Respiratory System - Control Mechanisms

Topics: Respiratory physiology, Blood, Respiratory system Pages: 5 (828 words) Published: July 31, 2011
Control mechanisms – Local + CNS

Higher CNS centers (cerebral cortex, limbic system, hypothalamus)-> brain stem -> spinal cord -> respiratory system

To control respiration, what cells should you actually control? -control skeletal muscles involves in inhalation and exhalation

These cells control respiratory minute volume – how do you control them? -respiratory minute volume involves the freq. and volume of a respiratory cycle -motor neurons control skeletal muscle
-both voluntary and involuntary control – from several CNS control centers

how do we know when control is needed/where do the signals originate? -cognitive input via 5 senses (visual, auditory, olfactory, gustatory, touch) -sensory input stimulates changes in the CNS control centers


Control of respiration
-peripheral and alveolar capillaries maintain balance during gas diffusion bu:
-changes in depth and rate of respiration
-changes in blood flow and O delivery
-this requires excellent coordination between respiratory and cardiovascular systems

*ventilation (air flow) -> perfusion (blood flow) coupling 1. blood flow toward alveolar capillaries directed toward lung lobules where PO2 levels are relatively high (CO2 levels are low)
-alveolar capillaries constrict when PO2 is low
-blood is directed to area to pick up O2
2. smooth muscle cells in walls of bronchioles are sensitive to PCO2
-increased PCO2 causes bronchiodilation
-air flow directed toward lobules where PCO2 is high and CO2 is decreased (CO2 is bad) -these lobules contain CO2 obtained from blood
(decreased PCO2 causes bronchioconstriction)

Local controls – respiratory and cardiovascular systems
-scenario: cells in interstitum are very active, so
O2 is being used and PO2 decreases
CO2 is being produces (PCO2 increases)
-O2 is good and CO2 is bad so you want to bring in O2 and remove CO2

-to bring in a gas, you open up the tube in which is flows/ you dilate that tube
-dilate tube by relaxing muscles – vasodilate or bronchiodilate -to slow/restrict flow of a gas – you constrict the tube in which it flows
-vasoconstrict or bronchioconstrict
-PO2 ratio (95 mm blood vs 40 mm interstitum) gets steeper so more O2 goes to interstitium -PCO2 ratio changes (45 mm interstitium vs. 40 mm blood) so more CO2 goes to blood + increased CO2 causes smooth muscle relaxation in systemic BVs (vasodilation, blood flow increases and CO2 leaves)

CNS control of respiration
1. voluntary centers - thinking about it
-in cerebral cortex affect:
-respiratory centers of pons and medulla oblongata
-motor neurons that control respiratory muscles
2. involuntary centers – not thinking about it
-brain stem
-regulate respiratory muscles
-in response to sensory information
-resulting in changes in respiration patterns

5 sensory modifiers of respiratory center activities
1. chemoreceptors – are sensitive to PCO2, PO2, or pH of blood or cerebrospinal fluid 2. baroreceptors – in aortic or carotid sinuses are sensitive to changes in blood pressure 3. stretch receptors – respond to changes in lung volume 4. irritating physical or chemical stimuli – in nasal cavity, larynx, or bronchial tree – sneezing and coughing 5. other sensations – including pain, changes in body temp, abnormal visceral sensations

chemoreceptor stimulation
-responses to changes in blood pH or PO2
-in carotid or aortic bodies (in carotid + aorta blood vessels) -leads to increased depth and rate of respiration
-subject to adaptation – decreased sensitivity due to chronic stimulation central:
-receptors monitoring CSF by chemoreceptors
-on ventrolateral surface of medulla oblongata
-respond to increase PCO2 results in decrease in pH of CSF
-chemoreceptors increase rate/depth of breathing
-causes more air to move in and alveolar CO2 concentrations decrease *Same idea: if the pH is more acidic – correlates with...
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