Respiratory Ch 8

What other factors are included in integrated responses?

pH and exercise

What receptors lie in the airway smooth muslce and is charge in response to lung distension?

pulmonary stretch receptors

When PCO2 is low, what happens to the sensivity to PO2?

sensitivity is decreased When will receptors begin to respond to decreases PO2 with a low PCO2?

What are the general players in the respiratory control system?

sensors > Central controller > effecters

What nerve sends impulses from irritant receptors?

vagus nerve

What nerve sends the impulses from the pulmonary stretch receptors?

vagus nerve

What happens to ventilation during exercise?

ventilation increases before physiologic demands (before PaCO2 increases and PaO2 falls)

What do the central chemoreceptors regulate?

ventilation rate ** remember they are in the medulla --> main function is rhythm of ventilation

When peripheral chemoreceptors do respond to low oxygen levels, what is the nature of the response?

very rapid response, much faster than the central chemoreceptors

If the arterial baroreceptors detect hypotension, what will happen to ventilation?

will result in hyperventilation in order to increase MAP

What do the central chemoreceptors respond to stimulate ventilation?

1) Increased CO2 2) decreased pH (increased H ions, acidity) (to blow off CO2)

Where are other receptors of the respiratory system?

1) Nose and upper airways (pull out nose hairs and sneeze) 2) Joints and muscle (triggered before there is a physiologic need for increased ventilation) 3) Gamma system 4) arterial baroreceptors 5) pain and temperature

What do the central chemoreceptors respond to in order to inhibit ventilation?

1. decreased CO2 2. Increased pH

Where in the brian is the apneustic center? What is its function?

2) in the pons, role is unclear --> causes inspiratory gasps **if animal has catastrophic brain injury- if apneustic center is affected- get strange breathing pattern (arrhythmic gasping pattern)- associated with near the end of a case

What is the main function of the medullary respitatory center?

Basic rhythm of ventilation (inspiratory and expiratory centers)

What is the main central controller of the respiratory control system?

Brainstem

What receptors respond to chemicals in bronchial circulation and respond with rapid shallow breathing, bronchoconstirction and mucus secretion?

Bronchial C fibers- cause rapid shallow breathing in response to certain chemicals **A fibers- big, myelineated, rapid transmission **C fibers- small, unmyelenated fibers

What do central chemoreceptors respond to?

CO2 and pH in the brain

What causes the peripheral chemoreceptors to stimulate ventilation?

Decreased arterial PO2 and pH Increased arterial PCO2

Dose arterial PO2 increase or decrease during exercise?

Depends on the intensity: 1. Moderate exercise- PO2 can increase 2. Intense exercise- PO2 can decrease

What do the chemoreceptors actually sense? What channels are stimulated in order to cause depolarization?

H ion opens TASK channels K causes depolarization

What causes H ions to increase in the brain CSF? Can H ions cross the blood brain barrier?

H20 CO2 <-> H2CO3 <-> HCO3 H only CO2 crosses BBB, if PCO2 increases, more crosses the BBB, shifts equation to the right and increases acidity

What is the result of the reflex response to inflation? What is the name of this reflex?

Hering-Breuer Inflation reflex: main effect is slowing of respiratory frequency by increasing expiratory time *also initiates inspiratory activity following DEFLATION

In the arterial baroreceptors, what does hypertension do to ventilation?

Hypertension leads to hypoventilation Why does hypoventilation decrease MAP?

What will happen to the response to PCO2 if an animal is hypoxemic?

Ventilation will be higher for a given PCO2 (the ventilatory response to changes in PCO2 is steeper)

What receptors are in alveolar walls and respond to pulmonary capillary chemicals, engorgement, and interstitial edema? What nerve transmits these signals?

J receptors- via vagus nerve

What parts of the brain stem are involved in the central control of the respiratory system?

Medulla Apneustic center Pneumotaxic center Cortex

Does arterial PCO2 increase during exercise?

No, never increases, but could fall during intense exercise

What factors contribute to the sensitivity PO2? (integrated response to oxygen)

PCO2

What is the most important factor in the control of ventilation under normal conditions?

PCO2 in arterial blood * during daily activity, PCO2 is held with 3 mmHg

What receptors are found near the carotid bodies at the bifurcation of the common carotid arteries, aortic bodies above and below the aortic arch?

Peripheral chemoreceptors

What center can switch off or inhibit inspiration?

Pneumotaxic center- regulates inspiratory volume (and also rate)

At what partial pressure of oxygen are the peripheral chemoreceptors sensitive? When do they actually respond?

Sensitive around 500 mmHg, but there is little response until PaO2 < 100 mmHg

When PCO2 is high, what happens to the response to changes in PO2?

Sensitivity to PO2 increases, so ventilation is more greatly increased for a given PO2 When does a response to PO2 begin in times of high CO2?

What is the extent of the combined response to PCO2 and PO2 in comparison to the sum of the individual responses?

The integrated response to changes in both PCO2 and PO2 will exceed the sum of the individual responses (if one was abnormal and the other was normal)

What do the peripheral chemoreceptors respond to?

arterial PO2, pH, and PCO2

What happens to minute ventilation if pH decreases (increased H ions)?

as pH decrease, minute ventilation increases!!!! (to blow off CO2) **this is used for acid-base regulation

What is the response to impulses from irritant receptors?

bronchoconstriction and hypernea **irritant receptors are responsible sneezing in a bright light

What is the response of activation of J receptors?

causes tachypnea (shallow, rapid breathing) **important in left heart failure, when blood vessels become engorged in pulmonary vasculature

What receptors espond to change in chemical composition of blood/CSF/brain interstitial fluid and are found on the ventral surface of medulla?

central chemoreceptors

What reduces sensitivity of the central chemoreceptors?

chronic changes in PCO2 (example: acclimitization to high altitude)

What does the gamma system control and where are they found?

controls strength and contraction in intercostal muscles and diaphragm

What is responsible for voluntary ventilation?

cortex

When are the expiratory areas of the medullary respiratory center turned on?

during forceful breathing

If receptors detect pain or temperature, what will happen to ventialation?

hyperventilation

The pulmonary stretch receptors reflex is a response to what?

inflation

What receptors are found between airway epithelial cells and respond to noxious gases, smoke, dust, and cold air?

irritant receptors

How is the responsiveness of peripheral chemoreceptors to PCO2 compared to central chemoreceptors?

less responsive to PCO2, so less important when compared to central chemoreceptors

What will cause the senstivity of PCO2 to increase? (integrated response to CO2)

lowered arterial PCO2

What is the most important chemical that peripheral chemoreceptors respond to?

most important response to arterial PaO2- most important for hypoxemia **primarily hypoxia sensors, but also sense H ions through carbonic acid equation between oxygen and response: slope is steeper between change in partial pressure and maximal response (relationship is more powerful with higher gain)

What type of system is the respiratory control system?

negative feedback system **body is constantly measuring BP, Blood volume, etc- constantly making adjustments **sensors afferent to brain- efferent to heart/lungs **O2, pH, inspiratory stretch, CO2, etc **feedback goes to respiratory muscles