Chapter 7 Part 2

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University of Toronto Scarborough
Janelle Leboutillier

The Structure of the Nervous System o There are 12 pairs of cranial nerves that arise from the brain stem and innervate (mostly) the head.  Oh, Oh, Oh To Touch And Feel Very Green Vegetables AH! Some-CN 1 – olfactory nerve Say-CN II – optic nerve Marry-CN III – oculomotor nerve Money-CN IV – trochlear nerve But-CN V – trigeminal nerve My-CN VI – abducens nerve Brother-CN VII – facial nerve Say-CN VII – vestibulocochlear nerve Bad-CN IX – glossopharyngeal nerve Business-CN X – vagus nerve Marry-CN XI- spinal accessory nerve Money-CN XII- hypoglossal nerve  Some of the cranial nerves are part of the CNS, others are part of the somatic PNS, and still others are part of the visceral PNS.  Many cranial nerves contain complex mixture of axons that perform different functions o The CNS does not come into direct contact with the overlying bone. It is protected by a three membranes collectively called the meninges which consists of the dura mater, arachnoid membrane, and the pia mater a. Dura mater – in Latin means “hard mother,” an accurate description of the dura’s leather like consistency. It forms a touch, inelastic bag that surrounds the brain and spinal cord. b. Arachnoid membrane – in latin “spider,” this meningeal layer has an appearance and a consistency resembling a spider web.  While there is no space between the dura and arachnoid, if blood vessels passing through the dura are ruptured, blood can collect here and form what is called a subdural hematoma  The buildup of fluid in this subdural space can disrupt brain function by compressing parts of the CNS. This disorder is treated by drilling a hole within the skull and draining the blood. c. Pia mater – in latin the “gentle mother,” is a thin membrane that adheres closely to the surface of the brain. Along the pia run many blood vessels that ultimately dive into the substance of the underlying brain.  The pia is separated from the arachnoid by a fluid-filled space referred to as the subarachnoid space which is filled with salty clear liquid called the cerebrospinal fluid (CSF)  Thus brain floats inside the head in this thin layer of CSF o The fluid-filled caverns and canals inside the brain constitute the ventricular system – fluid that runs in this system is the CSF, the same fluid as the fluid in the subarachnoid space.  CSF is produced by a special tissue, called the choroid plexus, in the ventricles of the cerebral hemispheres  CSF flows from the paired ventricles of the cerebrum to a series of connected, unpaired cavities at the core of the bra
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