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NERVOUS SYSTEM
GENERAL ROLE : uses electrical
impulses as communication to
control every thought, action and
emotion
3 FUNCTIONS
1.
2.
3.
Collects SENSORY INPUT from the
environments both inside and outside
the body called STIMULI
Processes the input and makes decisions
as to the reaction called INTEGRATION
Effects a response called MOTOR
OUTPUT
Structural Classifications


CENTRAL NERVOUS SYSTEM (CNS)consists of brain and spinal cord
PERIPHERAL NERVOUS SYSTEM (PNS)consists of nerves that extend from
the brain and spinal cord
FUNCTIONAL CLASSIFICATION

SENSORY OR AFFERENT NERVES- nerve fibers send
impulses TO the central nervous system
-impulses coming from the body skin, muscles, and
joints called “SOMATIC SENSORY FIBERS”
-impulses coming from visceral organs called
VISCERAL SENSORY FIBERS
MOTOR OR EFFERENT NERVES- nerve fibers carry
impulses AWAY from the central nervous system
(Activate muscles or glands)

Types of Motor Nerves


SOMATIC NERVOUS SYSTEM
(VOLUNTARY) examples are skeletal
muscles
AUTONOMIC NERVOUS SYSTEM
(INVOLUNTARY) examples are cardiac
muscle, smooth muscle and “stretch
reflex” in skeletal muscle
2 TYPES OF AUTOMONIC
NERVOUS SYTEM
1. SYMPATHETIC - “Fight or Flight”
2. PARASYMPATHETIC- “Rest and digest”
digestive system activated
Graphic organizer
2 CELL TYPES
1.Neurons – information
processing and transmission of
electrical signals
 Nerve
impulse – basic unit of
information = “action potential”
2 CELL TYPES
2. Glia (neuroglia) – support,
protect, nurse the neurons
Anatomy of a Neuron

Soma (“cell body”)houses cellular
machinery
 Nucleus (&
nucleolus),
mitochondria,
Golgi bodies,
endoplastic
reticulum, etc..
DENDRITE

1 to many slender
processes from soma


Receives
information from
sensory structure or
other neuron
“receiver”
AXON

long slender cellular
process from soma
 carries electrical
impulse away
from cell
(“transmitter”)
 multiple
collaterals
branch off of
axon called
AXONAL
TERMINALS
SYNAPSE
Specialized structure at end of
axon
Chemically transmits nerve
impulse to target tissue with
neurotransmitters (small mol wt
chemicals-acetylcholine)
 Also Transfers impulse from
neuron to neuron
SYNAPSES
SYNAPTIC CLEFT
– Gap between
synaptic terminal
and target tissue
(approx. 20 nm in
width)
Myelin Sheath
SCHWANN CELLS- grow
around the axon and
produce the myelin
sheath in the PNS
MYELIN SHEATH- white,
fatty, waxy material called
MYELIN which covers the
axon and increases the
rate or transmission
NODES OF RANVIER- tiny
gaps of the myelin sheath
SUPPORTING CELLS
“NEUROGLIA”

ASTROCYTES- star shaped and anchor neurons
to their blood supply- keep harmful blood
contaminates from getting to neuron

MICROGLIA- phagocytes that dispose of debris

EPENDYMAL CELLS- have cilia that circulate
cerebrospinal fluid

OLIGODENDROCYTES- create myelin sheath in
CNS
Types of Cells found in the CNS

WHITE MATTER- contains myelin sheaths

GRAY MATTER- unmyelinated fibers
MULTIPLE SCLEROSIS (MS)



Myelin sheath is slowly destroyed
Sheaths become hardened called
Scleroses
Person loses the ability to control his/her
muscles
Types of NEURONS (page 209)



SENSORY (AFFERENT)- cell bodies are always
found outside the CNS in a GANGLION- axon
travels into the CNS
MOTOR (EFFERENT)- soma is in the CNS but the
axon leaves and becomes peripheral
INTERNEURONS (ASSOCIATION) –always found
in the CNS “relayers”
TYPES OF SENSORY
RECEPTORS
1. Naked nerve endings- feel pain and temperature
2. Meissner’s Corpuscles- feel touch
3. Pacinian Corpuscle- deep pressure
4. Muscle spindle- PROPRIOCEPTORS – located in
muscle or tendon concerned with locomotion
and posture
GANGLIA

Defined as a small collection of cell bodies found
outside the CNS
SHAPES OF NEURONS

MULTIPOLAR-
(interneurons and
motor neurons)

One soma, with
one axon and
multiple
dendrites
SHAPES OF NEURONS
UNIPOLAR Single branch running to cell body




Branches into 2
One branch is a Long axon which
runs to spinal cord
Second branch runs to body and
serves as receptors
Soma found in ganglion
SHAPES OF NEURONS

Bipolar
 found in eyes,
nose, ears
“receptors for
special senses”
 Cell has one
axon & one
dendrite with
soma in
between
NAME THE PARTS
REFLEXES



Rapid, predictable, and involuntary responses to
stimuli
REFLEX ARC- neural pathways that reflex travel
down
ALL REFLEX ARCS a minimum of 5 items
1. sensory receptor (receives initial stimuli)
2. afferent neuron
3. integration center- CNS
4. efferent neuron
5. effector organ (muscle or gland stimulated)
TYPES OF REFLEXES


SOMATIC REFLEXES- all the reflexes that
stimulate skeletal muscle
AUTONOMIC REFLEXES- reflexes that
don’t involve skeletal muscleexamples- smooth muscles (digestion
and blood pressure) cardiac muscle,
glands (saliva, adrenaline) eye pupils
(pupillary reflex)
TWO NEURON REFLEX ARC
Monosynaptic (page 214)

KNEE-JERK REFLEX and the BABINSKI
SIGN (no interneuron)
1. Sensory receptors in patella
tendon receive stimuli
2. Afferent neuron sends to CNS
3. Efferent neuron leaves CNS
4. Effector moves (quadricep
contracts)
3 NEURON RELEX ARC
Polysynaptic

WITHDRAWAL REFLEX- (FLEXOR)-causes
affected muscle to flex
1. Sensory receptors in foot
receive stimuli
2. Afferent neuron sends to CNS
3. Interneuron
4. Efferent neuron leaves CNS
5. Effector moves (quadricep
contracts)
Crossed fiber reflex–
reflex arc stimulates
flexors and inhibits
extensors on side of
injury while
simultaneously
stimulates extensors
and inhibits flexors on
contralateral (opposite
side) of body
CNS

Spinal cord
31 segments
(between each
vertebrae a nerve
arises)
 Cervical
enlargement (for
arm/hand muscles
and receptors)
 Lumbar
enlargement (for
leg muscles and
receptors)

SPINAL CORD



17 inches long- (42 cm)
Ends at the last thoracic vertebrae (T12)
located at the last rib
Spinal Nerves to the lower extremities of
the body (lumbar and sacral nerves) are
no longer the spinal cord but many nerves
fanning out, resembling a tail called the
CAUDA EQUINA- which literally means
“horse’s tail”
Protection of the Central Nervous System
MENINGES- 3 protective layers of the CNS
1. duramater- outermost
2. arachnoid mater- middle
3. pia mater- innermost
Layers of meninges
DURAMATER (page 221)
Tough and leathery
Double layered membrane around skull



One layer is attached to skull
Inner layer forms the outermost covering of
the brain
Only a single layer around spinal cord
ARACHNOID MATER



Weblike 2nd layer
Subarachnoid space- filled with
cerebrospinal fluid (located between
arachnoid mater and pia mater)
Arachnoid villi- projections into the dura
mater where cerebrospinal fluid is
absorbed into the venous blood
PIA MATER


Extremely delicateCan hardly distinguish during dissections
MENINGITIS
inflammation of the meninges. Can be
serious if bacteria or virus spreads to the
brain.
ENCEPHALITIS- inflammation of the brain
HYDROCEPHALUS- accumulation of CSF in
the brain.
CEREBROSPINAL FLUID




circulates around brain and spinal cord as
cushion, nourishes the brain and removes
waste
Similar to blood plasma- extremely watery
Contains less proteins and more vitamin C
Drains through 3 openings in the 4th
ventricle which allows it to travel around
the outside of the brain
Cranial Nerve II

Optic nerves - sensory only
 arise from retina and pass through optic foramina
 OPTIC CHIASMA- location of partial crossover of
fibers
Cranial Nerve I

Olfactory nerve – Sensory only
Most anterior
 Olfactory receptors pass their axons through cribiform plate
of the ethmoid bone into olfactory bulb.
Cranial Nerve III



Oculomotor Nerve
motor fibers from midbrain
Motor neurons to 4 of 6 eye muscles
and eyelids

autonomic nervous system neurons –
controls iris diameter.

Cranial
Nerve
IV
Trochlear nerves

Motor neurons from midbrain
 Neurons to 5th eye muscle – superior oblique
Cranial Nerve V


Trigeminal- large nerve
that breaks into 3
divisions
Can be both sensory and
motor
 Ophthalmic division –
sensory inputs from
eye (non-retinal), tear
gland, anterior scalp
and forehead and
upper eyelid
Cranial Nerve V
Maxillary
division –
sensory from
upper teeth,
upper gums,
upper lip,
facial, oral
mucous linings
Cranial Nerve V
 Mandibular
division –
motor and sensory
 Sensory – from
scalp posterior to
ear, jaw skin,
lower teeth, lower
gums, lower lip
 Motor - to
chewing muscles
(masseter and
temporalis)
Cranial Nerve X

Vagus nerve
 Motor and sensory neurons go to medulla
 Motor – to larynx (speech & swallow)
 Sensory – from pharynx, larynx, esophagus
 Sensory – from abdominal and thoracic
viscera
 key Autonomic Nervous System signal
 To glands and viscera of thorax and
abdomen
VENTRAL RAMI



The ventral ramus of each thoracic spinal nerve
(T1-T12) serve the corresponding rib. Motormuscle and sensory- skin, muscle, etc.
All other Ventral rami (Cervical, Lumbar, and
Sacral) will join together to form 4 complex
nerve networks called PLEXUS
Dorsal rami never form plexuses
CROSS SECTION OF SPINAL CORD

CENTRAL CANAL –
directly in the middle
(cerebrospinal fluid flows
through)
GREY MATTER- makes
the butterfly shapesoma of motor and
interneurons
 WHITE MATTERsurrounds the butterflyaxons ascending and
descending to the brain

CROSS SECTION OF SPINAL CORD

Prominent landmarks
 DORSAL HORNS –
(posterior) will always
reach to the outsideprovides input from
sensory nerves
 VENTRAL HORN
(anterior)- typically
wider and doesn’t
reach outside-provides
output from spinal cord
(motor neurons)
REGIONS OF THE BRAIN
Cerebrum
 Brain stem
 Diencephalon
 Cerebellum

CEREBRUM







Most superior part of brain
Larger than the other 3 branches combined
Divided into 2 hemispheres – left and right
LOBES- divisions of the hemispheres named for
the bone that covers them
GYRI- elevated ridges of tissue
SULCI- shallow grooves that separate gyri
FISSURE- deep groove that separate regions of
the brain
CEREBRUM



LONGITUDINAL FISSURE- separates the
two hemispheres
CENTRAL SULCUS- across the top of the
head – separates the frontal lobe from the
parietal lobe
LATERAL SULCUS- across the sides of the
brain- separates the temporal lobe from
the frontal and parietal lobes
CEREBRUM


CONTROLS SPEECH, MEMORY, LOGICAL
AND EMOTION RESPONSE
ALSO CONTROLS CONSCIOUSNESS,
INTERPRETATION OF SENSATIONS, AND
VOLUNTARY MOVEMENT
LEFT HEMISPHERE



Analysis, logical interpretation of
information.
Language, mathematics, abstraction and
reasoning.
Memory stored as language
Right Hemisphere
Multi-sensory functioning
Visual spatial skills, dancing and gymnastics
Memories stored as visual or auditory
FRONTAL LOBE

CONTAINS THE PRIMARY MOTOR AREA
-ALLOWS
US TO CONSCIOUSLY MOVE OUR SKELETAL
MUSCLES
-MOST OF THE NEURONS ARE FOR FINE MOTOR CONTROL –
face, mouth , and hands

PREFRONTAL AREA- ability to concentrate,
inhibitions, personality and emotional
traits

- language and motor speech
PARIETAL LOBE

CONTAINS SOMATIC SENSORY AREA
-Impulses from the body’s receptors are localized and
interpreted here
-Most sensitive areas (lips and fingertips) make up a
large part of this area
BODY ORIENTATION
OCCIPITAL LOBE
- VISION is located in the most posterior part
TEMPORAL LOBE




The AUDITORY SENSES (hearing) are
located here
The OLFACTORY SENSES (smelling) are
located here.
Memory- information retreival
Expressed behavior-
HIPPOCAMPUS

Takes memories and sorts them for
retrieval
BROCAS AREA-SPEECH AREA


LOCATED AT THE JUNCTION OF THE
PARIETAL, TEMPORAL, AND OCCIPITAL
LOBES
TYPICALLY ONLY FOUND ON ONE SIDE
OF THE BRAIN (LEFT)
BROCA’S AREA

GYRUS JUST ANTERIOR TO CENTRAL SULCUS
CEREBRAL CORTEX

GRAY MATTER

OUTERMOST AREA OF THE CEREBRUM

WHERE MOST OF THE MOTOR AND
SENSORY NEURONS ARE FOUND
CEREBRAL WHITE MATTER
CORPUS CALLOSUM- (white matter fiber
tracts)
- joins the two hemispheres
- located above the brain stem
- Handles hemisphere to hemisphere
communication
BASAL NUCLEI
Deep brain structures that modify and relay
motor commands
Gray matter islands located inside the white
matter
DIENCEPHALON



Older brain structure
Located atop the brain stem
Consists of thalamus, hypothalamus and
epithalamus
 thalamus – sensory relay structure
(ascending fiber tracts synapse here,
interneurons then carries data to parietal
lobe)
THALAMUS
– sensory relay structure (ascending
fiber tracts synapse here,
interneurons then carries data to
parietal lobe)
 Distinguishes between pain and
pleasure

HYPOTHALAMUS
“emotional-visceral brain”
– homeostatic control center Heart rate, temperature, water and ion
balance, hunger, weight, stomach, hormones,
sleep, reproduction
 Infundibulum – stalk that attaches hypothalamus
to pituitary gland (hormones!)

PITUITARY GLAND



Hangs from infundibulum
Produces hormones to activate various
glands (thyroid, testes, ovaries, adrenal
gland)
Growth hormone- growth of bones and
muscles- “Giantism” or “Pituatary
Dwarfism”
PINEAL BODY
Produces melatonin which allows us proper
sleep cycles
BRAIN STEM

CONSISTS OF




MIDBRAIN
PONS
MEDULLA OBLONGATA
PATHWAY FOR MANY ASCENDING AND
DESCENDING NERVES
Midbrain and pons (inferior to diencephalon)
Some motor processing and sensory relay
BRAIN STEM
PONS- breathing control
MEDULLA OBLONGATA

Medulla oblongata (on top
of spinal cord)
 Key centers of basal
body survival
 Cardiac center –
increase/decrease heart
rate
 Vasomotor center –
controls vascular tone
(BP)
 Respiratory center –
controls breathing
rhythm
RETICULAR FORMATION
Grey matter in the brainstem
Involved in motor control of visceral organs
Consciousness and awake/sleep cycles
CEREBELLUM


Provides precise timing for skeletal muscle
activity and controls balance and
equilibrium
Ataxia- condition when movements
become clumsy and disorganized “appear
drunk”
CEREBROSPINAL FLUID (CSF)
CEREBROSPINAL FLUID- circulates around
brain and spinal cord as cushion,
nourishes the brain and removes waste
Where is Cerebrospinal fluid
made?
CHOROID
PLEXUScapillaries that
are located in
the roof of the
ventricles that
make CSF
VENTRICLES of the BRAIN
4 Ventricles
1 on each hemisphere
3rd ventricle located in diencephalon below the
corpus callosum
4th ventricle located between cerebellum and
medulla oblongata
Pathway of CSF

From Lateral Ventricles (left and right) 
3rd ventricle  Through the CEREBRAL
AQUEDUCT 4th ventricle can exit and
circle brain or enter CENTRAL CANAL of
spinal cord absorbed into bloodstream
at the ARACHNOID VILLI
BLOOD BRAIN BARRIER
The brain is surrounded by the least permeable
capillaries. (of water soluble molecules) Only
water, glucose and essential amino acids can
pass through.
Fat soluble molecules can enter easily. Examples
are alcohol, nicotine, and anesthetics.
Toxins, urea, proteins and most drugs are
prevented from entering the brain tissues.
STRUCTURE OF A NERVE (page 229)
NERVE- a bundle of neuron fibers each is
wrapped in protective connective tissue
Smallest layer to largest layer
AXON FASCICLE  NERVE
Axon- part of single neuron
Fascicle- group of axons together
Nerve- group of fascicles together

NERVE COVERINGS

Inner most covering to outermost
Endoneurium Perineurium Epineurium
Endoneurium- protective covering of a
single axon
Perineurium- protective covering of a
fascicle
Epineurium- protective covering of the
entire nerve
CRANIAL NERVES



12 nerves that are located in the brain
that primarily serve the head and the neck
Always numbered using Roman Numerals
Nerve X- the Vagus nerve controls
digestive activity
Cranial Nerves




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






Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
Oh
Oh
Oh
To
Touch
And
Feel
Very
Good
Velvet
A
H!
SPINAL NERVES


31 PAIRS- that attach directly to the spinal cord
and exit between each segment of vertebrae
Spinal nerve splits into branches called RAMI
which move dorsally or ventrally
CERVICAL PLEXUS


PHRENIC NERVE- serves muscles of
shoulder and neck and DIAPHRAGM
Injury to phrenic nerve leads to
respiratory paralysis
BRACHIAL PLEXUS





MUSCULOCUTANEOUS NERVE- controls
the flexor of the arm  bicep
AXILLARY NERVE- deltoid muscle
RADIAL NERVE-(along the radius bone)
triceps  triceps and wrist extensor
MEDIAN NERVE- (down the middle of the
arm) wrist flexor hand
ULNAR NERVE (inside of the elbow
“funny bone”-wrist flexor hand
LUMBAR PLEXUS


FEMORAL NERVE- lower abdomen 
rectus femoris
OBTURATOR NERVE- hip adductor muscles
SACRAL PLEXUS


SCIATIC NERVE- largest nerve in the body
which splits to fibular and tibial nerves
Controls most of the leg activity
knee extension
dorsiflexion
plantar flexion
hip abduction
TRAUMATIC BRAIN INJURIES



CONCUSSION-slight injury resulting in dizziness
CONTUSION- tissue damage occurs- if to the
brain stem then coma can occur- if to cerebral
areas subject may remain conscious
CEREBRAL EDEMA- swelling on the brain due to
injury- compresses vital brain tissue
Brain injuries cont’d


INTRACRANIAL HEMORRHAGE- bleeding
from a ruptured blood vessel- compresses
vital neurons.
STROKE (CEREBROVASCULAR
ACCIDENT)- 3rd leading cause of deathblood circulation is blocked
AUTONOMIC NERVOUS SYSTEM

no conscious effort needed
-Contains the Sympathetic (“fight or flight”)
and Parasympathetic (“rest and digest”)
divisions
-The impulses of one division will inhibit the
impulse of the other division.
Autonomic Motor Pathways vs.
Somatic Motor Pathway


AMP-Contains 2 neurons
outside of the CNS (pg
238) and one GANGLION(group of cell bodies)
outside the CNS
SMP- contains no
ganglions outside the
central nervous system
axon reaches all the way
to effector
Autonomic Motor Pathways


PREGANGLIONIC NEURON- axons leave
the CNS (either the brain or spinal cord)
and synapses at the ganglion
POSTGANGLIONIC NEURON- extends
from the ganglion to the visceral organ
PARASYMPATHETIC DIVISION


The preganglionic axons originate only
from cranial nerves III, VII, IX, and X
(major factor) and the Sacral spinal
nerves.
TERMINAL GANGLION – ganglion located
near the effector organ
PARASYMPATHETIC DIVISION
“ rest and digest”



Constricts pupils of the eyes, bronchioles
Relaxes sphincters of digestive and
urinary system
No effect on blood vessels, sweat glands,
and epinephrine/norepinephrine
production
Sympathetic Division





EXAMPLES
Dilates pupils of the eyes, bronchioles,
blood vessels in muscles and heart
Constricts sphincters of digestive and
urinary system and blood vessels to skin
Increases metabolic rate, blood sugar
levels, cardiac rate, blood pressure
production of epinephrine/norepinephrine,
sweat
SYMPATHETIC DIVISION (page
239)


All the preganglionic axons originate from
the spine between the T1 and the L2
vertebrae and are connected together
SYMPATHETIC CHAIN (or TRUNK)-located
just outside the CNS on the ventral ramus
and connect vertically with the ganglion
above it
Identify the sympathetic trunk, preganglionic
nerve, postganglionic nerve
NERVE IMPULSES (pg 212)

CONDUCTIVITY-(motor)The ability to transfer impulses to other
neurons, muscles, or glands.

Irritability-(sensory)- the ability to respond to a stimulus and
results in a nerve impulse

Irritability is an “all-or-none” response. Once impulse reaches the
THRESHOLD STIMULUS- weakest stimulus capable of producing a
response

NERVE IMPULSE- Quick depolarization followed by a quick
repolarization

The impulse will travel at full strength throughout the length of the
axon.
POLARIZATION
1. Resting neurons must be polarized to
receive impulse “RESTING POTENTIAL”
Resting neurons have 10 times more
positive ions (Na) outside the cell than
inside.
(Potassium ions inside the cell are just
the reverse but used for repolarization)
2. Resting neurons must receive enough
stimulus to activate “THRESHOLD
STIMULUS”
3, DEPOLARIZATION -When the neuron
is stimulated then “sodium gates”
open, allowing sodium ions to rush
into the cell via diffusion. This rush
equals out the ion charge
REPOLARIZATION
4 REPOLARIZATION -Potassium gates open
allowing the potassium ions to rush out
reestablishing the polarization- A neuron
cannot conduct another impulse until it is
repolarized.

Sodium –Potassium pump will move the
proper ions back to their respective resting
potentials
MYELINATED NEURONS


The myelin sheath is a good conductor for
the impulse and allows it to travel faster.
IMPULSE jumps across myelin sheath from
NODE OF RANVIER to NODE OF RANVIER
because Myelin Sheath does not have any
sodium gates underneath it.