The Nervous System The brain relays messages by way of the spinal cord through nerve fibers. Nerves radiate to every part of the body to provide connections for input and output data. The nervous system is divided into the central nervous system which - PowerPoint PPT Presentation

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The Nervous System The brain relays messages by way of the spinal cord through nerve fibers. Nerves radiate to every part of the body to provide connections for input and output data. The nervous system is divided into the central nervous system which

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Title: The Nervous System The brain relays messages by way of the spinal cord through nerve fibers. Nerves radiate to every part of the body to provide connections for input and output data. The nervous system is divided into the central nervous system which


1
The Nervous SystemThe brain relays messages by
way of the spinal cord through nerve fibers.
Nerves radiate to every part of the body to
provide connections for input and output
data.The nervous system is divided into the
central nervous system which includes the brain
and spinal cord, and the peripheral nervous
system which is composed of the cranial nerves,
spinal nerves, autonomic nerves and ganglia
2
Nervous system cells are called neurons. All
neurons have a cell body (soma) one axon and one
or more dendrites. The cell body has a nucleus
which is responsible for maintaining the life of
the cell. The dendrites extend like tiny trees
conducting nerve impulses toward the cell body
The axon is a single process that extends out
from the cell body and ends in a fine spreading
branch called a terminal twig
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The dendrites and axons are also called nerve
fibers. Bundles of these fibers found together
are called nerves. There are several types of
nerve fibers. Some are myelinated with a white
fatty material called the myelin sheath. The
myelin sheath is interrupted along the length of
the fiber at regularly spaced intervals called
nodes of Ranvier
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Some fibers have only a thin layer of myelin and
are called non-myelinated. These fibers are found
especially in the autonomic nervous system.The
nerve cells and filaments are held together and
supported by a specialized type of tissue called
neuroglia
7
The neuroglial cells form a dense network between
neurons. They are divided into four main
typesastrocytesmicrogliaoligodendrogliaSch
wann cells
8
Neurons are divided into sensory, motor and
connector neuronsNormally impulses pass in only
one direction.Sensory neurons conduct impulses
from the sensory organs to the spinal cord.Motor
neurons conduct impulses from the brain and
spinal cord to muscles and glands.
9
The point at which an impulse is transmitted is
called the synapse. There is no physical contact
between the neurons at the synapse. The
electrical impulse causes chemical release.The
neurotransmitter chemical is released to activate
other impulses in the dendrites of connecting
neurons
10
VideoNEURONS AND NEUROTRANSMITTERS
11
The Central Nervous SystemThe central nervous
system includes the brain and the spinal cord.
It is also called the cerebrospinal system.The
CNS contains both white and gray matter.White
myelinated fibersGray masses of nerve bodies
12
The MeningesThree membranes that envelop the
central nervous system that are composed of white
fibrous connective tissue.They separate the
brain and spinal cord from the body cavitiesthe
dura mater (outermost layer) the arachnoid
(middle layer)the pia mater (innermost layer)
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The space between the dura mater and the
arachnoid is known as the subdural space.
Between the arachnoid and pia mater is the
subarachnoid space
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The brain
18
The brain contains about 100 billion neurons.
The canine brain is more immature than the human
brain at birth but maturation of cerebral
function proceeds at a higher rate. The divisions
of the brain arethe fore brainthe
midbrainthe hindbrain
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The ForebrainThe cerebrum is the largest part of
the brain and is divided into two hemispheres.
The outer surface is made up of gray matter. As
the gray matter increases in size each hemisphere
is thrown into folds called gyri. The gyri are
separated by furrows called sulci and deeper
furrows called fissures
21
The cerebral cortex is separated into the
frontal, temporal, parietal and
occipital.Frontal voluntary movementParietal
sensations Temporal awareness and auditory
Occipital visual perception and visual memory
22
The left hemisphere controls the right side of
the body. In humans the left hemisphere is
usually dominant and involves language, logic,
analytic thinking ordering of events and
symbols.The right hemisphere is linked to
imagination, creativity, spatial and depth
perception.
23
The diencephalon is the part of the forebrain
that contains the thalamus, epithalamus and
hypothalamus.Thalamus plays a role in
integrating sensationsEpithalamus olfactory
correlations and circadian rhythms.Hypothalamus
controls body temp, sleep, and behavior for
eating and drinking.
24
The MidbrainThis contains auditory, visual and
muscle control centers. It is also involved with
body posture and equilibrium
25
The HindbrainComposed of the cerebellum, the
pons and the medulla oblongata.The cerebellum
fine tunes motor activity and muscle tone.The
pons serve as a bridge to connect the cerebrum,
cerebellum and medulla oblongata.The medulla
oblongata controls respiration and circulation
26
The Limbic Systemthis is the center for
emotional activity and behavior. The term limus
means border.
27
The brain contains four large fluid filled
cavities called ventricles. The cerebrospinal
fluid is a thin transparent watery fluid that
serves as a protective cushion and provides some
nutrients. It is produced by a network of
capillaries called the choroid plexus.
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The Spinal CordThis is an extension of the
brain. Sensations are received by the sensory
nerves and are relayed to the spinal cord where
they are transferred to the brain or to motor
nerves. If the sensation is transferred to a
motor nerve it travels to a muscle or gland and
produces an action
30
The spinal cord is enclosed in the vertebral
column. Like the brain it has a pia mater,
arachnoid mater and dura mater an it is bathed in
cerebrospinal fluid. It is made of an inner core
of gray matter and an outer core of white matter.
In cross section the gray matter resembles a
butterfly.
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The outer white matter contains the tracts. The
ascending tract conducts afferent (sensory) nerve
impulses and the descending tract conducts the
efferent (motor) impulses.
33
The Peripheral Nervous SystemThis provides a
means of communication where stimuli are
transmitted from receptor organs to the central
nervous system and visa versa. The peripheral
nervous system includes all of the nerves and
ganglia located outside the brain and spinal cord.
34
The Cranial NervesThe first segment of the
peripheral nervous system consists of the 12
pairs of cranial nerves. The are numbered in
Roman Numerals.
35
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36
The Spinal NervesThese nerves arise from the
spinal cord and emerge from the vertebrae. After
leaving the spinal cord the nerves are named
after their corresponding vertebrae. A spinal
nerve has a dorsal and ventral root. The dorsal
root carries afferent (sensory) impulses and the
ventral root carries efferent (motor) impulses.
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The spinal nerves generally supply fibers to the
region of the body in the region where they
emerge from the spinal cord. In some areas they
merge and form a plexus. The spinal nerves
extend beyond the level of the spinal cord and is
called the cauda equina
39
Autonomic Nervous SystemThis is an element of
the peripheral nervous system. It functions
automatically and is composed of the sympathetic
and parasympathetic.
40
SympatheticThe nerve cells of origin are located
in the thoracic and lumbar segments of the spinal
cord
41
ParasympatheticThis system originates in the
brain stem
42
The sympathetic nerves are involved in flight or
fight and the parasympathetic nerves are involved
with restful situations Examples of the
opposition of these groups are
43
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