Transcript The Nervous System

The Nervous System
Medical Term “Neuro”
Overview
• The entire nervous system relies on the
transmission of electrical impulses
– These impulses are done by neurons, the operating
cells of the brain and spinal cord
• Nervous impulses travel from neuron to neuron
as they send information from one area of the
body to another.
• The speed is almost instantaneous! (268
miles/hour)
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)
– All nerve tissue (neurons) outside
the brain and spinal cord. They
include:
• 12 Cranial (head) nerves that
enervate the head/senses
• 31 pairs of spinal nerves that
enervate the arms, trunk, and
legs
Motor vs Sensory
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Fundamental understanding of
nervous system
Sensory Nerves (“you sense”)
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These nerves receive sensory info from
the body
Also known as Afferent Nerves
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Motor Nerves (“you move”)
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The brain sends out impulses to
muscles
Also known as Efferent Nerves
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e.g. smell, taste, touch, sight
Breeze against your face
That impulse is sent from the nerves in
your body to your brain via the spinal
cord
You move your arm
You blink
e.g. Burning your hand on the stove.
Most nerves are both sensory and
motor
Neurons
• Neurons
– 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
– Contains nucleus and organelles.
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2. Dendrites
– Short, stubby branches that carry
impulses to the cell body from
another neuron
– They are the “receiving” part of
neuron
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3. Axons
– Long extension that carries
impulses from the cell body
– They transmit impulses to
dendrites of the next neuron.
– They are the “giver” part of a
neuron.
– Axons are surrounding by fat
which helps accelerate the
electrical impulse.
Neurons (cont)
• Synapse
– Open area where the axon of
one neuron communicates
with the dendrite of the next
one.
– Neurotransmitter
• The Chemical released there to
send the “message” across
• Famous neurotransmitters
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Epinephrine (Adrenaline)
Dopamine
Serotonin
Acetylcholine
Glial Cells
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Glial cells are the “bodyguards” of neurons
They are not responsible for electrical impulse
Their job is to:
– Surround the neurons to anchor them in place
– Produce the fat (myelin) of the axon to speed
transmission
– Destroys pathogens
– Supplies nutrients to neurons.
Activity
• Get into your groups
– Write down 10 examples of sensory impulses
– Write down 10 examples of motor impulses
The Brain
The Brain
• Responsible for every physical and
mental activity of the body
– Memory, emotion, thought, judgment,
reasoning, consciousness, etc.
– It is made of white and grey matter
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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 and uppermost part of brain
– It has 2 hemispheres (left and right)
– Corpus Callosum- joins hemispheres
together and quickens
communication b/t the two sides.
– Left side of cerebrum focus on logic
and reason
– Right side focus on creativity
– Gyri (sing. gyrus) are the folds or
mountains on the cerebrum
– Sulci (sing. sulcus) are the dips or
cracks on the cerebrum.
Arrangement of Neurons
• Most neurons in the brain are arranged in either
two layouts.
• 1) Long layers of neurons
– Cerebral Cortex is the outermost layer of the
cerebrum made of Grey Matter
– Consists of layers of neurons about 4 mm thick
– Responsible for thought, awareness,
consciousness and learning
• 2) Cluster of neurons (aka brain nuclei)
– Seen mostly in deeper parts of the brain
(hypothalamus, thalamus)
Grey vs White Matter
• The brain is comprised of Grey Matter and White Matte
• Grey Matter is made largely from layers of the bodies of neurons.
• White matter is mostly comprised of glia and the long axons of
neurons connecting one part of the brain to another.
1. The Cerebrum
• Each hemisphere of the
cerebrum is divided into 5
lobes
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Frontal
Parietal
Temporal
Occipital
• These 4 named after the bone
that is directly above them
• Insula (Limbic)
– The inner side of hemisphere
that faces the other
hemisphere.
– Includes Hippocampus
Temporal Lobe of Cerebrum
• Responsible for hearing
• Features the hippocampus
– Main area for memory
Frontal Lobe of Cerebrum
• Responsible for emotions
Occipital Lobe of Cerebrum
• Responsible for vision processing
Parietal Lobe of Cerebrum
Limbic Lobe of Cerebrum
• Includes the Hippocampus
– Responsible for memory and spatial
navigation
– Alzheimer’s and other forms of dementia
affect the Limbic.
2. Diencephalon (Interbrain)
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2 main parts
– Thalamus “The Relayer”
• Receives all sensory info from the
body and sends it to the
appropriate part of the brain for
processing
• Also, it receives impulses from the
cerebrum and relays them to
various parts of body via efferent
motor nerves
– The Hypothalamus
• Regulates the Autonomic Nervous
System (ANS)
• Heartbeat, body temperature,
smooth muscle control, fluid
balance.
• Things you can’t control
3. Cerebellum “Baby Brain”
• 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
4. Brain Stem
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Comprised of:
1. Midbrain
2. Pons
3. Medulla
• Brain stem is a pathway
for impulse conduction
between the brain and
spinal cord
Are you left or right brained?
• Based on this picture,
extrapolate 5 characteristics of
people who are predominately:
– Right-brain
– Left-brain
Meninges (sing. Meninx)
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3 layers of matter that surround the brain
– 1. Dura mater
• Hard, fibrous material
– 2. Arachnoid Space
• Web-like middle space bathed in cerebro-spinal fluid (CSF)
– 3. Pia mater
• Thin layer actually on the brain
– Meningitis-infection of the brain layers.
Cerebro-spinal Fluid (CSF)
• Syrupy fluid that
bathes and protects
the brain and spinal
cord.
• Ventricles
– Chambers full of CSF
fluid that are inside the
brain
• Lateral
• 3rd Ventricle
• 4th Ventricle
Spinal Cord
• Transmits sensory
impulses from the body to
the brain, and
• Transmits motor impulses
from the brain to the body
• Located in the spinal
cavity of the vertebrae
with spinal nerves exiting
between each vertebrae
to enervate the arms,
trunks, and legs.
• Spinal cord runs from the
brain and to Lumber 3.
• Cauda Equina- strands of
nerves that run down the
Plexus
• Big branches of nerves
that come off of spinal
cord
– Brachial
• Comes of the spine near
lower c-spine
• Enervates the upper
extremity
– Lumbar
• Comes off L-spine
• Enervates hips, groin,
abdominal area
– Sacral
• Comes off sacrum
• Enervates the lower
extremity
Cranial Nerves
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Most important nerves in the body.
There are 12
– All originate off the brain stem
– Listed in Roman numerals
• I-(Olfactory)-Smell
• II-(Optic)-Eyesight
• III (Oculomotor), IV (Trochlear),
and VI (Abducents)-Eye
Movement
• V (Trigeminal)-Facial Sensation
• VII (Facial)-Facial motor
• VIII (Vestibulocochlear)-Ear
• IX (Glossopharyngeal) and XII
(Hypoglossal)- Tongue and
Swallowing
• X (Vagus) -Controls diaphragm, all
organs in body
• XI- (Spinal)
Pathology
• 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
– Mal-development in utero
– May develop during adulthood by a tumor,
infection, etc
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Signs
– Disease occurs in infants
– Head swells as brain pushes unsutured
cranial bones apart
– Scalp veins dilate
– Decreased mental abilities
Hydrocephalus
• Diagnosis
– Lumbar tap
– CT/MRI
– Treatment
• Shunt
– A shunt is a tube inserted in
the ventricles to move the
excess fluid to the right atrium
or abdomen.
Seizures
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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)
– Occurs in children
– Lasts a few seconds, twitches and lip smacking
ensue
– Child returns to normal c no memory of it
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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.
Seizures
• Treatment
– Anti-convulsive and
sedative drugs are given to
lessen chance of seizure or
to minimize outbursts.
Huntington’s Disease
• 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
• Chronic mental condition
which features the following
symptoms:
– 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
• 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:
Herniated Disc
• The intervertebral disc is comprised of
two components:
– 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
• Identify the following terms:
– Neuron
– Dendrite
– Axon
– Synaptic Gap
– Cerebellum
– Corpus Callosum