Lesson 1 Chapter 13 – The Nervous System

Lesson 1 Chapter 13 – The Nervous System Unit 5 Study Guide The Nervous System The nervous system includes all of the neural tissue in the body. It has two anatomical subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. It is responsible for integrating, processing, and coordinating sensory input and motor output. Also the seat of high functions. The PNS includes all of the neural tissue outside the CNS. The PNS provides sensory input to the CNS and carries commands from the CNS to peripheral tissues and systems. It has two divisions: - Afferent division: brings sensory information to the CNS Begins at receptors (ie. Dendrite, eye) and provides it to the CNS Efferent division: carries motor commands to muscles and glands. Begins at effectors (muscle gland, gland cell, or specialized cell) to perform specific functions 1 Lesson 1 Chapter 13 – The Nervous System Cellular Organization in Neural Tissue Neural tissue contains two distinct cell types: - Nerve cells or neurons Supporting cells or neuroglia Neurons are responsible for the transfer and processing information in the nervous system. Neurons can be classified based on structure or function: - - Structural classification Based on placement of the cell body Based on the number of processes extending from the cell body Functional classification Sensory (afferent) Motor (efferent) Interneuron (Involved with both sensory and motor) Structural Classification of Neurons - Anaxonic Bipolar Pseudounipolar Multipolar Has many process but cannot differentiate b/w axon and dentrites The cell body is between two axons The cell body is off to one side of the axon Typically has a single axon and multiple dendrites 2 Lesson 1 Chapter 13 – The Nervous System Functional Classification of Neurons - - Sensory Sends info from the PNS to CNS Somatic sensory (collect info concerning external and internal environment) Visceral sensory (transmit info about internal conditions and status of other organs) Motor Sends info from CNS to periphery Interneurons Situation between motor and sensory neurons Analyze sensory input and coordinate motor outputs Can be excitatory or inhibitory 3 Lesson 1 Chapter 13 – The Nervous System 4 Classifications of Neuroglia (aka Glial cells) Supporting cells, or neuroglia, isolate the neurons, providing a supporting framework for the neural tissue, help maintain the intercellular environment, and act as phagocytes. Neuroglia = Glia = Glial cells (yes, with an L at the end). Their function: 1. 2. 3. 4. 5. Support nutrition Poison Defense Support electrical communication EMT services And much, much more…. :-) Here we have 3 main (Macroglia, Microglia and sub-categories and sub- types of glial cells Ependymal glia) with sub categories: A. Macroglia  Macro – stands “bigger” than other glial for “big.” These cells are cells. Macroglia are divided The Astrocytes and the into two sub-categories: Oligodendrocytes. 1. Astrocytes Lesson 1 Chapter 13 – The Nervous System 5 As the prefix implies – Astro means star, astrocytes look like stars with lots of branches (look similar to dendrites – but they are NOT dendrites!) Astrocytes have two sub-categories themselves: a. Protoplasmic astrocytes They are found in the gray matter b. Fibrous astrocytes – They are found in the while matter. 2. Oligodendrocytes The prefix “oligo” means “few”, and “dendro” sounds like “dendrites”. Basically this cell looks like an astrocyte except that it is a little smaller, and has only a few branches. Oligodendrocytes have 3 sub-categories (I told you this would be tough – I’ll try to make it short!): a. Satellite oligodendrocyte – Myelin sheath creation b. Interfascicular oligodendrocyte – They are found in between axons (“inter”) and can “myelinate” more than one axon at a time. c. Vascular oligodendrocyte – They are found close to small capillaries. B. Microglia These are the smallest types of glia (they are micro!) This small size is what allows them to proliferate around a site of injury in the CNS C. Ependymal glia They are involved in neuronal development.  Mnemonic for the CNS: ”Mark And Peter Found Online Some Indian Veal – Micro Epic.” (Macroglia Astroctyte Protoplasmic Fibrous Oligodendrocyte Satellite Intrafascicular Vascular – Microglia Ependymal) We’re almost finished! We only have two types of neuroglia left in the Peripheral Nervous System (PNS). In the Peripheral Nervous System (~spinal cord) A. Satellite cells (don’t confuse them with the satellite oligodendrocytes). These have similar functions as the Macroglia we just covered. B. Schwann cells – These glial cells are responsible for creating and repairing the myelin sheath of axons in the PNS. They can only myelinate one axon at a time OK! We’re done! Lesson 1 Chapter 13 – The Nervous System Minimum to Remember About Neuroglia A neuron may innervate (1) other neurons, (2) skeletal muscles fibers, or (3) gland cells. A single neuron would not innervate all three. 6 Lesson 1 Chapter 13 – The Nervous System 7 Lesson 1 Chapter 13 – The Nervous System Anatomical Organization of the Nervous System An intro to the terms commonly used when describing neuroanatomy 8 Lesson 1 Chapter 13 – The Nervous System 9