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Lecture 5

Physiology 3120 Lecture Notes - Lecture 5: Pulmonary Stretch Receptors, Partial Pressure, Headache

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Tom Stavraky

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Physiology 3120
Dr. Veldhuizen
Regulation of Respiration (5)
True or false:
The pressure-volume relationship of the lungs in humans can only be measured by the helium dilution
method. F (human dilution method is not a way to measure pressure-volume curves)
Control of respiration: the voluntary system
- When you want you can change you breathing pattern !!!
- Examples: breath hold, speaking, etc.
- Signals from Cerebral Cortex through corticospinal tract to spinal neurons that drive respiratory
muscles to control breathing
- Limited: ultimately, the automatic system takes over can’t hold breath forever
The automatic system
- The automatic system for control of ventilation is responsible for maintaining normal blood gas
values under a variety of conditions
o PO2: 100 in lungs and systemic arteries, PCO2: 40
- This control is extremely efficient!!!!!
- Central controller is the brain and it sends signals to respiratory muscles that are involved in
- There are receptors in the body that send signals back to the brain to adjust ventilation
Control of respiration: the automatic system
- Central controller: coordinates and responds to the information provided by the receptors and
sends signals to the muscles
- Receptors: collect information of the current status of blood gases and other factors
- Respiratory muscles: receive impulses from the controller to ultimately affect ventilation
The central controller
- Neurons located in 4 areas
o Inspiratory area
o Pneumotaxic area
o Apneustic center
o Expiratory area
1. Inspiratory area
- Location:
o Dorsal group of neurons in the medulla
- Properties:
o Critical in respiration and sending signals for inspiration
o Most important part for inspiration
o Has rhythmic signals that it sends to the muscles of respiration
o Inherent rhythmic excitability
o Initiates inspiratory drive and ventilation
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2. Pneumotaxic area
- Location:
o Group of neurons in the pons
- Properties:
o If there is damage to this area, they take very big breaths
o Fine-tuning of respiration but not essential
o Limits duration of inspiratory drive - switch off
o Control of inspiratory volume and respiratory rate
3. Apneustic center
- Location:
o Group of neurons in the lower pons
- Properties:
o Not sure what it exactly does and if it is really relevant
o opposite of pneumotaxic center in that it can prolong inspiration
o Pneumotaxic center overrides apneustic center
o In healthy situations, this does not contribute to respiration (only if there is damage to
the pneumotaxic center)
4. Expiratory area
- Location:
o Ventral group of neurons in the medulla
- Properties:
o When needed*, these neurons send signals to expiratory muscles resulting in active
o * (remember expiration is normally a passive process at rest)
Central controller
- Inspiratory area sends signals in regular intervals to muscles to provide regular breathing
- Pneumotaxic area is involved in fine tuning in the system and controls respiratory rate and
- Apneustic center could prolong inspiration if it had a chance but it doesn’t because pneumotaxic
center inhibits it
- Expiratory area allows for active expiration if needed (passive at rest)
- Collect information of the current status of blood gases and other factors
- Send signals to controller to change ventilation
- There are 4 types of receptors
o Central chemoreceptors
o Peripheral chemoreceptors
o Lung receptors
o Other receptors
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