Histo Lecture 6
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Histo Lecture 6
Control of Pulmonary Ventilation
What part of the lung has larger Va/Q ratio?
Top of the lung
During exercise, increased blood flow and ventilation optimize what?
Va/Q ratios in all parts of the lungs
Pulmonary venous blood is diluated by what as it hits the left side of the heart?
Bronchial venous blood
Drop from 104 to 95mmHg
What percentage of Hemoglobin is bound to Oxygen?
Normal blood has how many grams of Hgb?
15g in 100 ml of blood
What is the Bohr effect?
Hgb affinity for oxygen is decreased when blood CO2 and acid [H+] increases
What are 3 ways CO2 is transported in the blood?
Dissolved in blood
Directly attached to Hgb
"exists" as bicarbonate and H+
What is the Haldane Effect?
O2 binding to Hgb decreases Hgb affinity for CO2
What is the normal amount of O2 delivered to blood from tissues?
5ml per 100ml of blood
What is the normal amount of CO2 delivered from tissues to the blood?
4ml per 100 ml of blood
How much more of an affinity does CO have on Hgb than O2?
When CO is bound to hemoglobin, PO2 levels of blood remain near ______ levels
What else does DO bind to?
myoglobin and cytochrome oxidase (aerobi respiration enzyme)
What are symptoms of CO poisoning?
What is the Respiratory Control Center?
Set of nuclei in the medulla and ons that control ventilation
What does the dorsal respiratory group control?
What does the ventral respiratory group control?
What does the pneumotaxic center control?
controls rate of breathing
What does the apneustic center control?
control depth of breathing
What do the dorsal group neurons receive peripheral input from?
Vagus and glossopharyngeal nerves
baroreceptors (aorta, carotid arteries)
lung receptors (chemo and mechano receptors)
How does the dorsal group control breathing?
Discharges begin weakly, with steady increases in a "ramping" manner
Where is the pneumotaxic center located?
parabrachialis of the pons
What affects peripheral chemoreceptors (carotid, aortic bodies)?
Blood oxygen concentrations
What do chemoreceptors signal to increase ventilation?
Carotid bodies send signals via CN9
Aortic bodies send signals via CN10
What is the chemosensitve area?
Area in the medulla, anterior to VRG and DRG
Stimulated by increased levels of CO2 and H+
Results in increased ventilation
What does stimulation of chemosensitive area result in?
Increased signaling to the other portions of the respiratory center
What is the ventilation reflex?
Prevents over-inflation of the lung
Smooth muscle stretch receptors stimulate the reflex
CN X sends inhibitory signals to inspiratory center to "stop" inspiration
What are some factors that can affect respiration?
Voluntary control of respiration
Irritants in the airways
How can brain edema affect breathing?
Increased cerebral pressures can depress or inactivate the respiratory center
What is Hypoxemia?
Low blood O2 levels created by:
-Shunting of deoxygenated blood past the lungs
What is Hypoxia?
Low levels of tissue O2
Availability of O2 to cells is decreased
What is Hypercapnia?
Excess CO2 in the blood
Usually a result of hypoventilation and/or circulatory deficiency (in the lungs)
What is Cyanosis?
Blueness of the skin due to excessive amounts of
in the blood (hypoxemia, hypoxia)
Cyanosis is dependent on the presence of
to create the bludish color
What are some examples of Cyanosis?
Anemia (low Hgb in the blood) does NOT create cyanosis
Polycythemia (excess Hgb) readily creates cyanosis due to high levels of Hgb
What is Dyspnea?
Mental anguish associated with the inability to ventilate enough to satisfy O2 demands
What are three factors associated with developing dyspnea?
Abnormal respiratory gases in body fluids (mainly hypercapnia, less influenced by hypoxia)
Amount of work performed by respiratory muscles
State of mind (neurogenic, emotional dyspnea)