BIOL 2457 1st Edition Lecture 31Outline of Last Lecture The Brain and Cranial Nerves Outline of Current LectureThe Brain and cranial nerves Current LectureCerebral White Matter White matter tractsCommissural tractsConnect gyri in one hemisphere to corresponding gyri in the other hemisphere Corpus callosum, anterior commissure, posterior commissureAssociation tractsConduct nerves impulses between gyri in the same hemisphereProjection tractsConduct nerves impulses from the cerebrum to lower parts of the CNSBasal Ganglia Nuclei Three nuclei deep within each cerebral hemisphere make up basal nuclei. They are globus pallidus, putamen, and caudate nucleus. Help initiate and terminate movements, suppress unwanted movements and regulate muscle tone.The basal nuclei Caudate nucleus – learning, memory feedback processing & emotional esthetics (OCD) Nucleus accumbins – head of caudate n. reward, delayed gratification, caution, addiction, placebo effect associated Globus pallidus – extrapyramidal motor system (muscle memory) Putamen – controls muscle tone & coordinate learned movement patternsThe Limbic System A ring of structures on the inner border of the cerebrum and floor of the diencephalon Includes cingulate gyrus, hippocampus, dentate gyrus, amygdala, mammillary bodies, thalamus, and the olfactory bulb “Emotional brain” as it governs emotional aspects of behavior Also involved in olfaction and memoryFunctional Organization of the Cerebral Cortex: Sensory Areas Primary somatosensory area- postcentral gyrus. Primary visual area- occipital lobe. Primary auditory area- temporal lobe. Primary gustatory area- base of the postcentral gyrus. Primary olfactory area- temporal lobe. Cortex functions & hemispheric differencesPrefrontal cortexCoordinates information from secondary and special association areasPerforms abstract intellectual functions Hemispheric differencesLeft hemisphere typically contains general interpretive and speech centers and is responsible for language based skillsRight hemisphere is typically responsible for spatial relationships and analysesGeneral interpretive & speech areas General interpretive area [Wernicke] Receives information from all sensory areas Present only in left hemisphere Speech center [Broca] Regulates patterns of breathing and vocalizationFunctional Organization of the Cerebral Cortex: Association AreasControl our ability to understand sensory information and coordinate a responseSomatic sensory association areaVisual association areaSomatic motor association area Somatosensory association area- posterior to primary somatosensory area. Visual association area- occipital lobe. Auditory association area- temporal lobe. Wernicke’s area- left temporal and parietal lobes. Prefrontal cortex- anterior portion of the frontal lobe.Brain WavesElectroencephalogram: Recording of the electrical activity within the brain. Alpha waves Beta waves Theta waves Delta wavesCranial Nerves Number 12 pairs. Types Sensory, motor and mixed nerves. Identification Name Roman numeric numbersOlfactory (I) Nerve Sensory nerve Sense of smell Olfactory cells converge to become olfactory nerveOptic (II) Nerve Sensory nerve Ganglion cells in the retina of each eye join to form an optic nerve Nerve of visionOculomotor (III) Nerve Motor cranial nerve Originates in the midbrain Supplies extrinsic eye muscles to control movements of the eyeball and upper eyelidTrochlear (IV) Nerve Motor cranial nerve Smallest of the 12 cranial nerves Origin: midbrain Controls movement of the eyeballTrigeminal (V) nerve Largest cranial nerve Mixed nerve Three branches: opthalmic, maxillary and mandibular. Deals with sensation of touch, pain and temperature. Motor axons supply muscles of mastication Abducens (VI) Nerve Motor cranial nerve Originates from the pons Causes abduction of the eyeball (lateral rotation)Facial (VII) Nerve Mixed cranial nerve Sensory portion extends from the taste buds of the anterior two-thirds of the tongue Motor portion arises from the pons and deals with facial expressionVestibulocochlear (VIII) Nerve Sensory cranial nerve Originates in the inner ear Vestibular branch carries impulses for equilibrium Cochlear branch carries impulses for hearingGlossopharyngeal (IX) Nerve Mixed cranial nerve Sensory axons carry signals from the taste buds of the posterior one-third of the tongue Motor neurons arise from the medulla and deal with the release of salivaVagus (X) Nerve Mixed cranial nerve distributed from the head and neck into the thorax and abdomen Sensory neurons deal with a variety of sensations such as proprioception and stretching Motor neurons arise from the medulla and supply muscles of the pharynx, larynx, and soft palate that are involved in swallowing and vocalization Parasympathetic axons supply glands of the GI tract and smooth muscle of the respiratory passageways and digestive organsAccessory (XI) Nerve Motor cranial nerve Divided into cranial accessory and spinal accessory nerves Supplies sternocleidomastoid and trapezius muscles to coordinate head movementsHypoglossal (XII) Nerve Motor cranial nerve Conducts nerve impulses for speech and
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