Insight: Some cranial nerve disorders Brain and Cranial Nerves (Ch. 15) Human Anatomy lecture I. Overview (Directional terms: rostral = toward the forehead caudal = toward the spinal cord) A. 3 Major parts KNOW Fig. 15.1 1. Brain stem medulla oblongata pons midbrain diencephalon (many texts disagree and consider this a 4 th part on its own) 2. Cerebrum 3. Cerebellum B. Major landmarks Cerebrum cerebral hemispheres separated by longitudinal fissure corpus callosum thick band of connecting fibers at bottom of longitudinal fissure gyrus (pl. = gyri) = ridge sulcus = groove C. Protection and coverings 1. Same 3 meninges; 2. Dura mater has 2 layers Fig. 15.3 3. 3 Extensions of dura help anchor (Fig. 15.3 & 15.5) falx cerebri falx cerebelli tentorium cerebelli Brain & CN Page 1 of 6
D. Cerebrospinal fluid (CSF) 1. Circulates around and within the brain 2. a. 60% produced by ependymal cells b. 40% produced by KNOW Fig. 15.4 & 15.5 3. Pathway: 4. Reabsorbed 5. Functions CNS blood : buoyant: 1500g vs. 50g! Brain & CN Page 2 of 6
E. Blood supply 1. 4 prong supply through cerebral arterial circle (Review) 2. Brain capillaries less leaky II. Brain stem A. Medulla oblongata Fig. 15.6, but label Fig. 15.23 1. Continuous caudally with spinal cord, rostrally with pons ~ 3 cm 2. Anterior bulges Lateral bulges 3. Functions conduction pathway CNS nuclei B. Pons (= bridge ) 1. Connects medulla with midbrain; both to cerebellum(via cerebellar peduncles) 2. Nuclei for little feet C. Midbrain 1. rostral to pons; caudal to diencephalon 2. cerebral peduncles 3. cerebral aqueduct 4. corpora quadrigemina (= quadruplets ) superior colliculi inferior colliculi 5. several other nuclei, D. Diencephalon Fig. 15.11 1. Thalamus (80%) 2 large masses bulge medially into 3 rd ventricle and laterally into lateral ventricles connected by intermediate mass major function 2. Epithalamus posterior roof Pineal gland neuroendocrine organ pine cone Brain & CN Page 3 of 6
3. Hypothalamus floor 4. Third ventricle III. Cerebellum KNOW Fig. 15.9 A. Structure 1. dorsal to brain stem, 2. central vermis 3. flat folia leaf 4. 5. B. Functions (Fig. 15.10) 1. regulates voluntary, skilled movements by comparing intent with performance 2. regulates posture and balance 3. many others, including sensory & motor (only 10% of brain s mass but 50% of its neurons 100 billion!) IV. Cerebrum Fig. 15.12 A. Structure 1. cerebral cortex grows rapidly in the fetus, why is gray matter on outside of cerebral/cerebellar cortex but on inside of spinal cord? sketch 2. some sulci separate each hemisphere into lobes (named after overlying bone) Brain & CN Page 4 of 6
3. white matter under cortex Fig. 15.13 association tracts commissural tracts projection tracts 4. basal nuclei (ganglia) Fig. 15.16 5. limbic (= border) system Fig. 15.15 bilateral interconnected rings of structures includes hippocampus (= seahorse), B. Functions (NRF text detail) 1. sensory areas 2. motor areas 3. association areas 4. basal nuclei 5. limbic system V. Cranial nerves KNOW CHART: Number, Name, Function, Attachment (NRF text detail) 12 pairs, part of PNS numbered with Roman numerals rostral caudal use mnemonic? p. 437 Insight: p. 431 KNOW FIG. 15.23 left side labels and only I VI note that midbrain should be hypothalamus Brain & CN Page 5 of 6
CRANIAL NERVE SUMMARY NUMBER AND NAME SITE OF ATTACHMENT FUNCTION I olfactory cerebrum smell II optic thalamus vision III oculomotor midbrain eyeball & eyelid movement, pupil constriction, muscle IV trochlear midbrain eyeball movement; muscle ( pulley ) V trigeminal ( triplets ) V 1 = ophthalmic V 2 = maxillary V 3 = mandibular pons chewing; muscle facial sensation VI abducens pons eyeball movement, muscle VII facial pons muscles of facial expression, saliva & tear secretion; taste, muscle VIII vestibulocochlear pons & medulla oblongata balance & hearing IX glossopharyngeal medulla oblongata saliva secretion, taste, blood pressure regulation X vagus ( wanderer ) XI accessory (spinal accessory) medulla oblongata medulla oblongata anterior gray horns, C 1 C 5 visceral smooth muscle control, digestive secretion; visceral sensations, muscle head, neck & shoulder movements; swallowing, muscle XII hypoglossal medulla oblongata tongue movement (swallowing & speech); muscle NOTE: 1. Which 3 cranial nerves are primarily sensory? 2. There are no pure motor nerves because motor nerves also carry muscle (proprioception) from the muscles they serve. However, 5 cranial nerves are primarily motor and traditionally classified this way. Give the name & number of those 5. 3. Which 3 cranial nerves are involved in taste perception? 4. Which 3 cranial nerves are involved in eyeball movement? Brain & CN Page 6 of 6