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Discuss the Nervous System and its relationship to alveolar ventilation.
It automatically adjusts the rate of alveolar ventilation almost exactly to the body's demands. t
What effect does the nervous system have on arterial PO2 and PCO2?
They are hardly modified even with moderate to intense exercise or other respiratory distress
What is the Repiratory center composed of?
Several groups of neurons located bilaterally in the brain stem of the CNS specifically at the medulla oblongata and pons
List location of Dorsal Resp Group and function
- -Dorsal portion of medulla oblongata.
- -Mainly inspiration
List location of Ventral Resp Group and function
- -Ventrolateral portion of medulla
- -Inspiration or expiration depending on the nerves stimulated
List location of Pneumotaxic center and function
- -Dorsally located in the pons
- -rate and pattern of breathing
What is the most important role the dorsal resp group plays
- -controlling respiration
- -it receives information from the chemoreceptors and other receptors in the lungs that help in the control
What is a ramp signal?
The signal transmitted to the primary inspiratory muscles (diaphragm and external intercostals)
Discuss the process of transmitting a ramp signal.
-Starts from 0 and continues with a steady increase for about 2 seconds.
-Stops for 3 sec and starts again thus causing a steady increase in the pulmonary volume during inspiration instead of inspiratory gasps
The duration of expiration is determined by what?
The duration of inspiration
What does the pneumotaxic center limit?
It limits the duration of inspiration and increases the resp rate
What is the result of strong signals from the pneumotaxic center?
Stong signals reduce the time of inspiration while weak signals increase it.
What is the ventral group mostly involved in?
In increased levels of ventilation
What is the ultimate goal of resp?
To maintain proper H+, O2 and CO2 in tissues, something achieved by the resp activity
What causes "DIRECT" stimulation of the resp center?
- An increase in H+ and CO2.
- -Causes an increase of the inspiratory and expiratory signals
Does O2 have a "direct" effect on the resp center?
- -It acts through the peripheral chemoreceptors located in the carotid and aortic bodies
What occurs after fresh O2 gets to the alveoli?
The next step is its diffusion into the pulmonary blood and CO2 in the opposite direction
What is the net diffusion of a gas?
The net diffusion of a gas in one direction is a direct effect of its concentration gradient and its pressure against a surface is caused by the constant impact of kinectically moving molecuels against that surface.
What is the rate of diffuion of O2, CO2 and N2?
The rate of diffusion of each of these gases is directly proportional to the pressure caused by this gas alone, known as the partial press of the gas
What is the partial pressure of N2?
79% or 600mm/Hg at sea level
What is the partial pressure of O2?
21% or 160 mm/Hg at sea level
What is total pressure?
The sum of all partial pressures
What results from gases dissolved in H2) or the body tissues?
They exert pressure because the dissolved molecules are moving randomly and have kinetic energy.
-When they encounter a surface like the membrane of a cell the result is the same
What determines the pressure of a gas in a solution?
Its concentration and the solubility coefficeint of the gas
What is Henry's Law?
- Pressure = [Dissolved Gas]
- Solubility Coefficient
What is the solubility coefficient at body temp of O2, CO2, CO, N2 and He2?
- O2= 0.024
- CO2= 0.57
- CO = 0.018
- N2= 0.012
- He= 0.008
What effect does the partial pressure of each gas have on a solution?
It tends to force molecules of that gas into the solution, first in the alveolar membrane and then in the blood of the alveolar capillaries
What is the rate at which each gas escapes a medium?
The rate at which they escape from one medium to another is directly proportional to their partial pressure in the blood
-the net diffusion is determined by the diff b/w the two partial press.
What causes the net diffusion of gases through fluids?
The pressure difference
What is the pressure difference for diffusion?
The gas press difference b/w two areas
Explain why alveolar air doesn't have the same composition of the atmospheric air.
- b/c alveolar air is only partially replaced with each breath
- - O2 is going to the blood
- -CO2 is coming from the blood
What happens to dry atmospheric air that enters the resp pathways?
It is immediately humidified even before reaching the alveoli
What is tidal volume and its measurement in an average adult male?
- -500 ml
- -amt of air inhaled or exhaled w/ each breath under resting conditions
What is inspiratory reserve volume and its measurement in an average adult male?
- -3100 ml
- -amt of air that can be forcefully inhaled after a normal tidal volume inhalation
What is expiratory reserve volume and its measurement in an average adult male?
- -1200 ml
- -amt of air that can be forcefull exhaled after a normal tidal volume exhalation
What is residual volume and its measurement in an average adult male?
- -1200 ml
- -amt of air remaining in the lungs after a forced exhalation
What is total lung capacity (TLC) and its measurement in an average adult male?
- -6000 ml
- -max amt of air contained in lungs after a max inspiratory effort
- -TLC = TV+IRV+ERV+RV
What is vital capacity (VC) and its measurement in an average adult male?
- -4800 ml
- -max amt of air that can be expired after a max inpiratory effort (should be 80% TLC)
What is inspiratory capacity and its measurement in an average adult male?
- -3600 ml
- -max amt of air that can be inspired after a normal expiration
- -IC= TV+IRV
What is functional residual capacity (FRC) and its measurement in an average adult male?
- -2400 ml
- -volume of air remaining in the lungs after a normal tidal volume expiration
- -FRC= ERV+RV