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Unit 9 CNS Structured Overview—use in conjunction with lecture notes! BRAIN DEVELOPMENT (WITH CRANIAL NERVES, CN) Ectoderm Prosencephalon Telencephalon Cerebrum (stimulated (forebrain) Diencephalon Epithalamus by Thalamus notochord) Hypothalamus Mesencephalon Mesencephalon Midbrain neural tube Rhombencephalon Metencephalon Cerebellum (hindbrain) Pons Myelencephalon Medulla oblongata BRAIN STRUCTURE & FUNCTION Medulla Relay center Brain stem— Basic life support Autonomic centers Lateral ventricles CN 1 3rd ventricle CN 2 aquaduct of Sylvius CN 3-4 4th ventricle CN 5-8 CN 8-12 Sensory tracts Motor tracts Cardiovascular center Respiratory center Other centers Pons Midbrain Relay center Control functions: Relay center Corpora quadragemina Substantia nigra Red nuclei Cerebellum Reticular formations Mixed axons & cell bodies Peduncles To brain stem Vermis connects R/L cerebellar hemispheres Cortex Medulla Ant/Post Lobes Flocculonodular lobe Processing: Olives—proprioception Pyramids—decussation: contralateral connections Heart rate & force Breathing depth & rate Rhythmicity (with pons) Coughing, sneezing, hiccuping, swallowing, vomitting Connects medulla with midbrain Breathing rhythmicity (with medulla) Connects pons with diencephalon (thalamus) Superior colliculi Head/eye movement in scanning/following objects Inferior colliculi Startle reflex; auditory signal relay to thalamus Muscle tone/coordination—dopamine. Parkinson’s = degeneration of dopamine-secreting nuclei. Unconscious motor activities. Relay center Spinal cord to thalamus Arousal from sleep Control functions Consciousness Filters sensory input Relay: ipselateral connections Grey matter Folia White matter Arbor vitae Coordination of skeletal muscle movement initiated by cerebrum Regulates posture, equilibrium & balance Input from inner ear (semicircular canals, utricle & saccule) Evaluation Recommendation to cerebrum on Cerebrum how to proceed of Proprioceptors signals Inner ear Putman/Pierce College Biol 241 09 00/20100416/Page 1 Diencephalon Hypothalamus Relay function Joins midbrain to thalamus Infundibulum of pituitary attaches inferiorly Visceral Mammillary bodies: Olfactory reflex control ANS control: Sympathetic & parasympathetic Endocrine system control Control function (12 nuclei) Emotion perception/response through medulla Cerebrum Thalamus Large; lateral lobes joined by interthalmic adhesion Epithalamus Pineal gland Anatomy Lateral hemispheres Medulla: White matter Circadian rhythms Temperature homeostasis Osmoregulation of blood Nutrient levels in blood Relay function— Hypothalamus & cerebrum connects Cerebral hemispheres Control functions: Evaluates sensory input into cerebrum Regulates mood & emotion (with limbic system) Melatonin—triggers sleep (with hypothalamus) Split by longitudinal fissure Joined by corpus callosum Tracts Association: Gyri in same hemisphere Commissural: Gyri between hemispheres (corpus callosum) Projection: Gyri to/from lower parts of brain/spinal cord—corona radiata Basal Include Lentiform Putamen nuclei nucleus Globus pallidus Caudate nucleus Amygdaloid nucleus Connections Nuclei connect to one another Input: Cerebral cortex Output: Thalamus to motor control centers of cerebrum Functions Begin/end motor & cognitive functions Regulates rhythmic movement Inhibits unnecessary movement Integrates with limbic system to control emotions Limbic Includes thamic & hypothalmic nuclei system (mammillary bodies) Connections Input: Lower & higher brain regions Output through hypothalamus Functions Emotions: Recognition/ generation (amygdala) Memory Smell memory Hippocampus accesses Amygdala associates with emotions Psychosomatic illnesses Emotion vs logic Putman/Pierce College Biol 241 09 00/20100416/Page 2 Cortex: Grey matter, 2-3 mm thick General functions Functional divisions Structural divisions w/ functions Consciousness & self awareness Cognition, thought, memory Reception & interpretation of sensory signals Voluntary movement Sensory areas Receive stimuli Homunculus map Association areas—evaluate sensory signals, memory, upper cognition & personality Motor areas Send motor signals Homunculus map Frontal lobe Somatic motor function (primary motor cortex) incl. Broca’s area Advanced problem solving Cognition & personality General sensory processing (primary sensory cortex) Reading & speech interpretation, incl. Wernicke’s area Temporal lobe Hearing (primary auditory cortex) Smell (primary olfactory cortex)— cranial nerve I Memory Occipital lobe Sight (primary visual cortex) R hemisphere: Somatic sensory input from L side “The arts & Somatic motor output to L side senses” Music/art abilities & perceptions Emotion recognition, language assn. Facial discrimination & recognition Mental imaging Odor discrimination & identification L hemisphere: Somatic sensory input from R side “Analysis & Somatic motor output to R side language” Reasoning & logic Analytical skills; mathematics Language Spoken Written Sign Parietal lobe Hemisphere Lateralization: R/L hemispheres not functionally symmetrical! Putman/Pierce College Biol 241 09 00/20100416/Page 3 MENINGES Dura mater Epidural space Toughest meningeal layer Dural sinuses Extensions of dura mater Arachnoid mater Pia mater Spinal cord Well-developed; CT including adipose Brain Poorly-developed Dense-irregular CT Drain blood from skull—internal jugular vein Arachnoid villi—CSF absorption Falx cerebri—separates R/L cerebral hemispheres Falx cerebelli—separates cerebellar hemispheres Tentorium cerebelli—separates cerebrum from cerebellum Subdural space—interstitial fluid Delicate tissue—collagen & elastin Subarachnoid space—CSF Arachnoid villi—extend into dural sinuses; site of CSF absorption Delicate tissue—collagen & elastin Denticulate ligaments—spinal cord only CEREBROSPINAL FLUID (CSF) Formation Circulation: systolic pressure waves; 2 by ependymal cilia Reabsorption Ependymal cells Line ventricles & central canal Choroid plexi Lateral ventricles/roof of third ventricle (choroid papilli) Fourth ventricle 1. Lateral ventricles (separated by septum pellucidum) (Produces CSF) 2. Interventricular foramina 3. Third ventricle 4. Aquaduct of Sylvius 5. Fourth ventricle (adds Into subarachnoid Lateral apertures CSF), CSF exits: space via Medial aperture Into central canal 6. Down central canal to end, into subarachnoid space 7. Posteriorly down subarachnoid space of spinal cord 8. Anteriorly up subarachnoid space of spinal cord into brain Arachnoid villi; CSF reabsorbed into venous circulation in dural sinus. Hydrocephalus BLOOD BRAIN BARRIER Structure/ physiology Permeability CNS capillaries highly impermeable Astrocyte foot processes regulate permeability Can’t pass through: Large molecules: basement membrane stops Nitrogenous wastes & waste-forming molecules: Proteins Antibiotics Antibodies Ammonia, urea, uric acid, creatine Nonessential amino acids Proteins Pass through via passive transport: Glucose Essential amino acids Most ions (not K+) Pass through via simple diffusion Water Can pass through: Respiratory gases (O2, CO2) lipid solubles Vitamins Fats & fatty acids Alcohol Nicotine Anaesthetics Actively transported K+ out: Nonessential amino acids Putman/Pierce College Biol 241 09 00/20100416/Page 4 CNS ENERGY ISSUES: ENERGY SOURCE Not amino acids Toxic nitrogenous wastes Glucose Aerobic respiration: needs O2 High vascularization required Anaerobic respiration avoided Lactate buildup = brain swelling Blockage = brain goes anaerobic SPINAL CORD ANATOMY Spinal nerves, paired Cervical 8 Thoracic 12 Lumbar 5 Sacral 5 Coccygeal 1 Enlargements Cervical Lumbar Lumbar region Conus medullaris—L1 Cauda equina; L3 lumbar punctures Functional anatomy White matter External Myelinated Divided by Grey matter: external Posterior median sulcus Anterior median fissure Joined by anterior white commissure Tracts of myelinated axons: Sensory tracts Motor tracts Internal Nonmyelinated R & L horns Posterior Associative neurons (dorsal) grey Input: Lateral: Somatic sensory horns Dorsal roots Medial: Visceral sensory Lateral grey Thoracic & lumbar areas only horns Cell bodies Output: Visceral motor neurons Ventral roots Anterior Cell bodies (ventral) Output: Somatic motor neurons gray horns Ventral roots Grey Connects R & L horns commissure Central canal Putman/Pierce College Biol 241 09 00/20100416/Page 5