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UWL BIO 312 - Brain

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Lecture 14 Lecture Outline:I Braina. Support and protectionb. The cerebrumc. Diencephalond. Brain stemi. Midbrainii. Ponsiii. Medullae. CerebellumII Limbic systemIII Reticular formationIV Cranial NervesV Diseases of the NSThe Brain: divided into 4 major regionsVentricles of the brain: filled with cerebrospinal fluid- Lateral ventricles: lies below and behind the corpus callosum and is separated by the septum pellusidum- Third ventricle: lies completely in the diencephalon- Fourth ventricle: connected to the third ventricle via the cerebral aqueduct, posterior to third ventricleProtection and Support of brain: - Brain has jello-like consistency and needs extensive protection- Protected by the meninges and skull- Meninges: three layers of connective tissue to protect braino Dura mater: most superficial layer, thickest and toughest layero Arachnoid mater: middle layer, thinner than dura mater Sub arachnoid space: space between below arachnoid, filled with CSF and blood vessels CSF cushions and supports brain in cranial cavityo Pia mater: thinnest and inner most layer, directly connected to the brain and brain stem- Choroid plexus: clumps of ependymal cells that secrete about 500 mL of CSFo CSF absorbed into blood stream as new CSF is secreted- Hydrocephalus: accumulation of CSF usually due to blocked reuptake of CSFo Causes brain to compress in adults, treatment is to insert shunt from ventricle to neck- Blood-brain barrier: astrocyte processes surround walls of capillaries, allows for limited exchangeThe Cerebrum: makes up about 80% of the volume of brain, consists of 2 cerebral hemispheres- Outer cerebral cortex (gray matter): lots of cell bodies and cell bodieso Wrinkles increase surface area (ridges = gyri; wrinkles = sulci)o Divided into regions called lobes based off ones of the skullo Involved in sensory reception, voluntary control of movement, language/speech, conscious thoughts and intellect, memory, emotiono Each region of cortex is dedicated to one major function, but also relies on other parts for help- Inner white matter: consists of myelinated axonsBio 312o Association fibers: connect regions in same hemisphereo Commissural fibers: connects two hemispheres, make up corpus callosumo Projection fibers: connect completely different types of brain such as thalamus and cerebral cortex- Nuclei embedded deep in white matter (basal nuclei): deep in cerebrumo Basal nuclei: regions of gray matter embedded in hemisphere Involved with subconscious control of skeletal muscle activity important in coordinating slow and sustained movements Parkinson’s disease: deficiency of dopamine in basal nuclei, resting tremorThe Diencephalon: located in center of brain, composed mostly of the thalamus- Thalamus: major relay station for ascending sensory informationo Intermediate mass: connects two sides of thalamuso Contains many nuclei (group of nerve cell bodies in CNS with common function) with various functionso Serves as filter for sensory information- Hypothalamus: single most important control area for regulating homeostasiso Connected to pituitary gland by infundibulumo ADH, oxytocin, emotional centers, innate drives, hunger/thirst centers, thermoregulation, circadian rhythms, control over autonomic nervous system- Epithalamus: composed mainly of pineal glando Secretes melatonin: helps regulate sleep/wake cyclesBrain stem: connection point for cranial nerves, contains midbrain, pons, and medulla oblongata- Midbrain: coordinated head and eye movements and auditory reflexeso Corpora quadrigemina:  Composed of superior and inferior colliculus (head/eye movement, auditory reflex respectively)- Pons: helps control breathing- Medulla oblongata: important centers for controlling CV and respiratory functions, swallowing, vomiting, coughing and sneezingCerebellum: involved in coordinating smooth coordinated muscular movements- All subconscious activityLimbic System: group of interconnected brain parts in cerebrum and diencephalon- Involved in emotions, behavior, learning, memory, motivation, sex driveReticular formation: network of neurons pasing through brain stem up to thalamus- Initial processing/filtering of sensory info (LSD blocks this)- Sends signals to keep cortex arousedCranial Nerves: 12 pairs that attach to brain- Serve head and special sense organs- Olfactory Nerve: sense of smell- Optic Nerve: originates at optic disc, travels to optic chiasm, carries visual information - Oculomotor: controls extrinsic eye muscles- Trochlear nerve: certain extrinsic eye muscles- Trigeminal Nerve: sensory information from large part of face and teeth- Abducens nerve: motor neurons for extrinsic eye muscles- Vagus Nerve: major nerve of parasympathetic nervous system, innervates all major internal organsDiseases of nervous system:- Stroke: cerebrovascular accidento Caused by loss of blood flow to a part of brain (clot or rupture)o Hemorrhagic stroke: caused by rupture in blood vessel, most deadly Intracerebral hemorrhage: stroke deep in brain Subarachnoid hemorrhage: rupture of blood vessel in subarachnoid space Brain stem: rupture of blood vessel in brain stem, most deadlyo Ischemic Stroke: more common form, caused by clot in blood vessel of brain Cerebral thrombosis: blocking of blood vessel Cerebral embolism: blood clot that forms in a larger artery that dislodges and gets stuck /blocks smaller blood vessel in the brain Can occur in brain


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