Ch 8 Control Flashcards
What is the chief function of the lung?
To exchange O2 and CO2 between blood and gas.
What are the three basic elements of the respiratory control system?
- Sensors
- Central controller
- Effectors
Where does the normal automatic process of breathing originate?
In impulses from the brainstem.
What is the role of the central pattern generator in respiration?
It controls the periodic nature of inspiration and expiration.
Which group of neurons is essential for generating the respiratory rhythm?
The Pre-Botzinger Complex.
What is the function of the pneumotaxic center?
To switch off or inhibit inspiration.
What type of breathing pattern is seen if the apneustic center is activated?
Prolonged inspiratory gasps interrupted by transient expiratory efforts.
What is the role of the cortex in respiratory control?
To provide voluntary control over breathing.
What are the primary muscles involved in respiration?
- Diaphragm
- Intercostal muscles
- Abdominal muscles
- Accessory muscles
Where are central chemoreceptors located?
Near the ventral surface of the medulla.
What stimulates central chemoreceptors?
Changes in H+ concentration in the extracellular fluid.
What is the most important receptor for minute-by-minute control of ventilation?
Central chemoreceptors.
What happens to ventilation when there is an increase in H+ concentration?
It stimulates ventilation.
Where are peripheral chemoreceptors located?
- Carotid bodies
- Aortic bodies
What is the primary response of peripheral chemoreceptors?
To decreases in arterial Po2 and pH, and increases in arterial Pco2.
What is the sensitivity threshold for peripheral chemoreceptors to changes in arterial Po2?
Begins around 500 mm Hg.
How do peripheral chemoreceptors respond to arterial hypoxemia?
They are responsible for all the increase in ventilation.
What happens to ventilation in the absence of peripheral chemoreceptors during severe hypoxemia?
It may depress ventilation.
What is the effect of chronic hypoxia on the carotid bodies?
Hypertrophy of the carotid bodies.
True or False: The peripheral chemoreceptors have a more important response to arterial Pco2 than central chemoreceptors.
False.
What does the response of peripheral chemoreceptors to arterial Pco2 allow for?
Rapid adjustment of ventilation to abrupt changes in Pco2.
What is the normal pH of cerebrospinal fluid (CSF)?
7.32.
Fill in the blank: The __________ regulates ventilation chiefly by its effect on the pH of the CSF.
CO2 level in blood.
What occurs when blood Pco2 rises?
CO2 diffuses into the CSF, liberating H+ ions.
What is a potential consequence of uncoordinated respiratory muscle activity in newborns?
Sudden infant death syndrome.
What are central chemoreceptors primarily sensitive to?
Pco2 in the arterial blood
Central chemoreceptors play a crucial role in regulating ventilation by responding to changes in carbon dioxide levels.
What percentage of the ventilatory response can be attributed to peripheral chemoreceptors when breathing a CO2 mixture?
Less than 20%
Peripheral chemoreceptors respond more rapidly than central chemoreceptors to changes in Pco2.
Which bodies respond to a fall in arterial pH?
Carotid bodies
The carotid bodies respond to changes in pH regardless of whether the cause is respiratory or metabolic.
What is the main reflex effect of stimulating pulmonary stretch receptors?
Slowing of respiratory frequency
This effect is part of the Hering-Breuer inflation reflex, which helps regulate breathing.
What happens during the Hering-Breuer reflex when the lungs are inflated?
Inhibits further inspiratory muscle activity
The reflex provides a self-regulatory mechanism for respiration.
What type of receptors are stimulated by noxious gases and cigarette smoke?
Irritant receptors
These receptors can cause reflex responses like bronchoconstriction and hyperpnea.
What are J receptors also known as?
Juxtacapillary receptors
They are located in the alveolar walls and respond to changes in the pulmonary circulation.
What is the primary function of bronchial C fibers?
Respond to chemicals in the bronchial circulation
Their stimulation leads to rapid shallow breathing and bronchoconstriction.
What reflex responses do nose and upper airway receptors mediate?
Sneezing, coughing, bronchoconstriction
These responses are triggered by mechanical and chemical stimulation.
What do gamma system receptors in muscles sense?
Elongation of muscle
This information helps control the strength of contraction and can be involved in the sensation of dyspnea.
What effect does an increase in arterial blood pressure have on respiration?
Causes reflex hypoventilation or apnea
This response is mediated through aortic and carotid sinus baroreceptors.
What is the most important factor in controlling ventilation under normal conditions?
Pco2 of the arterial blood
The sensitivity of this control is significant, maintaining tight regulation during daily activities.
How much does ventilation increase for each 1 mm Hg rise in Pco2?
About 2 to 3 liters·min−1
This relationship shows the responsiveness of ventilation to changes in carbon dioxide levels.
What happens to the ventilatory response to CO2 as age increases?
It is reduced
Factors such as sleep and increasing age diminish the sensitivity of the respiratory center.
What is the response to hypoxia in terms of ventilation?
Stimulates ventilation through peripheral chemoreceptors
This response is negligible under normoxic conditions but becomes critical at high altitudes.
What happens to ventilation when arterial blood pH decreases?
Stimulates ventilation
This response is primarily mediated by peripheral chemoreceptors.
What is a notable change in ventilation during exercise?
Ventilation increases significantly, matching O2 uptake and CO2 output
Fit individuals can experience over 15 times their resting ventilation during strenuous activity.
True or False: Hypoxemia stimulates ventilation by acting on central chemoreceptors.
False
Hypoxemia primarily stimulates peripheral chemoreceptors; central chemoreceptors do not respond to low oxygen levels.
Fill in the blank: The __________ response to CO2 is reduced by sleep, increasing age, and certain drugs.
ventilatory
Various factors can influence the effectiveness of the respiratory center’s response to carbon dioxide.
What happens to the brain barrier during exercise?
The brain barrier becomes partly permeable to H+ ions.
How much can ventilation increase during strenuous exercise?
Ventilation may reach very high levels, exceeding 150 liters·min–1.
Does the arterial Pco2 increase during exercise?
No, it typically falls slightly during severe exercise.
What happens to the arterial Po2 during exercise?
It usually increases slightly, but may fall at very high work levels.
What occurs to the arterial pH during heavy exercise?
It falls due to the liberation of lactic acid.
What stimulates ventilation during the first few seconds of exercise?
Passive movement of the limbs.
What is one hypothesis for increased ventilation during exercise?
Oscillations in arterial Po2 and Pco2 may stimulate peripheral chemoreceptors.
True or False: The ventilatory response to inhaled CO2 is a reliable guide to what happens during exercise.
False.
What is Cheyne-Stokes respiration?
A pattern of periodic breathing with periods of apnea separated by hyperventilation.
Where are the respiratory centers located?
In the pons and medulla of the brainstem.
What do central chemoreceptors respond to?
Changes in pH of the CSF caused by CO2 diffusion.
Where are peripheral chemoreceptors primarily located?
In the carotid bodies.
What is the most important factor controlling ventilation under normal conditions?
Pco2 of the blood.
What happens to ventilation in response to hypoxia at high altitude?
It becomes the major stimulus to ventilation.
Fill in the blank: Exercise causes a large increase in ventilation, but the cause is _______.
poorly understood.
What physiological changes occurred in the 23-year-old student during his ascent to high altitude?
Increased pH, decreased Pco2, decreased Po2.
What happened to the student’s hemoglobin concentration during his stay at the research station?
It increased to 16.5 g·dl−1.
Which component of the blood is most affected by chronic obstructive pulmonary disease?
Pco2 increases.
What would you expect in the cerebrospinal fluid of a patient with chronic obstructive pulmonary disease?
Increased bicarbonate concentration.
What is the expected change in arterial blood gas for a person with removed carotid bodies at high altitude?
Higher Pco2.
What change is expected in a woman’s arterial pH at high altitude compared to sea level?
Decreased arterial pH.
True or False: The cortex can override the function of the respiratory centers.
True.
What effect does increased body temperature have during exercise?
It stimulates ventilation.
What is the role of the motor cortex concerning breathing?
It can override the output of respiratory centers.
What is the response of peripheral chemoreceptors to increased Pco2?
They respond rapidly but less marked than central chemoreceptors.
Fill in the blank: The Pco2 of the blood is the most important factor controlling _______.
ventilation.
