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

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16 4 control of breathing respiratory center brainstem control both inspiration and expiration

16.4 CONTROL OF BREATHING

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


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

DORSAL 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

VENTRAL RESPIRATORY GROUPS

  • Quiet during normal breathing.

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


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

PNEUMOTAXIC AREA

  • 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

FACTORS AFFECTING BREATHING

  • 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

  • Adding carbon dioxide to air can stimulate the rate and depth of breathing.

  • Ordinary air is about 0.04% CO2

  • Inhaling air containing 4% CO2 doubles the breathing rate.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

Inflationreflex: 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

When voluntarily stop 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

Pg. 443 fainting


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

16.5 ALVEOLAR GAS EXCHANGES

- 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


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

DIFFUSION ACROSS THE RESPIRATORY MEMBRANE

  • 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 4 control of breathing respiratory center brainstem control both inspiration and expiration

16.6 GAS TRANSPORT

  • 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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

Hypoxia: deficiency of 02 reaching the tissues.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

CARBON DIOXIDE TRANSPORT

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.


16 4 control of breathing respiratory center brainstem control both inspiration and expiration

Carbaminohemoglobin: carbon dioxide bonded with hemoglobin.

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.


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