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16.4 CONTROL OF BREATHING Respiratory center (brainstem) -control both inspiration and expiration. - pons and medulla oblongata Medullary rhythmicity area -two neuron groups that extend the length of the medulla oblongata. Dorsal respiratory group Ventral respiratory group.
Respiratory center (brainstem)
-control both inspiration and expiration.
-pons and medulla oblongata
-two neuron groups that extend the length of the medulla oblongata.
Adding carbon dioxide to air can stimulate the rate and depth of breathing.
Peripheral chemoreceptors: found in carotid bodies and aortic bodies sense changes in blood oxygen concentration.
In walls of certain large arteries (carotid and aorta) in the neck and thorax.
Transmit impulses to the respiratory center, increasing the breathing rate.
(blood oxygen conc. must be very low to trigger this mechanism)
Oxygen plays a minor role in control of normal respiration.
Inflationreflex: occurs when stretched lung tissues stimulate stretch receptors in the visceral pleura, bronchioles, and alveoli.
Blood conc. Of carbon dioxide and hydrogen ions rise, and oxygen concentration falls.
Stimulate the respiratory center, and soon the urge to inhale overpowers the desire to hold the breath.
Hyperventilation: increase breath-holding time by breathing rapidly and deeply in advance.
Lowers the blood carbon dioxide concentration.
Following hyperventilation, it takes longer than usual for the carbon dioxide concentration to produce an overwhelming effect ont eh respiratory center.
*** can cause abnormally low blood oxygen levels. Hyperventilation should never be used to help hold the breath while swimming because the person may lose consciousness underwater and drown.
- Respiratory membrane: two thicknesses of epithelial cells and a layer of fused basement membranes separate the air in an alveolus from the blood in a capillary
Blood flowing through capillaries gain carbon dioxide because tissues have a relatively high PCO2
Blood transports carbon dioxide to the lungs in one of three forms, carbon dioxide dissolved in plasma, part of a cmpd formed by bonding to hemoglobin, or in the form of a bicarbonate ion.
Hemoglobin can transport both gases at the same time.
CO2 + H2O H2CO3
Most important form of CO2 transport.
Carbonic anhydrase: speeds the rxn between carbon dioxide and water.
Carbonic acid dissociates, releasing H+ and bicarbonate ions.
Bicarbonate ions diffuse out of RBC and enter the plasma
Released in alveoli.