Resp 212 Beachy chapter 11 Control of ventilation Flashcards
Where do the neural Impulses responsible for breathing originate?
Medula Oblongata of the Brainstem
What Does the Dorsal Respiratory Group Do? 3 points, include nerves involved with signals etc.
- Consists mainly of** inspiratory** neurons
- the neurons send impulses to the phrenic and external intercostal motor nerves in the spinal chord, providing the main stimulus for inspiration.
- Vagus and Glossopharyngeal nerves transmit impulses to the DRG from the lungs, airways, peripheral chemoreceptors and joint proprioceptors, MODIFYING THE BASIC BREATHING PATTERN GENERATED IN THE MEDULLA
Describe the two neuron populations of the DRG
The DRG consists of 2 neuron populations,
- Inhibited by deep lung inflation (causing cessation of inspiratory effort)
- Excited by lung inflation (causing continued inspiratory effort)
These neurons are involved in the HERING-BREUER AND HEAD REFLEXES
What Does the Ventral Respiratory Group do? 3 points
- Contains both inspiratory and expriatory neurons.
- Nuceus Ambiguus- contains inspiratory neurons that innervate the laryngeal and pharyngeal muscles through the vagus nerve.
- Their impulses abduct the vocal chords of the larynx , increasing the diameter of the glottis and decreasing the inspiratory airways resistance.
Nucleus Retroambiguous 2 parts, what are they, what they contain, and what they do.
- Caudal area: mostly expiratory stimuli, drive the internal intercostal and abdonminal expiratory muscles. These muscles are normally active only at high ventilatory rates when expiratory muscle activity is required.
- Rostral: Mostly inspiratory discharge patterns.
a. they help DRG neurons drive the diaphragm and external intercostal muscles
Botzingers Complex
- The most rostral (toward the head) part of the **VRG **
- Contains the only expiratory neurons known to inhibit the **inspiratory **VRG and DRG impulses.
Botzinger Complex, and Pre-Botzinger complex
2 major theories of rythm generation
- May have a role in the rythmic breathing pattern
- Pacemaker hypothesis
- cells with intrinsic self-exciting pacemaker properties
- Network hypothesis
- Rythm is a result of interconnections pattern between I and E neurons: assumed that neurons inhibit one another and that after initial firing, neuron impulses die down
Inspiratory Ramp Signal
Gradual firing of impulses after expiration ends
- progressively stronger contraction of inspiratory muscles
- Gradual inflation of the lung
During Exercise
- Peripheral receptors and reflexes send impulses that create a steeper inspiratory ramp signal
- more rapid lung filling
I time shortened (inspiration time) = increased respiration rate.
Inspiratory ramp signal
Dorsal and ventral inspiratory neurons do not send an abrupt burst of impulses to the inspiratory muscles.
RATHER
their firing rate increases gradually after expiration ceases.
CREATING
a smoothly increasing ramp signal
LEADING to
progressively stronger contraction of inspiratory muscles
SMOOTHLY and GRADUALLY
INFLATING the lungs instead of filling them in an abrupt inspiratory gasp.
During exercise, this happens more rapidly
as the INSPIRATORY RAMP SIGNAL STRENGTHENS, inhibitory neruons begin to fire with increasing frequency.
after about 2 seconds these respiratory signals become strong enough to abruptly switch off the inspiratory signal.
Expiration then occurs for 3 seconds
as expiration begins, inspiratory neruons fire briefly, braking the early phase of expiration by maintaining some inspiratory muscle tone
Inspiratory neruonal activity completely stops in the last phase of expiration.
Inhibitory Neurons that switch off the inspiratory ramp arise from the pneumotaxic center and pulmonary strech receptors.
Pontine Centers
- Apneustic center
- Pneumotaxic center
What does the Apneustic Center do?
- Sends signals to the DRG
- Prevents Inspiratory ramp signal from being switched off
-
Apneusis: prolonged inspiratory gasps interrupted by occasional expirations
2. ***Pneumotaxic Center***
- Controls off - switch point of DRG’s inspiratory ramp signal
- Strong signal shortens inspiratory time: increased breathing rate.
- Weak signal prolongs inspiratory time: increases tidal volume
Pontine impulses “fine tune” medullary rhythm
Pneumotaxic center Roles
- Controls off-switch point of DRG’s Inspiratory ramp signal
- Strong signal shortens inspiratory time: increases rate
- Weak signal prolongs inspiratory time: Increases tidal volume.
Figure 11-2 and 11-3 Beachy
- Neural inspiratory signals during ventilation.
Breathing patterns produced by transections of the brainstem at different levels
**Hering-Breuer **Inflation reflex
- Stretch receptors in smooth muscle of large and small airways
- Inhibit inspiration via vagal impulses to DRG
- Stops further inspiration
- Activated only with large tidal volumes ~0.8-1.0L
- Regulates rate and depth during exercise
- If decreased lung compliance
- Increased inspiratory effort= increased mechanical stress on stretch receptor: Increases firing rate,** which shortens inspiratory time = faster breathing rate
Hering-Breuer Deflation Reflex
- Sudden lung collapse stimulates breathing
- Hypernea observed with pneumothorax
- Due to decreased stretch receptor activity?
- Due to irritant receptor stimulation?
-vagus nerve is the pathway from lung to medulla
