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Anatomy & Physiology Lecture 10: Chapter 14 The Brain and Cranial Nerves Pages : 451 - 494 Lecturer: Dr. Barjis Room P313 /P307 Phone: (718) 260-5285 E-Mail: [email protected] Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Frederic H. Martini Fundamentals of Learning Objectives • Name the major regions of the brain and describe their functions. • Discuss the formation, circulation and functions of the CSF. • List the main components of the medulla oblongata, the pons, the cerebellum, the mesencephalon, the diencephalon, and the limbic system and specify their functions. Learning Objectives • Identify the major anatomical subdivisions of the cerebrum. • Locate the motor, sensory and association areas of the cerebral cortex and discuss their functions. • Describe representative examples of cranial reflexes. An Introduction to the Organization of the Brain Major regions and landmarks • Six regions in the adult brain • Cerebrum • Diencephalon • Mesencephalon • Pons • Cerebellum • Medulla oblongata • Brain contains extensive areas of neural cortex • Layer of gray matter on the surface of the cerebellum and cerebrum The Adult Brain The Adult Brain The Adult Brain An Introduction to Brain Functions Embryology of the brain • Brain forms from three swellings at the tip of the developing neural tube • Prosencephalon • Forms the telencephalon and eventually the cerebrum and diencephalon • Telecephalon will become cerebrum • Mesencephalon • Mesencephalon will become midbrain • Rhombencephalon • Forms the metencephalon (cerebellum and pons) and myelencephalon (medulla oblongata) Ventricles of the brain • Central passageway of the brain enlarges to form ventricles (cavity) • Contain cerebrospinal fluid (CSF) Ventricles of the Brain Animation: Brain Dissections (see tutorial) Protection and Support of the Brain The cranial meninges • Continuous with the three layers of the spinal cord • Folds of dura mater help stabilize the position of the brain • Falx cerebri • Tentorium cerebelli • Falx cerebelli The Relationship among the Brain, Cranium, and Meninges Cerebrospinal fluid (CSF) • CSF cushions delicate neural structures • Supports the brain • Transports nutrients, chemical messengers, and waste products • Pathway of CSF • Produced at the Choroid plexus, • Travels through the lateral and medial apertures to the subarachnoid space, • Diffuses across the arachnoid granulations into the superior sagittal sinus The Circulation of Cerebrospinal Fluid Blood supply to the brain • Blood brain barrier isolates neural tissue from general circulation • Incomplete barrier in areas • Parts of the hypothalamus • Pituitary gland • Pineal gland • Choroid plexus Medulla oblongata • Connects the brain with the spinal cord • Contains relay stations and reflex centers • Olivary nuclei – relay impulses from proprioceptor (receptors monitoring joint and muscle position) to cerebellum. • Cardiovascular and respiratory rhythmicity centers • Other nuclei in the medulla control reflexes such as vomiting, coughing, sneezing, blood pressure. • Reticular formation begins in the medulla oblongata and extends into more superior portions of the brainstem The Diencephalon and Brain Stem The Diencephalon and Brain Stem The Medulla Oblongata and Pons The Medulla Oblongata and Pons The pons The pons contains • Sensory and motor nuclei for four cranial nerves • Nuclei that help control respiration • Connects part of the brain with one another: • Nuclei and tracts linking the cerebellum with the brain stem, cerebrum and spinal cord • Connections are provided by bundles of axons (tracts). • Ascending, descending and transverse tracts The Medulla Oblongata and Pons The Medulla Oblongata and Pons The cerebellum • Adjusts postural muscles and tunes on-going movements • Cerebellar hemispheres • Anterior and posterior lobes – govern subconscious aspects of skeletal muscle. • Vermis – the central area • Flocculonodular lobe – contributes to equilibrium and balance. • Superior, middle and inferior cerebellar peduncles link cerebellum with brain stem, diencephalon, cerebrum, and spinal cord • Interconnects the two cerebellar hemispheres The Cerebellum The Cerebellum The mesencephalon • The tectum (roof) contains the corpora quadrigemina (four rounded elevations) • Two Superior - they serve as a reflex centers for some visual activities. • Two inferior colliculi – are part of auditory pathway • The mesencephalon contains many nuclei • Red nucleus • Substantia nigra • Cerebral peduncles • RAS (Reticular Activating System) headquarters The Mesencephalon The diencephalon The diencephalon is composed of • Epithalamus • Hypothalamus • Thalamus The thalamus • Final relay point for ascending sensory information • Coordinates the activities of the cerebral cortex and basal nuclei The Thalamus The hypothalamus • Controls somatic motor activities at the subconscious level • Controls autonomic function • Coordinates activities of the endocrine and nervous systems • Secretes hormones • Produces emotions and behavioral drives • Coordinates voluntary and autonomic functions • Regulates body temperature • Coordinates circadian cycles of activity The Hypothalamus in Sagittal Section The Hypothalamus in Sagittal Section The limbic system The limbic system or motivational system includes • Amygdaloid body • Cingulated gyrus • Parahippocampal gyrus • Hippocampus • Fornix • Functions of the limbic system: • emotions and behavioral drives • linking conscious intellectual functions of cortex with unconscious and autonomic functions • Facilitate memory storage and retrival The Limbic System The Brain in Section The Brain in Section The cerebral The cerebral cortex • Surface contains gyri and sulci or fissures • Longitudinal fissure separates two cerebral hemispheres • Central sulcus separates frontal and parietal lobes • Temporal and occipital lobes also bounded by sulci White matter of the cerebrum • Contains association fibers • Commissural fibers • Projection fibers The White Matter of the Cerebrum The basal nuclei • Caudate nucleus • Globus pallidus • Putamen • Control muscle tone and coordinate learned movement patterns Motor and sensory areas of the cortex • Primary motor cortex of the precentral gyrus directs voluntary movements • Primary sensory cortex of the postcentral gyrus receives somatic sensory information • Touch • Pressure • Pain • Taste • Temperature The Cerebral Hemispheres PLAY Association areas • Control our ability to understand sensory information and coordinate a response • Somatic sensory association area • Visual association area • Somatic motor association area general interpretive and speech areas • General interpretive area • Receives information from all sensory areas • Present only in left hemisphere • Speech center • Regulates patterns of breathing and vocalization cortex functions and hemispheric differences • Prefrontal cortex • Coordinates information from secondary and special association areas • Performs abstract intellectual functions • Hemispheric differences • Left hemisphere typically contains general interpretive and speech centers and is responsible for language based skills • Right hemisphere is typically responsible for spatial relationships and analyses Hemispheric Lateralization PLAY Electroencephalogram (EEG) • Measures brain activity • Alpha waves = healthy resting adult • Beta waves = concentrating adult • Theta waves = normal children • Delta waves = normal during sleep Brain Waves PLAY Focus: Cranial Nerves • 12 pairs of cranial nerves • Each attaches to the ventrolateral surface of the brainstem near the associated sensory or motor nuclei Origins of the Cranial Nerves PLAY Origins of the Cranial Nerves PLAY Origins of the Cranial Nerves PLAY Olfactory nerves (I) • Carry sensory information responsible for the sense of smell • Synapse within the olfactory bulb The Olfactory Nerve PLAY cranial nerves II, III, IV • Optic nerves (II) • Carry visual information from special sensory receptors in the eyes • Occulomotor nerves (III) • Primary source of innervation for 4 of the extraocular muscles • Trochlear nerves (IV) • Innervate the superior oblique muscles Cranial Nerves Controlling the Extra-ocular Muscles PLAY cranial nerves V, VI, VII • Trigeminal nerves (V) • Missed nerves with ophthalmic, maxillary and mandibular branches • Abducens nerve (VI) • Innervates the lateral rectus muscles • Facial nerves (VII) • Mixed nerves that control muscles of the face and scalp • Provide pressure sensations over the face • Receive taste information from the tongue The Trigeminal Nerve PLAY The Facial Nerve PLAY cranial nerves VIII, IX • Vestibulocochlear nerves (VIII) • Vestibular branch monitors balance, position and movement • Cochlear branch monitors hearing • Glossopharyngeal nerves (IX) • Mixed nerves that innervate the tongue and pharynx • Control the action of swallowing cranial nerves X • Vagus nerves (X) • Mixed nerves • Vital to the autonomic control of visceral function The Vestibulocochlear Nerve PLAY The Glossopharyngeal Nerve PLAY The Vagus Nerve PLAY cranial nerves XI, XII • Accessory nerves (XI) • Internal branches • Innervate voluntary swallowing muscles of the soft palate and pharynx • External branches • Control muscles associates with the pectoral girdle • Hypoglossal nerves (XII) • Provide voluntary motor control over tongue movement The Accessory and Hypoglossal Nerve PLAY Cranial reflexes • Involve sensory and motor fibers of cranial nerves You should now be familiar with: • The major regions of the brain and their functions. • The formation, circulation and functions of the CSF. • The main components of the medulla oblongata, the pons, the cerebellum, the mesencephalon, the diencephalon, and the limbic system and their functions. • The major anatomical subdivisions of the cerebrum. • The motor, sensory and association areas of the cerebral cortex. • Representative examples of cranial reflexes.