A&P II Ch 11 Functional Organization of Nervous Tissue (Part 1) PDF

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Dr. Regan Chapter 11 part 1 lecture notes...

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BSC 251 — Chapter 11 (part 1) Notes : The Nervous System 11.1 Functions of the Nervous System Coordination of The Body's Organ Systems: •

Nervous System - communicates through electrical activity (action potentials) - communication is fast and short lived

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Endocrine System - communicates through chemical messengers released into the bloodstream (hormones) - communication is slow, but effect lasts long because the substances stay in the bloodstream

Major Functions of the Nervous System: 1. Sensory Input: detect changes in the environment 2. Integration: process information from the sensory input; how the sensory input is recognized 3. Control Effectors: how to respond to the changes in the environment; cardiac muscle, smooth muscle and glands 4. Homeostasis 5. Mental Activity 11.2 Divisions of the Nervous System Two Major Anatomical Divisions of The Nervous System 1. Central Nervous System (CNS) - composed of the brain and spinal cord - Function: integration, processing and coordinating sensory data and motor commands 2. Peripheral Nervous system ( PNS ) - all neural or nervous tissue outside of the CNS (nerves, receptors, and sensory organs) - Function: delivery system to and from the CNS - bundles of axons (nerve fibers) carry information and motor commands - nerves are bundles of nerve fibers with the blood vessels and connective tissues - cranial nerves are connected to brain - spinal nerves are connected to spine The Two Divisions of The Peripheral Nervous System 1. Sensory (Afferent) Division - brings sensory information to CNS from receptors in tissues and organs - receptors detect changes in environment - receptors may be neurons or other specialized cells

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BSC 251 — Chapter 11 (part 1) Notes : The Nervous System 2. Motor ( Efferent ) Division - carries motor commands from CNS to effectors such as muscles and glands - Components of The Motor (Efferent) Division of The Peripheral Nervous System: 1. Somatic Nervous System - controls skeletal muscles, voluntary or involuntary 2. Autonomic Nervous System (ANS) - controls smooth muscle, cardiac muscle and glandular activity - divided into two divisions — the Sympathetic and Parasympathetic divisions 11.3 Cells of the Nervous System - Specialized to conduct electrical impulses - Two types of cells of the NS: neurons and glial cells 1. Neurons: functional units 2. Glial Cells: supporting units Neuron Structure 1. Soma: cell body - contains nucleus and most of the organelles - lack centrioles - body of the cell 2. Dendrites: extend from the soma - sensitive processes - branched - eyes and ears of cell 3. Axon: long cytoplasmic process - propogates action potential - trigger zone - sends signals away grin cell body to other structures - mouth of the cell - Axolemma: (cell membrane) phospholipid bilayer with channels; may or may not be covered by sections of glial cells (referred to as myelination) - Collaterals: branches of the axon, allowing the one cell to communicate with multiple cells - Presynaptic Terminals: multiple branches to communicate with multiple cells ‘ Page 2

BSC 251 — Chapter 11 (part 1) Notes : The Nervous System Structural Classification of Neurons - based on dendrite relationship with the soma and axon of the cell 1. Bipolar Neuron: dendrites extend in one direction from the soma and the axon in the other direction from the soma - rare type of axon - found in sensory organs 2. Pseudo-Unipolar Neuron: processes are continuous; soma lies to the side - often representing sensory neurons - found in the PNS 3. Multipolar Neuron: multiple dendrites and one axon - motor neurons and many CNS neurons Functional Classification of Neurons - classified based on the type of signal conveyed 1. Sensory Neurons: part of the Afferent (sensory) Division of the PNS - usually unipolar - Function: carry information from receptors to the CNS - Somatic Sensory Neuron: detect changes in the external environment - Visceral (Autonomic) Sensory Neuron: detect changes in the internal environment 2. Motor Neurons: part of the Efferent (motor) Division of the PNS - Function: carries commands from the CNS to effectors and modifies the activity of peripheral tissues and organs (causes effectors to respond to some stimulus) - Somatic Motor Neuron: communicates with skeletal muscle via a communication junction called a synapse - Visceral (Autonomic) Motor Neuron: communicates with all other tissue types (cardiac muscle, smooth muscle, and glands) 3. Interneurons: association neurons - found only in the CNS - Function: connection between the sensory and motor neurons; distribute information; coordinate motor activities Supporting Cells of The Nervous System - Glial Cells: supporting cells of the Nervous System that do NOT conduct nerve impulses - Four types of glial cells in the CNS - Two types of glial cells in the PNS Page 3

BSC 251 — Chapter 11 (part 1) Notes : The Nervous System Glial Cells of The Central Nervous System (CNS) - CNS Glial Cells — 1. Ependymal Cells: type of epithelial cell found in central canal of the spinal cord and the ventricles of the brain - Function: secretes cerebrospinal fluid (CSF) 2. Astrocytes: maintain a barrier between the interstitial fluid of the CNS and the blood - Function: provide a structural framework for the CNS, stabilize injured tissue, and adjust composition of the CSF 3. Oligodendrocytes: extensions of these cells wrap around the axons of neurons (myelination) - Function: myelinated the axons of CNS neurons 4. Microglia: clean up debris, surveillance, and fight against pathogens Glial Cells of The Peripheral Nervous System (PNS) - PNS Glial Cells — 1. Satellite Cells: provide nutrients to neurons, protect neuron from poisons, support and insulate the soma of the cell 2. Schwann Cells: insulate and myelinate axons 11.4 Organization of Nervous Tissue Matter of Nervous Tissue - Gray Matter: groups of cell bodies and their dendrites. Cells bodies are clustered together in a group. - Nucleus: group of cell bodies in CNS - Ganglion: group of cell bodies in PNS - White Matter: bundles of axons. - Nerve Tract: bundle of axons in CNS is a nerve tract - Nerve: bundle of axons in PNS

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