The nervous system is the body’s control
and communication center.
 It serves to organize incoming data into
useful information that can be used for
internal functions and, by interpreting
external dangers and initiating
movement, physical activities necessary
for survival

Neuron: is designed to transmit various
levels of information from one cell to
another.
 There are three main types of neuron:

› Sensory neurons: Transmit impulses back
toward the brain and spinal cord
› Motor neurons: Carry impulses away from the
brain and spinal cord to the muscles and
glands of the body
› Associative neurons: Carry impulses from
sensory neurons to motor neurons

Parts of neurons:
› Dendrites: receive information
from another cell and transmit
the message to the cell body.
› Axon: conducts messages away
from the cell body.
Multipolar neurons: neurons with many
dendrites and one axon. EX: brain and
spinal cord
 Bipolar neurons: neurons with only one
dendrite and one axon. EX: found only in
the inner ear, the olfactory area of the
nose, and the retina of the eye
 Unipolar neuron: Most sensory neurons
are unipolar meaning that they have
only one extension

The axon is covered by an insulating
material called the neurilemma, also
known as the myelin sheath.
 It speeds up the electrical signal and
prevents it from interacting with other
signals.
 Nodes of Ranvier: refers to the gaps in
the myelin sheath.

› These gaps allow ions to flow freely from
extracellular fluid to the axons.
 These
cells do not transmit impulses
like the neurons, but instead insulate,
support, and protect the neurons.
› Astrocyte – Serve as part of the blood
brain barrier, which helps to prevent
certain substances from entering the
brain.
› Oligodendroglia – Provide support by
forming rigid connections between
neurons, also produce myelin for
insulation.
› Microglial – Protect the neurons through
phagocytosis(destroying foreign materials)
Nerve cells generate electrical impulses
through a process called membrane
excitability
 The membrane that separates the
cytoplasm on the inside of the cell from
the extracellular fluids on the outside of
the cell separates two areas of different
chemical composition.


Synapse: is an area between the
terminal branches of an axon and the
ends of a branched dendrite
Ex: Pg. 173
Reflex: an involuntary reaction to an
external response is called a reflex.
 The reflex arc has the following
components:

› A sensory receptor on the skin
› An afferent neuron(Sensory)
› Associated neurons within the spinal cord
› An efferent neuron (motor)
› An effector organ
The nervous system of the human body is
divided into two systems:
 Central nervous system: composed of
the brain and spinal cord.
 Peripheral nervous system: composed of
the nerves that link the various of the
body to the CNS. Includes the cranial
nerves.


The primary functions of the nervous
system are:
› Sensory: detects alterations of internal and
external stimuli
› Integrative: sensory information is analyzed
and appropriate behaviors are selected in
response
› Motor: the appropriate behaviors are
implemented
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The PNS can be divided into the somatic
nervous system and the autonomic nervous
system.
The SNS connects the CNS to skin and skeletal
muscles via the cranial and spinal nerves,
initiating voluntary responses.
The ANS connects the CNS to visceral organs
via the cranial and spinal nerves, initiating
involuntary responses.
A sympathetic response prepares the body to
deal with emergencies through the
expenditure of energy
Parasympathetic response restores
homeostatic balance and conserves energy.
Approximately 100 billion neurons that
communicate with each other through
electrochemical pulses.
 These complex interactions are ultimately
responsible for all human physical and
mental function
 Neurons are the same as other body cells
except they are specialized to gather and
evaluate information from the internal and
external environment, and then coordinate
a response to that information.

Meninges: Three layers of protective
tissue; cover the brain and spinal cord
 Dura mater: outermost layer; composed
of tough fibrous connective tissue
 Arachnoid mater: thin weblike
membrane lacking blood vessels
 Pia mater: it contains blood vessels and
nerves for the nourishment of the
underlying neural tissue.

Epidural space: a space between bone
and dura.
 Subarachnoid space: The space created
between the arachnoid mater and the
pia mater; contains CSF

Is a layer of neurons on the surface of the
brain that is approximately 2-4mm thick.
 These neurons are specialized functions,
are distributed across layers in the cortex.
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Represents that largest portion of the
human brain
Divided into separate halves, or
hemispheres, by a prominent central
groove called longitudinal fissure.
The transverse fissure separates the
cerebrum from the cerebellum.
Left Hemisphere generally handles speech
functions, whereas the Right Hemisphere
deals with nonverbal, intuitive behaviors.
90% of the population the left hemisphere is
the dominate hemisphere because it
controls verbal, computational and
analytical skills.
Refer to Pg. 178
The two hemispheres are connected by
a thick bundle of commissural nerve
fibers referred to as the corpus callosum
and anterior and posterior commissures.
 These structures allow for communication
between the brain halves.

Ventricles: A series of interconnected
canal and cavities within the brain.
 The first two ventricles are referred to as
the lateral ventricles(right and left)
 The large ventricles, which are located in
each cerebral hemisphere, connect to
the smaller third ventricle, located
between the halves of the thalamus, by
way of interventricular foramen
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The third ventricle connects to the even smaller fourth
ventricle, located by way of cerebral aqueduct.
The fourth ventricle is continuous with the central
canal of the spinal cord.
The ventricles are filled with a clear, colorless fluid
containing small amounts of protein, glucose, lactic
acid, urea, and potassium, as well as a relatively
large amount of sodium chloride.
The fluid, known as CSF, helps to support and cushion
the brain and spinal cord, and stabilizes the ionic
concentration of the CNS.
It also acts to filter the waste products of metabolism
and other substances that diffuse into the brain from
blood.
Basal ganglia: collection of nuclei
embedded deep within the white matter
of the cerebral hemispheres.
 They act with the cerebellum to modify
movement from moment to moment.

The second largest structure of the brain
and is located posterior to the medulla
oblongata and inferior to the cerebrum’s
occipital lobe.
 Separated from the cerebrum by the
transverse fissure.
 Acts to coordinate skeletal muscle
movement by comprising input from the
motor cortex of the frontal lobe with
proprioceptive feedback from the
extremities, and correcting any perceived
problems.

Located between the midbrain and the
cerebrum.
 Surrounds the third ventricle
 Primary structures include:

› Thalamus
› Hypothalamus
› Posterior pituitary gland
› Pineal gland
Thalamus: acts as a relay station to the
cerebral cortex for all sensory data from the
cerebellum, brainstem, spinal cord, and
other parts of the cerebrum
 Hypothalamus: collection of nuclei located
just inferior to the thalamus. It regulates
homeostasis of the body through
coordination of activities of the ANS. Serves
as a link between the endocrine system
and the nervous system.

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Section of the brainstem located
between the diencephalon and the
pons.

Connects the diencephalon to the spinal cord
and consist of the following:
› Medulla Oblongata:
 connect the brain with the spinal cord.
 Five of the 12 cranial nerve nuclei
 Responsible for breathing rhythm, heart rate, and blood
pressure
› Pons:
 Connects the brain with the spinal cord and other brain
parts.
 Four of the 12 cranial nerves
 Works with the medulla for regulation of breathing
› Midbrain:
 Inferior to the thalamus
 Contains center for visual reflexes( movement of the
head and eyes)
Column of nervous tissue that begins at the
level of the foramen magnum and
terminates at the level of the first and
second lumbar disks.
 Protected by the same three meningeal
coverings as the brain(dura, arachnoid,
and pia mater)
 Function is to conduct impulses and serve
as a spinal reflex center
 At the level of the first lumbar vertebra, a
collection of spinal roots descends from the
inferior spinal cord, resembling the hairs of a
horse’s tail. These nerves are known
collectively as the cauda equina.

There are 12 pairs of cranial nerves
 Originate in the brainstem with the
exception of the 1st and 2nd
 Roman numerals that indicate the order
in which they arise from the
brainstem(from the front to the back)

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Olfactory (I) - (instrumental in the sense of smell)
Optic (II) - (transmits visual information from the

Ocularmotor (III) - (controls most of the eye's

Trochlear (IV) - (“somatic efferent” that
retina to the brain)
movement, constriction of the pupil, and maintains
an open eyelid)
innervates a single muscle: the superior
oblique muscle of the eye)
 Trigeminal (V) - (responsible for sensation in
the face)Pg. 186
 Abducens (VI) - (“somatic efferent” nerve
that controls the movement of a single
muscle, the lateral rectus muscle of the eye)
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Facial (VII) - muscles of facial expression,
conveyance of taste sensations from the anterior
two-thirds of the tongue and oral cavity
Vestibulocochlear (VIII) – sound and
equilibrium (balance) information from the inner
ear to the brain
Glossopharyngeal (IX) – visceral sensory
ears, pharynx, back one thirds of tongue
Vagus(X) - innervates the viscera, conveys
sensory information about the state of the body's
organs
Accessory (XI) – control the
sternocleidomastoid and trapezius muscles of the
neck
Hypoglossal (XII) - innervates the muscles of
the tongue
The spinal cord is made up of continuous
nerve tracts and cell columns that can
be divided into segments.
 31 spinal nerve roots:

› 8 cervical
› 12 thoracic
› 5 lumbar
› 5 sacral
› 1 coccygeal