Chapter 10 Key Terms
Acetylcholine
Afferent Neurons
Astrocytes
Axon Terminals
Dendrites
Neurons
Schwann Cells
Serotonin
Horns
1
Epinephrine
Efferent Neurons
Axon
Dopamine
Endorphins
Reflex Arc
Synapse
Gray Matter
Dura Mater
2
ANATOMY & PHYSIOLOGY
CHAPTER 10: NERVOUS SYSTEM
INTRODUCTION, SPINAL CORD, AND SPINAL NERVES
3
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
Nervous
System
4
CNS
PNS
Brain
Spinal Cord
Cranial nerves
Spinal nerves
Afferent
Efferent
Somatic
Sympathetic
Autonomic
Parasympathetic
5
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
6
Organization

PNS
 Afferent
 Take
 Efferent
 Take
Peripheral System
info from sensory receptors to CNS
Peripheral System
info from CNS to muscles and glands
7
Organization

Efferent
 Autonomic
 Impulses
Nervous System (ANS)
from CNS to smooth muscle, cardiac muscle, and glands
 Involuntary
 Somatic
Nervous System (SNS)
 Impulses
from CNS to skeletal muscle
 Voluntary
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Organization

ANS
 Sympathetic
 Speeds
 “Fight
 Uses
division
up activity
or flight” response
norepinephrine as neurotransmitter
 Parasympathetic
 “Rest
and digest” response
 Stimulates
 Uses
vegetative activities (digestion…)
acetylcholine as neurotransmitter
9
Classification of Nerve Cells

Nervous tissue is a composition of 2 types of cells
 Neuroglia
 Support
 Make
(glial cells) – “nerve glue”
and protect neurons
up 60% of all brain cells
 Neurons
 Nerve
cells that transmit nerve impulses through electrochemical
changes

Nerves
 Bundle
of nerve cells or fibers
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Classification of Nerve Cells

Neuroglia
 Astrocyte:
attach nerve cell to blood vessel for nutrients
 Oligodendoglia:
 Microglial:
protect CNS by destroying microbes
 Ependymal:
 Schwann:
support between nerve cells
line fluid-filled cavities of brain
form myelin sheath around nerve fibers in PNS
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Structure of
a Neuron
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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
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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
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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
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Nerve Impulse

Depolarization (Action Potential)
 Na+
 As

rush into cell, causing positive charge inside cell
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
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Nerve Impulse

All-or-None Law
 If
a nerve fiber carries any
impulse, it will carry a full
strength impulse
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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

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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
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Reflexes
Involuntary reaction to an external stimulus
 Reflex Arc

 Pathway
5
that results in a reflex
parts
 Sensory
receptor in skin
 Afferent/Sensory neuron
 Association neuron in spinal cord
 Efferent/Motor neuron
 Effector (Muscle)
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Common Reflexes

Knee-jerk reflex

Blushing

Cough reflex

Shivering

Yawning

Babinski Reflex (Video)

Eye-blink reflex
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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
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Spinal Cord

Functions
 Transmit
 Also

impulses to and from the brain
is center for reflexes
Posterior/Dorsal Root
 Contains

only sensory fibers
Anterior/Ventral Root
 Contains
only motor fibers
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Spinal Cord

Posterior Gray Horn
 Sensory

fibers
Anterior Gray Horn
 Motor
fibers
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Spinal Nerves

5 regions for the 31 spinal nerves
 Cervical
(8)
 Thoracic
(12)
 Lumbar
 Sacral
(5)
(5)
 Coccygeal
(1)