On a Snellen chart we determine the line that the person can just recognize. If that line is twice as large as the reference standard (20/20), we state that that personâs MAgnification Requirement (MAR) is 2x. If the MAgnification Requirement is 2x, the visual acuity is 1/2 (20/40).
Posterior cranial fossa: It is the deepest and most capacious of the 3 cranial fossae. It contains the cerebellum, pons, and medulla oblongata. The foramen magnum is located centrally and inferiorly in the posterior fossa.
System (CNS) and the Peripheral Nervous System (PNS). ï§CNS is composed of the brain (located in the cranial cavity) and the spinal cord (located in the vertebral cavity), which. serve as the main control centers for all body activities. ï§PNS is composed of nerves derived from the brain and spinal. cord (12 pairs of cranial nerves and 31 pairs of spinal. nerves) which serve as linkage between the CNS and the. body. Â© 2017 Ebneshahidi. ANS Versus SNS. ï§PNS can be subdivided into sensory (afferent) nerves and motor (efferent) nerves.