Respiratory System Flashcards
- Which of the following neurotransmitters is released from postganglionic parasympathetic nerves and causes bronchoconstriction?
a) Norepinephrine
b) Dopamine
c) Acetylcholine
d) Nitric oxide
Answer: c) Acetylcholine
Explanation: Acetylcholine is released from postganglionic parasympathetic nerves and activates the M3 muscarinic receptors on the airway smooth muscle, causing bronchoconstriction
- What is the approximate partial pressure of oxygen in the alveolar air?
a) 40 mmHg
b) 100 mmHg
c) 160 mmHg
d) 200 mmHg
Answer: b) 100 mmHg
Explanation: The partial pressure of oxygen (pO2) in alveolar air is approximately 100 mmHg, considering the calculation involving the atmospheric pressure and water vapor pressure
- Which receptors inhibit the release of acetylcholine from parasympathetic nerves?
a) β2-adrenergic receptors
b) M2 muscarinic receptors
c) M3 muscarinic receptors
d) α1-adrenergic receptors
Answer: b) M2 muscarinic receptors
Explanation: M2 muscarinic receptors are located on parasympathetic nerves and inhibit the release of acetylcholine, counteracting the effects of M3 receptor activation
- In humans, sympathetic innervation of which of the following is absent?
a) Blood vessels
b) Submucosal glands
c) Airway smooth muscle
d) Parasympathetic ganglia
Answer: c) Airway smooth muscle
Explanation: In humans, there is little evidence of sympathetic innervation of airway smooth muscle. Sympathetic nerves primarily innervate parasympathetic ganglia, submucosal glands, and blood vessels
- What is the main function of hypoxic pulmonary vasoconstriction (HPV)?
a) Increasing blood pressure
b) Diverting blood to better-ventilated areas
c) Increasing heart rate
d) Enhancing mucus secretion
Answer: b) Diverting blood to better-ventilated areas
Explanation: HPV diverts blood away from poorly ventilated regions of the lung to better-ventilated areas, optimizing ventilation/perfusion matching and enhancing gas exchange
- Which ion channel is primarily responsible for hypoxic pulmonary vasoconstriction?
a) L-type Ca2+ channel
b) Na+ channel
c) K+ channel
d) Cl- channel
Answer: a) L-type Ca2+ channel
Explanation: Hypoxia inhibits O2-sensitive K+ channels, leading to depolarization of the plasma membrane and subsequent activation of L-type Ca2+ channels, which triggers contraction in hypoxic pulmonary vasoconstriction
- What happens to the partial pressure of carbon dioxide in the blood when moving from the pulmonary arteries to the alveoli?
a) Increases
b) Decreases
c) Remains constant
d) Fluctuates
Explanation: The partial pressure of carbon dioxide (pCO2) in the blood decreases as CO2 diffuses from the blood (pCO2 46 mmHg) to the alveoli (pCO2 40 mmHg)
- Which condition results from chronic hypoxic pulmonary vasoconstriction?
a) Pulmonary embolism
b) Pulmonary hypertension
c) Asthma
d) Chronic obstructive pulmonary disease (COPD)
Answer: b) Pulmonary hypertension
Explanation: Chronic hypoxic pulmonary vasoconstriction can lead to elevated pulmonary pressure, potentially resulting in pulmonary hypertension and associated conditions like right ventricular hypertrophy and right heart failure
- What is the primary role of surfactant in the lungs?
a) Enhancing gas exchange
b) Reducing surface tension
c) Increasing blood flow
d) Facilitating bronchoconstriction
Answer: b) Reducing surface tension
Explanation: Surfactant is a detergent-like substance that reduces surface tension in the alveoli, preventing their collapse and reducing the effort required for inspiration
- Which of the following mechanisms primarily regulates the partial pressure of CO2 in the blood?
a) Kidney activity
b) Liver metabolism
c) Lung function
d) Pancreatic secretion
Answer: c) Lung function
Explanation: The partial pressure of CO2 (PCO2) in the blood is primarily regulated by the lungs through the processes of ventilation and gas exchange
- Which component of the respiratory system does NOT contain cartilaginous structures?
a) Trachea
b) Primary bronchi
c) Conducting bronchioles
d) Respiratory bronchioles
Answer: d) Respiratory bronchioles
Explanation: Respiratory bronchioles do not contain cartilaginous structures. Cartilage is found in the trachea and primary bronchi, while conducting bronchioles have smooth muscle but not cartilage
- During which phase of the respiratory cycle does the diaphragm contract and flatten?
a) Passive expiration
b) Active expiration
c) Inspiration
d) Post-expiration pause
Answer: c) Inspiration
Explanation: During inspiration, the diaphragm contracts and flattens, increasing the capacity of the thoracic cavity and reducing intra-pleural pressure to draw air into the lungs
- Which respiratory group is located in the nucleus tractus solitarius of the brain?
a) Dorsal respiratory group
b) Ventral respiratory group
c) Pontine respiratory group
d) Apneustic center
Answer: a) Dorsal respiratory group
Explanation: The dorsal respiratory group is located in the nucleus tractus solitarius of the brain and is involved in regulating the rhythm of respiration
- What effect does stimulation of β2-adrenergic receptors have on airway smooth muscle?
a) Bronchoconstriction
b) Bronchodilation
c) Increased mucus secretion
d) Decreased blood flow
Answer: b) Bronchodilation
Explanation: Stimulation of β2-adrenergic receptors on airway smooth muscle induces bronchodilation and decreases airway resistance
- In the chloride shift, bicarbonate ions diffuse out of red blood cells in exchange for which ion?
a) Sodium (Na+)
b) Potassium (K+)
c) Chloride (Cl-)
d) Calcium (Ca2+)
Answer: c) Chloride (Cl-)
Explanation: In the chloride shift, bicarbonate ions generated in red blood cells diffuse out into the plasma in exchange for chloride ions (Cl-) to maintain electroneutrality
- Which term describes normal breathing patterns?
a) Apnoea
b) Eupnoea
c) Hyperpnoea
d) Hypopnoea
Answer: b) Eupnoea
Explanation: Eupnoea (or eupnea) describes normal breathing patterns, characterized by regular, unlabored breathing
- What is the role of nitric oxide (NO) in the noncholinergic parasympathetic pathway in the lungs?
a) Inducing bronchoconstriction
b) Enhancing mucus secretion
c) Providing relaxant innervation
d) Increasing airway resistance
Answer: c) Providing relaxant innervation
Explanation: Nitric oxide (NO) in the noncholinergic parasympathetic pathway provides relaxant innervation to the airways, counteracting the contractile effects of the cholinergic pathway
- What percentage of carbon dioxide is transported in the blood as bicarbonate ions?
a) 7%
b) 23%
c) 50%
d) 70%
Answer: d) 70%
Explanation: Approximately 70% of carbon dioxide in the blood is transported as bicarbonate ions, formed through the reaction of CO2 with water, catalyzed by carbonic anhydrase
- Which respiratory center must be inhibited for inspiration to terminate and expiration to commence?
a) Pneumotaxic center
b) Apneustic center
c) Dorsal respiratory group
d) Ventral respiratory group
Answer: b) Apneustic center
Explanation: The apneustic center stimulates the medullary inspiratory center to prolong inspiration and must be inhibited for inspiration to terminate and expiration to commence
- What is the effect of decreased compliance on lung function?
a) Easier expansion of the lungs
b) Reduced resistance to expansion
c) Stiffening of the lungs
d) Increased surface tension in alveoli
Answer: c) Stiffening of the lungs
Explanation: Decreased compliance leads to the stiffening of the lungs, making them more resistant to expansion, which impairs efficient ventilation
- What type of respiratory center is responsible for sending impulses to the expiratory muscles during active expiration?
a) Inspiratory center
b) Expiratory center
c) Apneustic center
d) Pneumotaxic center
Answer: b) Expiratory center
Explanation: The expiratory center, located near the inspiratory center, sends impulses to the expiratory muscles during active expiration to reinforce respiratory effort
- Which of the following is NOT a function of the pleura in the thoracic cavity?
a) Reducing friction between lung surfaces
b) Exerting negative pressure
c) Conducting air to respiratory surfaces
d) Suction force aiding lung expansion
Answer: c) Conducting air to respiratory surfaces
Explanation: The pleura do not conduct air to respiratory surfaces. Instead, they reduce friction, exert negative pressure, and provide suction force aiding lung expansion
- How does hypoventilation affect arterial PCO2 levels?
a) Decreases PCO2
b) Increases PCO2
c) Has no effect on PCO2
d) Causes variable PCO2
Answer: b) Increases PCO2
Explanation: Hypoventilation reduces the removal of CO2 from the blood, leading to increased arterial PCO2 level
- What is the primary determinant of the respiratory drive under normal conditions in healthy individuals?
a) Arterial oxygen levels
b) Arterial carbon dioxide levels
c) Blood glucose levels
d) Blood pressure
Answer: b) Arterial carbon dioxide levels
Explanation: The respiratory center in healthy individuals is more sensitive to rising levels of carbon dioxide sensed by central chemoreceptors than to decreasing oxygen levels【
- Which muscle is the most important during inspiration?
a) External intercostal muscles
b) Internal intercostal muscles
c) Diaphragm
d) Serratus anterior
Answer: c) Diaphragm
Explanation: The diaphragm is the most important muscle during inspiration, contracting and flattening to increase thoracic cavity capacity and draw air into the lungs
- What is the role of central chemoreceptors in the medulla of the brain?
a) Sensing blood glucose levels
b) Detecting changes in pH and PCO2
c) Monitoring blood pressure
d) Regulating heart rate
Answer: b) Detecting changes in pH and PCO2
Explanation: Central chemoreceptors in the medulla are sensitive to changes in pH and PCO2, primarily responding to pH changes caused by alterations in arterial carbon dioxide
- Which structure forms the trunk of the tracheobronchial tree?
a) Bronchi
b) Bronchioles
c) Trachea
d) Alveoli
Answer: c) Trachea
Explanation: The trachea forms the trunk of the tracheobronchial tree, conducting air from the mouth and nose towards the lungs
- What is the primary function of the apneustic center in the brain?
a) Inhibiting inspiration
b) Prolonging inspiration
c) Facilitating expiration
d) Regulating heart rate
Answer: b) Prolonging inspiration
Explanation: The apneustic center stimulates the medullary inspiratory center to prolong inspiration. It must be inhibited for inspiration to terminate and expiration to commence
- What happens to hemoglobin’s affinity for oxygen when blood pH decreases?
a) Increases
b) Decreases
c) Remains constant
d) Fluctuates
Answer: b) Decreases
Explanation: A decrease in blood pH (acidic conditions) reduces hemoglobin’s affinity for oxygen, facilitating the release of oxygen to the tissues. This is known as the Bohr effect
- What is the effect of increased sympathetic stimulation on airway smooth muscle?
a) Bronchoconstriction
b) Bronchodilation
c) Increased mucus production
d) Decreased blood flow
Answer: b) Bronchodilation
Explanation: Increased sympathetic stimulation relaxes airway smooth muscle, leading to bronchodilation and reduced airway resistance
- Which part of the respiratory system is primarily responsible for the exchange of gases?
a) Trachea
b) Bronchi
c) Respiratory bronchioles
d) Conducting bronchioles
Answer: c) Respiratory bronchioles
Explanation: The respiratory bronchioles are primarily responsible for the exchange of gases between the air in the alveoli and the blood in the pulmonary capillaries
- What is the typical respiratory rate for a healthy adult at rest?
a) 6-8 breaths per minute
b) 12-14 breaths per minute
c) 20-24 breaths per minute
d) 30-36 breaths per minute
Answer: b) 12-14 breaths per minute
Explanation: The typical respiratory rate for a healthy adult at rest is approximately 12-14 breaths per minute
- Which type of receptor primarily detects low arterial oxygen levels?
a) Central chemoreceptors
b) Peripheral chemoreceptors
c) Mechanoreceptors
d) Baroreceptors
Answer: b) Peripheral chemoreceptors
Explanation: Peripheral chemoreceptors, located in the carotid and aortic bodies, primarily detect low arterial oxygen levels (hypoxemia) and send signals to the respiratory center
- What is the main function of the pneumotaxic center?
a) Prolonging inspiration
b) Inhibiting the apneustic center
c) Enhancing mucus secretion
d) Detecting blood pressure changes
Answer: b) Inhibiting the apneustic center
Explanation: The pneumotaxic center inhibits the apneustic center and the inspiratory center, facilitating expiration and regulating the rhythm of breathing
- What is the primary effect of acetylcholine on airway smooth muscle?
a) Bronchodilation
b) Bronchoconstriction
c) Increased blood flow
d) Decreased mucus production
Answer: b) Bronchoconstriction
Explanation: Acetylcholine released from postganglionic parasympathetic nerves activates the M3 muscarinic receptors on the airway smooth muscle, causing bronchoconstriction
- Which type of blood vessel has thinner walls and less smooth muscle compared to systemic vessels?
a) Pulmonary arteries
b) Pulmonary veins
c) Systemic arteries
d) Systemic veins
Answer: a) Pulmonary arteries
Explanation: Pulmonary arteries have thinner walls and less smooth muscle compared to systemic arteries, allowing them to accommodate the low-pressure system of the pulmonary circulation
- What is the effect of increased temperature on the oxygen dissociation curve of hemoglobin?
a) Shifts to the left
b) Shifts to the right
c) Remains unchanged
d) Becomes hyperbolic
Answer: b) Shifts to the right
Explanation: Increased temperature causes the oxygen dissociation curve of hemoglobin to shift to the right, reducing hemoglobin’s affinity for oxygen and promoting oxygen release to tissues
- What is the primary role of carbonic anhydrase in red blood cells?
a) Catalyzing the conversion of CO2 to carbonic acid
b) Facilitating oxygen binding to hemoglobin
c) Enhancing mucus secretion
d) Regulating blood glucose levels
Answer: a) Catalyzing the conversion of CO2 to carbonic acid
Explanation: Carbonic anhydrase catalyzes the conversion of CO2 to carbonic acid (H2CO3), which then dissociates into H+ and HCO3-, playing a crucial role in CO2 transport and pH regulation
- Which factor does NOT affect the association of oxygen with hemoglobin?
a) pH
b) Temperature
c) 2,3-DPG
d) Blood pressure
Answer: d) Blood pressure
Explanation: The association of oxygen with hemoglobin is affected by pH, temperature, and 2,3-DPG (an intermediate in glucose breakdown), but not directly by blood pressure
- What is the main cause of respiratory acidosis?
a) Increased CO2 retention
b) Decreased HCO3- levels
c) Increased oxygen levels
d) Decreased glucose levels
Answer: a) Increased CO2 retention
Explanation: Respiratory acidosis is primarily caused by increased CO2 retention, which leads to a decrease in pH. This can occur in conditions like respiratory depression
- Which condition is characterized by decreased arterial PCO2 and increased pH?
a) Respiratory acidosis
b) Metabolic acidosis
c) Respiratory alkalosis
d) Metabolic alkalosis
Answer: c) Respiratory alkalosis
Explanation: Respiratory alkalosis is characterized by decreased arterial PCO2 and increased pH, often caused by hyperventilation or chronic oxygen decrease
- What effect does metabolic acidosis have on respiration?
a) Stimulates hyperventilation
b) Inhibits respiration
c) Causes hypoventilation
d) Has no effect on respiration
Answer: a) Stimulates hyperventilation
Explanation: Metabolic acidosis stimulates hyperventilation as the body attempts to expel CO2 and increase pH by reducing hydrogen ion concentration
- What is the physiological response to increased HCO3- levels in metabolic alkalosis?
a) Increased respiration
b) Inhibited respiration
c) Increased CO2 retention
d) Decreased CO2 retention
Answer: b) Inhibited respiration
Explanation: In metabolic alkalosis, increased HCO3- levels lead to inhibited respiration to retain CO2 and decrease pH, counteracting the alkalosis
- Which respiratory structure is responsible for producing surfactant?
a) Trachea
b) Bronchi
c) Alveoli
d) Conducting bronchioles
Answer: c) Alveoli
Explanation: The alveoli, specifically the Type II alveolar cells, are responsible for producing surfactant, which reduces surface tension and prevents alveolar collapse
- Which gas has the highest partial pressure in inspired air?
a) Oxygen
b) Carbon dioxide
c) Nitrogen
d) Water vapor
Answer: c) Nitrogen
Explanation: Nitrogen has the highest partial pressure in inspired air, making up approximately 78% of the atmospheric gases
- What is the primary function of peripheral chemoreceptors?
a) Detecting changes in blood pH
b) Monitoring blood glucose levels
c) Sensing arterial oxygen levels
d) Regulating heart rate
Answer: c) Sensing arterial oxygen levels
Explanation: Peripheral chemoreceptors primarily sense arterial oxygen levels (hypoxemia) and send signals to the respiratory center to modulate breathing patterns
- Which respiratory structure relies on smooth muscle and elastic fibers to maintain wall integrity?
a) Trachea
b) Bronchi
c) Bronchioles
d) Alveoli
Answer: c) Bronchioles
Explanation: The bronchioles rely on smooth muscle and elastic fibers to maintain their wall integrity and regulate airway diameter
- What happens to bicarbonate ions in red blood cells during the chloride shift?
a) They are converted to CO2
b) They are exchanged for chloride ions
c) They bind to hemoglobin
d) They increase blood pressure
Answer: b) They are exchanged for chloride ions
Explanation: During the chloride shift, bicarbonate ions diffuse out of red blood cells in exchange for chloride ions to maintain electroneutrality
- Which respiratory center is NOT involved in the rhythm of breathing?
a) Inspiratory center
b) Expiratory center
c) Apneustic center
d) Cardiac center
Answer: d) Cardiac center
Explanation: The cardiac center is not involved in the rhythm of breathing. The inspiratory, expiratory, and apneustic centers play key roles in regulating the respiratory cycle
- What is the role of pulmonary capillaries in gas exchange?
a) Conducting air to alveoli
b) Exchanging gases between air and blood
c) Producing mucus
d) Regulating blood pressure
Answer: b) Exchanging gases between air and blood
Explanation: Pulmonary capillaries surround the alveoli and facilitate the exchange of gases (oxygen and carbon dioxide) between the air in the alveoli and the blood
- What is the effect of the Bohr effect on hemoglobin’s oxygen affinity?
a) Increases affinity at high pH
b) Decreases affinity at low pH
c) Increases affinity at low temperature
d) Decreases affinity at high altitude
Answer: b) Decreases affinity at low pH
Explanation: The Bohr effect refers to the decrease in hemoglobin’s oxygen affinity at low pH (acidic conditions), promoting oxygen release to the tissues
- Which neurotransmitter is primarily associated with noncholinergic relaxant pathways in the lungs?
a) Acetylcholine
b) Norepinephrine
c) Nitric oxide
d) Dopamine
Answer: c) Nitric oxide
Explanation: Nitric oxide is associated with noncholinergic relaxant pathways in the lungs, providing relaxant innervation to the airway smooth muscle
- Which muscle group is primarily involved in forced expiration?
a) Diaphragm
b) Internal intercostal muscles
c) External intercostal muscles
d) Scalenus muscles
Answer: b) Internal intercostal muscles
Explanation: The internal intercostal muscles, along with the abdominal muscles, are primarily involved in forced expiration, actively decreasing thoracic cavity capacity and expelling air
- What is the primary role of the dorsal respiratory group in the brain?
a) Inhibiting inspiration
b) Sending signals for inspiration
c) Monitoring blood pH
d) Regulating heart rate
Answer: b) Sending signals for inspiration
Explanation: The dorsal respiratory group in the nucleus tractus solitarius of the brain sends signals to the inspiratory muscles, regulating the rhythm of breathing
- Which factor primarily determines the contractile state of vascular smooth muscle?
a) Blood glucose levels
b) Ion channel activity
c) Surfactant production
d) Mucus secretion
Answer: b) Ion channel activity
Explanation: The contractile state of vascular smooth muscle, or vascular tone, is primarily determined by ion channel activity, which regulates membrane potential and intracellular calcium levels
- What is the effect of sympathetic stimulation on submucosal glands in the lungs?
a) Decreases mucus secretion
b) Increases mucus secretion
c) Causes bronchoconstriction
d) Causes bronchodilation
Answer: b) Increases mucus secretion
Explanation: Sympathetic stimulation increases mucus secretion from the submucosal glands in the lungs by activating β2-adrenergic receptors
- Which gas law explains the movement of gases from an area of high pressure to low pressure?
a) Boyle’s Law
b) Charles’s Law
c) Dalton’s Law
d) Henry’s Law
Answer: c) Dalton’s Law
Explanation: Dalton’s Law explains that gases move from an area of high pressure to low pressure by diffusion, which is fundamental to gas exchange in the lungs
- What happens to the partial pressure of oxygen in venous blood compared to arterial blood?
a) It increases
b) It decreases
c) It remains constant
d) It fluctuates
Answer: b) It decreases
Explanation: The partial pressure of oxygen (pO2) in venous blood is lower compared to arterial blood, as oxygen is delivered to the tissues from the arterial blood
- What is the role of the pontine respiratory group in the brain?
a) Regulating blood pressure
b) Controlling heart rate
c) Modulating respiratory rhythm
d) Producing surfactant
Answer: c) Modulating respiratory rhythm
Explanation: The pontine respiratory group, including the pneumotaxic and apneustic centers, modulates respiratory rhythm by influencing the activity of the medullary respiratory centers
- Which condition results from decreased compliance of the lungs?
a) Increased airway resistance
b) Stiffening of the lungs
c) Enhanced gas exchange
d) Increased lung elasticity
Answer: b) Stiffening of the lungs
Explanation: Decreased compliance leads to stiffening of the lungs, making them more resistant to expansion and impairing efficient ventilation
- What is the primary function of the trachea in the respiratory system?
a) Gas exchange
b) Conducting air to the lungs
c) Producing surfactant
d) Regulating blood pH
Answer: b) Conducting air to the lungs
Explanation: The trachea conducts air from the mouth and nose towards the lungs, forming the main trunk of the tracheobronchial tree
- What is the effect of decreased arterial oxygen levels on peripheral chemoreceptors?
a) Decreases respiratory rate
b) Inhibits the cough reflex
c) Stimulates the respiratory center
d) Reduces mucus secretion
Answer: c) Stimulates the respiratory center
Explanation: Decreased arterial oxygen levels stimulate peripheral chemoreceptors, which send signals to the respiratory center to increase the respiratory rate and improve oxygen uptake
- Which part of the respiratory system contains ciliated epithelium for filtering air?
a) Alveoli
b) Respiratory bronchioles
c) Conducting bronchioles
d) Pulmonary capillaries
Answer: c) Conducting bronchioles
Explanation: The conducting bronchioles contain ciliated epithelium, which continues to filter air as it moves towards the respiratory surfaces
- What is the role of the diaphragm during inspiration?
a) Relaxing and ascending
b) Contracting and flattening
c) Expelling air from the lungs
d) Increasing airway resistance
Answer: b) Contracting and flattening
Explanation: During inspiration, the diaphragm contracts and flattens, increasing the capacity of the thoracic cavity and reducing intra-pleural pressure to draw air into the lungs
- What is the effect of hyperventilation on arterial PCO2 levels?
a) Increases PCO2
b) Decreases PCO2
c) Has no effect on PCO2
d) Causes variable PCO2
Answer: b) Decreases PCO2
Explanation: Hyperventilation increases the expulsion of CO2 from the blood, leading to decreased arterial PCO2 levels
- Which structure provides the primary contractile input to the airways in the parasympathetic pathway?
a) Adrenergic neurons
b) Cholinergic postganglionic neurons
c) Noncholinergic neurons
d) Sensory neurons
Answer: b) Cholinergic postganglionic neurons
Explanation: Cholinergic postganglionic neurons provide the primary contractile input to the airways in the parasympathetic pathway, causing bronchoconstriction when activated
- What is the primary component of mucus produced by submucosal glands in the lungs?
a) Glucose
b) Surfactant
c) Mucins
d) Hemoglobin
Answer: c) Mucins
Explanation: Mucins are the primary component of mucus produced by submucosal glands, giving mucus its gel-like properties and facilitating the trapping of particles and pathogens
- Which type of receptor primarily responds to irritative chemical triggers in the lungs?
a) Peripheral chemoreceptors
b) Central chemoreceptors
c) Mechanoreceptors
d) Baroreceptors
Answer: c) Mechanoreceptors
Explanation: Mechanoreceptors, specifically rapid adapting irritant receptors, respond to irritative chemical triggers in the lungs and initiate the cough reflex
- What is the main function of alveolar macrophages?
a) Producing surfactant
b) Filtering inspired air
c) Phagocytosing pathogens and debris
d) Regulating blood pressure
Answer: c) Phagocytosing pathogens and debris
Explanation: Alveolar macrophages are immune cells that phagocytose pathogens and debris in the alveoli, playing a crucial role in lung defense
- What is the primary effect of increased 2,3-DPG levels on hemoglobin?
a) Increased oxygen affinity
b) Decreased oxygen affinity
c) Increased CO2 affinity
d) Decreased CO2 affinity
Answer: b) Decreased oxygen affinity
Explanation: Increased levels of 2,3-DPG decrease hemoglobin’s affinity for oxygen, promoting the release of oxygen to the tissues
- Which structure serves as the primary respiratory surface in the lungs?
a) Trachea
b) Bronchi
c) Alveoli
d) Conducting bronchioles
Answer: c) Alveoli
Explanation: The alveoli serve as the primary respiratory surface in the lungs, facilitating gas exchange between the air and blood
- What is the role of the ventral respiratory group in the medulla?
a) Regulating blood pressure
b) Sending signals for active expiration
c) Detecting blood pH changes
d) Producing surfactant
Answer: b) Sending signals for active expiration
Explanation: The ventral respiratory group in the medulla sends signals for active expiration, reinforcing respiratory effort during increased respiratory demand
- Which ion channel is primarily involved in the depolarization of vascular smooth muscle during hypoxic pulmonary vasoconstriction?
a) Sodium channel
b) Calcium channel
c) Potassium channel
d) Chloride channel
Answer: b) Calcium channel
Explanation: During hypoxic pulmonary vasoconstriction, the inhibition of O2-sensitive K+ channels leads to the activation of L-type Ca2+ channels, causing depolarization and contraction of vascular smooth muscle
- What is the effect of the chloride shift on CO2 transport in the blood?
a) Increases CO2 solubility
b) Enhances bicarbonate ion formation
c) Inhibits hemoglobin buffering
d) Reduces blood pH
Answer: b) Enhances bicarbonate ion formation
Explanation: The chloride shift enhances bicarbonate ion formation in red blood cells, facilitating CO2 transport and maintaining electroneutrality
- Which condition is characterized by an increase in arterial PCO2 and a decrease in blood pH?
a) Respiratory alkalosis
b) Metabolic alkalosis
c) Respiratory acidosis
d) Metabolic acidosis
Answer: c) Respiratory acidosis
Explanation: Respiratory acidosis is characterized by an increase in arterial PCO2 (carbon dioxide retention) and a decrease in blood pH
- What is the primary function of the pneumotaxic center in the brain?
a) Enhancing mucus secretion
b) Prolonging inspiration
c) Inhibiting the apneustic center
d) Regulating blood pressure
Answer: c) Inhibiting the apneustic center
Explanation: The pneumotaxic center inhibits the apneustic center and the inspiratory center, facilitating expiration and regulating the rhythm of breathing
- Which gas law relates to the calculation of partial pressure exerted by a gas in a mixture?
a) Boyle’s Law
b) Charles’s Law
c) Dalton’s Law
d) Henry’s Law
Answer: c) Dalton’s Law
Explanation: Dalton’s Law relates to the calculation of partial pressure exerted by a gas in a mixture, which is crucial for understanding gas exchange in the lungs
- What is the primary effect of the apneustic center on respiration?
a) Inhibiting inspiration
b) Prolonging inspiration
c) Enhancing expiration
d) Regulating blood pH
Answer: b) Prolonging inspiration
Explanation: The apneustic center stimulates the medullary inspiratory center to prolong inspiration. It must be inhibited for inspiration to terminate and expiration to commence
- Which respiratory structure primarily conducts air from the mouth and nose towards the lungs?
a) Alveoli
b) Bronchi
c) Bronchioles
d) Trachea
Answer: d) Trachea
Explanation: The trachea conducts air from the mouth and nose towards the lungs, forming the main trunk of the tracheobronchial tree
- What is the role of peripheral chemoreceptors in respiratory regulation?
a) Detecting blood glucose levels
b) Monitoring blood pressure
c) Sensing arterial oxygen levels
d) Regulating heart rate
Answer: c) Sensing arterial oxygen levels
Explanation: Peripheral chemoreceptors primarily sense arterial oxygen levels (hypoxemia) and send signals to the respiratory center to modulate breathing patterns
- Which respiratory structure contains cartilaginous rings to maintain its patency?
a) Alveoli
b) Bronchi
c) Respiratory bronchioles
d) Conducting bronchioles
Answer: b) Bronchi
Explanation: The bronchi contain cartilaginous rings or plaques in their walls to maintain patency and ensure the airway remains open
- What is the primary function of central chemoreceptors in the medulla?
a) Monitoring blood pressure
b) Detecting changes in pH and PCO2
c) Regulating heart rate
d) Producing surfactant
Answer: b) Detecting changes in pH and PCO2
Explanation: Central chemoreceptors in the medulla are sensitive to changes in pH and PCO2, primarily responding to pH changes caused by alterations in arterial carbon dioxide
- What is the effect of increased temperature on the oxygen dissociation curve of hemoglobin?
a) Shifts to the left
b) Shifts to the right
c) Remains unchanged
d) Becomes hyperbolic
Answer: b) Shifts to the right
Explanation: Increased temperature causes the oxygen dissociation curve of hemoglobin to shift to the right, reducing hemoglobin’s affinity for oxygen and promoting oxygen release to tissues
- Which respiratory center sends signals to the inspiratory muscles?
a) Pneumotaxic center
b) Apneustic center
c) Dorsal respiratory group
d) Expiratory center
Answer: c) Dorsal respiratory group
Explanation: The dorsal respiratory group in the nucleus tractus solitarius of the brain sends signals to the inspiratory muscles, regulating the rhythm of breathing
- What is the primary effect of acetylcholine on airway smooth muscle?
a) Bronchodilation
b) Bronchoconstriction
c) Increased blood flow
d) Decreased mucus production
Answer: b) Bronchoconstriction
Explanation: Acetylcholine released from postganglionic parasympathetic nerves activates the M3 muscarinic receptors on the airway smooth muscle, causing bronchoconstriction
- What is the primary determinant of the respiratory drive under normal conditions in healthy individuals?
a) Arterial oxygen levels
b) Arterial carbon dioxide levels
c) Blood glucose levels
d) Blood pressure
Answer: b) Arterial carbon dioxide levels
Explanation: The respiratory center in healthy individuals is more sensitive to rising levels of carbon dioxide sensed by central chemoreceptors than to decreasing oxygen levels
- Which muscle is the most important during inspiration?
a) External intercostal muscles
b) Internal intercostal muscles
c) Diaphragm
d) Serratus anterior
Answer: c) Diaphragm
Explanation: The diaphragm is the most important muscle during inspiration, contracting and flattening to increase thoracic cavity capacity and draw air into the lungs
- What is the primary function of the trachea in the respiratory system?
a) Gas exchange
b) Conducting air to the lungs
c) Producing surfactant
d) Regulating blood pH
Answer: b) Conducting air to the lungs
Explanation: The trachea conducts air from the mouth and nose towards the lungs, forming the main trunk of the tracheobronchial tree
- What is the effect of decreased arterial oxygen levels on peripheral chemoreceptors?
a) Decreases respiratory rate
b) Inhibits the cough reflex
c) Stimulates the respiratory center
d) Reduces mucus secretion
Answer: c) Stimulates the respiratory center
Explanation: Decreased arterial oxygen levels stimulate peripheral chemoreceptors, which send signals to the respiratory center to increase the respiratory rate and improve oxygen uptake
- Which respiratory structure contains ciliated epithelium for filtering air?
a) Alveoli
b) Respiratory bronchioles
c) Conducting bronchioles
d) Pulmonary capillaries
Answer: c) Conducting bronchioles
Explanation: The conducting bronchioles contain ciliated epithelium, which continues to filter air as it moves towards the respiratory surfaces
- What is the role of the diaphragm during inspiration?
a) Relaxing and ascending
b) Contracting and flattening
c) Expelling air from the lungs
d) Increasing airway resistance
Answer: b) Contracting and flattening
Explanation: During inspiration, the diaphragm contracts and flattens, increasing the capacity of the thoracic cavity and reducing intra-pleural pressure to draw air into the lungs
- What is the effect of hyperventilation on arterial PCO2 levels?
a) Increases PCO2
b) Decreases PCO2
c) Has no effect on PCO2
d) Causes variable PCO2
Answer: b) Decreases PCO2
Explanation: Hyperventilation increases the expulsion of CO2 from the blood, leading to decreased arterial PCO2 levels
- Which structure provides the primary contractile input to the airways in the parasympathetic pathway?
a) Adrenergic neurons
b) Cholinergic postganglionic neurons
c) Noncholinergic neurons
d) Sensory neurons
Answer: b) Cholinergic postganglionic neurons
Explanation: Cholinergic postganglionic neurons provide the primary contractile input to the airways in the parasympathetic pathway, causing bronchoconstriction when activated
- What is the primary component of mucus produced by submucosal glands in the lungs?
a) Glucose
b) Surfactant
c) Mucins
d) Hemoglobin
Answer: c) Mucins
Explanation: Mucins are the primary component of mucus produced by submucosal glands, giving mucus its gel-like properties and facilitating the trapping of particles and pathogens
- Which type of receptor primarily responds to irritative chemical triggers in the lungs?
a) Peripheral chemoreceptors
b) Central chemoreceptors
c) Mechanoreceptors
d) Baroreceptors
Answer: c) Mechanoreceptors
Explanation: Mechanoreceptors, specifically rapid adapting irritant receptors, respond to irritative chemical triggers in the lungs and initiate the cough reflex
- What is the main function of alveolar macrophages?
a) Producing surfactant
b) Filtering inspired air
c) Phagocytosing pathogens and debris
d) Regulating blood pressure
Answer: c) Phagocytosing pathogens and debris
Explanation: Alveolar macrophages are immune cells that phagocytose pathogens and debris in the alveoli, playing a crucial role in lung defense
- What is the primary effect of increased 2,3-DPG levels on hemoglobin?
a) Increased oxygen affinity
b) Decreased oxygen affinity
c) Increased CO2 affinity
d) Decreased CO2 affinity
Answer: b) Decreased oxygen affinity
Explanation: Increased levels of 2,3-DPG decrease hemoglobin’s affinity for oxygen, promoting the release of oxygen to the tissues
- Which structure serves as the primary respiratory surface in the lungs?
a) Trachea
b) Bronchi
c) Alveoli
d) Conducting bronchioles
Answer: c) Alveoli
Explanation: The alveoli serve as the primary respiratory surface in the lungs, facilitating gas exchange between the air and blood
- What is the role of the ventral respiratory group in the medulla?
a) Regulating blood pressure
b) Sending signals for active expiration
c) Detecting blood pH changes
d) Producing surfactant
Answer: b) Sending signals for active expiration
Explanation: The ventral respiratory group in the medulla sends signals for active expiration, reinforcing respiratory effort during increased respiratory demand
- Which ion channel is primarily involved in the depolarization of vascular smooth muscle during hypoxic pulmonary vasoconstriction?
a) Sodium channel
b) Calcium channel
c) Potassium channel
d) Chloride channel
Answer: b) Calcium channel
Explanation: During hypoxic pulmonary vasoconstriction, the inhibition of O2-sensitive K+ channels leads to the activation of L-type Ca2+ channels, causing depolarization and contraction of vascular smooth muscle
