Control of Breathing Flashcards
Where does the rhythmic cycle of breathing originate?
brainstem (mainly from neurons in the medulla)
What is the DRG?
dorsal respiratory group
What does the DRG consist of?
inspiratory neurons
What is the VRG?
ventral respiratory group
What does the VRG consist of?
intermingled inspiratory and expiratory neurons
Where do the DRG neurons send impulses and why?
phrenic and external intercostal nerves to provide the main stimulus for inspiration
Where do the inspiratory VRG neurons send impulses?
- some to laryngeal and pharyngeal muscles
- others to diaphragm and external intercostal nerves
Through what nerve do the inspiratory VRG neurons transmit impulses?
vagus
Why do the inspiratory VRG neurons send impulses to the laryngeal and pharyngeal muscles?
to abduct the vocal cords and increase the diameter of the glottis
Where do the expiratory VRG neurons send impulses?
internal intercostal and abdominal expiratory muscles
What is the botzinger complex?
assumes that certain populations of inspiratory and expiratory neurons inhibit one another
DRG and VRG neurons fire with rate ___ gradually after expiration ceases, leading to an increasing ramp signal
increasing
What does an increasing ramp signal lead to?
stronger contraction of inspiratory muscles, smoothly and gradually inflating the lungs
As expiration begins, the inspiratory neurons are ____ and switch off the ____ abruptly
inhibited; inspiratory signal
What is the apneustic center?
a center in the lower pons that prevents inspiratory ramp signal from being switched off
What is the pneumotaxic center?
a center in the upper pons that controls the length of inspiration
What is the hering-breur inflation reflex?
stops further inspiration when receptors are stretched
What tidal volumes are the hering-breur inflation reflex activated?
> or = to 800-1000
What is the deflation reflex?
a sudden collapse of the lung stimulating inspiratory efforts and increases the RR
What nerve is the pathway for the deflation reflex?
vagus
What head’s reflex?
used to maintain large tidal volumes during exercise and is involved in periodic deep sighs during quiet breathing
What is the purpose of periodic sighs?
help prevent alveolar collapse or atelectasis
What reflex is used to stimulate the first breaths of a newborn infant?
head’s reflex
What do inhaled irritants stimulate?
epithelium of large conducting airways that have vagal sensory nerve fibers
What happens when the epithelium is stimulated?
reflexes of bronchoconstriction, coughing, sneezing, tachypnea and narrowing of glottis
Stimulation of the reflexes in the epithelium causes what?
laryngospasm, bronchospasm, coughing and slowing of HR
What are J receptors?
c-fibers in the lung parenchyma near pulmonary capillaries
How are J receptors stimulated?
- pneumonia
- CHF
- edema
Stimulation of the J receptors causes?
- rapid, shallow breathing
- sensation of dyspnea
- expiratory narrowing of the glottis
What are proprioreceptors?
receptors that are found in muscles, tendons and joints. also pain receptors found in skin and muscle
What are chemoreceptors?
receptors that are stimulated by an increase in H+ in the blood and transmit impulses to the medulla, increasing ventilation
How are peripherally located chemoreceptors indirectly sensitive to CO2 and hypoxemia?
they are sensitive to H+
Medullary located chemoreceptors are extremely sensitive to and why?
CO2. The H+ surrounding them is dependent on their reaction between CO2 and H2O in their local environment
What is the BBB almost impermeable to?
H+ and HCO3-
What is the BBB freely permeable to?
CO2
What are peripheral chemoreceptors?
small, highly vascular tissues known as the carotid and aortic bodies which increase their firing rate when arterial H+ is increased
What nerve do the carotid bodies send their impulses over?
glossopharyngeal
What nerve do the aortic bodies send their impulses over?
vagus
What is the ultimate effect of hypoxemia?
to increase the neural firing rate of the peripheral chemoreceptors, which increases minute ventilation
T/F: increased PaCO2 increases blood H+, directly exciting the carotid bodies and stimulates ventilation
true
When do the peripheral receptors respond 5 times faster?
a rise in arterial H+
T/F: if PaCO2 gradually increases over years, the kidneys compensate and keep the pH within normal limits
true
T/F: chronically hypercapnic patients’ central chemoreceptors experience less stimulation than those of a health person for the same increase in PaCO2
true
What is cheyne stokes breathing?
RR and VT gradually increase and then gradually decrease to complete apnea
What is biot’s breathing?
normal RR and VT with periods of apnea
What does apneustic breathing indicate?
damage to the pons
What is central reflex hyperpnea?
continuous deep breathing
T/F: CO2 helps regulate cerbreal blood flow
true
