DAANCE Anatomy and Physiology 2 — Questions and Answers
Question 1: The trigeminal nerve (CN V) is the primary sensory nerve of the face. Which division provides sensory innervation to the maxillary teeth?
- Ophthalmic division (V1)
- Maxillary division (V2) (Correct answer)
- Mandibular division (V3)
- Facial nerve (CN VII)
Correct answer: Maxillary division (V2)
The maxillary division (V2) innervates the maxillary teeth, upper lip, cheek, and part of the nasal cavity via the superior alveolar nerves.
The trigeminal nerve three divisions: V1 (ophthalmic - forehead, eye, upper nose), V2 (maxillary - mid-face, upper jaw, maxillary teeth), V3 (mandibular - lower jaw, mandibular teeth, tongue, chin). The superior alveolar nerves (anterior, middle, posterior) are branches of V2 that supply the maxillary teeth.
Question 2: The Frank-Starling mechanism describes the relationship between:
- Blood pressure and heart rate during exercise
- Ventricular end-diastolic volume and stroke volume (the more the ventricle fills, the more it contracts) (Correct answer)
- Oxygen saturation and hemoglobin concentration
- Respiratory rate and tidal volume during spontaneous breathing
Correct answer: Ventricular end-diastolic volume and stroke volume (the more the ventricle fills, the more it contracts)
The Frank-Starling law states that increasing preload (ventricular filling) stretches myocardial fibers, increasing contractility and stroke volume - within physiologic limits.
As venous return increases preload, cardiomyocytes are stretched, optimizing actin-myosin cross-bridge formation and increasing force of contraction. This auto-regulatory mechanism ensures the heart pumps what it receives. It explains why IV fluid boluses increase cardiac output in hypovolemia.
Question 3: The hypoglossal nerve (CN XII) controls which function relevant to airway management?
- Sensation of the posterior tongue and pharynx
- Secretomotor function of the parotid gland
- Motor innervation of the intrinsic and extrinsic tongue muscles (Correct answer)
- Proprioception of the temporomandibular joint
Correct answer: Motor innervation of the intrinsic and extrinsic tongue muscles
CN XII provides motor innervation to all intrinsic and most extrinsic tongue muscles (except palatoglossus), controlling tongue movement and position.
Airway management maneuvers (jaw thrust, chin lift, tongue blade displacement) work partly by repositioning the tongue. Sedation reduces hypoglossal nerve activity, causing the tongue to fall posteriorly and obstruct the oropharynx - the most common mechanism of upper airway obstruction during sedation.
Question 4: The carotid body is a peripheral chemoreceptor that responds primarily to:
- Increasing arterial CO2 (PaCO2 rising above 45 mmHg)
- Decreasing arterial O2 (PaO2 falling below 60 mmHg) and rising H+ (acidosis) (Correct answer)
- Blood pressure changes via baroreceptor stretch
- Cerebral blood flow velocity changes
Correct answer: Decreasing arterial O2 (PaO2 falling below 60 mmHg) and rising H+ (acidosis)
Carotid body chemoreceptors are stimulated primarily by hypoxemia (PaO2 below 60 mmHg), hypercapnia, and acidosis, triggering increased ventilatory drive.
Peripheral chemoreceptors (carotid and aortic bodies) respond to hypoxemia, hypercapnia, and acidosis. Sedative drugs can suppress both central and peripheral chemoreceptor responsiveness, reducing the hypoxic and hypercapnic ventilatory responses.
Question 5: The alveolar-arterial oxygen gradient (A-a gradient) is useful in assessing:
- Cardiac output and circulatory efficiency
- Whether hypoxemia results from hypoventilation alone or includes a pulmonary gas exchange problem (Correct answer)
- Hemoglobin affinity for oxygen at various pH levels
- Tidal volume and functional residual capacity relationship
Correct answer: Whether hypoxemia results from hypoventilation alone or includes a pulmonary gas exchange problem
A normal A-a gradient suggests hypoxemia from hypoventilation; an elevated gradient suggests ventilation-perfusion mismatch or diffusion impairment from pulmonary disease.
The A-a gradient measures the difference between alveolar O2 tension and arterial O2 tension. Normal is below 10 mmHg in young adults. In sedation-induced hypoventilation with a normal lung, the gradient remains normal. Aspiration, pneumothorax, or pulmonary embolism widens the gradient.
Question 6: Which type of drug interaction occurs when two sedatives are combined and produce an effect greater than the sum of their individual effects?
- Additive interaction
- Antagonistic interaction
- Synergistic (potentiation) interaction (Correct answer)
- Tachyphylaxis
Correct answer: Synergistic (potentiation) interaction
Synergistic (potentiation) interactions produce effects exceeding the sum of individual effects - critical safety knowledge when combining opioids and benzodiazepines.
Synergism occurs when combined drugs produce greater effects through complementary mechanisms. Opioid plus benzodiazepine synergy on respiratory depression is a major cause of sedation-related adverse events. Practitioners must reduce individual drug doses when using combinations and monitor more intensively than with a single agent.
DAANCE Anatomy and Physiology 2
The trigeminal nerve (CN V) is the primary sensory nerve of the face.
Which division provides sensory innervation to the maxillary teeth?