Mid Term Revision Neuroanatomy block-Anatomy Editing file This file was done by: ● Abdulrahman Shadid ● Ateen Almutairi Boys team: Girls team : ● Abdullah Basamh All team members ● Alwaleed Alsaleh ● Salman Alagla Special thanks to May babaeer ● Abdulrahman Al-Bedaiwi Lecture 1: Organization of The Nervous System (1/1) Organizations of the nervous system Structural organization Functional organization (Central nervous system) (Peripheral nervous system) -brain & spinal cord (Sensory-afferent) (Motor-efferent) -nerve, ganglion & receptors -occupies the dorsal cavity Consists of nerve fibers Consists of nerve fibers -integrating/command center that convey impulses that convey impulses from receptors located from the CNS to the 1)Ganglion: group of neurons 1)Nucleus: group of neurons in various parts of the effector muscles, organs outside CNS within CNS body to the CNS. and glands. 2)Nerve: group of nerve fibers 2)Tract: group of nerve fibers outside CNS within CNS -Functions of the nervous system: 1) collection of sensory input 2) integration 3) motor output -Nervous tissue: 1) Grey matter: cell bodies/processes of neuron/neuroglia/B.V 2) White matter: same as grey matter BUT without cell bodies Autonomic nervous system Neurons that detect changes and control the activity of the viscera. Its components are present in both the central and peripheral nervous systems. Sympathetic Parasympathetic (Thoracolumbar outflow) (Craniosacral outflow) Divisions are generally have antagonistic effects on the structures that they innervate E.g. Sympathetic increases the heart rate, while the parasympathetic decreases the heart rate. Parts of The Brain Tissue of cerebral Cerebral hemispheres Cerebellum hemispheres The largest part of the brain. The outer layer is the gray matter or cortex. Cerebellum has 2 cerebellar They have elevations, called gyri that Deeper is located the white matter or hemispheres with convoluted surface. are separated by depressions called medulla, composed of bundles of nerves and fibers carrying impulses to and from the It has an outer cortex of gray matter sulci. cortex. and an inner region of white matter. Each hemisphere is divided into 4 lobes Basal nuclei are gray matter that are It provides precise coordination for named according to the bone above. located deep within the white matter to help body movements and helps maintain Lobes are separated by deeper grooves the motor cortex in regulation of voluntary equilibrium. called fissures or sulci. motor activities. Brainstem Diencephalon The diencephalon is located between It is connected to the cerebellum the 2 cerebral hemispheres and is with 3 paired peduncles superior, linked to them and to the brainstem. middle and inferior. The major structures of the The brainstem has three parts: diencephalon are: 1. Midbrain. 1. Thalamus 2. Pons. 2. Hypothalamus 3. Medulla oblongata. 3. Subthalamus 4. Epithalamus. Brain ventricles Meninges Cerebrospinal fluid ● ● Brain is bathed by the cerebrospinal fluid ● There are three connective tissue CSF is constantly produced by the choroid (CSF). membranes invest the brain and plexuses inside the ventricle. ● ● Inside the brain, there are 4 ventricles filled the spinal cord, from outward to Inside the brain, CSF flows from the lateral with CSF. inward: ventricles to the 3rd and 4th ventricles ● ● The 4 ventricles are: 1. Dura matter. From the 4th ventricle, part of the CSF flows - 2 lateral ventricles: One in each 2. Arachnoid matter. down in the central canal of the spinal cord. ● hemispheres. 3. Pia matter. Most of the CSF drains from the 4th - 3rd ventricle: in the Diencephalon. ventricle to distribute in the subarachnoid - 4th ventricle: between Pons, Medulla space around the brain and returns to the oblongata & Cerebellum. dural venous sinuses through the Cerebral aqueduct: arachnoid villi. connects the 3rd to the 4th ventricle. 2 Lecture 2: Anatomy of the Spinal Cord (1/2) Spinal Cord Shape & Pathway ● It is elongated, cylindrical, thickness of the little Function & Protection finger,suspended in the vertebral canal Features ● Continuous above with the medulla oblongata. extends ● The primary function of spinal ● Gives rise to 31 pairs of spinal from foramen magnum to 2nd lumbar (L1-L2) vertebra. cord is nerves: (In children it extends to L3). a transmission of neural signals between 8 Cervical, 12 Thoracic, In adults, its Length is approximately 45 cm the brain and the (PNS) then to the rest of 5 Lumbar, 5 Sacral, the body by: 1 Coccygeal. ● The tapered inferior end forms Conus Medullaris, which 1. Sensory. is connected to the coccyx by a non-neuronal cord called 2. Motor. ● Spinal cord has two Filum Terminale. 3. Local reflexes. enlargements: 1. Cervical enlargement: supplies ● The bundle of spinal nerves extending inferiorly from ● Protected by vertebrae and upper limbs. lumbosacral enlargement and conus medullaris surrounded by the meninges and 2. Lumbosacral enlargement: surround the filum terminale and form cauda equina cerebrospinal fluid (CSF) supplies lower limbs Cross section of the Spinal cord Central canal A cerebrospinal-filled space that runs longitudinally through the entire length of the spinal cord. The spinal cord is Commissure Lined by ependymal (ciliated columnar Incompletely divided epithelium) into two equal parts: Grey commissure: Continuous with the ventricular system of Anteriorly by a short, Composed of grey A Transverse bridge of grey matter connecting the anterior the brain shallow median fissure. matter in the and posterior gray horns on each side Superiorly opens into the 4th ventricle Posteriorly by a deep centre surrounded Is pierced by the central canal that divides it into anterior Inferiorly in the conus medullaris, it narrow septum, the by white matter and posterior part. expands into the fusiform terminal posterior median supported by White commissure: ventricle and terminates below at the root septum. neuroglia. Lies ventral to the gray commissure. of filum terminale. Mainly contains decussating nerve fibers. Grey matter ● The arrangement of grey matter resembles the shape of the letter H, ● having two posterior, two anterior and two lateral horns/columns. ● Consists of nerve cell bodies and their processes, neuroglia, and blood vessels ● The nerve cells are multipolar and are of three main categories: 1. Sensory neurons (Tract cells): receive impulses from the periphery of the body and whose axons constitute the ascending fasciculi of the white matter, are located in the Dorsal horns. 2. Lower motor neurons: transmit impulses to the skeletal muscles, are located in the ventral horns (similar neurons in the lateral horn are the preganglionic neurons of the autonomic system). 3. Interneurons (connector neurons): linking sensory and motor neurons, at the same or different levels, which form spinal reflex arcs. ❏ Arrangement of the nerve cells group: ❏ Dorsal horn ❏ ventral horn ❏ lateral horn : Small column composed of small neurons extend from: • T1 to L2-3 segments, give rise to preganglionic sympathetic fibers • S2-4 segments, give rise to preganglionic parasympathetic fibers Intermediolateral Nucleus (IMN): Located in the intermediate column and lateral horn. relays sensory information from visceral to the brain, and autonomic signals from the brain to the visceral organs. (Lamine VII). Groups of cells in the Dorsal Horn Name Location Function and features Marginal at the tip of the dorsal horn. Important for relaying pain and temperature sensation to the brain. zone (MZ) (Laminae I) Substantia at the apex of the posterior Dorsal root fibers relaying pain, temperature, and light touch sensation to the Gelatinosa horn brain. (SG): (Laminae II). Composed of large neurons and Extends throughout the length of spinal cord Nucleus In the neck of the dorsal horn Dorsal root fibers concerned with half of crude touch, concerned with senses of Proprius (anterior to substantia position & movement. gelatinosa) .(Laminae IV). Composed of large neurons and Extends throughout the length of spinal cord Nucleus at the base of dorsal horn dorsal root fibers concerned with information from muscle spindles and Dorsalis (Laminae VII). tendon organs (relays unconscious proprioceptive information to the brain) Composed mostly of large neurons and Extends from C8 to L3-4 segments Visceral lateral to nucleus dorsalis • Afferents: Visceral afferents Afferent Rexed • Composed mostly of medium size neurons • Extends from T1 to L3 segments Nucleus (Lamina VII) 3 Lecture 2: Anatomy of the Spinal Cord (2/2) 1. The Rexed laminae comprise a system of ten layers of grey matter (I-X) 2. These layers are called the Laminae of Rexed, that are numbered consecutively by Roman numerals, starting from the tip of (Rexed Laminae) the dorsal horn and moving ventrally into the ventral horn. 3. Cells of the same type are clustered into groups, which occur in long columns. 4. In transverse section, these columns appear as layers, especially within the dorsal horn. Groups of cells in the Ventral Horn The ventral horns contain: 1. Motor neurons, also called lower motor neurons. and has two type: ● Large multipolar cells ➢ Numerous ➢ Axons pass out in the ventral roots of spinal nerves as alpha efferents ➢ Innervate extrafusal muscle fibers ● Smaller multipolar cells ➢ Less numerous ➢ Axons pass out in the ventral roots of spinal nerves as gamma efferents ➢ Innervate intrafusal muscle fibers of neuromuscular spindles *Both alpha and gamma motor neurons are under the influence of descending pathways (upper motor neurons) from