Chapter 10 Key Terms 1 AcetylcholineEpinephrine Afferent NeuronsEfferent Neurons AstrocytesAxon Axon TerminalsDopamine DendritesEndorphins NeuronsReflex Arc Schwann CellsSynapse SerotoninGray Matter HornsDura Mater

ANATOMY & PHYSIOLOGY CHAPTER 10: NERVOUS SYSTEM INTRODUCTION, SPINAL CORD, AND SPINAL NERVES 2

Nervous System  Control system of the body  Controls organs and systems of the body  Interprets stimuli from environment  Helps us react to those stimuli  Helps maintain homeostasis 3

4 Nervous System CNS Brain Spinal Cord PNS Cranial nerves Spinal nerves AfferentEfferentSomaticAutonomicSympatheticParasympathetic

Organization  Central Nervous System (CNS)  Controls the whole system  Includes brain and spinal cord  Peripheral Nervous System (PNS)  Consists of all nerves that connect the CNS with sensory receptors, muscles, and glands  Divided into two categories 5

Organization  PNS  Afferent Peripheral System  Take info from sensory receptors to CNS  Efferent Peripheral System  Take info from CNS to muscles and glands 6

Organization 7  Efferent  Autonomic Nervous System (ANS)  Impulses from CNS to smooth muscle, cardiac muscle, and glands  Involuntary  Somatic Nervous System (SNS)  Impulses from CNS to skeletal muscle  Voluntary

Organization 8  ANS  Sympathetic division  Speeds up activity  “Fight or flight” response  Uses norepinephrine as neurotransmitter  Parasympathetic  “Rest and digest” response  Stimulates vegetative activities (digestion…)  Uses acetylcholine as neurotransmitter

Classification of Nerve Cells  Nervous tissue is a composition of 2 types of cells  Neuroglia (glial cells) – “nerve glue”  Support and protect neurons  Make up 60% of all brain cells  Neurons  Nerve cells that transmit nerve impulses through electrochemical changes  Nerves  Bundle of nerve cells or fibers 9

Classification of Nerve Cells  Neuroglia  Astrocyte: attach nerve cell to blood vessel for nutrients  Oligodendoglia: support between nerve cells  Microglial: protect CNS by destroying microbes  Ependymal: line fluid-filled cavities of brain  Schwann: form myelin sheath around nerve fibers in PNS 10

Structure of a Neuron 11

Structural Classification  Multipolar  Contains several dendrites and one axon  Bipolar  One dendrite and one axon  Two processes come off the cell  Unipolar  Only one process from the body  Most sensory neurons 12

Functional Classification  Sensory Neuron (Afferent)  Receive impulse directly from receptor  Unipolar neurons  Association Neuron  Transmit impulse to appropriate part of brain for processing  Multipolar neurons found in brain and spinal cord (most common)  Motor Neuron (Efferent)  Final cell to receive impulse – causes reaction to the stimulus 13

Nerve Impulse  Neuron contains concentrations of ions inside and outside of cell  Greater concentration of Na + ions outside of cell  Greater concentration of K + ions inside cell  Concentration maintained by sodium-potassium pump  Resting Potential  Positive charge outside cell, negative charge inside cell 14

Nerve Impulse  Depolarization (Action Potential)  Na + rush into cell, causing positive charge inside cell  As this happens, K + move outside to restore resting potential  Repolarization  Sodium-Potassium pump restores equilibrium  Pumps sodium back outside cell membrane and potassium back inside cell membrane  Transmission occurs only at nodes of Ranvier 15

Nerve Impulse  All-or-None Law  If a nerve fiber carries any impulse, it will carry a full strength impulse 16

Synaptic Transmission  Synapse  Area where axon terminals are anchored close to dendrites of another neuron  Neurotransmitters connect to receptors on postsynaptic neuron  This triggers an influx of sodium in postsynaptic neuron 17

Synaptic Transmission  Acetylcholine is the most common neurotransmitter  Acetylcholinesterase breaks down Acetylcholine after it has performed its function  Other notable neurotransmitters:  Serotonin  Epinephrine  Dopamine  Endorphins 18

Reflexes  Involuntary reaction to an external stimulus  Reflex Arc  Pathway that results in a reflex  5 parts  Sensory receptor in skin  Afferent/Sensory neuron  Association neuron in spinal cord  Efferent/Motor neuron  Effector (Muscle) 19

Common Reflexes  Knee-jerk reflex  Blushing  Cough reflex  Shivering  Yawning  Babinski Reflex (Video)  Eye-blink reflex 20

Spinal Cord  Begins as continuation of the brain stem  Surrounded and protected by vertebrae (bone) and intervertebral disks (fibrocartilage)  Made up of 31 segments  Also protected by a series of connective tissue membranes called spinal meninges  Also protected by cerebrospinal fluid 21

Spinal Cord  Functions  Transmit impulses to and from the brain  Also is center for reflexes  Posterior/Dorsal Root  Contains only sensory fibers  Anterior/Ventral Root  Contains only motor fibers 22

Spinal Cord  Posterior Gray Horn  Sensory fibers  Anterior Gray Horn  Motor fibers 23

Spinal Nerves  5 regions for the 31 spinal nerves  Cervical (8)  Thoracic (12)  Lumbar (5)  Sacral (5)  Coccygeal (1) 24