Home > Uncategorized > Respiratory Physiology Lecture 2: Ventilation

Respiratory Physiology Lecture 2: Ventilation

Overview

Today is an hour long lecture on ventilation of the lungs. 

https://www.youtube.com/watch?v=lIFFrq1uJVA&feature=bf_next&list=SPE69608EC343F5691

Details

The gas exchange is very closely regulated. 

Sensors – Central Controller – Effectors

This is a negative control system.  Inputs are opposed, not reinforced. 

The central controller is the pons and medulla oblongata.   The medulla is associated with  dorsal inhalation,  ventral expiration, pattern generation.  The pre Botzinger complex  is the pattern generator and ventral respiratory group. 

The pons is associated with excitatory function, pneutaxic center which can inhibit inspiration.   

Cortex can exercise voluntary control. 

The limbic system and hypothalamus from emotional states. 

hyperventilation can change pO2 levels. 

The effectors are diaphragm, inhalation intercostals, abdominal exhalation, and the lats.

H20 + CO2 = H2CO3 = H+ + HCO3-

The Sensors:

Central chemoreceptor

A chemoreceptors response to a change in the chemical composition of the blood or another fluid.  CSF

Its in the ventral medulla, superficial. 

The brain gas barrier is very sensitive to pH.  7.4 is normal blood pH.  CSF has lower buffer capacity.  CO2 diffuses across the BBB.  Normal CSF pH is 7.32.  CSF bicaronate controlled by choroid plexus.  Reponds to pH of ECF.

Peripheral chemoreceptors

The carotid junction and the aortic body.  Glomis cells have high amounts of dopamine.   Response to PO2, pCO2 and pH.  Little response to normoxia.  Very high blood flow.  Respond to arterial, not venous pO2.  Fast response.  Carotid body.

Lung Receptors

Pulmonary stretch receptors are responsible for Hering Breuer reflex.

Irritant receptors

J receptors

Arterial baroreceptors

Pain and temperature

Nose and upper airway

Joint and muscle

Gamma system shortness of breath   

arteriol blood

lung receptors

Response to CO2

Primary factor in the control of ventilation

measured by rebreathing from a bag

Inspiratory pressure following break occulsion

Response is altered by sleep, age, genetic factors

Reduced by increasing the work of breathing

response to Reduced pO2

no role under normoxic conditions

measured by rebreathing from a bag

increased response if the pCO2 is raises

important at high altitude, peripheral receptors

importation in patients with chronic lung disease

Response to reduced pH

Sensed by the peripheral chemoreceptors

Important in metabolic acidosis

If the reduction is severe, central chemoreceptors may be stimulated.

Response to Exercise

Blood gases are normal

pH is normal except at heavy exercise

Cortex, impulses from limbs, increased temperature, resetting of CO2 reference level

Sleep Apnea

Obstructive: very common, often associated with obesity, sleep deprivation may cause daytime somnolence and impaired cognitive function

Central: respiratory depression during sleep, recognized by the absence of respiratory efforts

During obstructive, the muscles are trying to breathe.  In central, not. 

Arterial pCO2 only varies by 4 millibar in the 24 hour period.   

Review

Visible Light – 400 to 700 nm

Aromatic: planar, cyclic, Huckels Rule – 4n+2 electrons

Fibrous – sclera, cornea

Sensory – retina

Vascular – choroid, iris, pupil, ciliary body

Kingdoms – monera, protista, fungi, plant, animal

HSbF6 pKa = 25

Electrophiles are positive, nucleophiles are negative

EDTA is a tetraprotic acid.

Activators donate electrons to the ring, deactivators take electrons from the ring

Acetone pKa = 24.2

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