lec 6 Control of respiration Flashcards
3 Components of neural control of respiration:
1) factors that generate alternating inspiration and expiration
2) Factors that control the magnitude of ventilation
3) factors that modify respiratory activity
Medullary respiratory centers:
2 neuronal clusters:
Dorsal respiratory center:
controls quiet inspiration
Ventral respiratory group:
-inspiratory neurons and expiratory neurons.
-controls active expiration
The primary respiratory control centre and other ones:
1) medulla respiratory center
2) the Pons- pneumotaxic (inhibits inspiration) and apneustic center (excitatory Inspiration)
Dorsal group of neurons:
-Contain i neurons (inspiratory neurons)
-tractus solitarus is the sensory termination of afferent fibres in the **glossopharyngeal **nerve and Vagus nerve
-they receive impulses from chemoreceptors, aortic and carotid baroreceptors
-Ramp allows inspiration process
-starts weak then becomes stronger then fades away
-2 sec + 3 sec= 5 sec cycle, so theres 12 cycles per minute
-Causes progreszive expansion of the lungs
- controlled by pneumotaxic center and Vagi impulses
Ventral group of neurons:
-include ambigious and retroambiguous nucleus
-both I and E neurons.
-this group only stimulated during active expiration e.g exercise.
-isnt active during quiet inspiration
Apneustic center:
in lower pons
-inhibits pneumotaxic center, has opposite effects to pneumotaxic center
Neural control of PONS: pneumotaxic and apneustic
-Located in upper pons
-has 2 nuclei
-signals from pneumotaxic centre have inhibitory effects on the quiet inspiration aka Dorsal group of medulla
Stronger signals from pneumotaxic area, terminate Ramp signal early, therefore increasing respiratory rate
**weak signals mean ramp signals are longer and therefore slower respiratory rate **
impulses from higher centers:
during emotional states, respiration is modified by cortex, limbic system, hypothalamus
Impulses from proprioreceptros:
present in joints and deeper parts of skin, they respond to changes in position and movement.
active during exercise
VERY IMPORTANT :
IMPULSES FROM STRETCH RECEPTROS IN LUNG: hering breuer reflex
Inhibits over inflation of lungs, when tidal volume reaches 1.5 liters
i.e inhbits the DGN, inhibiting respiration
Impulses from irritant receptors:
involved in cough and sneezing reflex.
-irritate the epithelium in respiratory airways
Impulses from J receptors:
these cause rapid breathing when theres and irritant chemical or edema.
i.e increase respiratory rate in DGN
Visceral reflexes:
short apnea during swallowing, vomiting, defecation
effect of temperature on respiratory centre:
direct: directly stimulate breathing
indirect: increase in PCO2, decrease PO2, H ions con increases, leading to hyperventilation
Influence of chemical factors on respiration:
affect the ventilation indirectly
central chemoreceptors:
present in medulla oblongata
periphral chemoreceptors:
present in aortic and aortic bodies
-carotid bodies carried by glossopharygeal nerve
-aortic bodies impulses carried by afferent nerve fibres in vagi
PCO2 on chemoreceptors:
-it dissociates into bicarbonate ions and H+ ions
-H+ ions are the most powerful stimuli to the central chemoreceptros, and have a weaker effect on the periphral chemoreceptors
-H+ ions in the CSF are much more potent stimulators than the H+ ions produced in the brain
H ion concentration effect:
-H+ ions cant cross blood brain barrier like CO2
-the periphral chemoreceptors adjust H+ levels to monitor acidosis.
-as H+ stimulate hyperventilation to breathe out CO2
Changes in PO2:
-via the periphral chemoreceptros
-stimulated when PO2 falls to low levels, below 60mmHg
- COPD patients and high altitude patients are susceptible
regulation of respiration during exercise:
at the start of an exercise, impulses from proprioreceptors from the joints go to respiratory centre to stimulate ventilation.
