Brain Intro SDL PDF

Introduction to the brain, neurons and glia, overview of the nervous system and its development, structure of the CNS Class Year 2, Semester 1 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected]...

Introduction to the brain, neurons and glia, overview of the nervous system and its development, structure of the CNS Class Year 2, Semester 1 Lecturer DR. VIJAYALAKSHMI S B Department of Anatomy Email id: [email protected] 1  Learning Outcomes Define basic neuroanatomical terms Describe the features and characteristics of cells of the nervous system and myelin Differentiate projections, commissures and association fibres Identify the meningeal layers List the main components of the nervous system Describe the process of neural tube formation and early brain development (fore-, mid- and hindbrain) Describe the parts of the central nervous system Identify the parts of the ventricular system Describe the structure of the different components of the peripheral nervous system (cranial and spinal nerves) Explain cauda equina syndrome Nervous System  Divisions of nervous system ◼Anatomical (structural): ◼Functional: ◼Central nervous system ◼Somatic nervous system (CNS) Motor components Brain and spinal cord Sensory components White and grey matter ◼Autonomic nervous system Protection (ANS) ◼Peripheral nervous system Sympathetic NS (PNS) Parasympathetic NS Cranial nerves – 12 pairs Spinal nerves – 31 pairs Ganglia CNS & PNS ANS  What is it made up of? Neurons (nerve cells) Conduct impulses transfer information Glial (neuroglial cells) Nuture and protect the neurons support neurons enhance the efficiency of information transfer Neuron Structure Receptor Dendrites Cell body membranes Conduction – Axon Transmitter – Axon terminal Nissl Body Staining  Types of Neurons Based on the arrangement of the cell body processes E.g., Retina E.g., Spinal ganglia E.g., Motor neuron; Interneuron  Types of Neurons Based on the functions Afferent (Sensory) neurons carry impulses from the sensory receptor to the CNS 3 neuron pathways – Ends in post-central gyrus Efferent (Motor) neurons carry impulses from the CNS to the effector cells 2 neuron pathways - Starts in pre-central gyrus  Glial Cells (Supporting Cells) Six types of glial cells Four in the CNS Two in the PNS Provide supportive functions for neurons Cover non-synaptic regions of the neurons NOTE: It is glial cells that most often give rise to brain tumours: Gliomas  Types of Glial Cells in the CNS Astrocytes Ependymal Cells Microglia Oligodendrocytes  Serves and supports the neurons (structurally) Blood brain barrier Myelination in the CNS In the PNS we have Schwan cells Protection of the NS Cerebrospinal fluid (CSF) secretion  Supporting Cells in the PNS Satellite cells – surround neuron cell bodies within ganglia Schwann cells (neurolemmocytes) – surround axons in the PNS Form myelin sheath around axons of the PNS  Myelin Sheaths Segmented structures composed of the lipoprotein myelin Surround thicker axons Form an insulating layer Increase the speed of impulse conduction  Myelin Sheaths in the PNS Formed by Schwann cells Schwann cells wrap in concentric layers around the axon Cover the axon in a tightly packed coil of membranes Clinical correlates: ❑ Multiple Sclerosis An autoimmune disease - Immune system attacks the myelin around axons in the CNS Cause is incompletely understood Slowing of axonal conduction and neurological dysfunction Plaques of demyelination ❑ Guillain-Barre syndrome Immune-mediated destruction of myelin in the PNS Triggered by an infective condition  Ganglia Collection of cell bodies of neurons present outside the CNS Two types: Spinal ganglia - Present at the course of the dorsal root of spinal nerves Autonomic ganglia 1. Sympathetic ganglia are present in the sympathetic chain 2. Parasympathetic ganglia are located close to the organs to which they supply REFERENCES