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16.4 CONTROL OF BREATHING Respiratory center (brainstem) -control both inspiration and expiration. - PowerPoint PPT Presentation

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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.

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Respiratory center (brainstem)

-control both inspiration and expiration.

-pons and medulla oblongata

Medullaryrhythmicity area

-two neuron groups that extend the length of the medulla oblongata.

  • Dorsal respiratory group

  • Ventral respiratory group


  • Controls the basic rhythm of inspiration.

  • Emit bursts of impulses that signal the diaphragm and other inspiratory muscles to contract.

  • Inactive while expiration occurs.


  • Quiet during normal breathing.

  • Forceful breathing is required, these neurons generate impulses that increase inspiratory movements.


  • Transmit impulses that inhibit the inspiratory bursts from the dorsal respiratory group.

  • Control breathing rate

  • When pneumotaxic inhibition is strong, the inspiratory bursts are shorter, and the the breathing rate increases.

  • When pneumotaxic inhibition is weak, the inspiratory bursts are longer, the breathing rate decreases.


  • Chemosensitiveareas: located in the ventral portion of the medulla oblongata near the origins of the vagus nerves, sense changes in the CSF concentrations of CO2 and hydrogen ions.

  • If these concentrations rise, the chemoreceptors signal the respiratory center, and respiratory rate and tidal volume increase.

  • Result: increased ventilation, more carbon dioxide is exhaled.

Peripheral depth of breathing.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.

Inflation depth of breathing.reflex: occurs when stretched lung tissues stimulate stretch receptors in the visceral pleura, bronchioles, and alveoli.

  • Shorten the duration of inspiratory movements.

  • Prevents overinflation of the lungs during forceful breathing.

When voluntarily stop breathing: depth of breathing.

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.

Pg. 443 fainting rapidly and deeply in advance.

16.5 ALVEOLAR GAS EXCHANGES rapidly and deeply in advance.

- 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


  • Partial pressure: amount of pressure each gas contributes.

  • Pressure is proportional to its concentration.

  • 21% oxygen (of 760mmHg or 160mm)

  • PO2

  • Diffusion: between blood and the inside the alveolar, pressure is greater in alveolar, until the pressures become equal between the two regions.

16.6 GAS TRANSPORT rapidly and deeply in advance.

  • hemoglobin: transports oxygen

  • Forming – oxyhemoglobin

  • Unstable bonds

  • As the PO2 decreases, the oxygen will be released.

  • Diffuses into nearby cells that need oxygen.

  • More oxygen is released as the blood concentration of carbon dioxide increases, as blood becomes more acidic, or as blood temperature increases.

  • Explains why more oxygen is released to skeletal muscles during physical exercise.

Hypoxia: deficiency of 0 rapidly and deeply in advance.2 reaching the tissues.

CARBON DIOXIDE TRANSPORT rapidly and deeply in advance.

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.

Carbaminohemoglobin: carbon dioxide bonded with hemoglobin. rapidly and deeply in advance.

Bicarbonate ions:

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.