PowerPoint Lecture Outlines to accompany Hole’s Human Anatomy and Physiology Tenth Edition Shier w Butler w Lewis Chapter 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10-1

Chapter 10 Nervous System I Purpose - To generates and conducts electrical impulses !!! Coordinates all body systems by !!! electrochemical current The structural and functional unit of the nervous system is a NEURON (nerve cell)

Functions of Nervous System Sensory Function sensory receptors gather information information is carried to the Central Nervous System (CNS) Motor Function decisions are acted upon impulses are carried to effectors through the Peripheral Nervous System (PNS) Integrative Function sensory information used to create sensations memory thoughts decisions 10-6

Two Major Systems of the Nervous System 1. Central Nervous System (CNS) brain spinal cord 2. Peripheral Nervous System (PNS) peripheral nerves (43 nerves) cranial nerves (12 pair) spinal nerves (31 Pair) 10-1

Two Divisions of Nervous System Sensory Division INPUT INTO CNS (afferent neurons) picks up sensory information and delivers it to the CNS. 2. Motor Division (made up of two divisions) OUTPUT FROM CNS to PNS (efferent neurons) carries information to muscles and glands 10-4

Two Division of the Motor Division 1.Somatic – carries information to skeletal muscle. 2. Autonomic (made up of two divisions) – carries information to smooth muscle, cardiac muscle, and glands

Two Divisions of the Autonomic Division PARASYMPATHETIC Usually promotes those activities associated with a normal state. HOMEOSTASIS!!! SYMPATHETIC Effects are generally associated with emergency situations FIGHT OR FLIGHT!!!

Divisions Nervous System 10-5

Histology of Nervous Tissue Two principal cell types Neurons—excitable cells that transmit electrical signals Neuroglia (glial cells)—supporting cells: Astrocytes (CNS) Microglia (CNS) Ependymal cells (CNS) Oligodendrocytes (CNS) Satellite cells (PNS) Schwann cells (PNS)

Histology of Nervous Tissue Neuroglia (glial cells)—supporting cells: Astrocytes (CNS) Microglia (CNS) Ependymal cells (CNS) Oligodendrocytes (CNS) Satellite cells (PNS) Schwann cells (PNS)

Neuron Structure 10-7

Types of Neurons Bipolar two processes eyes, ears, nose Unipolar one process ganglia Multipolar many processes most neurons of CNS 10-9

Classification of Neurons Sensory Neurons afferent carry impulse to CNS most are unipolar some are bipolar Interneurons link neurons multipolar in CNS Motor Neurons multipolar carry impulses away from CNS carry impulses to effectors 10-10

STOP HERE!!!!

Types of Neuroglial Cells Schwann Cells peripheral nervous system myelinating cell Astrocytes CNS scar tissue mop up excess ions, etc induce synapse formation connect neurons to blood vessels Oligodendrocytes CNS myelinating cell Ependyma CNS ciliated line central canal of spinal cord line ventricles of brain Microglia CNS phagocytic cell 10-11

Types of Neuroglial Cells 10-12

Regeneration of A Nerve Axon 10-13

Resting Membrane Potential inside is negative relative to the outside polarized membrane due to distribution of ions Na+/K+ pump 10-14

Potential Changes at rest membrane is polarized threshold stimulus reached sodium channels open and membrane depolarizes potassium leaves cytoplasm and membrane repolarizes 10-15

Local Potential Changes occur on membranes of dendrites and cell bodies caused by various stimuli chemicals temperature changes mechanical forces if membrane potential becomes more negative, it has hyperpolarized if membrane potential becomes more positive, it has depolarized graded summation can lead to threshold stimulus that starts an action potential 10-16

Action Potentials nerve impulse occur on axons all-or-none refractory period absolute - time when threshold stimulus does not start another action potential relative – time when stronger threshold stimulus can start another action potential 10-17

Nerve Impulse (NI) The transmission of an action potential along a neuron. NI is an electrical impulse. This is similar to a row of dominos (one falls, they all fall) NI begins on a dendrite run towards the cell body, through the cell body, and then down the axon

Action Potentials 10-18

Impulse Conduction 10-19

Impulse Conduction The manner in which the NI runs down the neuron. Unmyelinated Neurons – NI must travel the length of the neuron. Myelinate Neurons – Jump from Node of Ranvier to Node of Ranvier. SALTATORY CONDUCTION!!! *VERY FAST TRANSMISSION*

Saltatory Conduction 10-20

The Synapse Nerve impulses pass from neuron to neuron at: Synapses – the junction between two neurons where a nerve impulse is transmitted 10-21

Synaptic Cleft Occurs between the axon of one neuron and the dendrite of a second neuron. NOTE!!! The two neurons DO NOT TOUCH!!! This is called the synaptic cleft 10-22

Synaptic Potentials EPSP excitatory postsynaptic potential graded depolarizes membrane of postsynaptic neuron action potential of postsynaptic neuron becomes more likely IPSP inhibitory postsynaptic potential graded hyperpolarizes membrane of postsynaptic neuron action potential of postsynaptic neuron becomes less likely 10-23

Summation of EPSPs and IPSPs EPSPs and IPSPs are added together in a process called summation More EPSPs lead to greater probability of action potential 10-24

Neurotransmitters 10-25

Impulse Processing Neuronal Pools groups of interneurons that make synaptic connections with each other interneurons work together to perform a common function each pool receives input from other neurons each pool generates output to other neurons 10-26

Convergence neuron receives input from several neurons incoming impulses represent information from different types of sensory receptors allows nervous system to collect, process, and respond to information makes it possible for a neuron to sum impulses from different sources 10-27

Divergence one neuron sends impulses to several neurons can amplify an impulse impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction 10-28

Clinical Application Multiple Sclerosis Causes Symptoms myelin destroyed in various parts of CNS hard scars (scleroses) form nerve impulses blocked muscles do not receive innervation may be related to a virus Symptoms blurred vision numb legs or arms can lead to paralysis Treatments no cure bone marrow transplant interferon (anti-viral drug) hormones 10-29