Functional Human Neuroanatomy - ANA 417G CNS Organization I - Brain PDF

ANA 417G Functional Human Neuroanatomy CNS Organization I: Brain Richard C. Grondin, Ph.D. Professor Department of Neuroscience MN210 Medical Sciences Bldg Email: [email protected] Office Hours by Email Request  CNS Organization I: Brain L...

ANA 417G Functional Human Neuroanatomy CNS Organization I: Brain Richard C. Grondin, Ph.D. Professor Department of Neuroscience MN210 Medical Sciences Bldg Email: [email protected] Office Hours by Email Request  CNS Organization I: Brain Learning Objectives 1. Identify the 4 lobes of the cerebral hemispheres and 3 key anatomical landmarks 2. Identify the location of primary motor, auditory, visual and somatosensory cortices 3. Describe the motor and somatosensory homunculus 4. Describe the meninges 5. Describe the ventricular system, including: CSF Production CSF Directional flow CSF Role Causes and Consequences of CSF buildup 6. Identify the main arteries of the CNS and corresponding vascular territories for the brain RC Grondin  Brain Hemispheres Rostral The brain is divided into 2 cerebral hemispheres by the longitudinal fissure. The cerebral hemispheres are connected by commissural fibers within the corpus callosum. The normal brain is not smooth but rather has numerous grooves called sulci and bumps called gyri, each with specific names and functions. RC Grondin Dorsal View Caudal Brain Lobes 1) Frontal Frontal Parietal 2) Parietal 3) Temporal 4) Occipital pi t a l Temporal Sulci Oc c i The central sulcus separates the frontal cortex from the parietal cortex. It begins in the Lateral View longitudinal fissure and stops short of the lateral sulcus. The lateral sulcus (aka Sylvian fissure) separates the temporal cortex from parietal and frontal cortices. RC Grondin Brain Lobes Frontal 1) Frontal Pa rie 2) Parietal t al 3) Temporal 4) Occipital pi t a l Oc c i Temporal Corpus callosum Sulci Medial View The parieto-occipital sulcus (on the medial surface) separates the parietal cortex from the occipital cortex. RC Grondin  Primary Brain Cortices Motor-Auditory-Visual-Somatosensory Frontal Lobe central sulcus Parietal Lobe Precentral gyrus Postcentral gyrus Primary motor cortex Primary somatosensory cortex conscious awareness of general somatic senses (touch, pain, temperature) Lateral sulcus Occipital Lobe Temporal Lobe Primary visual cortex Transverse gyri of Heschl receives visual Primary auditory cortex information from retina (see next slide)  Primary Auditory Cortex The transverse gyri of Heschl (primary auditory cortex) are located on the superior aspect of the temporal lobe, deep within the lateral sulcus. Gray matter (neuron cell bodies) White matter (ascending and descending myelinated fibers) RC Grondin Lateral View  Motor Homonculus Upside down body mapping in each hemisphere of: motor outputs from the primary motor cortex in frontal lobe to motor neurons in brainstem or spinal cord (Right panel) Leg nd Ha longitudinal ce fissure F a lateral temporal sulcus lobe Primary motor cortex (pre-central gyrus)  Sensory Homonculus Upside down body mapping in each hemisphere of: sensory inputs from the periphery to the primary somatosensory cortex in parietal lobe (Left panel) Leg nd Ha longitudinal ace F fissure lateral sulcus temporal lobe Primary somatosensory cortex (post-central gyrus)  Cranial Cavity The brain is located in the cranial cavity and protected by a number of bones: frontal, ethmoid, temporal, parietal, sphenoid and occipital. Anterior cranial fossa: Contains the frontal lobe Middle cranial fossa: Contains the temporal lobe Posterior cranial fossa: Contains the occipital lobe, cerebellum and brainstem RC Grondin  Meninges The brain is protected by three (3) layers of connective tissue: 1) Dura mater 2) Arachnoid mater 3) Pia mater Dura mater Pia mater Arachnoid Skull mater (cross section)  Meninges – Dura Mater Periosteal Superior Sagittal Layer Meningeal Sinus Layer Dura mater Skull Dura Mater: Periosteal and Meningeal Layers Outer most, double-layered The two layers are adherent to one another except where they separate to form dural venous sinuses responsible for conveying blood away from the brain  Meninges – Pia Mater Periosteal Superior Sagittal Layer Meningeal Sinus Layer Dura mater Skull Pia mater Pia mater Inner most Closely covers surface of the brain  Meninges – Arachnoid Mater Periosteal Superior Sagittal Layer Meningeal Sinus Layer Dura mater Skull Pia mater Subarachnoid space Trabeculae Arachnoid mater On the deep side of the dura mater Connected to pia mater by bridges of connective tissue (trabeculae) = subarachnoid space filled with cerebrospinal fluid (CSF)  Meninges – Arachnoid Mater Arachnoid Superior Sagittal granulations Meningeal Sinus Layer Dura mater Skull Pia mater Subarachnoid space Trabeculae Arachnoid granulations Extensions of the arachnoid membrane that protrude through the meningeal layer of the dura mater into the superior sagittal sinus One-way flow re-absorption of CSF from the subarachnoid space into the blood  Ventricular System During brain formation, the hollow space of the neural tube forms an interconnected system of chambers called the ventricular system: – Two lateral ventricles, one in each hemisphere – Third ventricle (in the middle, between the two thalami) – Fourth ventricle (between pons and cerebellum) Lateral Ventricle 3rd ventricle 4th ventricle cerebellum Ventricular System – CSF Production The ventricular system is filled with clear cerebrospinal fluid (CSF) Choroid plexus derived from the pia mater and located in all ventricles produce CSF at a rate of about ~500 ml/day The choroid plexus is composed of highly vascular secretory epithelial tissue Lateral Ventricle 3rd ventricle 4th ventricle  Ventricular System – CSF Role CSF provides support -- human brain weighs ~1,500 grams; while the net weight of the brain suspended in CSF ~25-50 grams CSF provides protection (fluid cushion) against external forces CSF provides nourishment (contains glucose, proteins, lipids, and electrolytes) CSF helps remove waste material Lateral Ventricles Interventricular foramen 3rd ventricle Cerebral aqueduct 4th ventricle  Ventricular System – CSF Flow Lateral ventricle -> Third ventricle via interventricular foramen Third ventricle -> Fourth ventricle via cerebral aqueduct Fourth ventricle -> Cisterna magna/subarachnoid space via 1 medial and 2 lateral openings in the fourth ventricle Lateral Ventricles Interventricular foramen 3rd ventricle Cerebral aqueduct 4th ventricle  Ventricular System – Hydrocephaly CSF buildup in the ventricular system causing ventricles to expand Can be present at birth (= congenital) or in adults (= acquired) Hydrocephaly – Root Causes Genetic abnormality Infection in the uterus — such as rubella — during pregnancy which can cause inflammation in fetal brain tissues Tumors/Cysts Head injury (in acquired hydrocephalus) Hydrocephaly – Clinical Signs Nausea and vomiting Headaches Visual impairments (e.g., double vision) Lethargy Enlarged head (in young children because their skull bones are not yet fully fused)  Ventricular System – Hydrocephaly Sagittal View Horizontal View Hydrocephaly – Types Communicating hyrdocephalus can be caused by CSF overproduction or poor absorption in the venous blood. Non-communicating hyrdocephalus can be Non-communicating obstructive hydrocephalus: caused by CSF flow MRI showing dilatation of lateral ventricles with interruption stretching of corpus callosum and dilatation of the fourth ventricle caused by obstruction of the foramina of Luschka and Magendie. http://emedicine.medscape.com Updated: Apr 13, 2016 Author: Stephen L Nelson, Jr, MD, PhD, FAAP  Blood Supply – Brain The brain is supplied in blood from the internal carotid arteries and the vertebral arteries Internal carotid arteries supply the brain by giving rise to: anterior cerebral arteries (ACA) middle cerebral arteries (MCA) *posterior cerebral arteries (PCA) (*derived from vertebral arteries) Ventral View  Blood Supply – Brain Middle Cerebral Arteries (MCA) MCA supply lateral aspects of: Frontal lobe including most of precentral gyrus (except midline aspect) Parietal lobe including most of postcentral gyrus (except midline aspect) Temporal lobe Lateral View (Left Hemisphere)  Blood Supply – Brain Anterior Cerebral Arteries (ACA) Posterior Cerebral Arteries (PCA) ACA supply medial aspect of: Frontal lobe Parietal lobe PCA supply: Occipital lobe Medial aspect of temporal lobe ACA PCA Medial View (Right Hemisphere)  PRACTICE QUIZ CNS Organization I: Brain REVIEW (Learning Objective 5) Which of the following statements is INCORRECT concerning CSF circulation in the ventricular system? A)CSF enters the spinal cord subarachnoid space through the fourth ventricle B)CSF circulates from the 4th to the 3rd ventricle via the central canal C)CSF is reabsorbed into the venous circulation D)blockage of CSF circulation can cause hydrocephaly E)CSF circulates from the lateral to the 3rd ventricle via the interventricular foramen REVIEW (Learning Objective 6) Which of the following CNS regions could possibly be damaged following a stroke of the middle cerebral artery (MCA)? A. Neurons in the cerebellum B. Neurons in the occipital lobe C. Neurons in the brainstem D. Neurons in the frontal lobe E. Neurons in the spinal cord