Download The Nervous System Epilepsy

The Nervous System
Epilepsy
By Diane Bui, Kim Lai, and Cade Wong
An Overview of the Nervous System
● Nervous system : the part of an
animal’s body that coordinates its
voluntary and involuntary actions
and transmits signals between
different parts of the body
- consists of circuits of neurons and
supporting cells
- communication within and
throughout the body
- two main parts: CNS and PNS
Human Nervous System (above)
What is Epilepsy? (General Overview)
● Epilepsy : a central nervous system
disorder (neurological disorder) in
which nerve cell activity (electrical
rhythms) in the brain is disturbed,
causing seizures or periods of unusual
behavior
● in more than half the patients with
epilepsy, the cause is still unknown
● nerve cells in brain send out wrong
signals → seizures
CNS and PNS
The Peripheral
Nervous System
(PNS) consists
of cranial
nerves, spinal
nerves, and
ganglia outside
the CNS.
The Central
Nervous
System (CNS)
consists of
the brain and
spinal cord.
The Vertebrate Nervous System
Neurons and Nerves
● Nerves : a ropelike bundle of neuron
fibers (axons) tightly wrapped in
connective tissue
- organizes and transmits information
to various parts of body
- send/receive signals from neurons
● Neurons : electrically excitable
cells that process and transmit
information through chemical
and electrical signals
- electrical synaptic signaling
- conducts nerve impulses
● Bundles of neurons make up nerves
● Larger groups of neurons make up the brain and spinal cord
● Nerves are found in the PNS, while neurons are found in the
brain, spinal cord, and the peripheral nerves
Central Nervous System
two main organs of CNS:
- brain and spinal cord
● process center for the
nervous system
● controls most functions of
the body and mind
● responsible for integrating
sensory information
● receives and sends
information to the peripheral
nervous system
The Brain
● control center of the body; major functional unit
● makes up the largest portion of CNS
● consists of three main
components:
○ Forebrain
○ Midbrain/Brainstem
○ Hindbrain
Forebrain
● receives and processes sensory
information
● controls motor functions
● thinking, perceiving, producing
and understanding language
contains the cerebrum
(largest part of brain) and
diencephalon
Midbrain/Brainstem
● Midbrain contains only a portion of the
brainstem
● connects the hindbrain
and the forebrain
● involved in auditory &
visual responses as
well as motor functions
Hindbrain
includes pons,
cerebellum, and the
medulla oblongata
● maintains balance and
coordination
● conduction of sensory
information
● medulla oblongata
controls autonomic
functions
Components Of The Brain
Two Types of Tissue
Grey Matter
White Matter
Grey Matter
● Processes info in the
brain
● Composed of neuronal cell bodies
and unmyelinated axons
● Directs sensory motor stimuli to the nerve cells
Glial cells and capillaries
give the tissue the greyish pink color
Glial Cells
● Transports nutrients and
energy to the neurons
● Influences efficiency of
function and communication
White Matter
● The inner layer of the brain cortex
● Axons contain a myelin sheath which gives
it the white color
●
● Myelin acts as an insulator and affects
the speed of the nerve signalling
Spinal Cord
● a cylindrical shaped bundle of nerve
fibers that is connected to the brain;
connects brain & PNS
● extends from the neck to the lower
back
● spinal cord nerves transmit info from
body organs and external stimuli to
the brain and send information from
the brain to other areas of the body
Spinal Cord
● 3 major functions:
- passage for motor information
- passage for sensory information
- center for coordinating certain reflexes
Spinal Cord
●
Ascending
nerve tracts
carry sensory
information
from the body
to the brain
- travels up the
spinal cord
●
Descending
nerve tracts
carry motor
information
from the brain
to the rest of
the body
Ex: muscle
movements
- travels down
the spinal cord
Reflexes
● Reflexes are associated
with the central and
peripheral nervous
systems
● A rapid, involuntary, and instantaneous
movement in response to a stimulus
● Built-in safety mechanisms that help
keep people safe
Reflexes include
coughing, sneezing,
and blinking
Primitive reflexes are ones
infants are born with but
later outgrow
Cerebrospinal Fluid
● Cerebrospinal Fluid
(CSF) is a colorless
body fluid that is found
in the brain and spinal
cord
● Is produced in the
choroid plexus of the
brain
● It is used as a cushion
for the brain’s cortex
Functions of CSF
●
Buoyancy
- allows the brain to
maintain its density
without cutting off blood
supply and killing
neurons
- the brain is immersed
in fluid, reducing the net
weight
- pressure at the base of
brain is reduced
●
Protection
- protects brain
tissue from any
jolts or hits to
the head
- cushions a blow
to the head and
lessens impact
Function of CSF
●
Prevention of
Ischemia
- decrease of the
CSF in the limited
space of the skull
decreases
intracranial
pressure
●
An ischemic
stroke occurs
when an artery
in the brain
becomes
blocked.
Clearing waste
- rinses the metabolic
waste from the central
nervous system
- the one-way flow from
the CSF to the blood
takes potentially harmful
metabolites, drugs and
other substances away
from the brain
Neurons
Neurons are the basic units of the nervous system and contain nerve processes which are "fingerlike" projections that extend from the nerve cell body.
SYNAPSE
- contains a small
gap separating
neurons
- permits a neuron to
pass an electrical or
chemical signal to
another cell
DENDRITES
- structures that
extend away from
cell body
- receives signals
from other neurons
and carry them
towards the cell
body
CELL BODY
- control center
- recycling and
manufacturing plant
AXON
- carry signals away from the cell body to other neurons
AXON TERMINAL
- lies at the end of the
axon
- contain
neurotransmitters,
which are the
chemical medium
through which signals
flow from one neuron
to the next at chemical
synapses
How Neurons Communicate
●
●
●
communicate through an electrochemical process
electrical process:
Sensory receptors interact with stimuli such as light,
sound, temperature, and pain which is transformed into a
code that is carried to the brain by a chain of neurons.
Then systems of neurons in the brain interpret this
information. The information is carried along axons and
dendrites because of changes in electrical properties
which we call action potential. An action potential is
initiated when a messenger attaches itself to a receptor.
chemical process:
When that occurs, an electrical signal is triggered to be
generated through the neuron. Once the signal reaches
the end of an axon, which is at the end of a neuron, a
neurotransmitter is released and the process repeats.
Example
3.
2.
1.
Sensors detect a
sudden stretch in
the quadriceps.
The reflex is initiated
artificially by tapping
the tendon connected
to the quadriceps
muscle.
Sensory neurons convey the
information to the spinal cord.
4.
In response to signals from the sensory
neurons, motor neurons convey signals
to the quadriceps, causing it to contract
and jerking the lower leg forward.
5.
Sensory neurons
also communicate
with interneurons
in the spinal cord.
6.
The interneurons inhibit
motor neurons that lead
to the hamstring
muscle. This inhibition
prevents contraction of
the hamstring, which
would resist the action
of the quadriceps.
How Neurons Communicate
Electrical signal
along nerve cell
triggers release
of
neurotransmitter
Synaptic signaling
: A nerve cell releases
neurotransmitter
molecules into a synapse,
stimulating the target cell
Neurotransmitter
diffuses across
synapse
Target cell is stimulated
Neurons
3 types of neurons:
● Motor
- carry information from CNS to organs, glands, and
muscles
● Sensory
- send information to the CNS from internal organs or from
external stimuli
● Interneuron
- relay signals between motor and sensory neurons
Peripheral Nervous System
● transmits information to and from
the CNS and plays a large role in
regulating an animal’s movement
and internal environment
● connect the CNS to the limbs and
organs, essentially serving as a
communication relay going back
and forth between the brain and
the extremities
functional hierarchy of peripheral nervous system
Sensory-Somatic Nervous System
The sensory-somatic system consists of
● 12 pairs of cranial nerves and
● 31 pairs of spinal nerves
The cranial nerves connect the brain with
locations mostly in organs of the head and
upper body.
Ex: olfactory nerve - sense of smell
The spinal nerves run between the spinal cord and
parts of the body below the head.
Autonomic Nervous System
● controls involuntary muscles, such as smooth and
cardiac muscle
● also called the involuntary nervous system
● 3 divisions
- sympathetic → (“fight-or-flight” response)
- parasympathetic → (“rest and digest”)
- enteric
3 Divisions of the Autonomic
Nervous System
Activation of the
parasympathetic
division generally
causes opposite
responses that
promote calming and
a return to selfmaintenance functions
(“rest and digest”)
Ex : Increased activity
in the
parasympathetic
division lowers heart
rate and enhances
digestion
Activation of the
sympathetic division
corresponds to arousal
and energy generation
(“fight-or-flight”
response)
Ex: heart beats fister,
digestion is inhibited,
etc.
3 Divisions of the Autonomic
Nervous System
The enteric division consists of
networks of neurons in the digestive
tract, pancreas, and gallbladder
● neurons of the enteric division
control secretion
● normally regulated by the
sympathetic and parasympathetic
divisions
Epilepsy: The Basics
● new cases of epilepsy common in children and
after the age of 55
● common in those who have suffered brain
trauma
● affects 50,000,000
people worldwide
● 30% diagnosed
are children
Epilepsy: Causes and Symptoms
● ⅔ of patients are diagnosed
with an unknown cause
● severe head injury
● brain infection or disease
● stroke
● oxygen deprivation
● temporary confusion
● staring spells
● loss of consciousness
● psychic symptoms
Epilepsy: types of seizures
There are two types of epileptic seizures with
different symptoms
● focal (partial)
● generalized
Epilepsy: focal seizures
● these occur when there is
abnormal activity in one area
of the brain
● also known as partial
seizures
● broken down into two
subcategories with different
symptoms
○ simple partial seizures
○ complex partial seizures
Epilepsy: simple focal seizures
● don’t cause a loss of
consciousness
● may alter emotions or modify
the sensitivity of the senses
● can result in involuntary
jerking of body parts
● can cause dizziness, tingling
and sensitivity to flashing lights
Epilepsy: complex focal seizures
● involves a change or loss of
consciousness
● spelling spells may occur
● little or no response from
environmental stimuli
● performance of repetitive movements such as
hand rubbing, chewing, and walking in circles
Epilepsy: Generalized seizures
● these occur when there is abnormal activity in all
areas of the brain
● broken down into six subcategories with different
symptoms
○ absence seizures
○ tonic-clonic seizures
○ tonic seizures
○ atonic seizures
○ clonic seizures
○ myoclonic seizures
Epilepsy: Absence seizures
● known as petit mal
seizures
● staring into space or
subtle body movements
● may occur in clusters
● can cause brief loss of
awareness
Epilepsy: tonic-clonic seizures
● known as grand mal
seizures
● can cause abrupt loss of
consciousness
● body stiffening and
shaking
● loss of bladder control
● biting of the tongue
Epilepsy: tonic and atonic seizures
Tonic seizures cause
stiffening of muscles
● usually affect muscles in Atonic seizures
back, legs, arms
cause a loss of
● can cause a fall
muscle control
● also known
as drop
seizures
● can cause a sudden collapse
or fall
Epilepsy: clonic and myoclonic
seizures
Clonic seizures are associated
with repeated, jerking muscle
movements
● usually affect the neck,
face, arms
Myoclonic seizures are
sudden, brief jerks or
twitches
● normally occur in the
arms and legs
Epilepsy: Cell Signaling
Pathways
A normal brain with healthy
cell signaling pathways
A epileptic brain with diseased brain
areas that are darker. Has diseased
cell signaling pathways
Epilepsy: Cell Signaling Pathways
Epilepsy: Prognosis
● no cure but can be
controlled with the right
drugs
● ketogenic diets
● avoiding alcohol & getting
enough sleep
● surgery
Anti-epileptic Drugs
● Prescribed to control
seizures
● Enters the
bloodstream
● Alters and reduces
the excessive
electrical activity
● Not fully understood
Epilepsy: Current Research
● Each year NIH spends over $30 billion on research and but less
than 1% is spent on epilepsy
● A genetic mutation found in the heart had been identified to
cause severe and potentially deadly seizures
● CURE: addresses prevention, advancement of the search for the
cure, elimination of treatment side effects
Epilepsy Phenome/Genome Project
● Collects phenotypic and genomic information on
patients with epilepsy
● To identify the underlying determinant
for epilepsy
● Goal: to shape the future of clinical care of people
with epilepsy
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