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Accounts for 80% of the brain's mass.
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cerebrum
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The second major structure of the brain.
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cerebellum
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Contains some of the most vital centers of body activity.
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diencephalon
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contains structures associated with visual reflexes and hearing
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midbrain or mesencephalon
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functions as a relay center within the brain.
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The pons
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Together with the pons makes up the brain stem.
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medulla oblongata
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This is made up by the pons and medulla oblongata together.
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brain stem
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The three membranes which protect the brain and spinal cord.
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meninges
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The outermost layer of the meninges, which contacts the cranium.
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dura mater
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The thinner, more delicate, middle layer of the meninges.
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arachnoid
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The innermost layer of the meninges.
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pia mater
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Projections into the brain ventricles which produce cerebrospinal fluid.
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choroid plexus
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The raised portions of the cerebellar surface.
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gyri
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A triangular membrane separating the anterior horns of the lateral ventricles.
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septum pellucidum
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A general term meaning nerve cell.
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neuron
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Deep grooves which divide the lobes of the cerebral hemispheres.
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fissures
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The posterior rounded end of the corpus callosum; it conveys visual information.
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splenium of corpus callosum
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A general term for an arch-like structure or the vault created by such a structure.
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fornix
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Grooves between the gyri.
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sulci
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A site of union of common parts.
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commissure
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An arched mass of white matter found in the depths of the longitudinal fissure.
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corpus callosum
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Part of the hypothalamus formed by the crossing of the optic nerves.
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optic chiasm
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A general term used to describe any anatomical structure shaped like a knee.
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genu
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Located near the pituitary gland.
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mammillary body
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Part of the mesencephalon.
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corpora quadrigemina
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The "master gland."
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pituitary
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These merge with the basilar artery at the circle of Willis.
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Internal carotid arteries
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The sense of smell. There are numerous olfactory nerves which relay sensory impulses of smell from the membranes of the nasal cavity. Damage to these nerves results in a loss of smell.
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Cranial nerve I: olfactory nerve
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Vision. This is a sensory-only nerve which conducts impulses from the retina of the eye. It originates in the back of the eyeball. Damage to these nerves results in blindness.
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Cranial nerve II: optic nerve
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This nerve controls all movement of the eyeballs. It is primarily a motor nerve. It comes out of the midbrain and serves four of the six eye muscles, as well as the muscle of the eyelid, iris (which causes pupil dilation), and ciliary body. Damage to these nerves can cause a droopy eyelid, constant dilated pupil, or the inability to rotate the eyeball.
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Cranial nerve III: oculomotor nerve
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This is a very small nerve, both sensory and motor, which innervates the superior oblique muscle of the eye.
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Cranial nerve IV: trochlear nerve
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This is the largest of the cranial nerves. It is primarily sensory, but does send motor impulses to the muscles of mastication (chewing). It has three large sensory divisions the ophthalmic branch innervating the orbital region of the face, the maxillary branch innervating the nose and upper jaw, and the mandibular branch innervating the lower jaw.
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Cranial nerve V: trigeminal nerve
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This is a small nerve which provides both motor and sensory innervation to the lateral rectus eye muscle. Damage to this nerve causes the eyeball to be pulled medially, and makes it unable to move laterally at all.
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Cranial nerve VI: abducens nerve
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This is a mixed nerve. The motor fibers innervate facial, scalp, and superficial neck muscles. The salivary glands are also innervated by this. The sensory fibers arise from the taste buds on the tongue. Damage to these nerves distorts taste perception, particularly with sweets, and causes the face to sag.
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Cranial nerve VII: facial nerve
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Hearing and equilibrium. This is also called the acoustic nerve. It is a sensory nerve which arises within the inner ear. The vestibular branch controls equilibrium and balance, while the cochlear portion controls hearing. Damage to these nerves can cause deafness or dizziness and inability to maintain balance.
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Cranial nerve VIII: vestibulocochlear nerve acoustic nerve
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This is a mixed nerve which innervates the tongue and pharynx. The sensory portion transmits impulses from the tonsils, salivary gland, and back third of the tongue. The motor fibers innervate the muscles of the pharynx which help with swallowing. Damage to these nerves would result in a loss of bitter and sour taste or could cause difficulty swallowing.
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Cranial nerve IX: glossopharyngeal nerve
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This arises from the medulla and has both motor and sensory fibers which serve autonomic organs of the thoracic and abdominal cavities. It is associated with such functions as breathing, heartbeat, hunger pangs, and peristalsis. One of its branches supplies the larynx and controls speech. Damage to both of these nerves would result in death; with damage to one, only speech and swallowing would be affected.
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Cranial nerve X: vagus nerve
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This is a motor nerve only. It innervates the muscles of the pharyngeal region as well as the sternocleidomastoid and trapezius muscles. Damage to this nerve would make it difficult to rotate the head or shrug the shoulders.
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Cranial nerve XI: accessory nerve
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This supplies motor fibers to the muscles of the tongue. Damage would cause difficulty speaking, swallowing, or sticking out the tongue.
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Cranial nerve XII: hypoglossal nerve
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Nerves which resemble a horse's tail.
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cauda equina
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Nerve controlling the sense of smell.
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olfactory
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Innervates the thoracic and abdominal cavities.
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vagus nerve
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The impulse originates in the organ and is transmitted to the central nervous system.
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afferent
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The largest of the cranial nerves.
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trigeminal
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Controls hearing and balance.
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vestibulocochlear
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A fatty white material supporting a neuron.
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myelin
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Point at the second lumbar vertebra, where the spinal cord tapers. It is cone-shaped.
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conus medullaris
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A small nerve to the lateral rectus eye muscle.
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abducens
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Supplies motor fibers to the muscles of the tongue.
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hypoglossal
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A band of connective tissue which extends to the coccyx.
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filum terminale
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