Respiratory System

It automatically adjusts the rate of alveolar ventilation almost exactly to the body's demands. t

They are hardly modified even with moderate to intense exercise or other respiratory distress

Several groups of neurons located bilaterally in the brain stem of the CNS specifically at the medulla oblongata and pons

• -Dorsal portion of medulla oblongata.
• -Mainly inspiration

• -Ventrolateral portion of medulla
• -Inspiration or expiration depending on the nerves stimulated

• -Dorsally located in the pons
• -rate and pattern of breathing

• -controlling respiration
• -it receives information from the chemoreceptors and other receptors in the lungs that help in the control

The signal transmitted to the primary inspiratory muscles (diaphragm and external intercostals)

-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 inspiration

It limits the duration of inspiration and increases the resp rate

Stong signals reduce the time of inspiration while weak signals increase it.

In increased levels of ventilation

To maintain proper H+, O2 and CO2 in tissues, something achieved by the resp activity

• An increase in H+ and CO2.
• -Causes an increase of the inspiratory and expiratory signals
• -

• -No.
• -It acts through the peripheral chemoreceptors located in the carotid and aortic bodies

The next step is its diffusion into the pulmonary blood and CO2 in the opposite direction

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.

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

79% or 600mm/Hg at sea level

21% or 160 mm/Hg at sea level

The sum of all partial pressures

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

Its concentration and the solubility coefficeint of the gas

• Pressure = [Dissolved Gas]
•                 --------------------
•                Solubility Coefficient

• O2= 0.024
• CO2= 0.57
• CO = 0.018
• N2= 0.012
• He= 0.008

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

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.

The pressure difference

The gas press difference b/w two areas

• b/c alveolar air is only partially replaced with each breath
• - O2 is going to the blood
• -CO2 is coming from the blood 

It is immediately humidified even before reaching the alveoli

• -500 ml
• -amt of air inhaled or exhaled w/ each breath under resting conditions

• -3100 ml
• -amt of air that can be forcefully inhaled after a normal tidal volume inhalation

• -1200 ml
• -amt of air that can be forcefull exhaled after a normal tidal volume exhalation

• -1200 ml
• -amt of air remaining in the lungs after a forced exhalation

• -6000 ml
• -max amt of air contained in lungs after a max inspiratory effort
• -TLC = TV+IRV+ERV+RV

• -4800 ml
• -max amt of air that can be expired after a max inpiratory effort (should be 80% TLC)
• -VC=TV+IRV+ERV

• -3600 ml
• -max amt of air that can be inspired after a normal expiration
• -IC= TV+IRV

• -2400 ml
• -volume of air remaining in the lungs after a normal tidal volume expiration
• -FRC= ERV+RV