Lecture 1 PHCL2610 Nervous System PDF

Lecture 1 PHCL2610 Nervous System Ana Maria Oyarce Ph.D. Department of Pharmacology – HEB280C Office hours: TBD or by appointment Phone: (419)383-1919 Email: [email protected] 1  Lecture 1 Topics  Nervous Sys...

Lecture 1 PHCL2610 Nervous System Ana Maria Oyarce Ph.D. Department of Pharmacology – HEB280C Office hours: TBD or by appointment Phone: (419)383-1919 Email: [email protected] 1  Lecture 1 Topics  Nervous System  Cell Types of Neuro System  Myelination of axons Material Vander’s Human Physiology 16th Edition. Copyright 2023 Chapter 6. Section A: Cells of the Nervous System 2  Uploaded Quizzes and Assignments for Module 1 SB Neuronal Signaling 1/27/25 SB Nervous System 2/3/25 Quiz Neuron Connect 2/3/25 Quiz 1 Neuron BB 2/3/25 Bonus Quiz Nervous System 2/6/25 Bonus Orientation video 2/17/25 Bonus Smart Book video 2/17/25 3  The Nervous System The nervous system has two major divisions or parts 1. The central nervous system (CNS), composed of the brain and spinal cord Brain controls all the body’s functions Spinal cord has nerves that branch out to organs and body parts 2. The peripheral nervous system (PNS), consisting of nerves that connect the brain or spinal cord with the body’s muscles, glands, sense organs, and other tissues  The nervous system uses specialized cells (neurons) for cell communication 4  Cell Types In The Nervous Tissue  There are two principal cell types in the nervous system 1. Neurons  The functional units of the nervous system → cell to cell communication  Excitable cells → use electrical and chemical signals to send messages through the body  They do not divide 2. Neuroglia or Glial Cells  They are non-neural cells that surround neurons they outnumber neurons  Provide support, nourishment and protection to the neurons  They divide 5 Parts of a Neuron and Their Functions 6  Types of Neurons Neurons are classified based on structure and function Structural classification According to the number of processes extending from the body Functional classification Based on the direction of the nerve impulse with respect to the CNS 7  Structural Classification of Neurons  Multipolar neurons have  Bipolar neurons have a  Unipolar neurons have several short dendrites single axon and one main cell body off to one side and a single long axon dendrite (Ex. neurons of and a single axon divided (Ex. motor neurons, sensory organs; eyes, in two branches (Ex. neurons in the brain and ear and nose) most sensory neurons in in the spinal cord) skin, muscles & joints and internal organs) 8  Functional Classification of Neurons  There are three types of neurons: sensory, motor, and interneurons  Send information (impulses) from the tissues and organs toward the brain or spinal cord (CNS)  Most are unipolar neurons  Connect sensory and motor neurons within the CNS  Multipolar neurons  Carry info away from CNS to effector cells like muscles, glands and other cell types  Multipolar neurons (soma and dendrites in CNS and axon extend to the periphery) 9  Axonal Transport Important to maintain the structure and function of the neuron It moves cargo from the soma (cell body) to the axon terminal and back to the soma Two types of directional transports Anterograde transport Retrograde transport 10 Types of Axonal Transports  Anterograde transport  From soma to axon terminal  Moves nutrients, enzymes, mitochondria, neurotransmitter- filled vesicles, and other organelles  It is mediated by Kinesin  Retrograde transport  From axon terminal back to the soma  Moves recycled membrane vesicles and substances that enter the neuron (eg., nerve growth factor, tetanus toxin and viruses)  It is mediated by dynein 11  Glial Cells or Neuroglias They surround the axon and/or dendrites of neurons They provide the neurons with physical and metabolic support They can divide → tumors gliomas Different glial cells are found in the CNS and PNS Main functions we will discuss  Blood brain barrier  Myelin formation 12  Glial Cells in PNS Two cell types in PNS  Satellite cells  Schwann cells 13  Glial Cells in CNS Four cell types in CNS  Oligodendrocytes, astrocytes, microglia & ependymal cells 14  Astrocytes: Blood-Brain Barrier Semi-permeable barrier composed of brain blood vessels and astrocytes Protects the brain from harmful substances (toxins), germs and things in the blood that could cause damage  Astrocytes processes cover the capillaries  Astrocytes processes stimulate the formation of tight junctions (protein complexes) → solid connection between cells 15 Myelination or Formation of Myelin Sheath The axons of many neurons are covered by sheaths of myelin Myelin sheath 80% lipids, 20% proteins and water Function → it insulates the axon and increases nerve impulse speed It is formed by Oligodendrocytes in the CNS and by Schwann cells in the PNS 16  Myelination in PNS by Schwann Cells Each Schwann cell produces part of the myelin sheath surrounding one PNS axon → A Schwann cell myelinates one segment of an axon Cells wrap around PNS axons Inner portion is myelin sheath Outer portion is the neurilemma 17 Myelination in CNS by Oligodendrocytes 18  Node of Ranvier in Myelinated Axons Periodic gaps in the myelin sheath → spaces between adjacent myeline section Facilitates the rapid conduction of nerve impulses Electrical impulses hop from one node to another 19  Unmyelinated Axons in PNS  Unmyelinated or non-myelinated axons are not protected by myelin sheath  Axons are usually thinner and conduct nerve impulses at a low speed  Schwann cells wrap very thinly the axons without forming myelin 20