Oxygen Concentration and Partial Pressure in the Alveoli. The oxygen concentration in the alveoli, and its partial pressure is controlled by: The rate of absorption of oxygen into the blood
Dr. Mudassar Ali Roomi (MBBS, M.Phil.)
Assist. Prof. Physiology
1. Dorsal Respiratory Group (DRG)
2. Ventral Respiratory Group (VRG)
3. Pneumotaxic center
4. Apneustic center
Significance of ramp signals
Full cycle of respiration
Following chemical stimuli stimulate the respiration:
Central in spinal cord between C3 & C5 to form phrenic nervechemosensitivearea
Hering N to Glossopharyngeal N
They have a weak effect but stimulation by way of the peripheral chemoreceptors occurs as much as five times as rapidly as central stimulation
An abnormality of respiration
is characterized by slowly waxing and waning respiration occurring about every 40 to 60 seconds
Under normal conditions, this mechanism is highly Damped the brain stem loses about four fifths of its sensitivity to changes in Pco2 and hydrogen ions.
But in two conditions it occurs
Alternate periods of Respiration & Apnea, but transition of one period to other is abrupt, not gradual.
Disease affecting medulla.Biot Breathing / Cluster respiration:
1. Narrow pharyngeal passage, and relaxation of these muscles during sleep causes the pharynx to completely close so that air cannot flow into the lungs.
2. The snoring proceeds, often becoming louder, and is then interrupted by a long silent period during which no breathing (apnea) occurs.
3. decreases in PO2 and increases in PCO2, which greatly stimulate respiration.
4. This, in turn, causes sudden attempts to breathe, which result in loud snorts and gasps followed by snoring and repeated episodes of apnea.
5. excessive daytime drowsiness as well as other disorders, including increased symphatetic activity