14 The Brain and Cranial Nerves PowerPoint® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris © 2012 Pearson Education, Inc. An Introduction to the Brain and Cranial Nerves • The Adult Human Brain • Average weight about 1.4 kg (3 lb) © 2012 Pearson Education, Inc. 14-1 The Brain • Six Regions of the Brain 1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Mesencephalon 5. Pons 6. Medulla oblongata © 2012 Pearson Education, Inc. 14-1 The Brain • Cerebrum • Largest part of brain • Controls higher mental functions • Divided into left and right cerebral hemispheres • Surface layer of gray matter (neural cortex) © 2012 Pearson Education, Inc. 14-1 The Brain • Cerebrum • Neural cortex • Also called cerebral cortex • Folded surface increases surface area • Elevated ridges (gyri) • Shallow depressions (sulci) • Deep grooves (fissures) © 2012 Pearson Education, Inc. 14-1 The Brain • Cerebellum • Second largest part of brain • Coordinates repetitive body movements • Two hemispheres • Covered with cerebellar cortex © 2012 Pearson Education, Inc. Figure 14-1 An Introduction to Brain Structures and Functions Left cerebral hemisphere Gyri CEREBRUM Sulci • Conscious thought processes, Fissures intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions CEREBELLUM • Coordinates complex Spinal somatic motor cord patterns • Adjusts output of other somatic motor centers in brain and spinal cord © 2012 Pearson Education, Inc. 14-1 The Brain • Diencephalon • Located under cerebrum and cerebellum • Links cerebrum with brain stem • Three divisions of the diencephalon 1. Left thalamus 2. Right thalamus 3. Hypothalamus © 2012 Pearson Education, Inc. 14-1 The Brain • Diencephalon • Thalamus • Relays and processes sensory information • Hypothalamus • Hormone production • Emotion • Autonomic function © 2012 Pearson Education, Inc. 14-1 The Brain • Diencephalon • Pituitary gland • Major endocrine gland • Connected to hypothalamus • Interfaces nervous and endocrine systems © 2012 Pearson Education, Inc. 14-1 The Brain • The Brain Stem • Processes information between: • Spinal cord and cerebrum or cerebellum • Includes: • Midbrain • Pons • Medulla oblongata © 2012 Pearson Education, Inc. 14-1 The Brain • Midbrain • Also called mesencephalon • Processes sight, sound, and associated reflexes • Maintains consciousness • Pons • Connects cerebellum to brain stem • Is involved in somatic and visceral motor control © 2012 Pearson Education, Inc. 14-1 The Brain • 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 • Processing of visual stem and auditory data • Generation of reflexive somatic motor responses • Maintenance of consciousness PONS • Relays sensory MEDULLA OBLONGATA information to cerebellum and • Relays sensory information to thalamus and thalamus to other portions of the brain stem • Subconscious • Autonomic centers for regulation of visceral somatic and visceral function (cardiovascular, respiratory, and motor centers digestive system activities) © 2012 Pearson Education, Inc. 14-1 The Brain • Ventricles of the Brain • Each cerebral hemisphere contains one large lateral ventricle • Separated by a thin medial partition (septum pellucidum) © 2012 Pearson Education, Inc. 14-1 The Brain • Ventricles of the Brain • Third ventricle • Ventricle of the diencephalon • Lateral ventricles communicate with third ventricle • Via interventricular foramen (foramen of Monro) © 2012 Pearson Education, Inc. 14-1 The Brain • Ventricles of the Brain • Fourth ventricle • Extends into medulla oblongata • Becomes continuous with central canal of the spinal cord • Connects with third ventricle • Via narrow canal in midbrain called the cerebral aqueduct © 2012 Pearson Education, Inc. Figure 14-2a Ventricles of the Brain Cerebral hemispheres Ventricles of the Brain Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Pons Medulla oblongata Spinal cord Central canal Ventricular system, lateral view © 2012 Pearson Education, Inc. Figure 14-2b Ventricles of the Brain Ventricles of Cerebral hemispheres the Brain Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Central canal Cerebellum Ventricular system, anterior view © 2012 Pearson Education, Inc. 14-1 The Brain • 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 • Are produced in the neural cortex of the cerebral hemispheres © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Physical Protection of the Brain • Bones of the cranium • Cranial meninges • Cerebrospinal fluid • Biochemical Isolation • Blood–brain barrier © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • The Cranial Meninges • Have three layers 1. Dura mater 2. Arachnoid mater 3. Pia mater • Are continuous with spinal meninges • Protect the brain from cranial trauma © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • The Cranial Meninges • Dura mater • Inner fibrous layer (meningeal layer) • Outer fibrous layer (endosteal layer) fused to periosteum • Venous sinuses between two layers © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • The Cranial Meninges • 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 © 2012 Pearson Education, Inc. Figure 14-3a The Relationship among the Brain, Cranium, and Meninges Dura mater (endosteal layer) Dural sinus Cranium (skull) Dura mater (meningeal layer) Subdural space Arachnoid mater Subarachnoid space Arachnoid trabeculae Pia mater Cerebral cortex Cerebral cortex Cerebellum Medulla oblongata Spinal cord A lateral view of the brain, showing its position in the cranium and the organization of the meninges © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • Surrounds all exposed surfaces of CNS • Interchanges with interstitial fluid of brain • Functions of CSF • Cushions delicate neural structures • Supports brain • Transports nutrients, chemical messengers, and waste products © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • Choroid plexus • Specialized ependymal cells and capillaries • Secrete CSF into ventricles • Produces about 500 mL of CSF/day © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • CSF circulates: • From choroid plexus • Through ventricles • To central canal of spinal cord • Into subarachnoid space via two lateral apertures and one median aperture around the brain, spinal cord, and cauda equina © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • CSF in subarachnoid space • Arachnoid villi • Extensions of subarachnoid space • Extend through dura mater to superior sagittal sinus © 2012 Pearson Education, Inc. Figure 14-4a The Formation and Circulation of Cerebrospinal Fluid Arachnoid Extension of choroid granulations plexus into lateral ventricle Choroid plexus Superior of third ventricle sagittal sinus Cerebral aqueduct Lateral aperture Choroid plexus of fourth ventricle Median aperture Arachnoid mater Central canal Subarachnoid space Spinal cord Dura mater Filum terminale © 2012 Pearson Education, Inc. Figure 14-4b The Formation and Circulation of Cerebrospinal Fluid Superior sagittal sinus Cranium Dura mater (endosteal layer) Arachnoid granulation Fluid movement Arachnoid trabeculae Cerebral Dura mater cortex (meningeal layer) The relation- Subdural ship of the space arachnoid granulations Arachnoid mater and dura Pia Subarachnoid mater. mater space © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Blood Supply to the Brain • Supplies nutrients and oxygen to brain • Delivered by internal carotid arteries and vertebral arteries • Removed from dural sinuses by internal jugular veins © 2012 Pearson Education, Inc. Figure 21–23 Arteries of the Neck and Head © 2012 Pearson Education, Inc. Figure 21–24a Arteries of the Brain © 2012 Pearson Education, Inc. Figure 21–24b Arteries of the Brain © 2012 Pearson Education, Inc. Figure 21–29a Major Veins of the Head, Neck, and Brain © 2012 Pearson Education, Inc. Figure 21–29b Major Veins of the Head, Neck, and Brain © 2012 Pearson Education, Inc. Figure 21–29c Major Veins of the Head, Neck, and Brain © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrovascular Disease • Disorders interfere with blood circulation to brain • Stroke or cerebrovascular accident (CVA) • Shuts off blood to portion of brain • Neurons die © 2012 Pearson Education, Inc. 14-3 The Medulla Oblongata • The Medulla Oblongata • Allows brain and spinal cord to communicate • Coordinates complex autonomic reflexes • Controls visceral functions • Nuclei in the Medulla • Autonomic