Brain Weighs about 3 pounds Contains about 100 billion neurons 900 billion neuroglia Cells only divide mitosis during the first several months after birth Attains its full size around age 18 Rewires itself during the teen years from back to front 6 Major Areas 1 Cerebellum 2 Cerebrum 3 Diencephan 4 Midbrain Brain Stem 5 Medulla Oblongata Brain Stem 6 Pons Brain Stem BRAIN STEM Medulla Oblongata Link between brain spinal cord About 1 inch Horizontal grooves separate it from the pons 2 pyramids or bulges appear on its ventral surface 2 olive project from the sides of its ventral surface Composed of white matter and a combination of gray and white matter reticular formation Reticular formation contains nuclei that serve as so called vital centers that control cardiac respiratory and vasomotor functions Passes sensory motor impulses along Serves as a reflex center Other centers include vomiting coughing sneezing hiccupping and swallowing Pons Superior to the medulla Composed of white matter reticular formation Contains reflex centers for numerous cranial nerves Helps regulate respiration Midbrain Superior to the pons and medulla lies beneath the third ventricle pineal body Composed of white matter and reticular formation Cerebral peduncles conduct impulses from the midbrain to the cerebrum these are rope like masses of white matter Corpora quadrigemina consist of 2 superior 2 inferior colliculus Visual centers in superior colliculus Contains reflex centers for certain cranial nerves Cranial Nerves 12 pairs 1 Olfactory 2 Optic 3 Oculomotor 4 Trochlear 5 Trigeminal 6 Abducens 7 Facial 8 Vestibulocochlear 9 Glossopharyngeal 10 Vagus 11 Accessory 12 Hypoglossal Arise from the undersurface of the brain mostly from the brain stem Names suggest function Numbered from front to back emergence Mixed certain axons of both sensory motor neurons 5 7 7 9 10 Sensory only contain sensory neurons 1 2 8 Motor only contain motor neurons 3 4 6 11 12 1 Olfactory First Sensory Run from nasal mucosa dendrites to the olfactory bulbs axon terminals 2 Optic Second Sensory Run from the retina through the optic chiasma where some fibers cross then to the thalamus to the visual area of the cortex while others terminate in the colliculi of the midbrain Some fibers take visual impulses from the thalamus to the visual area of the cortex while others terminate in the colliculi of the midbrain 3 Oculomotor Third Motor Run from the ventral midbrain to external eye muscles and intrinsic eye muscles iris e g 4 Trochlear Fourth Motor From midbrain to eye s superior oblique muscles 5 Trigeminal Fifth Mixed 3 sensory branches ophthalmic maxillary mandibular From head s skin and mucosa and teeth to the pons Motor runs from pons to mastication muscles 6 Abducens Sixth Motor From pons to lateral rectus muscles of the eye 7 Facial Seventh Mixed From the lower pons to superficial and facial and scalp muscles and to submaxillary and sublingual glands Sensory from taste buds to the medulla 8 Vestibulocochlear Eight Sensory From semicircular ear canals to the pons and medulla and the cerebellum From cochlea to pons medulla cochlear nuclei 9 Glossopharyngeal Ninth Mixed Sensory from back third of tongue pharynx to the medulla Motor from medulla to muscles in pharynx Also serves the carotids sinus which helps control blood pressure 10 Vagus Tenth Mixed Sensory from pharynx larynx heart trachea carotid body lungs esophagus stomach small intestine gall bladder to the medulla and pons Motor from medulla to muscles of pharynx larynx thoracic and abdominal viscera 11 Accessory Eleventh Motor From medulla to thoracic abdominal viscera 12 Hypoglossal Twelfth Motor From medulla to tongue Cerebellum Separated from the cerebrum by a transverse fissure Outside consists of gray matter inside of white matter or arbor vitae Below and behind the cerebrum Contains gyri and sulci Two hemispheres Tracts peduncles conduct impulses to and from the cerebrum with other parts of the brain Cerebellum Function Works with cerebellum cortex to control groups of muscle Controls skeletal muscles to maintain equilibrium Helps control posture Keeps movement smooth not jerky trembling Diseases include abscess hemorrhage tumors trauma Symptoms include lack of coordination tremors gait and equilibrium issues Diencephalon Structure Located between cerebrum and midbrain Consists of thalamus and hypothalamus Axons terminate in the thalamus from the cord brain stem cerebellum basal ganglia and cerebrum Neurons leave the thalamus for many areas of the cerebrum In other words the thalamus is the brain s major relay station The hypothalamus consists of a number of bodies including many nuclei and pituitary Diencephalon Function 1 Thalamus Recognizing crude sensations of pain temperature and pressure touch Relay sense impulses to the cerebrum Role in associating senses with emotions Role in arousal alertness mechanism Role in reflexes 2 Hypothalamus Links mind and body Links nervous and endocrine systems Pleasure centers for eating drinking mating 3 Hypothalamus Function Regulates coordinate autonomic activities Integrates and controls visceral efforts all over the body Plays an essential role in the waking state Regulates appetite when hungry and when full Maintains normal body temperature Cerebrum Structure Largest and uppermost region of the brain Two halves right left hemispheres Surface is known as the cerebral cortex composed of gray matter Many gyri sulci shallow grooves and fissures deeper grooves Fissure divide the cerebrum into lobes 1 Frontal 2 Parietal 3 Temporal 4 Occipital White matter lies under the cortex Projection tracts are extensions of those in the cord Association tracts go from gyrus to gyrus Commissural tracts go from a gyrus in one hemisphere to the corresponding gyrus in the opposite hemisphere these make up the corpus callosum Cerebrum Function 1 Sensory Register store evaluate compare 2 Motor Control voluntary movement 3 Integrative Consciousness Aware of self environment others Memory Long term in the cortex temporal parietal occipital Language Ability to speak write understand spoken written words frontal parietal temporal Emotions The limbic system the experience and expression of emotion Cerebrum functions continually throughout life creasing only at death Brain waves 1 Beta Fast low voltage indicate busyness 2 Alpha Slower high voltage indicate relaxing 3 Theta Slow low voltage indicate drowsiness 4 Delta Slowest high voltage indicate deep