Pulmonary II Flashcards
The normal automatic process of breathing originates from the
Brainstem
Neurons in the ______ and ______ control the unconscious breathing
medulla oblongata and pons
The _____ can override these centers if voluntary control is needed
Cortex
The automatic rhythm is controlled by neurons located in the
medulla rhythmicity center
Rhythm control of breathing
Respiratory nuclei in medulla
Medullary rhythmicity area:
Inspiratory center
- Dorsal respiratory group*
- frequent signals, you inhale deeply
- signals of longer duration, breath is prolonged
Medullary rhythmicity area:
Expiratory center
- Ventral respiratory group*
- involved in FORCED respiration
Rate and depth control
PONS
RESPIRATORY CENTER CONTROL:
(-) Pneumotaxic center
(in the Pons)
-sends continual inhibitory impulses to inspiratory center, as impulse frequency rises, breaths SHORTER, FASTER, and SHALLOWER
RESPIRATORY CENTER
(+)Apneustic center
(in the Pons)
-promotes maximal lung inflation and LONG, DEEP
breaths
-inspiration & expiration
DRG “Pacemaker”
in the Medula Oblongata
Vagus nerves
Pulmonary stretch receptors Herring -Breur
MEDULLA RESPIRATORY CENTER IS IN:
the reticular formation of the medulla beneath the floor of the fourth ventricle
The Pre-Botzinger Complex (part of the Ventral Group)
is essential for generation of the respiratory rhythm.
The Dorsal Respiratory Group (DRG)
sets the basic respiratory rhythm
Ventral Respiratory Group (DRG)
associated with FORCED respiration
Factors Affecting Airway Resistance
- Diameter of airway
- Flow (Laminar vs. Turbulent)
- Density of Gas (viscosity)
- Goverened by Poiseuille’s Law
V= P r4/8
PNEUMOTAXIC CENTER IN THE upper PONS
- Inhibits inspiration*
- limits the burst of action potentials in the phrenic nerve, effectively decrease the tidal volume and regulating the respiratory rate
- “Fine-tuning” of respiratory rhythm because normal rhythm can exist in the absence of this center
APNEUSTIC CENTER IN THE lower PONS
- Promotes inspiration*
- Excitatory effect on the Dorsal Respiratory Group in the medulla
- Sends signals to the Dorsal Respiratory Group in the medulla to delay the “switch off” signal provided by the pneumotaxic center
EXPIRATION OCCURS DUE TO:
elastic recoil of lung tissues and chest wall
Impulses from the Vagus (X) and Glossopharyngeal (IX) nerves _________ the output of inspiratory cells
modulate
T/F Dorsal and Ventral Respiratory Groups’ cells, even when all afferent stimuli is abolished, these cells generate repetitive action potentials that send impulses to the diaphragm and other respiratory muscles
True
Input to Respiratory Centers from limbic system and hypothalamus
-resp effects of pain and emotion
Input to Respiratory Centers from chemoreceptors
-monitor blood pH, CO2 and O2 levels
RATE AND DEPTH OF BREATHING ADJUSTED TO MAINTAIN LEVELS OF:
- pH
- Pco2
- Po2
what can exist in absence of pneumotaxic center
-“Fine tuning” of respiratory rhythm because a normal rhythm can exist in the absence of this center
PRIMARY STIMULUS FOR CENTRAL CHEMORECEPTORS
pH of CSF
Co2 easily crosses the
BBB
HYPERCAPNIA
Pco2> 45mmHg
in CSF the CO2 reacts with water and releases
H+
the cycle of inspiration:
-Crescendo of action potentials leading to a ramp of strengthening inspiratory muscles
-
-Inspiration action potentials cease and inspiratory muscle tone falls
-
-Expiration occurs due to elastic recoil of lung tissues and chest wall
central chemoreceptors strongly stimulate
inspiratory center
“blowing off” CO2 pushes reaction to the
left
RESPIRATORY ALKALOSIS
(PH>7.4)
hypocapnia
Pco2 < 35mmHg
hypoventilation (increases Co2) pushes reaction to the
right
ketoacidosis may be compensated for by _____ respirations
Kussmaul
peripheral chemoreceptors
-found in major blood vessels >AORTIC BODIES - (signals medulla via C.N. X) >CAROTID BODIES - (signal medulla by C.N. IX)
CENTRAL CHEMORECEPTORS
-in medulla
>primarily monitor pH of CSF
>↑H+ stimulates ventilation
>↓H+ inhibits it
central chemoreceptors mediate ___ % of ventilatory respons
80%
peripheral chemoreceptors mediate ____ % of ventilatory response
20%
NORMAL PH OF CSF
7.33
CSF has much less buffering capacity compared to blood, resulting in:
greater change in pH with changes in PCO2
With _______ disease, the hypoxic drive to ventilation becomes very important
severe lung disease
IF A HIGH 02 MIXTURE IS GIVEN TO RELIEVE HYPOXEMIA…
The ventilation may be grossly depressed
