3 - Respiration Flashcards
What are the three major components of the respiratory center?
- dorsal respiratory group (dorsal medulla, inspiration)
- Ventral respiratory group (ventrolateral medulla, exp)
- Pneumotaxic center (superior pons, rate and depth of breathing)
What does the dorsal respiratory group control?
inspiration and respiratory rhythm
Most of the neurons in the dorsal respiratory group are located in the _______
Nucleus of the tractus solitarius (NTS)
What is the NTS?
Nucleus tractus solitarius
Main component of the dorsal resp group
sensory termination of both the vagal and glossopharyngeal nn
Where is the basic rhythm of respiration generated?
the dorsal respiratory group
even when it’s completely severed from afferent and efferent nerves, it will still emit inspiratory action potentials!
Instead of sending bursts of inspiratory action potentials, the dorsal group signal is an inspiratory _______
ramp
steadily increases and then ceases abruptly
results in inspiration rather than gasping
How does the inspiratory ramp signal change with heavy respiration?
Increases the rate of increased signalling (increases the steepness of the ramp)
How is the inspiratory ramp modified to acheive a change in respiration?
the limiting point at which the ramp suddenly ceases is lengthened or shortened.
The earlier the ramp ceases, the shorter the duration of inspiration and therefore expiration, and therefore the more breaths that take place per minute
What is the function of the pneumotaxic center?
limits duration of inspiration and increases respiratory rate
When the pneumotaxic signal is strong, respiration is _____
increased
What is the function of the ventral respiratory group?
Overdrive mechanism when high levels of pulmonary ventilation are required
When there are an excess of signals to the dorsal ventral group, they “spill over” into the ventral respiratory group
How does the ventral respiratory group contribute to resting rate and rhythm?
It doesn’t. It’s completely inactive during normal quiet respiration
What is the Hering-Breuer Inflation Reflex?
Stretch receptors in the muscular walls of the bronchi and bronchioles send messages through the vagus when they’re overstretched
The signal causes a completely switching off of the dorsal group, preventing further inspiration
Mostly prevents against extreme overinflation, not triggered during normal inspiration
What is the effect of oxygen levels on the respiratory centers of the brain?
Pretty much no effect on the respiratory centers of the brain
acts almost entirely on peripheral chemoreceptors in the carotid and aorta, which transmits nervous signals to the respiratory center
How do CO2 and H interact with the respiratory center?
Indirectly
Changes in CO2 and H trigger the chemosensitive area (near the pneumotaxic center)
the chemosensitive area then excites other portions of the respiratory center
What is the primary stimulus for excitation of the chemosensitive area?
Hydrogen, not CO2
If CO2 does not readily cross the blood brain barrier, how is it the primary stimulus of the chemosensitive area?
In blood, CO2 is dissociated into carbonic acid, then bicarb and H, which is what the chemosensitive area responds to
Even though CO2 isn’t technically reaching the brain, an increase in the level of CO2 will trigger the chemosensitive area indirectly because of its buffered state
A change in blood [CO2] has a potent _______ effect but a weak _____ effect
acute
chronic
Subsides after a couple of days
Do chemoreceptors respond to arterial or venous O2 levels?
Arterial
They have a massive arterial supply with almost no O2 extraction, leading to accurate interpretation of PaO2
During hypoxia, which neurotransmitter is released by the carotid body glomus cells to trigger the respiratory center?
ATP!
Since CO2, O2, and pH levels remain constant throughout exercise, what stimulates the increased respiratory rate seen during strenuous exercise?
When motor impulses leave the brain to stimulate the exercising muscles, they transmit collateral impulses to the respiratory center
When a person begins to exercise, how quickly does respiration increase?
Almost immediately, before there are any chemical changes in the blood
In fact, PCO2 decreases below normal initially in anticipation of the increase in serum CO2
What are J receptors?
stimulated when the pulmonary capillaries become engorged or pulmonary edema occurs
May be responsible for the sensation of dyspnea
How does acute brain edema impact respiratory function?
depresses the respiratory center
