Neuro Anatomy Lecture 1 PDF

Neuroanatomy 2711212 Introduction about nervous system & anatomy of spinal cord Lecture 1  Table of contents 01 Introduction about nervous system. 02 Anatomy of spinal cord.  Neuron: 1. Neuron is composed of 3 major parts (cell...

Neuroanatomy 2711212 Introduction about nervous system & anatomy of spinal cord Lecture 1  Table of contents 01 Introduction about nervous system. 02 Anatomy of spinal cord.  Neuron: 1. Neuron is composed of 3 major parts (cell body, dendrites and axon). 2. The cell body (soma) contains the nucleus and is the metabolic center of the neuron. 3. Neurons have processes known as dendrites which extend outward from the cell body and arborize extensively. The dendrites are the receptive part of the neuron. 4. A typical neuron has long fibrous axon that originates from thickened area of the cell body; the axon of hillock. 10/12/2024 ❑ The first portion of the axon is ❑ The myelin consists of multiple called the initial segment. concentric layers of lipid-rich ❑ Axon near its end divides into membrane produced by Schwann many branches called presynaptic cells in the peripheral nervous terminals (synaptic knobs). system (PNS) and by ❑ They contain granules or vesicles oligodendrocytes (a type of glial in which the synaptic transmitters cell) in the central nervous system secreted by the nerves are stored. (CNS). ❑ The axon conducts electrical ❑ The myelin sheath is divided into signals from the initial segment segments about 1 mm long by (the proximal part of the axon, small gaps (1–2 μm long) where near the cell body) to the synaptic myelin is absent; these are the terminals (the conducting unit of nodes of Ranvier. the neuron). ❑ The smallest axons are ❑ Presynaptic terminals of axons are unmyelinated. Myelin functions as transmitting elements of the an insulator. In general, neuron. myelination serves to increase the ❑ Many axons are covered by speed of impulse conduction along myelin. the axon.  is a complex network of nerves and nerve cells (neurons) that carry signals or messages to and from the brain and spinal cord to different parts of the body. It is made up of the central nervous system and the peripheral nervous system. The neuron is the basic structural The nervous and functional unit of the nervous system The central nervous system system (CNS) contains about 100 billion neurons. It also contains 10–50 times this number of glial cells. 10/12/2024  NERVOUS SYSTEM It is divided into two main parts: The central nervous system: which consists of the brain (cerebral hemispheres, cerebellum and brain stem) and spinal cord. Bain also divides into: Forebrain: it includes the telencephalon, which contains cerebral hemispheres, and the diencephalon. Midbrain: It presents between hindbrain and forebrain. Hindbrain: It has three parts, namely medulla oblongata, pons and cerebellum. The peripheral nervous system: which consists of: 1- Cranial nerves and their ganglia: 12 pairs 2- Spinal nerves and their ganglia: 31 pairs Also, nervous system formed of: Somatic nervous system controls the voluntary activities. The autonomic nervous system is the part concerned with involuntary structures, such as the heart, smooth muscle, and glands. It is distributed throughout the central and peripheral nervous systems. The autonomic system is divided into the sympathetic and the parasympathetic parts. The activities of the sympathetic part of the autonomic system prepare the body for an emergency. The parasympathetic part is aimed at conserving and restoring energy.  Important terminology: Neurons: it is the building unit of nervous system that formed of nerve cell and its processes (dendrites and axons). Grey matter: consists of nerve cells bodies. White matter: consists of nerve fibers. Nucleus: is a group of nerve cells in CNS that have the same function. Ganglion: is a group of nerve cells in PNS that have the same function. Tract (fasciculus): is a group of nerve fibers in CNS that have the same origin, termination, and function. Nerve: is a group of nerve fibers in PNS that have the same origin, termination, and function.  Important terminology: Pathway: a chain of successive tracts having the same function Lemniscus: a collection of ascending tract in the brain stem Commissure: a band of white or grey matter connecting the both sides of CNS across the midline. Afferent: input Efferent: output Reticular formation: it is a highly intermixed network of nerve cells and nerve fibers scattered randomly in the brain stem  SPINAL CORD Position: - It lies in the vertebral canal - It begins just below the foramen magnum, where it is continues above with the medulla oblongata - It ends below at the level of the disc between the 1st & 2nd lumbar vertebrae  SPINAL CORD Shape: - It is a cylinder, lower end tapers into a cone. - Conus medullaris is lower conical end of spinal cord - Ventrally it has a deep midline groove, the anterior median fissure, and dorsally it shows a shallow posterior median sulcus, from which a posterior median septum extends into its substance. Posterior median septum Anterior median fissure Spinal enlargements: - The spinal cord possesses two symmetrical enlargements which occupy the segments of the limb Cervical plexuses: Enlargement 1Cervical enlargement (C5 to T1) for the brachial plexus 2Lumbosacral enlargement (L2 to S3) for the lumbar and sacral plexuses. Their levels measured by vertebrae are, of course, quite different; Lumboscral Enlargement the cervical enlargement is approximately opposite vertebrae C3 to T1, but the lumbosacral extends only from T9 to L1. Both enlargements are due to the greatly increased mass of motor cells in the anterior horns of grey matter for formation of nerve plexus. Spinal segments and nerves: The spinal cord divided into 31 segments called spinal segments. Each segment gives pair of spinal nerves. 8 cervical segments : 8 cervical nerves 12 thoracic segments: 12 thoracic nerves 5 lumbar segments: 5 lumbar nerves 5 sacral segments: 5 sacral nerves 1 coccygeal segment: 1 coccygeal nerve Each spinal nerve formed by: a)Dorsal root (sensory): enters the cord at the postero-lateral sulcus. It contains the dorsal root ganglion (D.R.G) b) Ventral root (motor): leaves the cord at anterolateral sulcus. It arises from anterior horn cells (A.H.Cs) The 2 roots unite with each other to form spinal nerve leaving vertebral canal through intervertebral foramen except 1st cervical nerve leaves above the atlas Upper 4 sacral nerves leave as ventral and dorsal rami through ventral & dorsal sacral foramina last sacral nerve& coccygeal nerve leave through sacral hiatus Cauda equina: a collection of nerve roots. In the lumbosacral region descend almost vertically below the cord around filum terminale because they resemble a horse’s tail. The spinal cord occupies the upper two-thirds of the adult vertebral canal within the vertebral column. The differences in levels between spinal segments and vertebrae are due to the rapid growth of VC more than that of the spinal cord. Direction of spinal nerve: - The cervical nerves are the shortest & run horizontally -The thoracic and upper lumbar roots increase in length & obliquely from above downwards -The lower lumbar, all sacral &coccygeal roots are the longest, and nearly vertical forming cauda equina. Blood supply: Arteries 1. Anterior spinal artery: in front of median sulcus 2. Right and left posterior spinal arteries: They travel in relation to dorsal root. 3. Radicular arteries: they run alongside the dorsal and ventral nerve roots. They arise from vertebral, intercostal, lumbar and sacral arteries. Veins: 6 longitudinal venous channels that drain by intervertebral veins into vertebral, intercostal, lumbar and sacral veins