Why does splashing cold water on the skin stimulate ventilation?

(Answer to Q. 1)  ANS: C
Proprioceptors in muscles, tendons, and joints, as well as pain receptors in muscles and skin, send stimulatory signals to the medullary respiratory center. Such stimuli increase medullary inspirato-ry activity and cause hyperpnea. For this reason, moving the limbs, slapping or splashing cold water on the skin, and other painful stimuli stimulate ventilation in patients with respiratory de-pression.

(Answer to Q. 2)  ANS: C
Interviewing furnishes unique information because it provides the patient's perspective. It serves the following three related purposes: (1) to establish a rapport between clinician and patient, (2) to obtain essential diagnostic information, and (3) to help monitor changes in the patient's symp-toms and response to therapy.

(Answer to Q. 3)  ANS: A
High altitude causes a healthy person's ventilation to increase because low barometric pressure decreases the inspired PO2, and thus the arterial PO2, which in turn raises the sensitivity of pe-ripheral chemoreceptors to H+. The resulting increase in ventilation is less than expected, though, because hyperventilation lowers the PaCO2 and raises arterial pH.

(Answer to Q. 4)  ANS: B
If a situation occurs where the higher pneumotaxic center and vagus nerves were severed, the DRG inspiratory neurons would fail to switch off, causing prolonged inspiratory gasps inter-rupted by occasional expirations (apneustic breathing). Vagal and pneumotaxic center impulses hold the apneustic center's stimulatory effect on DRG neurons in check.

(Answer to Q. 5)  ANS: D
Increased PCO2 dilates cerebral vessels, raising cerebral blood flow, whereas decreased PCO2 constricts cerebral vessels and reduces cerebral blood flow. In patients with traumatic brain inju-ry, the brain swells acutely; this raises the intracranial pressure in the rigid skull to such high lev-els that blood supply to the brain might be cutoff, causing cerebral hypoxia (ischemia). That is, high intracranial pressure may exceed cerebral arterial pressure and stop blood flow.