Quiz 115 · Functional Organization of Nervous System

Answers to Quiz 114 · Pulmonary Function Tests

1. Which of these CANNOT be measured by a spirometer?

   Answer: Functional residual capacity

   FRC contains the residual volume, and that air never leaves the lung, so no spirometer can record it. RV, FRC and TLC need helium dilution or total body plethysmography. Revise lung volumes, capacities and spirometry

2. Inspiratory capacity is made up of:

   Answer: IRV + TV

   IC is what a person can still breathe in starting from the resting expiratory level, which is IRV plus TV. ERV + RV is FRC, and IRV + TV + ERV is the vital capacity. Revise lung volumes, capacities and spirometry

3. In a normal adult, how much of the FVC is blown out in the first second?

   Answer: 80 to 85%

   One second clears 80 to 85%, two seconds 95% and three seconds 97%. That is why FEV₁ is quoted as over 80% of FVC. Revise lung volumes, capacities and spirometry

4. Lung compliance is defined as:

   Answer: Change in volume per unit change in transpulmonary pressure

   Compliance is a volume change per unit pressure change, the pressure being intrapleural or esophageal pressure minus mouth pressure, and it is measured under static conditions. Frictional resistance to airflow is airway resistance, and the last option is MMFR. Revise lung volumes, capacities and spirometry

5. The normal peak expiratory flow rate in an adult is about:

   Answer: 400 to 600 L/min

   PEFR is 400 to 600 L/min, or 6 to 10 L/s, and is read straight off a peak-flow meter dial. 125 to 170 L/min is the MVV range, which is a per-minute ventilation, not a peak flow. Revise lung volumes, capacities and spirometry

6. Which test assesses the strength of the inspiratory muscles?

   Answer: Maximal inspiratory pressure

   For MIP the patient empties to RV and then inspires hard against a closed airway; the pressure generated measures inspiratory muscle strength. Closing volume detects small-airway closure, and MMFR reports small-airway patency. Revise lung volumes, capacities and spirometry

7. In obstructive lung disease, which of these is increased?

   Answer: RV/TLC ratio

   Air trapped during expiration raises RV while TLC stays normal or rises less, so RV/TLC goes up. FEV₁/FVC and MMFR fall, and VC is frequently reduced because the large RV eats into it. Revise obstructive vs restrictive disease

8. Which set of findings is typical of restrictive lung disease?

   Answer: Reduced FVC with a normal or supernormal FEV₁/FVC

   Reduction in FVC is the hallmark of restriction, but the flow rates are preserved, so FEV₁ as a percentage of FVC is normal or higher than normal. A low ratio and a raised RV with a normal or large TLC are the obstructive picture. Revise obstructive vs restrictive disease

9. A patient with weak inspiratory muscles and otherwise normal lungs would show:

   Answer: Reduced TLC with an unchanged RV and preserved flow rates

   This is extraparenchymal restriction affecting inspiration: the distending force never reaches a normal lung, so TLC falls while RV and the expiratory flow rates are untouched. RV rises markedly only when the expiratory muscles are weak as well. Revise obstructive vs restrictive disease

10. Which of these decreases static lung compliance?

    Answer: Pulmonary edema

    Pulmonary edema makes the lung wet and stiff, so compliance falls. The other three narrow the airways and belong to the list of conditions that increase airway resistance. Revise obstructive vs restrictive disease

11. A young man with episodic wheeze has a reduced FVC, an FEV₁/FVC of 0.50, a raised residual volume and a normal TLC. The pattern is:

    Answer: Obstructive

    A low ratio with air trapping and a preserved TLC is obstruction, and FEV₁/FVC is the most sensitive indicator of it. Restriction would lower TLC and leave the ratio normal or supernormal. Revise obstructive vs restrictive disease

12. The normal ratio of ventilation to perfusion in the lung is:

    Answer: 0.8

    The normal overall V/Q ratio is 0.8. Neither ventilation nor perfusion is uniform in the erect posture, and altering the ratio affects PaO₂ far more than PaCO₂. Revise tests of gas exchange and pulmonary circulation

13. Which cause of hypoxemia leaves the alveolar–arterial O₂ gradient NORMAL?

    Answer: Generalized hypoventilation

    In generalized hypoventilation the whole lung is underventilated, so alveolar and arterial PO₂ fall together and the 5 to 15 mmHg gradient stays normal, while PaCO₂ rises and pH falls. All the other causes raise the gradient. Revise tests of gas exchange and pulmonary circulation

14. Breathing 100% oxygen fails to correct the low arterial PO₂ in:

    Answer: A right-to-left shunt

    Shunted blood bypasses oxygenation at the alveolar–capillary level, so the oxygen-rich gas never comes in contact with it. The other three still have ventilated alveoli, so raising the inspired O₂ helps. Revise tests of gas exchange and pulmonary circulation

15. Expired air for gas analysis is collected using a:

    Answer: Douglas bag

    A Douglas bag with a two-way valve collects mixed expired air. The Haldane–Priestley tube samples alveolar air, Van Slyke measures the O₂ carrying capacity of blood, and a Swan–Ganz catheter measures pulmonary pressures. Revise tests of gas exchange and pulmonary circulation

14 questions on chapter 115. Pick one answer for each, then save. Your answers stay in this browser, and the right ones are shown at the top of the next quiz.

1. In an adult, the spinal cord ends at the level of the:

Body of the tenth thoracic vertebraBody of the third lumbar vertebraBody of the first lumbar vertebraBody of the second sacral vertebra

2. The brainstem is made up of the:

Midbrain, pons and cerebellumThalamus, midbrain and ponsMidbrain, pons and medullaPons, medulla and cerebellum

3. The metencephalon consists of the:

Thalamus and hypothalamusCorpora quadrigemina and cerebral pedunclesPons and cerebellumMedulla oblongata alone

4. The central pattern generator for locomotion and the nuclei for the righting reflexes lie in the:

CerebellumMidbrainMedullaThalamus

5. How many pairs of spinal nerves arise from the spinal cord?

30331231

6. When a sensory signal reaches the brain, where is it relayed first, before the sensory cortex processes it?

Substantia nigraCerebellumThalamusHypothalamus

7. Which of these is a glial cell of the brain?

Purkinje cellEpendymal cellStellate cellBasket cell

8. The myelin sheath of axons in the brain and spinal cord is formed by:

Schwann cellsAstrocytesMicrogliaOligodendrocytes

9. The scavenger cells of the brain are the:

AstrocytesMicrogliaEpendymal cellsOligodendrocytes

10. Which statement about glial cells is correct?

They are fewer in number than neuronsThey form functional synapses with neuronsThey can multiply, and excess multiplication causes gliomasThey conduct action potentials like neurons

11. In a neuron, Nissl bodies are absent from the:

Proximal dendritesAxon hillockCytoplasm of the somaRegion around the nucleus

12. The spike initiation zone of a neuron, where the action potential normally begins, is the:

Soma around the nucleusInitial segment of the axonDistal part of the dendritesTerminal branches of the axon

13. A dorsal root ganglion cell, whose single axon divides into a central and a peripheral branch, is classed as:

PseudounipolarStellateMultipolarBipolar

14. What share of a neuron's total surface area do its dendrites make up?

More than 90%Less than 10%About 25%About 50%

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