This document contains lecture slides about the nervous system from a textbook on anatomy and physiology. It begins with an outline of the chapter on the nervous system and then covers topics like the main divisions and organization of the nervous system, different cell types (neurons and glial cells), membrane potentials including resting membrane potential and action potentials, and other key concepts. Diagrams and figures are referenced throughout to illustrate various anatomical structures and processes involved in the nervous system.

1. Seeley’s
ESSENTIALS OF
Anatomy &
Physiology
Tenth Edition
Cinnamon Vanputte
Jennifer Regan
Andrew Russo
See separate PowerPoint slides for all figures and tables
pre-inserted into PowerPoint without notes.
© 2019 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.

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Chapter 8
Nervous System
Lecture Outline

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Nervous System
Figure 8.1

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Nervous System Functions
1. Receiving sensory input
2. Integrating information
3. Controlling muscles and glands
4. Maintaining homeostasis
5. Establishing and maintaining mental activity

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Main Divisions of Nervous System1
Central nervous system (CNS)
• brain and spinal cord
Peripheral nervous system (PNS)
• All the nervous tissue outside the CNS
Sensory division
• Conducts action potentials from sensory receptors
to the CNS
Motor division
• Conducts action potentials to effector organs, such
as muscles and glands

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Main Divisions of Nervous System2
Somatic nervous system
• Transmits action potentials from the CNS to skeletal
muscles.
Autonomic nervous system
• Transmits action potentials from the CNS to cardiac
muscle, smooth muscle, and glands
Enteric nervous system
• A special nervous system found only in the digestive
tract.

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Organization of the Nervous System
Figure 8.2

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Cells of the Nervous System
Neurons
• receive stimuli, conduct action potentials, and
transmit signals to other neurons or effector organs.
Glial cells
• supportive cells of the CNS and PNS, meaning these
cells do not conduct action potentials. Instead, glial
cells carry out different functions that enhance
neuron function and maintain normal conditions
within nervous tissue.

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Neurons
A neuron (nerve cell) has a:
• Cell body – which contains a single nucleus
• Dendrite – which is a cytoplasmic extension from
the cell body, that usually receives information from
other neurons and transmits the information to the
cell body
• Axon – which is a single long cell process that leaves
the cell body at the axon hillock and conducts
sensory signals to the CNS and motor signals away
from the CNS

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Typical Neuron
Figure 8.3

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Structural Types of Neurons1
Multipolar neurons have many dendrites and a
single axon.
Most of the neurons within the CNS and nearly
all motor neurons are multipolar.
Bipolar neurons have two processes: one
dendrite and one axon.
Bipolar neurons are located in some sensory
organs, such as in the retina of the eye and in
the nasal cavity.

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Structural Types of Neurons2
Pseudo-unipolar neurons have a single process
extending from the cell body, which divides into
two processes as short distance from the cell
body.
One process extends to the periphery, and the
other extends to the CNS.
The two extensions function as a single axon
with small, dendrite-like sensory receptors at
the periphery.

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Types of Neurons
Figure 8.4

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Glial Cells1
Glial cells are the supportive cells of the CNS and
PNS.
Astrocytes serve as the major supporting cells in
the CNS.
Astrocytes can stimulate or inhibit the signaling
activity of nearby neurons and form the blood-
brain barrier.
Ependymal cells line the cavities in the brain
that contains cerebrospinal fluid.

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Glial Cells2
Microglial cells act in an immune function in the
CNS by removing bacteria and cell debris.
Oligodendrocytes provide myelin to neurons in
the CNS.
Schwann cells provide myelin to neurons in the
PNS.

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Types of Glial Cells
Figure 8.5

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Myelin Sheath1
Myelin sheaths are specialized layers that wrap
around the axons of some neurons, those
neurons are termed, myelinated.
The sheaths are formed by oligodendrocytes in
the CNS and Schwann cells in the PNS.
Myelin is an excellent insulator that prevents
almost all ion movement across the cell
membrane.

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Myelin Sheath2
Gaps in the myelin sheath, called nodes of
Ranvier, occur about every millimeter.
Ion movement can occur at the nodes of
Ranvier.
Myelination of an axon increases the speed and
efficiency of action potential generation along
the axon.
Multiple sclerosis is a disease of the myelin
sheath that causes loss of muscle function.

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Unmyelinated Neurons
Unmyelinated axons lack the myelin sheaths.
These axons rest in indentations of the
oligodendrocytes in the CNS and the Schwann
cells in the PNS.
A typical small nerve, which consists of axons of
multiple neurons, usually contains more
unmyelinated axons than myelinated axons.

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Myelinated and Unmyelinated Axons
Figure 8.6

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Organization of Nervous Tissue
The nervous tissue varies in color due to the
abundance or absence of myelinated axons.
Nervous tissue exists as gray matter and white
matter.
Gray matter consists of groups of neuron cell
bodies and their dendrites, where there is very
little myelin.
White matter consists of bundles of parallel
axons with their myelin sheaths, which are
whitish in color.

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Membrane Potentials
Resting membrane potentials and action potentials
occur in neurons.
These potentials are mainly due to differences in
concentrations of ions across the membrane,
membrane channels, and the sodium-potassium pump.
Membrane channels include leak channels and gated
channels.
Leak channels are always open, whereas gated
channels are generally closed, but can be opened due
to voltage or chemicals.

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Leak Membrane Channels
Leak channels are always open are and ions can
“leak” across the membrane down their
concentration gradient.
Because there are 50 to 100 times more K+ leak
channels than Na+ leak channels, the resting
membrane has much greater permeability to K+
than to Na+; therefore, the K+ leak channels have
the greatest contribution to the resting
membrane potential.

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Gated Membrane Channels
Gated channels are closed until opened by
specific signals.
Chemically gated channels are opened by
neurotransmitters or other chemicals, whereas
voltage-gated channels are opened by a change
in membrane potential.
When opened, the gated channels can change
the membrane potential and are thus
responsible for the action potential.

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Sodium-Potassium Pump
The sodium-potassium pump compensates for the
constant leakage of ions through leak channels.
The sodium-potassium pump is required to
maintain the greater concentration of Na+ outside
the cell membrane and K+ inside.
The pump actively transports K+ into the cell and
Na+ out of the cell.
It is estimated that the sodium-potassium pump
consumes 25% of all the ATP in a typical cell and
70% of the ATP in a neuron.

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Resting Membrane Potential1
The resting membrane potential exists because of:
• The concentration of K+ being higher on the inside of
the cell membrane and the concentration of Na+ being
higher on the outside
• The presence of many negatively charged molecules,
such as proteins, inside the cell that are too large to
exit the cell
• The presence of leak protein channels in the
membrane that are more permeable to K+ than it is to
Na+

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Resting Membrane Potential2
Na+ tends to diffuse into the cell and K+ tends to
diffuse out.
In order to maintain the resting membrane
potential, the sodium-potassium pump recreates
the Na+ and K+ ion gradient by pumping Na+ out of
the cell and K+ into the cell.

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Resting Membrane Potential3
Figure 8.7(1)

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Resting Membrane Potential4
Figure 8.7(2)

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Resting Membrane Potential5
Figure 8.7(3)

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Action Potential1
Action potentials allow conductivity along nerve
or muscle membrane, similar to electricity going
along an electrical wire.
The channels responsible for the action potential
are voltage-gated Na+ and K+ channels, which are
closed during rest (resting membrane potential).
When a stimulus is applied to the nerve cell,
following neurotransmitter activation of
chemically gated channels, Na+ channels open
very briefly, and Na+ diffuses quickly into the cell.

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Action Potential2
This movement of Na+, which is called a local current,
causes the inside of the cell membrane to become
positive, a change called depolarization.
If depolarization is not strong enough, the Na+ channels
close again, and the local potential disappears without
being conducted along the nerve cell membrane.
If depolarization is large enough, Na+ enters the cell so
that the local potential reaches a threshold value.
This threshold depolarization causes voltage-gated Na+
channels to open, generally at the axon hillock.

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Action Potential3
The opening of these channels causes a massive, 600-
fold increase in membrane permeability to Na+.
Voltage-gated K+ channels also begin to open.
As more Na+ enters the cell, depolarization continues at
a much faster pace, causing a brief reversal of charge –
the inside of the cell membrane becomes positive
relative to the outside of the cell membrane.
The charge reversal causes Na+ channels to close and Na+
then stops entering the cell.
During this time, more K+ channels are opening and K+
leaves the cell, resulting in repolarization.

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Action Potential4
At the end of repolarization, the charge on the cell
membrane briefly becomes more negative than the
resting membrane potential; this condition is called
hyperpolarization and occurs briefly.
Action potentials occur in an all-or-none fashion
All-or-none refers to the fact that if threshold is
reached, an action potential occurs; if the threshold
is not reached, no action potential occurs.
The sodium-potassium pump assists in restoring the
resting membrane potential.

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Action Potential5
Figure 8.9

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Action Potential6
Figure 8.8 (1)

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Action Potential7
Figure 8.8 (2)

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Action Potential8
Figure 8.8 (3)

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Unmyelinated and Myelinated Axon
Action Potentials
Action potentials are conducted slowly in
unmyelinated axons and more rapidly in
myelinated axons.
Action potentials along unmyelinated axons
occur along the entire membrane.
Action potentials on myelinated axons occur in a
jumping pattern at the nodes of Ranvier.
This type of action potential conduction is called
saltatory conduction.

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Unmyelinated Axon Conduction
Figure 8.10

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Myelinated Axon Conduction
Figure 8.11

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Axon Conduction Speed
The speed of action potential conduction varies
widely, even among myelinated axons; it is based
on the diameter of axon fibers.
Medium-diameter, lightly myelinated axons,
characteristic of autonomic neurons, conduct
action potentials at the rate of about 3 to 15
meters per second (m/s).
Large-diameter, heavily myelinated axons conduct
action potentials at the rate of 15 to 120 m/s.

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Synapse1
A neuroneuronal synapse is a junction where the
axon of one neuron interacts with another
neuron.
The end of the axon forms a presynaptic terminal
and the membrane of the next neuron forms the
postsynaptic membrane, with a synaptic cleft
between the two membranes.
Chemical substances called neurotransmitters
are stored in synaptic vesicles in the presynaptic
terminal.

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Synapse2
An action potential reaching the presynaptic
terminal causes voltage-gated Ca2
+ channels to
open, and Ca2
+ moves into the cell.
This influx of Ca2
+ causes the release of
neurotransmitters by exocytosis from the
presynaptic terminal.
The neurotransmitters diffuse across the synaptic
cleft and bind to specific receptor molecules on
the postsynaptic membrane.

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Synapse3
The binding of neurotransmitters to these membrane
receptors causes chemically gated channels for Na+,
K+, or Cl− to open or close in the postsynaptic
membrane.
The specific channel type and whether or not the
channel opens or closes depend on the type of
neurotransmitter in the presynaptic terminal and the
type of receptors on the postsynaptic membrane.
The response may be either stimulation or inhibition
of an action potential in the postsynaptic cell.

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Synapse4
If Na+ channels open, the postsynaptic cell
becomes depolarized, and an action potential will
result if threshold is reached.
If K+ or Cl− channels open, the inside of the
postsynaptic cell tends to become more negative,
or hyperpolarized, and an action potential is
inhibited from occurring.
There are many neurotransmitters, with the best
known being acetylcholine and norepinephrine.

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Synapse5
Neurotransmitters do not normally remain in the
synaptic cleft indefinitely, thus their effects are short
duration.
These substances become reduced in concentration
when they are either rapidly broken down by enzymes
within the synaptic cleft or are transported back into the
presynaptic terminal.
An enzyme called acetylcholinesterase breaks down the
acetylcholine.
Norepinephrine is either actively transported back into
the presynaptic terminal or broken down by enzymes.

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The Synapse
Figure 8.12

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Reflex
A reflex is an involuntary reaction in response to a
stimulus applied to the periphery and transmitted
to the CNS.
Reflexes allow a person to react to stimuli more
quickly than is possible if conscious thought is
involved.
Most reflexes occur in the spinal cord or
brainstem rather than in the higher brain centers.
A reflex arc is the neuronal pathway by which a
reflex occurs and has five basic components.

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Reflex Arc Components
1. A sensory receptor
2. A sensory neuron
3. Interneurons, which are neurons located
between and communicating with two other
neurons
4. A motor neuron
5. An effector organ (muscles or glands).
Note: The simplest reflex arcs do not involve
interneurons.

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Reflex Arc
Figure 8.13

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Neuronal Pathway (Converging)
The CNS has simple to complex neuronal
pathways.
A converging pathway is a simple pathway in
which two or more neurons synapse with the
same postsynaptic neuron.
This allows information transmitted in more than
one neuronal pathway to converge into a single
pathway.

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Neuronal Pathway (Diverging)
A diverging pathway is a simple pathway in which
an axon from one neuron divides and synapses
with more than one other postsynaptic neuron.
This allows information transmitted in one
neuronal pathway to diverge into two or more
pathways.

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Neuronal Pathways
Figure 8.14

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Summation1
A single presynaptic action potential usually does not
cause a sufficiently large postsynaptic local potential to
reach threshold and produce an action potential in the
target cell.
Many presynaptic action potentials are needed in a
process called summation.
Summation of signals in neuronal pathways allows
integration of multiple subthreshold local potentials.
Summation of the local potentials can bring the
membrane potential to threshold and trigger an action
potential.

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Summation2
Spatial summation occurs when the local potentials
originate from different locations on the postsynaptic
neuron—for example, from converging pathways.
Temporal summation occurs when local potentials
overlap in time.
This can occur from a single input that fires rapidly,
which allows the resulting local potentials to overlap
briefly.
Spatial and temporal summation can lead to stimulation
or inhibition, depending on the type of signal.

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The Nervous System
“The right half of the brain controls the left
half of the body. This means that only left
handed people are in their right mind.”

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Central Nervous System
• Made up of brain and
spinal cord
• Acts as body’s control
center, coordinates
body’s activities
– Impulses travel through
the neurons in your
body to reach the brain
• Central Nervous System
is yellow in this
diagram.

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Peripheral Nervous System
• Made up of all the nerves that
carry messages to and from the
central nervous system.
– Similar to telephone wires that
connect all of our houses in the
community
• Central Nervous System and
Peripheral Nervous System work
together to make rapid changes
in your body in response to
stimuli.
• Peripheral Nervous System is
green in this diagram.

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Peripheral Nervous System: 2 parts
• Somatic Nervous System
– Relay information between skin, skeletal muscles and central
nervous system
– You consciously control this pathway by deciding whether or
not to move muscles (except reflexes)
– Reflexes: Automatic response to stimulus
• Autonomic Nervous System
– Relay information from central nervous system to organs
– Involuntary: You do not consciously control these
– Sympathetic Nervous System: controls in times of stress,
such as the flight or fight response
– Parasympathetic Nervous System: controls body in times of
rest

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Neurons
• The basic unit of structure and function in the
nervous system
• Cells that conduct impulses.
– Made up of dendrites, cell body and an axon

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Neurons
• Dendrites: branch-like extensions that receive
impulses and carry them toward cell body.
• Axon: single extension of the neuron that
carries impulses away from the cell body.
• The axon branches out at ending to send
impulses to many different neurons.
Dendrites receive impulses from many other
axons.

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In other words, there’s a lot of traffic
going on in the neurons of your
Central Nervous System.

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3 types of neurons
• Sensory Neurons: carry impulses from inside and
outside the body to brain and spinal cord.
• Interneurons: found within brain and spinal cord,
process incoming impulses and pass them on to
motor neurons.
• Motor Neurons: carry impulses away from the brain
and spinal cord.

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So how do these neurons work if someone
taps you on the shoulder . . .
1. Receptors in the skin sense touch or other stimuli.
2. Sensory neurons transmit the touch message.
3. Information is sorted and interpreted in the brain. A
response in determined by interneurons.
4. Motor neurons transmit a response message to the
shoulder muscles.
5. The shoulder muscles are activated, causing the head
to turn.

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How is an impulse transmitted?
1. Stimulus excites sensory neuron.
2. Depolarization (a change in charge due to sodium ions) creates
a wave of changing charges down the axon.
3. Impulse moves across synapse (tiny space between one
neuron’s axon and another’s dendrites) with the help of
neurotransmitters
This is an image of neurons located
in the cerebral cortex of a hamster.

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Reflexes:
Are rapid, predictable and involuntary responses to stimuli
Occur over neural pathway called reflex arcs and involve both CNS and
PNS structures.
Somatic reflexes – include all reflexes that stimulate the skeletal
muscles.
Autonomic reflexes – regulate the activity of smooth muscles, the
heart, and glands. (salivary reflexes, pupillary reflex)

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Central Nervous System
Neural tube – a simple tube wherein the CNS first appear during
embryonic development
Ventricles – chambers formed by the enlarged four regions of the
brain
Brain – about two good fistfuls of pinkish gray tissue, wrinkled like a
walnut and with the texture of cold oatmeal, weighs a little over three
pounds.
Cerebral Hemispheres
The paired cerebral hemispheres, collectively called the cerebrum
Gyri – elevated ridges of tissue in the entire surface of cerebral
hemispheres

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Spinal Cord
Approximately 17 inches (42 cm) long. Extends from the foramen
magnum to the first or second lumbar vertebra. 31 pairs of spinal
nerves.
Enlarged in cervical and lumbar regions
Cauda equina – collection of spinal nerves at the inferior end of the
vertebral canal and it looks so much like a horse’s tail.

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Gray Matter of the SC and Spinal Roots
Looks like a butterfly or the letter H in cross section.
Two posterior projections are the dorsal/posterior horns; the two
anterior projections are the ventral/anterior horns.
The gray matter surrounds the central canal of the cord, which
contains CSF
Dorsal root ganglion – when damaged, sensation from the body area
served will be lost.
Dorsal and ventral roots fuse to form the spinal nerves.

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Peripheral Nervous System
Structure of a Nerve:
Nerve – a bundle of neuron fibers found outside the CNS.
Endoneurium – connective tissue sheath that surrounds each fiber
Perineurium – coarser connective tissue that wraps groups of fibers
(fascicles)
Epineurium – a tough fibrous sheath that bound all the fascicles
together

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Sulci – shallow grooves
Fissures – deeper grooves, separate large regions of the brain
Longitudinal fissure – single deep fissure that separates the cerebral
hemispheres
Cerebral Cortex
 Speech, memory, logical and emotional response, as well as
consciousness, interpretation of sensation, and voluntary movement
Primary somatic sensory area – located in the parietal lobe posterior
to the central sulcus. For recognition of pain, coldness, or light touch.
Occipital lobe – the visual area
Temporal lobe – auditory area, the olfactory area is found deep inside

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Primary motor area – allows us to consciously move our skeletal
muscles, anterior to the central sulcus in the frontal lobe. Corticospinal
tract/pyramidal tract the major voluntary motor tract.
Motor homunculus – body map of the motor cortex
Broca’s area – found at the base of the precentral gyrus. Damage to
this area causes inability to say words properly.
Frontal lobe – higher intellectual reasoning and socially acceptable
behavior
Temporal and frontal lobes – storage of complex memories
wernicke’s area) Speech area (- located at the junction of the
temporal, parietal, and occipital lobes

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Corpus callosum – large fiber tract that connects the cerebral
hemisphere
Basal nuclei or basal ganglia – help regulate voluntary motor activities
by modifying instructions (starting/stopping movement) sent to the
skeletal muscles by the primary motor cortex.
Diencephalon
-Or interbrain, sits atop the brainstem
Thalamus – relay station for sensory impulses passing upward to the
sensory cortex.
Hypothalamus – plays a role in the regulation of body temperature,
water balance and metabolism. Also the center for many drives and
emotions, and as such it is an important part of the so-called limbic
system, or “emotional visceral brain”. (thirst, appetite, sex, pain,
pleasure)

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*Mammillary bodies – reflex center involved in olfaction
Epithalamus- important parts are the pineal body (part of the
endocrine system) and the choroid plexus of the third ventricle
Brain Stem
About the size of the thumb in diameter and approximately 3 inches
long. Structures are midbrain, pons and medulla oblongata
Midbrain is a relatively small part of the brainstem. Cerebral aqueduct
is a tiny canal that travels through the midbrain and connects the third
ventricle to the fourth ventricle. Cerebral peduncles (little feet of the
cerebrum), convey ascending and descending impulses. Corpora
quadrigemina are reflex centers involved in vision and hearing

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Pons – means “bridge” , mostly fiber tracts, involved in the control of
breathing
Medulla Oblongata – regulate vital visceral activities; contains centers
that control heart rate, blood pressure, breathing, swallowing, and
vomiting.
Reticular formation – extending the entire length of the brain stem
which is a diffuse mass of gray matter, involved in motor control of the
visceral organ.
Reticular activating system (RAS) – special group of reticular
formation neurons that plays a role in consciousness and the
wake/sleep cycles. Damage to this area can result in permanent
unconsciousness (coma).

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Cerebellum – large, cauliflower-like that projects dorsally from the
occipital lobe. Provides the precise timing for skeletal muscle activity
and controls our balance and equilibrium. Damage can lead to ataxia.
Protection of the CNS
Meninges – three connective tissue membranes covering and protecting
the CNS structures
Dura mater – outermost layer, meaning “tough or hard mother”, is a
double-layered membrane
Arachnoid mater – the middle menigeal layer which is web-like
Pia mater – innermost layer, meaning “gentle mother”

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ROMBERG’S TEST

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Cerebrospinal Fluid (CSF) – is a watery “broth” similar in its makeup to
blood plasma. It is continually formed from blood by the choroid
plexuses. Forms and drains
at a constant rate so that its normal pressure and volume (150 ml- about
half a cup) are maintained.
The pathway of CSF circulation is as follows: choroid
plexus(lat venticle)→ interventricular foramen
(Foramen of Monro)→third ventricle→cerebral
aqueduct (Aqueduct of Sylvius)→fourth ventricle→
foramen in 4th ventricle(Foramen of Luschka and
Magendie)→ subarachnoid space.

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HYDROCEPHALUS

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Blood-brain Barrier – composed of least permeable capillaries in the
whole body. Of water-soluble substances, only water, glucose and
essential amino acids pass easily through the walls of these capillaries.
Metabolic wastes such as urea, toxins, proteins, and most drugs are
prevented from entering the brain tissue. Is virtually useless against fats,
respiratory gases, and other fat-soluble molecules that diffuse easily
through all plasma membranes. This explains why blood borne alcohol,
nicotine and anesthetics can affect the brain.
Brain dysfunctions:
Concussion – brain injury is slight. The victim may be dizzy, “see stars”,
or lose consciousness briefly, but no

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permanent brain damage occurs.
Contusion – result of marked tissue destruction
Cerebrovascular accidents (CVAs) or stroke – when a blood circulation to
a brain area is blocked.

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THE CRANIAL NERVES
Name Function Test
I. Olfactory
(Sensory)
Purely sensory; carries
impulses for the sense of
smell
Subject is asked to sniff
and identify aromatic
substances
II. Optic
(Sensory)
Purely sensory; carries
impulses for vision
Vision and visual field
are tested with an eye
chart
III. Oculomotor
(Motor)
Supplies motor fibers to
four of the six muscles
(superior, inferior, and
medial rectus, and
inferior oblique) that
direct the eyeball.
Pupils are examined for
size, shape, and size
equality; pupillary reflex
is tested with penlight.
IV. Trochlear
(Motor)
Supplies motor fibers for
one external eye muscle
(superior oblique)
Tested in common with
CN III for the ability to
follow moving objects.

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V. Trigeminal
(Mixed)
conducts sensory impulses
from the skin of the face
and mucosa of the nose
and mouth; also contains
motor fibers that activate
the chewing muscles
sensations of pain , touch,
and temperature are
tested with a safety pain
and hot or cold objects;
motor branch tested by
asking to open mouth
against resistance
VI. Abducens
(Motor)
Supplies motor fibers to
the lateral rectus
Tested in common with CN
III for the ability to move
each eye laterally
VII. Facial
(Mixed)
Activates the muscles of
facial expression and
lacrimal and salivary
glands; carries sensory
impulses from the taste
buds of anterior tongue
Anterior 2/3 of tongue is
tested for ability to taste;
subject is asked to close
the eyes, smile, whistle,
etc.
VIII. Vestibulocochlear
(Sensory)
Purely sensory; vestibular
branch for sense of balance
and cochlear branch for
sense of hearing
Hearing is checked by air
and bone conduction using
a tuning fork

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ANISOCORIA

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TRIGEMINAL NERVE

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IX. Glossopharyngeal
(Mixed)
Supplies motor fibers to
the pharynx that promote
swallowing and production
of saliva; carries sensory
impulses from taste buds
of posterior tongue
Gag and swallowing
reflexes are checked;
subject is asked to speak
and cough; posterior
tongue maybe tested for
taste
X. Vagus
(Mixed)
Carry sensory impulses
from and motor impulses
to the pharynx, larynx, and
the abdominal and thoracic
viscera; most motor fibers
are parasympathetic that
promote digestive activity
and help regulate heart
activity
Tested in common with CN
IX, because they both serve
muscles of the throat.
XI. Accessory
(Motor)
Mostly motor fibers that
activate SCM and trapezius
muscles
SCM and trapezius muscles
are tested for strength
XII. Hypoglossal
(Motor)
Motor fibers control
tongue movements
Subject is asked to stick out
tongue, and any position
abnormalities are noted

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Effects of the Sympathetic &
Parasympathetic Nervous System
ORGAN SYSTEM SYMPATHETIC PARASYMPATHETIC
Heart Increased heart rate Decreased heart rate
Blood vessels Constricts visceral and
brain vessels
Dilates visceral and
brain vessels
Lungs Dilates bronchi, ↑RR Constrict bronchi,↓RR
Gastrointestinal Decreases peristalsis Increases peristalsis
Anal Sphincter Closes anal sphincter Opens anal sphincter
Urinary Relaxes bladder, closes
sphincter
Contracts bladder,
opens sphincter
Eye Dilates pupil,
accommodates far vision
Constricts pupils,
accommodate near
vision

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Effects of the Sympathetic &
Parasympathetic Nervous System
ORGAN SYSTEM SYMPATHETIC PARASYMPATHETIC
Skin “Goose flesh”, pallor,
diaphoresis
Gastric &
Salivary
secretions
Decreases gastric and
salivary secretions
Increases gastric and
salivary secretions
Liver Stimulates glycogenolysis
(↑blood glucose levels)
Pancreas Diminishes secretion of
pancreatic enzymes
Increases secretion of
pancreatic enzymes
Adrenal
Medulla
Stimulates production of
norepinephrine
Penis Promotes ejaculation Causes erection