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Brain Integrative center of Nervous System Different regions/different fcn 100 billion neurons and neuroglia 3 main sections: Forebrain, midbrain, hindbrain(brainstem) Protected by: cranial bones, CSF, and meninges CSF and meninges are continuous with The Spinal cord Cerebral Spinal Fluid(CSF): 80-150ml (3-5oz) Filtered blood plasma(glucose, oxygen, H20) Cushions, supports, nourishes, waste removal Located in cavities within brain: ventricles Lateral, third, and fourth ventricles Dry weight of brain = 1400g(3.1 lb) Weight of brain in CSF= 50g (1.7 oz) Path of CSF: 1.Produced at choroid plexus(network of capillaries) in walls of lateral ventricles(middle of cerebrum) 2. Foramen of Monro to 3rd Ventricle(center of diencephalon) 3. Cerebral Aqueduct to 4. Fourth ventricle(between cerebellum and brainstem) 5 to central canal and subarachnoid space of SC 6. To cranial subarachnoid space passing out of arachnoid villi and into the Superior Sagittal Sinus(a large vein on top of brain) – ARACHNOID GRANULATIONS = clusters of arachnoid villi CSF under constant pressure/ continual flow Brain uses 20% of the bodies Oxygen supply!! (lysosomes in brain cells are sensitive to low O2 levels. If low O2 levels persist, cells die, leads to severe retardation or death) CEREBRUM(“higher brain”) Supported on brainstem Surface = gray matter(6 layers of nerve cell bodies) = cerebral cortex Cerebral white matter beneath cortex Folds of gray matter = Gyri Deep folds = fissures Shallow folds = sulci Longitudinal fissure separates cerebrum into 2 Hemispheres Corpus Collosum: white matter connects 2 hemispheres 4 Lobes per hemisphere Frontal, parietal, temporal, and occipital Each lobe has specific functions White matter = myelinated axons running in 3 directions Association fibers = transmit impulses in same hemisphere Commisural fibers= transmit impulses between 2 hemispheres Projection fibers = form ascending and descending tracts. Transmit impulses from cerebrum to other parts of brain and spinal cord LIMBIC SYSTEM The “emotional brain” Located in diencephalon(below corpus collosum) Emotional aspects of behavior related to survival and memory Amygdaloid(amydgda = almond shape) Controls behavior: pleasure, pain, fear, sorrow rage, sexual feelings, docility, affection Diencephalon: thalamus and hypothalamus Thalamus: surrounds 3rd ventricle Relay station for sensory impulses and involuntary motor impulses Early conscious recognition of pain pressure temp and touch(basic survival instincts) Pineal gland posterior margin(releases melatonin which inhibits release of GnRH) Hypothalamus: EMOTION Regulates food and water intake, waking and sleep patterns Control center for autonomic nervous system Digestion, respiration, heart rate Controls body temp Controls mind over body phenomenon Pituitary gland (stella turcica)= the master Endocrine gland of body MIDBRAIN: tiniest portion of brain – contains various nuclei and ascending and descending fibers Relays motor impulses from cerebral cortex to Pons and spinal cord Relays sensory impulses from SC to thalamus( via sensory nuclei = colliculi(little hill) Superior colliculi coordinate eye, head, neck movement in response to BRIGHT VISUAL stimuli Inferrior colliculi coordinate eye, head, neck movement in response to LOUD noise Motor nuclei for two cranial nerves – eye movement Connects Pons and diencephalon Cerebral Peduncles: anterior to midbrain Myelinated DESCENDING fibers, motor pathways cerebrum To cerebellum Corpora Quadrigemina: Posterior to midbrain Reflex centers, rapid eye, head and trunk movement Reticular Formation: integrates involuntary functions Interconnected nuclei extending length of brain stem Contains Reticular Activating System (RAS) – directly controls activity of cerebral cortex – RAS inactive – we are inactive/ RAS active – we are attentive and wakeful PARKINSON’S DISEASE: midbrain nuclei (BASAL NUCLEI) maintain muscle tone and posture – Substantia nigra inhibits activity of basal nuclei by releasing DOPAMINE Basal nuclei become more active with less Dopamine – increased muscle tone – Parkinson’s Disease have difficulty starting voluntary movements B/C opposing muscle groups DO NOT RELAX ( not enough Dopamine is excreted by substantia nigra BRAINSTEM(Hindbrain) Pons and Medulla Oblongata Pons: relays impulses within brain and between parts of brain and spinal cord Medulla oblongata: Connects brain to spinal cord Ascending and descending tracts Sensory or motor nuclei that act as relay stations for tracts VITAL AUTONOMIC FUNCTIONS: Cardiac center – regulates heart rate Vasomotor center – controls peripheral blood flow Respiratory center – set pace for breathing Coordinates swallowing, vomiting, coughing, sneezing, and hiccuping CEREBELLUM – automatic processing center FCN: adjust our posture to maintain balance Fine tune movements controlled at conscious and subconscious levels Ex: while walking our arms swing in unison with leg movement Posterior portion of hindbrain Vermis: wormlike midline between 2 hemispheres Arbor vitae – white matter pattern Transverse fissure: separates cerebellum from cerebrum Cerebellar peduncles: 3 paired bundles of myelinated Fibers Carry sensory info from muscles, Joints, and inner ear to mainTain equilibrium & balance Regulates performance of skeletal Muscles for coordination and Posture maintenance(acts like An automatic pilot) Damage by trauma or alcohol – ATAXIA = lack of order – inability to remain physically balanced MOTOR AREAS of BRAIN Frontal Lobe= Primary Motor area(anterior to central sulcus) Controls specific muscles: jaw, tongue, lips, face, hand, knee, ankle toes Stimulation of a specific point result in muscular contraction on opposite side of body Premotor Area: anterior to primary motor area Skilled movements(writing) Frontal Eye Field: frontal cortex Controls voluntary scanning movements of the eye Language area: motor speech area = BROCA’s area In Frontal Lobe Coordinates contractions of speech and breathing muscles to translate thought into speech HOMUNCULUS(see pg 303 Sensory and motor functional map Proportional to # of sensory or motor receptors in the designated area