Download The Nervous System

The Nervous System
Medical Term “Neuro”

Different
parts
of
the
Nervous
System
Central Nervous System (CNS)
Network of nerve tissue (neurons)
found in the brain and spinal cord
Peripheral Nervous System (PNS)
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All nerve tissue (neurons) outside the
brain and spinal cord. They include:
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12 Cranial (head) nerves that
enervate the head/senses
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31 pairs of spinal nerves that
enervate the arms, trunk, and legs.
Nerves can regenerate in the PNS but not
in the CNS
Also the nervous system boasts the
Autonomic Nervous System (ANS)
The ANS regulates involuntary actions
such as:
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Thirst
Appetite
Heart Rate
Temperature
Respiration.
Overview
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The entire nervous system relies
on the 1- way transmission of
electrical impulses
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These impulses are done by neurons,
the operating cells of the brain and
spinal cord
A collection of neurons is called a
nerve.
Nerves, like blood vessels, reach
every organ, every inch of our body.
Electrical impulses travel from
neuron to neuron as they send
information from one area of the
body to another.
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Motor vs Sensory
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All neurons are either:
1. Sensory Nerves (“you sense”)
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These nerves receive sensory info from
the body and transmit it TO the brain.
Also known as Afferent Nerves
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A=“At the brain”
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e.g. smell, taste, touch, sight
Breeze against your face
Most impulses are sent from the nerves
in your body to your brain via the
spinal cord
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2. Motor Nerves (“you move”)
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These neurons originate from the brain
and send impulses to muscles for
movement
Also known as Efferent Nerves
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E= “Exit the body”
e.g. You move your arm
You blink
e.g. Burning your hand on the stove.
Most nerve bundles in the PNS contain
both sensory and motor nerves.
Quick Assignment
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You may work as a group if you like.
On a piece of paper write down,
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10 feelings a sensory (afferent) neuron would
detect.
10 actions a motor (efferent) neuron would do.
Neurons
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Neurons
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Cells responsible for electrical
transmission
The brain, spinal cord, and
nerves are all comprised of
neurons
100 billion neurons just in
brain.
3 Major Parts of the Neuron
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1. Cell Body
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Contains nucleus and organelles.
2. Dendrites
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Short, stubby branches that carry
impulses to the cell body from
another neuron
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They are the “receiving” part of
neuron
3. Axons
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Long extension that carries
impulses from the cell body
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Some neurons have axons that are
several feet long!
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Axons transmit impulses to
dendrites of the next neuron.
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They are the “giver” part of a
neuron.
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Axons are surrounding by fat which
helps accelerate the electrical
impulse.
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These fat pads are called Myelin
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Muscular Dystrophy (MS) is
the condition in which myelin
deteriorates.
Neurons (cont)
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Synapse
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Open area where the axon of one neuron
communicates with the dendrite of the
next one.
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Neurotransmitter
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The Chemical released at the synapse which
allows the electrical impulse to jump across
the synapse to reach the next neuron.
Famous neurotransmitters
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Epinephrine (Adrenaline)
Dopamine (pleasure)
Serotonin (mood)
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Most depression meds attempt to
increase the amount of serotonin at
synapse.
Excito-toxins
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Neurotransmitters that destroy the
synapse by over stimulating it until
it explodes
Monosodium Glutamate (MSG)
Glial Cells
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Glial cells is the collective name for a group of cells that
care and protect neurons
Also called neuroglia
They are not responsible for electrical impulse
Their job is to:
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1. Surround the neurons to anchor them in place (“Glia”
means “glue” in Greek)
2. Produce the fat (myelin) of the axon to speed electrical
transmission
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3. Supplies nutrients to neurons.
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Schwann Cells are a type of Glial Cells that do this.
They also destroys pathogens
Astrocytes are a type of Glial Cells that do this.
Cell phone radiation
The Brain
Meninges (sing. Meninx)
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3 layers of matter that serve as a protective barrier between the cranium (bone)
and the brain.
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1. Dura mater (Outermost)
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2. Arachnoid Matter
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Hard, fibrous material
Beneath it is the Sub-Archnoid Space
Web-like space full of Cerebro-spinal fluid (CSF)
3. Pia mater(Innermost)
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Thin, transparent layer actually on the brain
The Brain
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Responsible for every physical and
mental activity of the body
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Memory, emotion, thought, judgment,
reasoning, consciousness, etc.
It is made of white and grey matter
Comprised of mostly fat
Protected by the cranium
Weighs 3 pounds
The four major structures of the brain
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1. Cerebrum
2. Cerebellum
3. Diencephalon
4. Brain Stem
1. Cerebrum
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Largest part of the 4 main sections of the
brain
Outermost layer of the cerebrum is called
the Cerebral Cortex
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It is made of Great Matter
The Cortex is divided into 4 regions
called Lobes.
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Most higher-level thinking of the brain
occurs in the cortex.
10-14 billion neurons
Frontal- Anterior aspect
Parietal- Superior aspect
Temporal- Lateral aspect
Occipital- Posterior aspect
Cortex is divided into Left and Right
Hemispheres
Longitudinal Fissure separates the two
hemispheres
1. Cerebrum (cont)
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Corpus Callosum- joins
hemispheres together and quickens
communication b/t the two sides.
Gyri (sing. gyrus) are the folds or
mountains on the cerebral cortex
Sulci (sing. sulcus) are the dips or
cracks on the cortex.
These peaks and dips are used
expand the surface area of the
cortex; therefore, allowing more
higher level of thinking than more
primitive mammals.
The brain has no pain receptors.
Grey vs White Matter
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The brain is comprised of Grey Matter and White
Matter
Grey Matter is made mostly of the cell bodies of
neurons
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Cerebral Cortex is Grey Matter
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Beneath the Cortex the remainder of the
Cerebrum and the Spinal Cord are White Matter
White Matter
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Mostly comprised of Glial cells and the long
axons of neurons connecting one part of the
brain to another.
In Short,
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Grey Matter
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Higher level thinking
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Mostly located in Cortex and Diencephalon
(Hypothalamus)
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White Matter
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Comprises most of the brain as it is the
axons of neurons in the cortex connecting to
various parts of the brain.
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Axons are wrapped in white fat (called
myelin) which gives white matter its color.
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Grey Matter more important than White.
Mammal Comparison
Temporal Lobe of Cerebral Cortex of Cerebrum
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Two (left and right)
Most lateral lobe; located near
the ear behind the temporal bone.
Interpretation of sounds and
language
Responsible for processing
auditory impulses
Features the Hippocampus
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Main area for memory
Occipital Lobe of Cerebral Cortex of Cerebrum
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Most posterior lobe
Located behind the occipital
bone
Responsible for processing
visual stimulus, colors, and
understanding words
Parietal Lobe of the Cerebral Cortex of
the Cerebrum
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Located on top of brain
underneath the parietal
bones.
Sensory Information,
touch, and pain
Frontal Lobe of Cerebral Cortex of Cerebrum
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Located behind the frontal
bone; largest of all lobes.
Responsible for emotions
reason and will
Higher level cognition
Motor Skills
Language
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Lobotomy
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Removal of piece of frontal lobe
in an effort to “tame” a person
who has emotional issues
Diencephalon (Interbrain)
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3 main parts
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Thalamus (Grey Matter)
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It is “The Relayer” for motor and sensory
impulses
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Receives all sensory info from the body and
sends it to the appropriate part of the brain for
processing
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Regulates sleep and consciousness
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The Hypothalamus (Grey Matter)
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Regulates the Autonomic Nervous System
(ANS), the “urges” system
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Heartbeat, body temperature, peristalsis
appetite, et al.
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Pituitary Gland
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Master Gland of the Body
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Sits inferior to the Hypothalamus in the
Sphenoid Bone
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Creates and controls many of the most
important hormones in body.
3. Cerebellum “Baby Brain”
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2nd largest part of the
brain
Sits in the posterior
portion of the skull,
next to occipital bone.
Maintains balance and
equilibrium
Coordinates muscular
movement
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4. Brain Stem
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Anterior to Cerebellum, but inferior
to Diencephalon and Cerebrum
Along with Diencephalon, the brain
stem is the oldest and most primitive
part of brain.
It is the pathway for communication
b/t the brain and spinal cord.
Comprised of (top to bottom):
1. Midbrain
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Sleep and temperature regulation
2. Pons- “bridge” in Latin
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Swallowing, urination, breathing
3. Medulla Oblongata
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Respiration
Cerebro-spinal Fluid (CSF)
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Syrupy fluid that bathes and protects the
brain and spinal cord.
Ventricles
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Chambers full of CSF fluid that are
inside the brain. There are 3
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Lateral (2)
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3rd Ventricle
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4th Ventricle
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After 4th Ventricle CSF
travels down spinal cord and
around the brain in the
Subarachnoid Space
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CSF is produced in the
Choroid Plexus of the
ventricle
Blood-Brain Barrier
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Prevents harmful elements in the
blood from reaching the blood
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Brain is normally sterile
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Cerebral Aqueduct
connects the 3rd Ventricle
with the:
Spinal Cord
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It serves 2 main purposes:
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Transmits sensory impulses from
the body to the brain, and
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Transmits motor impulses from
the brain to the body
The Spinal cord has 31 pairs of spinal
nerves exiting it to enervate the trunk,
arms, and legs.
It runs down the arch of the Vertebra
behind the Body
Spinal cord ends near L1.
The Spinal Cord ends there and
becomes the Cauda Equina “Horse
Tail” in Latin
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The Cauda are strands of nerves
that run down the rest of the spinal
cavity and exit the Sacrum to
enervate the legs.
BODY
ARCH
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Spinal Cord has
 Meninges
 CSF
 Grey matter (in
middle) and white
matter
 Nerve Root coming
off of each side with
both sensory and
motor neurons
included in it.
Peripheral Nervous System
Nerves and Neurons
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Nerves are a tight collection
of the very long axons of
several neurons wrapped in a
tight fiber
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No cell bodies are located in
nerves
Nerves are only located in
the Peripheral Nervous
System (PNS)
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In the CNS, there are only
neurons and glial cells.
Plexus
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A collection of nerve bundles
that come off of spinal cord
3 main ones
 Brachial Plexus
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Lumbar Plexus
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Comes of the spine near lower cspine
Enervates the upper extremity
Comes off L-spine
Enervates hips, groin, abdominal
area
Sacral Plexus
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These nerves come off of the
Cauda Equina of the spinal cord
and exit the Sacrum bone to:
Enervates the lower extremity
Cranial Nerves
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Most important nerves in the body. There are 12
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All originate off the Brain Stem
Always listed in Roman numerals
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Olfactory Nerve is CN I-Responsible for Smell
Optic Nerve is CN II-Responsible for Eyesight
Oculomotor Nerve is CN III
Trochlear Nerve is CN IV
Abducens Nerve is CN VI – All three are for Eye Movement
Trigeminal Nerve is CN V-Responsible for Facial Sensation
Facial Nerve is CN VII-Responsible for Facial Motor
Vestibulocochlear Nerve is CN VIII-Responsible for Hearing and Balance
Glossopharyngeal Nerve is CN IX- Responsible for Tongue Movement and
Swallowing
Vagus Nerve is CN X -Controls diaphragm, heartrate, and most organs in body
Accessory Nerve is CN XI- Responsible for Neck Movement
Hypoglossal Nerve is CN XII-Responsible for Speech and Swallowing
Dermatones
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Every region of your
body is enervated by a
particular PNS Spinal
Nerve
Therefore, doctors are
able to pinpoint the
location of nerve
damage by you telling
them where your pain
is located.
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Glans Penis
Middle of Patella
3rd Toe
Areola
The Ears
Medical Terms
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Meningitis – infection of meninges
Encephalitis- infection of the brain
Encephalopathy- chronic disease of the
brain.
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Chronic Trauma Encephalopathy (CTE)the medical term for the cumulative effect
concussions have on NFL players.
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Hydrocephalus- Increased amount of
CSF causes ventricles to swell up.
Parasthesia- tingling of skin with no
apparent physical cause.
Epilepsy- condition of periodic violent
seizures.
Bell’s Palsy- inability to move facial
muscles due to damage to Facial Nerve
(CN VII)
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Aphagia- Inability to swallow
Dysphagia- Difficulty swallowing
Aphasia- Inability to speak
Dysphasia- Difficulty speaking
Anosmia – Inability to detect odors
Ataxia- inability to move muscles in a
coordinated manner.
Pathology
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MeningitisInflammation of the
meninges
Concussion-Bruising
of brain tissue
HydrocephalusSwelling of the brain
due to increase
amount of CSF fluid
Encephalitis-Infection
of the brain, typically
Hydrocephalus “Water in the brain”
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Excess CSF fluid in the brain
The choroid plexus of the ventricles, the
cells responsible for producing CSF, either
produce too much, or the venous system
doesn’t absorb it fast enough
It compresses (squeezes) the brain tissue
which increases intracranial pressure.
Etiology
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Mal-development in utero
May develop during adulthood by a tumor,
infection, etc
Signs
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Disease occurs in infants
Head swells as brain pushes unsutured cranial
bones apart
Scalp veins dilate
Decreased mental abilities
Hydrocephalus
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Diagnosis
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Lumbar tap
CT/MRI
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Treatment
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Shunt
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A shunt is a tube inserted in
the ventricles to move the
excess fluid to the right atrium
or abdomen.
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Seizures
Uncontrolled, excessive discharge of neurons
Multiple causes and types
May be caused by external stimuli, drugs, secondary
disease.
Generalized seizure- loss of consciousness due to multiple
parts of the brain seizing
Partial- no loss of consciousness, normally only one part
of brain seizes.
Petit mal seizure (Generalized)
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Occurs in children
Lasts a few seconds, twitches and lip smacking ensue
Child returns to normal c no memory of it
Grand mal seizure (Generalized)
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Begins with twitching, nausea, depression
Aura-visual or auditory hallucination
Loss of consciousness follows
The tonic-clonic stage ensues of strong muscle
contraction/relaxation as the body contorts itself into
strange position. Foaming of the mouth, screaming, and
incontinence may ensue.
Contractions dissipate, patients wakes up achy and then
Seizures
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Treatment
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Anti-convulsive and sedative
drugs are given to lessen
chance of seizure or to
minimize outbursts.
Huntington’s Disease
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Genetic disorder, 13 from
House has it.
Progressive atrophy (or
deterioration) of neurons
Ventricles swell
Symptoms: Wild mood
swings, wild jerky
movements of extremities,
gradual loss of cognitive
and motor skills
Prognosis: Death!
Schizophrenia
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Chronic mental condition
which features the following
symptoms:
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Visual and auditory
hallucinations
Delusions of personal grandeur
The belief that people are
plotting against you.
Detachment, increased drug
use, and suicidal ideation.
Dissociative Identity Disorder
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Formerly Multiple
Personality Disorder.
Person has at least 2 distinct
personalities (alter egos)
One personality controls the
other
Main personality has time of
amnesia.
Cause: Trauma (physical/sexual)
Controversy:
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CIA
Herniated Disc
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The intervertebral disc is comprised of two
components:
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Nucleus pulposus- inner gelatinous filling
Annulus fibrosis- tough outer layer
Poor body mechanics, trauma, or
degenerative condition cause the nucleus to
leak out.
It impinges or touches either the spinal
cord or the nerve roots that go down the
arm or leg
Causes loss of motor or sensory sensation
and intermittent pain in leg or arm
(depending on which plexus it is
impinging).
Minor day surgery may fix it easily
Assignment
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Identify the following terms:
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Neuron
Dendrite
Axon
Synaptic Gap
Cerebellum
Corpus Callosum