pontine and medullary regions
Responsible for generation and maintennace of resp rhythm and reg of breathing pattern
Pontine center primary function and different centers
Regulate breathing pattern but NOT essential for maintaining respiration
Pneumotaxic - upper 1/3 …electrical stimulation causes rapid breathing
Apneustic cnter - lower 1/3 of pons…electrical stimulation causes apneusis (sustained contraction of inspiratory muscles)
Medullary centers (DRG)
Essential for maintaing resp rhythm
Located in dorsomedial medulla - in vicinity of NTS
Affarent inputs from vagal BP receptors and peripheral chemoreceptors
Source of rhythmic phrenic motor drive to diaphragm
VRG
Ventrolateral region of medulla
Rhythmic motor drive to internal and external intercostals, accessary muscles, and laryngeal msucles
Thoeries of resp rhythm genesis
Suprapontine structures
Pacemaker neurons
Neuronal network interaction…circuit so interuption of the circuit leads to the breathing pattern
Mid-brain, cerebral cortex ,and other higher
Rett syndrome
Cheyne-stokes
Mutation of MeCP2 gene
Oscillation between apnea and hyperpnea in .5-2 min cycles
Asphyxia
Apnea
Hyperpnea
Hyperventilation vs. tachypnea
Extreme decrease in oxygen and increase in CO2 in the body due to stop breathing
Long delay of inspiration
Increase in tidal volume
Tachyp is rapid rate but hyperventilation is increase in minute ventilation**
Chemoreceptors (central)
Detect changes in chemical compositions in arterial blood
Cental - near surface of ventrolateral medullla
Central stimulated by low pH in CSF…or high PCO2 (or low arterial pH), but NOT low arterial PO2
Peripheral chemoreceptors
Carotid bodies (main one) - on carotid artery
Aortic bodies - scattered near aortic arch
Stimulated by LOW arterial PO2**, high arterial PCO2 or low pH…ONLY sensors in the body that can detect hypoxia
BP sensory receptors
Play role in regulating breathing pattern and airway functions
Protect against inhaled irritants
Affarent nural activity in vagus nerves to the NTS in the medulla
BP stretch receptors
Slowly adapting
Volume expansio in the lung is stimulus (even within tidal volume range)…activated during inspiraiton…stops the inspiration
Slowly adapting play important role in regulaiton of breathing pattern
BP irritant receotrs
Rapidly adapting
Stimulated by decreased compliance or lung atelectasis and certain inhaled irritants
Reflex responses - sigh and cough
BP C fibers
Juxtacapillary receptors
75% of vagal sensory nerves in the lung
Stimulated by certain endogenous inflammatory mediators, inhaled chemical irritants
Reflex response - reflex bronchoconstriction, cough, increase in mucous secretion, dyspneic sensation
Cough reflex
Can be generated by inhaled irritants or aspiration, or airway inflammation/infection in patients
Cough in dz and defense function
Chronic cough as an airway dz
Def - protective against inhaled irritants or aspiration and expel excessive ariway secretion (or inhalaed irritants or allergens)
Larynx closes and will activate compression of the diaphragm…this causes an increase in pressure which creates high velocity flow
Cough sensors
Inhaled irritants
Endogenous inflammatory mediators
Very superficial
Ventilatory response to hypoxia
Not very sensitive to change in O2 in normal range of PO2…no significant change in ventilation until arterial PO2 falls below 60 mmHG
Response potentiated by hypercapnea
Reflex response elicited ONLY by stimulation or peripheral chemoreceptors
Response to hypercapnea
Very sensitive to change in CO2 in normal range of PCO2
Response potentied by hypoxia
Most of response is elicited by stimulation of central chemoreceptors
Difference between hypoventilation and other causes of hypoxia/hypercapnea
hypoventilation is MUCH more likely to cause hypercapnea than the other three
The other three will cause much more hypoxemia
Anesthesia effect
Drugs that act on CNS will decrease the minute ventilation and can therefore increase the PaCO2 by inducing hypoventilation
Dyspnea in healthy, pts with lung dz, and pts with heart dz
During exercise and exertion or in high altitude
Common in boht obstructive and restrictive dz
Congestive heart failure, acute cardiac ischemia…orthopnea (harder when lying down)
Receptors in generating dyspnea
Peripheral - hypoxia and acidosis
Vagal sensory innervating the lung and airways (C fibers or juxtacap receptors)…airway diseases
Mechanoreceptors in resp muscles
Also central motor commands and behavioral factors can be involved
