Normal intrapleural pressure at the onset of inspiration measures _________ mm Hg?
Show answer Hide answer
Answer: A. -2
Explanation
At the very start of inspiration, chest expansion decreases the intrapleural pressure to approximately -2 mm Hg. Contraction of the diaphragm and intercostal muscles enlarges the thoracic cavity, expanding the pleural space. This initial expansion creates a subatmospheric pressure of about -2 mm Hg relative to atmospheric pressure. Intrapleural pressure remains subatmospheric throughout normal breathing due to opposing elastic recoil forces. The lungs naturally tend to collapse, while the chest wall tends to spring outward, creating negative intrapleural pressure. During quiet inspiration, further enlargement of the thorax pulls the intrapleural pressure down to roughly -6 mm Hg.
A value of -5 mm Hg is typically reached later during peak inspiration rather than at the exact onset. Zero pressure equals atmospheric pressure, which would cause immediate lung collapse if present in the pleural space. A pressure of -7 mm Hg represents a deeper inspiratory effort rather than the resting condition at breath onset.
Related questions
Q1. The mineral vital for hemoglobin synthesis is_______________?
Show answer Hide answer
Answer: A. Copper
Copper acts as an essential cofactor for ceruloplasmin and other enzymes required for proper iron mobilization. Without adequate copper stores iron cannot be properly oxidized and incorporated into developing erythrocyte...
Q2. The neurotransmitter within the nigrostriatal pathway is_______________?
Show answer Hide answer
Answer: A. Dopamine
Dopamine serves as the primary neurotransmitter utilized within the nigrostriatal pathway to modulate motor control. Neurons originating in the substantia nigra release dopamine into the striatum to facilitate smooth mov...
Q3. A sub-zero BMR is associated with______________?
Show answer Hide answer
Answer: B. Thyroid disturbance
Thyroid hormones thyroxine and triiodothyronine are the primary regulators of cellular basal metabolic rate. Thyroid gland disorders directly alter hormone production, shifting the body's overall metabolic rate significa...
Q4. Noradrenaline differs from adrenaline due to an increase in___________?
Show answer Hide answer
Answer: C. Peripheral resistance
Noradrenaline causes a greater increase in peripheral vascular resistance due to strong vasoconstrictive alpha-1 receptor activation. Unlike adrenaline which can stimulate beta-2 receptors for vasodilation noradrenaline...
Q5. Blood from a healthy adult individual contains_____________?
Show answer Hide answer
Answer: B. 30% lymphocytes
In a healthy adult leukocyte differential, lymphocytes typically account for roughly 20 to 40 percent of cells. Lymphocytes represent the second most common type of circulating white blood cell in normal adult blood. Acc...
Q6. An incorrect statement regarding T3 and T4 is______________?
Show answer Hide answer
Answer: B. T4 binds to prealbumin
Thyroxine binds primarily to thyroxine-binding globulin rather than prealbumin as its main transport protein.