BIOL 2401 Fundamentals of Anatomy and Physiology Chapter

Chapter 14 The Brain and Cranial Nerves Lecture Presentation by Lee Ann Frederick University

An Introduction to the Brain and Cranial Nerves Learning Outcomes 14 -1 Name the major brain regions, vesicles, and ventricles, and describe the locations and functions of each. 14 -2 Explain how the brain is protected and supported, and discuss the formation, circulation, and function of cerebrospinal fluid. 14 -3 Describe the anatomical differences between the medulla oblongata and the spinal cord, and identify the main components and functions of the medulla oblongata. 14 -4 List the main components of the pons, and specify the functions of each. 14 -5 List the main components of the cerebellum, and specify the functions of each. 14 -6 List the main components of the midbrain, and specify the functions of each. 14 -7 List the main components of the diencephalon, and specify the functions of each. 14 -8 Identify the main components of the limbic system, and specify the locations and functions of each. 14 -9 Identify the major anatomical subdivisions and functions of the cerebrum, and discuss the origin and significance of the major types of brain waves seen in an electroencephalogram. 14 -10 Describe representative examples of cranial reflexes that produce somatic responses or visceral responses to specific stimuli. © 2012 Pearson Education, Inc.

An Introduction to the Brain and Cranial Nerves The Adult Human Brain Ranges from 750 cc to 2100 cc Contains almost 97% of the body’s neural tissue Average weight about 1. 4 kg (3 lb) Six Regions of the Brain Cerebrum Cerebellum Diencephalon Mesencephalon Pons Medulla oblongata © 2012 Pearson Education, Inc.

14 -1 The Brain Cerebrum—Largest part of the brain Controls higher mental functions Divided into left and right cerebral hemispheres Surface layer of gray matter (neural cortex) Neural cortex (cerebral cortex) Folded surface increases surface area Elevated ridges (gyri) Shallow depressions (sulci) Deep grooves (fissures) Cerebellum—second largest part of the brain Coordinates repetitive body movements Two hemispheres covered with cerebellar cortex 1 Which part of the brain is the largest? © 2012 Pearson Education, Inc.

14 -1 The Brain Diencephalon Located under cerebrum and cerebellum Links cerebrum with brain stem Three divisions of the diencephalon Left and right thalamus (relays and processes sensory information) Hypothalamus (hormone production, emotion, and autonomic function) Pituitary gland (major endocrine gland connected to hypothalamus) via the infundibulum (stalk). Interfaces nervous and endocrine systems The Brain Stem Processes information between: spinal cord and cerebrum or cerebellum Includes: Midbrain © 2012 Pearson Education, Inc. Pons Medulla oblongata

14 -1 The Brain Midbrain (mesencephalon) Processes sight, sound, and associated reflexes Maintains consciousness Pons Connects cerebellum to brain stem Is involved in somatic and visceral motor control Medulla Oblongata Connects brain to spinal cord Relays information Regulates autonomic functions Heart rate, blood pressure, and digestion © 2012 Pearson Education, Inc.

Figure 14 -1 An Introduction to Brain Structures and Functions DIENCEPHALON THALAMUS • Relay and processing centers for sensory information HYPOTHALAMUS • Centers controlling emotions, autonomic functions, and hormone production MIDBRAIN Brain stem • Processing of visual and auditory data • Generation of reflexive somatic motor responses • Maintenance of consciousness PONS • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers © 2012 Pearson Education, Inc. MEDULLA OBLONGATA • Relays sensory information to thalamus and to other portions of the brain stem • Autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities)

Table 14 -1 Development of the Brain Embryological Development Determines organization of brain structures. Neural tube is origin of brain Forebrain Midbrain Hindbrain 2 Which primary brain vesicle does not develop into a secondary brain vesicle? © 2012 Pearson Education, Inc.

14 -1 The Brain Ventricles of the Brain Origins of ventricles Neural tube encloses neurocoel which expands to form chambers (ventricles) lined with ependyma Each cerebral hemisphere contains one large lateral ventricle (I and II) separated by a thin medial partition, the septum pellucidum. Third ventricle (III) is ventricle of the diencephalon Lateral ventricles communicate with third ventricle via the interventricular foramen (Foramen of Monroe) Fourth ventricle (IV) extends into medulla oblongata and becomes continuous with the central canal of the spinal cord. Connects with third ventricle via the cerebral aqueduct © 2012 Pearson Education, Inc.

3 Which brain region is anterior to the fourth ventricle? Which is posterior to

14 -1 The Brain The brain is a large, delicate mass of neural tissue Containing internal passageways and chambers filled with cerebrospinal fluid Each of the six major brain regions has specific functions Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable Conscious thought and intelligence Physical Protection of the Brain Bones of the cranium Cranial meninges (stabilize brain in cranial cavity) Cerebrospinal fluid (protects against sudden movement and provides nutrients and removes wastes) Biochemical Isolation Blood–brain barrier and Blood-CSF barrier are produced in the neural cortex of the cerebral hemispheres. Selectively isolate brain from chemicals in blood © 2012 Pearson Education, Inc.

14 -2 Brain Protection and Support The Cranial Meninges Three layers: Dura mater Arachnoid mater Pia mater Dura mater (inner fibrous layer—meningeal layer) Outer fibrous layer (endosteal layer) fused to periosteum Arachnoid mater—covers brain Contacts epithelial layer of dura mater Subarachnoid space between arachnoid mater and pia mater Pia mater—attached to brain surface by astrocytes Dural Folds (folded inner layer of dura mater that stabilizes and supports brain) 4 What are three layers of the cranial meninges, from superficial to deep? © 2012 Pearson Education, Inc.

The relationship among the Brain, Cranium, and Meninges 5 Where is CSF reabsorbed? ©

14 -2 Brain Protection and Support Cerebrospinal Fluid (CSF) surrounds all exposed surfaces of CNS and interchanges with interstitial fluid of brain Functions: Cushions delicate structures, supports brain, transports Choroid plexus—specialized ependymal cells and capillaries Secrete CSF into ventricles—remove waste products from CSF— adjusts composition of CSF—produces about 500 m. L of CSF/day CSF circulates: From choroid plexus—through the ventricles—to the central canal of spinal cord—into subarachnoid space via two lateral apertures and one meian aperture around the brain, spinal cord, and cauda equina Blood Supply to the Brain—supplies nutrients and oxygen to brain. Delivered by internal carotid arteries and vertebral arteries and removed from dural sinuses by internal jugular veins © 2012 Pearson Education, Inc.

14 -2 Brain Protection and Support Blood–Brain Barrier (BBB) Isolates CNS neural tissue from general circulation Lipid-soluble compounds (O 2, CO 2), steroids, and prostaglandins Diffuse into interstitial fluid of brain and spinal cord Astrocytes control blood–brain barrier Blood–CSF Barrier Formed by special ependymal cells Surrounds capillaries of choroid plexus Limits movement of compounds transferred Allows chemical composition of blood and CSF to differ Valerie Harper has cancer of the Blood-Brain Barrier © 2012 Pearson Education, Inc.

14 -2 Brain Protection and Support Four Breaks in the Blood Brain Barrier Portions of hypothalamus Secrete hypothalamic hormones Posterior lobe of pituitary gland Secretes hormones ADH and oxytocin Pineal gland Pineal secretions Choroid plexus Where special ependymal cells maintain blood–CSF barrier © 2012 Pearson Education, Inc.

Review These Summary Tables The Medulla Oblongata (page 472) The Pons (page 473) The Cerebellum (page 474) The Midbrain (page 476) The Thalamus (page 478) The Hypothalamus (page 479) © 2012 Pearson Education, Inc.

14 -3 The Medulla Oblongata Allows brain and spinal cord to communicate Coordinates complex autonomic reflexes Controls visceral functions Nuclei in the Medulla Autonomic nuclei control visceral activities Sensory and motor nuclei of cranial nerves Relay stations along sensory and motor pathways © 2012 Pearson Education, Inc.

14 -3 The Medulla Oblongata Includes three groups of nuclei Autonomic Nuclei Controlling Visceral Activities (Reticular formation mass of gray matter that contains embedded nuclei. ) Reflex centers that control peripheral systems, cardiovascular centers, cardiac center, blood flow through peripheral tissues, respiratory rhythmicity centers Sensory and motor nuclei of cranial nerves (VIII, IX, X, Xi, and XII control the pharynx, neck, back and visceral organs of thoracic and peritoneal cavities) Relay stations along sensory and motor pathways (pass somatic sensory information to the thalamus) © 2012 Pearson Education, Inc.

14 -4 The Pons Sensory and motor nuclei of cranial nerves (V, VII, VIII) Nuclei involved with respiration Apneustic center of the lower pons appears to promote inspiration by stimulation of the neurons in the medulla oblongata providing a constant stimulus. Pneumotaxic center : a neural center in the upper part of the pons that provides inhibitory impulses on inspiration and thereby prevents overdistension of the lungs and helps to maintain alternately recurrent inspiration and expiration Nucei that process and relay information to and from cerebellum Ascending, descending, and transverse tracts © 2012 Pearson Education, Inc.

Figure 14 -6 c The Medulla Oblongata and Pons Tracts Ascending tracts Respiratory Centers Descending tracts Pneumotaxic center Apneustic center Transverse fibers Cerebellum Midbrain Fourth ventricle Pons Medulla oblongata Reticular formation Olivary nucleus Spinal cord Lateral view © 2012 Pearson Education, Inc.

14 -5 The Cerebellum Functions of the Cerebellum Adjusts postural muscles Fine-tunes conscious and subconscious movements Structures of the Cerebellum Folia (surface of cerebellum that is highly folded neural cortex) Anterior and posterior lobes (separated by primary fissure) Cerebellar hemispheres (separated at midline by vermis) Vermis (narrow band of cortex) Flocculonodular lobe (below fourth ventricle) © 2012 Pearson Education, Inc.

14 -5 The Cerebellum Structures of the Cerebellum Purkinje cells are large branched cells found in the cerebellar cortex. They receive input from up to 200, 00 synapses Arbor vitae (“tree of life”) Highly branched, internal white matter of cerebellum Cerebellar nuclei embedded in arbor vitae Relay information to Purkinje cells Disorders of the Cerebellum Ataxia (a disturbance in muscular coordination. If severe, the individual cannot sit or stand without assistance) Damage from trauma or stroke Intoxication (temporary impairment) Disturbs muscle coordination © 2012 Pearson Education, Inc.

14 -6 The Midbrain Structures of the Midbrain Tectum (roof of midbrain) Two pairs of sensory nuclei (corpora quadrigemina—process visual and auditory sensations) Tegmentum Cerebral peduncles Nerve fiber bundles on ventrolateral surfaces Contain: Descending fibers to cerebellum carrying voluntary motor commands from cerebral hemispheres © 2012 Pearson Education, Inc.

Figure 14 -8 a The Midbrain Thalamus Pineal gland Red nucleus Substantia nigra Corpora quadrigemina Cerebral peduncle Superior colliculus Inferior colliculus Reticular formation © 2012 Pearson Education, Inc. A posterior view. The underlying nuclei are colored only on the right.

14 -7 The Diencephalon Integrates sensory information and motor commands Thalamus, epithalamus, and hypothalamus The pineal gland is found in the posterior epithalamus. It secretes melatonin The Thalamus Filters ascending sensory information for primary sensory cortex Relays information between basal nuclei and cerebral cortex The third ventricle Separates left thalamus and right thalamus © 2012 Pearson Education, Inc.

14 -7 The Diencephalon The Hypothalamus Mamillary bodies Process olfactory and other sensory information Control reflex eating movements Infundibulum A narrow stalk Connects hypothalamus to pituitary gland Tuberal area Located between the infundibulum and mamillary bodies Helps control pituitary gland function © 2012 Pearson Education, Inc.

14 -7 The Diencephalon Eight Functions of the Hypothalamus Provides subconscious control of skeletal muscle Controls autonomic function Coordinates activities of nervous and endocrine systems Secretes hormones Antidiuretic hormone (ADH) and Oxytocin (OT; OXT) Produces emotions and behavioral drives The feeding center (hunger) The thirst center (thirst) Coordinates voluntary and autonomic functions Regulates body temperature Preoptic area of hypothalamus Controls circadian rhythms (day–night cycles) © 2012 Pearson Education, Inc.

Table 14 -7 The Limbic System includes nuclei and tracts along the border between the cerebrum and diencephalon. It is a functional grouping that: Establishes emotional states Links conscious functions of cerebral cortex with autonomic functions of brain stem Facilitates memory storage and retrieval Components of the Limbic System: Fornix—tract of white matter that connects hippocampus with hypothalamus © 2012 Pearson Education, Inc.

Stopping Point? © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Is the largest part of the brain Controls all conscious thoughts and intellectual functions Processes somatic sensory and motor information Gray Matter In cerebral cortex and basal nuclei White Matter Deep to basal cortex Around basal nuclei © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Structures of the Cerebrum Gyri of neural cortex (increase surface area - number of cortical neurons) Insula (“island” of cortex) Longitudinal fissure Separates cerebral hemispheres Lobes—Divisions of hemispheres Central sulcus divides: Anterior frontal lobe from posterior parietal lobe Lateral sulcus divides: Frontal lobe from temporal lobe Parieto-occipital sulcus divides: Parietal lobe from occipital lobe © 2012 Pearson Education, Inc.

Figure 14 -12 b The Brain in Lateral View Precentral gyrus Central sulcus Postcentral gyrus PARIETAL LOBE FRONTAL LOBE OCCIPITAL LOBE TEMPORAL LOBE Lateral sulcus Cerebellum Pons Medulla oblongata Lateral view © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Three Functional Principles of the Cerebrum Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body The two hemispheres have different functions, although their structures are alike Correspondence between a specific function and a specific region of cerebral cortex is not precise © 2012 Pearson Education, Inc.

14 -9 The Cerebrum The Basal Nuclei Are masses of gray matter Are embedded in white matter of cerebrum Direct subconscious activities Functions of Basal Nuclei Involved with: The subconscious control of skeletal muscle tone The coordination of learned movement patterns (walking, lifting) © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Association Areas Sensory association areas (regions of the cortex that interpret and monitor arriving information at sensory ares of cortex) Somatic sensory association area Interprets input to primary sensory cortex (e. g. , recognizes and responds to touch) Sensory Association Areas Visual association area—interprets activity in visual cortex Auditory association area—monitors auditory cortex Somatic motor association area (premotor cortex)—coordinates motor responses (learned movements) © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Integrative Centers (areas that receive information from many association areas and direct extremely complex motor activities). Are located in lobes and cortical areas of both cerebral hemispheres Receive information from association areas Direct complex motor or analytical activities © 2012 Pearson Education, Inc.

14 -9 The Cerebrum General Interpretive Area (Wernicke’s area) Present in only one hemisphere Receives information from all sensory association areas Coordinates access to complex visual and auditory memories Other Integrative Areas Speech center Is associated with general interpretive area Coordinates all vocalization functions Prefrontal cortex of frontal lobe Integrates information from sensory association areas Performs abstract intellectual activities (e. g. , predicting consequences of actions) © 2012 Pearson Education, Inc.

Figure 14 -15 b Motor and Sensory Regions of the Cerebral Cortex Frontal eye field Speech center Prefrontal cortex General interpretive area The left hemisphere generally contains the general interpretive area and the speech center. The prefrontal cortex of each hemisphere is involved with conscious intellectual functions. © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Hemispheric Lateralization (regional specialization in each of the two cerebral hemispheres) The Left Hemisphere In most people, left brain (dominant hemisphere) controls: Reading, writing, and math Decision making Speech and language The Right Hemisphere Right cerebral hemisphere relates to: Senses (touch, smell, sight, taste, feel) Recognition (faces, voice inflections) © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Monitoring Brain Activity Brain activity is assessed by an electroencephalogram (EEG) Electrodes are placed on the skull Patterns of electrical activity (brain waves) are printed out Four Categories of Brain Waves Alpha waves Beta waves Theta waves Delta waves 6 Which type of brain wave indicates emotional stress? © 2012 Pearson Education, Inc.

14 -9 The Cerebrum Alpha Waves Found in healthy, awake adults at rest with eyes closed Beta Waves Higher frequency Found in adults concentrating or mentally stressed Theta Waves Found in children Found in intensely frustrated adults May indicate brain disorder in adults Delta Waves During sleep Found in awake adults with brain damage © 2012 Pearson Education, Inc.

Brain Waves Alpha waves Beta waves Theta waves Delta waves © 2012 Pearson Education,

14 -9 The Cerebrum Synchronization A pacemaker mechanism Synchronizes electrical activity between hemispheres Brain damage can cause desynchronization Seizure Is a temporary cerebral disorder Changes the electroencephalogram Symptoms depend on regions affected © 2012 Pearson Education, Inc.

Clinical Case—The Neuroanatomist’s Stroke How would you know, just based on signs and symptoms, which side of Dr. Taylor’s brain has been Injured by a stroke? What is neuroplasticity and why was it important in Dr. Taylor’s recovery? © 2012 Pearson Education, Inc.

Figure 14 -15 a Motor and Sensory Regions of the Cerebral Cortex Special Sensory Cortexes Central sulcus Primary motor cortex (precentral gyrus) Primary sensory cortex (postcentral gyrus) Somatic motor association area (premotor cortex) PARIETAL LOBE Somatic sensory association area FRONTAL LOBE Visual association area Prefrontal cortex OCCIPITAL LOBE Gustatory cortex (taste receptors) Insula Visual cortex (sight receptors) Auditory association area Lateral sulcus Olfactory cortex (odor receptors) TEMPORAL LOBE Major anatomical landmarks on the surface of the left cerebral hemisphere. The lateral sulcus has been pulled apart to expose the insula. © 2012 Pearson Education, Inc. Auditory cortex (sound receptors)