The Nervous System rev 10-11

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The Nervous System rev 10-11

• Receives information and produces a meaningful,
  quick output.
• To do this, the nervous system
• quickly sorts through our memory bank
• decides the probable meaning of the input
• integrates the information
• Provides a quick response
• So, the nervous system controls and integrates
  all other body systems and functions

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• What are the characteristics of the nervous
  system that allow us to do this?
• It must receive information from our senses.
• It integrates information.
• -Integration is the process of taking different
  pieces of information from different sources,
  making sense of all of it at the same time, and
  coming up with an action plan.
• 3. The nervous system is fast it can do this
  within tenths of a second.

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• The CNS-Central Nervous System (the brain and
  spinal cord)
• is the integrating and command center of the
  nervous system
• It receives and interprets incoming sensory
  information and produces motor responses
• The PNS-peripheral nervous system is the part of
  the nervous system outside the CNS.
• it contains the communication lines that link all
  parts of the body to the CNS

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• The PNS consists of
• 12 pairs of cranial nerves carry impulses
  between brain and body
• 31 pairs of spinal nerves connect to spinal cord
  via dorsal and ventral roots
• Dorsal root has sensory neurons and transmit
  information TO the cord
• Ventral root has motor neurons that transmit
  information FROM the cord to the body

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• the Peripheral NS has 2 functional subdivisions
• the sensory or afferent division carries impulses
  TO the CNS
• keeps the CNS informed of events going on inside
  and outside of the body
• The motor or efferent division carries impulses
  FROM the CNS
• this division enables us to respond to stimuli

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• The Motor Division can be further subdivided into
  2 parts
• the Somatic nervous system
• Voluntary controls voluntary and involuntary
  skeletal muscle movements
• Motor neurons are activated either by conscious
  control from the brain or by an involuntary
  response called a reflex

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• Reflex Division
• Spinal reflexes
• Spinal reflexes are involuntary, automatic
  responses handled primarily by the spinal cord
  and spinal nerves

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AND the Autonomic nervous system (ANS)

• this division regulates involuntary activities
  the activity of smooth muscles, cardiac muscles,
  and glands (regulates anything that occurs
  automatically in the body)
• Requires 2 neurons to transmit information from
  the CNS to a target cell
• Preganglionic neurons cell bodies of the first
  neurons lie within the CNS
• The axons of these go to postganglionic neurons
  which lie outside the CNS
• Postganglionic axons extend to wherever in our
  body the target glands or organs are located

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• The ANS is further sub-divided into the
• SYMPATHETIC NERVOUS SYSTEM which mobilizes body
  systems during emergency situations.
• Origin thoracic or lumbar regions of the spinal
  cord
• Function releases neurotransmitters epinephrine
  and norepinephrine for fight-or-flight reaction
  opposes parasympathetic division
• reduces blood flow to organs that do not help
  with an immediate disaster

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• AND the PARASYMPATHETIC NERVOUS SYSTEM which
  conserves our energy and predominates during
  relaxing
• Origin brain or sacral area of spinal cord
  (craniosacral)
• Function releases acetylcholine to relax the
  body opposes sympathetic division
• In most organs, the actions of the sympathetic
  and parasympathetic divisions have opposite
  effects.
• The two divisions counterbalance each others
  activities to maintain homeostasis.

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Composition of the Nervous SystemNerves,
Neurons, Neuroglia

• The Nervous System is composed of
• Nerves which consists of the axons of many
  neurons wrapped together in a sheath of
  connective tissue
• Neurons are cells which are specialized for
  communication.
• Classification of neurons
• Sensory or Afferent neurons carry (sensory)
  information from receptors TO the CNS
• Motor (Efferent) Neurons carry messages AWAY FROM
  the CNS to the muscles and the glands

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• Interneurons or Association Neurons are located
  in the CNS and conduct impulses within the CNS.
  They receive information from sensory neurons,
  integrate the input, and then deliver the
  information to other neurons.
• are multipolar neurons
• Neuroglia (or Glia) are the supporting and
  protecting cells of the nervous system. We will
  speak more of these later.

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Neurons

• All neurons have
• a cell body (contains the nucleus)
• an axon (long slender tube of cell membrane
  specialized to carry electrical impulses)
• Axons of sensory neurons originate from a
  dendrite
• Axons of interneurons and motor neurons originate
  from a cone shaped area of the cell body called
  the axon hillock
• At its other end, the axon branches into slender
  extensions called axon terminals and the end of
  this is called an axon bulb
• dendrites (typically slender extensions of the
  cell body receive stimuli)

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Types of Neurons

• Unipolar Neurons have a single process which
  emerges from the cell body
• this process divides into a proximal and distal
  branch
• One branch behaves as an afferent branch and the
  other behaves as an efferent branch
• All unipolar neurons are sensory

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Unipolar
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• Bipolar Neurons
• have 2 processes emerging from a round cell body
• processes extend from opposite sides of the cell
  body
• found only in some of the special sense organs
  where they act as receptor cells

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Types of Neurons

• Bipolar Neuro

Bipolar
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• Multipolar Neurons
• have 3 or more processes
• are the most common neuron type in humans and
  major neuron type in the CNS

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Types of Neurons

• Multipolar

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• Interneurons or Association Neurons
• are a multipolar neuron
• located in the CNS
• conduct impulses within the CNS
• are the connecting link between sensory and motor
  neurons

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• Some neurons have a myelin sheath
• the myelin sheath
• is a fatty wrapping around the axon which
  provides insulation to the axon and thus saves it
  energy
• it speeds impulse transmission by allowing a
  leaping pattern of transmission called saltatory
  conduction
• The impulse jumps from one Node of Ranvier to
  another
• Between neighboring Schwann cells are short,
  uninsulated gaps called Nodes of Ranvier

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• Myelin
• in the peripheral nervous system is formed from
  Schwann Cells which wrap around the axon
• It helps damaged or severed axons of peripheral
  nerves regenerate
• in the CNS is formed by oligodendrocytes
• The oligodendrocyte sheath degenerates once the
  axon it protects is damaged or destroyed

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• Neuroglial cells
• Provide physical support to neurons
• Protection to neurons
• Help maintain concentrations of chemicals in the
  fluid surrounding them
• Neuroglial cells DO NOT generate or transmit
  impulses
• Example myelin sheath

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Impulse Transmission-Summary

• The function of a neuron is to transmit
  information from one part of the body to another.
• This is done in the form of electrical impulses.
• An impulse arrives at the dendrite
• When the impulse is strong enough, it depolarizes
  the membrane and the impulse is transmitted along
  the axon
• When the impulse reaches the axon terminals, the
  information needs to be converted to another form
  of energy in order for the information to be
  transmitted to its target (i.e. a muscle, a
  gland, or another neuron)
• A chemical, called a neurotransmitter, is
  released which allows the impulse to jump the
  synapse, or space, between the 2 cells

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Impulse Transmission- Definitions

• Resting or Membrane Potential a small
  difference in voltage across the cell membrane
  the cell is normally negatively charged.
• This allows the neuron to be ready to respond
  more quickly than it could if it were
  electrically neutral.
• Think about a car battery. It retains a charge
  so that the car will start as soon as the key is
  turned
• Unlike most body cells, neurons can alter the
  electrical charge across the neurolemma. The
  membrane potential alternates between -70 and 30
  millivolts. Charge differences are controlled by
  the movement of sodium and potassium ions
  entering and leaving the neuron
• Action Potential changes in the electrical
  activity of the nerve of sufficient intensity to
  reach the threshold necessary to move an
  electrical impulse down the axon

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• Threshold the level of stimulus a neuron needs
  in order to fire
• All or nothing phenomenon once the threshold
  level is reached, the nerve transmits an impulse
• Depolarization moving the negative charge within
  the axon closer to zero
• Na (sodium) moves into the cell via sodium
  channels which open
• Repolarization K (potassium) moves out of the
  cell
• Na channels close and the reversal of the
  membrane polarity triggers opening of the K
  channels so the K moves out of the cell. Loss
  of K means that the interior of the axon becomes
  negative again and the resting potential is
  restored
• Refractory period The part of the axon that has
  already fired is unable to fire again so the
  impulse must move forward (This prevents the
  impulse from moving backwards.)

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• Movie Clip
• http//brainu.org/files/movies/action_potential_ca
  rtoon.swf
• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter14/animation__transmission_acr
  oss_a_synapse.html
• http//www.sumanasinc.com/webcontent/animations/co
  ntent/actionpotential.html

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• Action potential Overview
• Abstracted from http//soe.ucdavis.edu/ss0708/egh
  balis/Notes/u12Notes.html
•  The functioning of the neuron is dependent on
  the separation of positive and negative ions,
  keeping the negative charge on the inside and the
  positive charge on the outside.
• Neurons are typically at a resting state or
  resting potential the amount of positive ions on
  one side and negative ions on the other side of
  the plasma membrane remains the same, creating a
  -70millivolt potential difference.
• How can the charge inside the cell be negative
  if the cell contains positive ions? In addition
  to the K, negatively charged protein and nucleic
  acid molecules also inhabit the cell therefore,
  the inside is negative as
• compared to the outside.
•   

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• In order for the neuron to send a message, there
  needs to be a change in the electrical charge,
  causing an impulse to be sent down the axon. This
  process is called an action potential.
• A stimulus causes voltage-gated sodium channels
  to open causing sodium ions to move into the
  cell. Because positive charges are coming inside,
  the inside of the membrane less negative (more
  positive).
• DepolarizationWhen the impulse becomes strong
  enough, (-55mV), an action potential begins. As
  sodium ions enter the axon, more sodium channels
  open causing even a greater influx of sodium
  ions.

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• Peak
• By the time the peak is reached (usually 50mV)
  the sodium channels have already begun closing,
  reducing the rise in the potential. As this
  happens, the voltage-gated potassium channels
  open.
• Repolarization The voltage gated potassium
  channels are open and potassium ions move out of
  the cell. This causes neurons to return to the
  negative membrane potential.
• Hyperpolarization The potassium channels will
  begin to close but they don't close fast enough
  and thus there is an overshoot of depolarization,
  making the membrane more negative than -70mV.
• Refractory Period During the next few seconds,
  there is a refractory period and during this time
  no action potential can take place

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• The following graph demonstrates how the electric
  potential of the membrane changes during an
  action potential. Initially, the cell is at rest
  (-70 mV).
• If there is enough increase in the voltage (to
  -55 mV) then an action potential takes place. If
  it's anything lower than that, nothing happens.
  This is an all or none response (you either get a
  signal, or not, there is no such thing as a weak
  signal).
• If the voltage reaches -55 mV, the cell membrane
  will depolarize and the voltage will increase
  rapidly to above 0mV. This is an action
  potential.

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• Then the membrane repolarizes (returns to normal)
  as potassium ions are released.  
• There is an over release of potassium ions,
  making the membrane more negative than the
  resting potential. Until the membrane returns to
  the resting potential, it is in that refractory
  period where the neuron cannot be stimulated
  again (cannot send another message).

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• Meninges--3 protective membranes of connective
  tissue enclose the brain and spinal cord
• Dura mater is the outermost and strongest layer
• Arachnoid mater is the middle layer it has
  spidery extensions which secure it to the
  innermost layer.
• Pia mater is the innermost layer and clings
  tightly to the CNS.

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• Cerebrospinal fluid (CSF) is found within and
  around the brain and spinal cord. It
• functions as a liquid shock absorber
• serves as a blood-brain barrier by isolating the
  CNS from infections
• aids in providing nutrients for cells and
  removing waste products from cells
• by floating the brain, the CSF effectively
  reduces brain weight by 97 and prevents the
  brain from crushing under its own weight

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• CSF is formed from blood plasma
• it is made in the choroid plexuses in the
  ventricles of the brain
• much of the fluid is found in the subarachnoid
  space

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Spinal Cord

• The spinal cord is located in the vertebral
  column.
• It is approximately the width of the thumb except
  at the cervical and lumbar areas.
• Cervical enlargement is where the nerves for the
  shoulder and arms enter and exit the cord.
• Lumbar enlargement is where the nerves for the
  legs enter and exit the cord.

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• The spinal cord does not extend to the end of the
  vertebral column. It ends at the level of L2
  (the area between the first and second lumbar
  vertebrae).
• The cord ends in a tapering cone shape which is
  called the conus medularis.
• The lumbar and sacral nerves angle sharply
  downward and travel through the vertebral canal
  before they exit through intervertebral foramina.
  
• The collection of these nerves is called the
  cauda equina because they resemble a horses tail.

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• The outer portion of the spinal cord consists
  primarily of bundles of axons called nerve
  tracts.
• These axons are usually myelinated so they have a
  white appearance and are called white matter.
• White matter is made up of ascending (sensory)
  and descending (motor) nerve tracts of myelinated
  axons.
• Near the center of the cord is an area called the
  gray matter. It is occupied primarily by cell
  bodies, dendrites and axons of neurons which are
  not myelinated.
• Is in the shape of an H or a butterfly this is
  where all synapses between sensory, association,
  and motor neurons takes place.

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Spinal Cord Anatomy

• The Central Canal is where the CSF circulates.
• The Ventral (or anterior) Root is where MOTOR
  axons exit the cord.
• The Dorsal (or posterior) Root is where SENSORY
  axons enter the cord.
• The Dorsal Root Ganglion is where sensory nerve
  cell bodies are located.

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The Reflex Arc

• Many of the bodys control systems belong to a
  general category known as reflexes.
• A reflex is a rapid, predictable motor response
  to a stimulus.
• It is automatic, involuntary, and protective.
• Both the spinal cord and the brain are reflex
  centers.

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• Reflex arcs include the following components
• 1. The receptor is the where the stimulus begins.
• 2. The sensory neuron transmits the afferent
  impulses to the CNS.
• 3. An association neuron receives the information
  and causes an instantaneous impulse to be
  transmitted to a motor neuron.
• 4. The motor neuron sends an impulse to the
  effector organ (organ which will cause a
  response).
• 5. The effector is the muscle or gland that
  responds in a characteristic way.
• This allows us to respond to a stimulus instantly
  and without thinking.

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• In more complex reflexes, some information goes
  to the brain to allow it to integrate
  information. This will allow you to learn from
  the situation.

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The Brain and the Spinal Cord

• The CNS controls and processes all information
  received by the body.
• Protection of the CNS
• Bone protects it from physical injury
• the brain is covered by the skull
• the spinal cord is surrounded by the vertebrae

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The Brain

• The brain is the central command center of the
  body
• Receives information in the form of action
  potentials from various nerves and the spinal
  cord, integrates it and generates the appropriate
  response.
• 3 major anatomical and functional divisions of
  the brain have been identified

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Brain Major Divisions

• Hindbrain coordinates basic, automatic, and
  vital functions
• Midbrain helps coordinate muscle groups and
  responses to sight and sound
• Forebrain receives and integrates sensory input
  from the external environment and determines most
  of our complex behavior

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Hindbrain movement and automatic functions

• Connected to the spinal cord
• Medulla Oblongata controls automatic functions
  of internal organs
• cardiovascular center- regulates heart rate and
  blood pressure
• respiratory center-controls rate and depth of
  breathing
• other centers which coordinates reflexes such as
  coughing, vomiting, swallowing, and sneezing

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• All information passing between the higher areas
  of the brain and spinal cord must pass through
  the medulla
• Motor nerves from one side of the forebrain cross
  over to the other side of the body in the medulla
• Left side of brain controls right side of body
• Right side of brain controls left side of body

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• Cerebellum
• Coordinates basic movements below the level of
  conscious control
• Stores and produces whole sequences of skilled
  movements
• Receives sensory input from many sources
• excessive alcohol disrupts normal functioning of
  the cerebellum

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• Pons
• Aids information flow
• connects the higher brain centers and the spinal
  cord
• its respiratory nuclei work with the respiratory
  centers of the medulla in regulating respiration
• coordinates the information flow between the
  cerebellum and higher brain centers

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• The Midbrainfunctions relate to vision and
  hearing
• Visual and auditory sensory inputs pass through
  the midbrain before being relayed to higher brain
  centers
• Coordinates movements of the head in response to
  vision and hearing
• controls movement of the eyes and pupil size
• monitors the unconscious movement of skeletal
  muscles so their actions are smooth and
  coordinated
• The reticular formation extends through the
  medulla, the pons, and the midbrain.
• works with the cerebellum to coordinate muscle
  activity to maintain posture, balance and muscle
  tone
• --The Reticular Activating System, within the
  reticular formation, is responsible for
  maintaining our level of wakefulness

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The forebrain and diencephalon emotions and
conscious thought

• Important areas are the cerebrum, thalamus,
  hypothalamus, and limbic system
• Also includes 2 glands the pineal gland and the
  pituitary gland
• Determines our most complex behavior including
  emotions and conscious thought.
• Hypothalamus and Thalamus maintain homeostasis
  and process information
• Hypothalamus is a small region at the base of the
  forebrain that coordinates some automatic
  functions including regulating homeostasis due to
  monitoring of sensory signals
• Also controls the pituitary gland

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• Thalamus located just above the hypothalamus
• Is primarily a receiving, processing and transfer
  center it sends signals to the cerebrum to be
  interpreted.
• Limbic System is a group of neuronal pathways
  which connect parts of the thalamus, hypothalamus
  and cerebrum.
• involved in emotions and memory.

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• Cerebrum deals with higher functions and is most
  highly developed
• is divided into left and right cerebral
  hemispheres by the longitudinal fissure
• each hemisphere controls the opposite side of the
  body

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• In the middle of the hemispheres is the corpus
  callosum which joins the 2 hemispheres and
  enables them to communicate and share information
• Below the corpus callosum in each hemisphere are
  the lateral ventricles which secrete CSF
• The outer layer of the cerebrum is called the
  cerebral cortex and is primarily gray matter
• The inner portion of the cerebrum is primarily
  white matter

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• surface tissue of the cerebrum is covered with
  sulci (grooves) and gyri (ridges) which increase
  the surface area for information exchange
• Each hemisphere is further divided into 4 lobes
  the frontal, parietal, temporal, and occipital
  lobes
• all 4 lobes are involved in memory storage

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• The frontal lobes initiate motor activity and are
  responsible for speech, conscious thought, and
  personality.
• these lobes may be further divided into the
  prefontal lobes or cortex which are the
  intellectual center
• the premotor cortex
• skilled repetitive activities (typing) and
  conditioned reflexes (Pavlovs dog)
• the primary motor cortex which initiates
  voluntary motor activity of the arms, legs, trunk
  and face
• In the dominant hemisphere only is our primary
  speech center

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• The parietal lobes house somatosensory cortex
• interpret sensory information from the skin and
  from proprioceptors in the muscles and joints.
• integrate different sensory inputs to allow us to
  interpret sensory information i.e. reaching into
  your pocket and being able to interpret the coins
  in it without using visual cues.
• The occipital lobes house the primary visual
  cortex and the visual association area
• The temporal lobes interprets auditory
  information and is responsible for perceptual
  judgment

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Cranial Nerves

• Twelve pairs of cranial nerves arise from the
  brain
• They have sensory, motor, or both sensory and
  motor functions
• Each nerve is identified by a number (I through
  XII) and a name

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Memory Storing and Retrieving Information

• Memory has 2 stages short term and long term
• Short term working memory, information from
  previous few hours
• Long term information from previous days to
  years
• The brain manages the 2 types of memory
  differently.
• STM goes into the limbic system and triggers a
  burst of action potentials so we can remember
  information for a few minutes.
• LTM if information important, it is transmitted
  to your cerebral cortex for storage as LTM.
  Neurons undergo a permanent change and create
  additional synapses so we can remember and
  retrieve information.

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Psychoactive Drugs

• Action affects higher brain functions
  (consciousness, emotions, or behavior) drugs
  influence the actions of brain neurotransmitters
  can cross the blood brain barrier
• Methamphetamine (crystal meth), cocaine, crack,
  alcohol, nicotine, heroin
• When the body releases neurotransmitters, their
  effects are typically short because the
  neurotransmitter remains in the synapse for a
  brief period of time
• These drugs block the reabsorption of the
  neurotransmitters so they remain in the synapse
  and stimulate the body again and again
• Dopamine is one of the most important
  neurotransmitters in areas of the brain
  associated with pleasure

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• But, as the neurotransmitter reuptake is blocked,
  the body releases less and less and the good
  feeling disappears
• Psychological dependence user craves the feeling
  associated with the drug
• Tolerance takes more of the substance to achieve
  the same affect
• Addiction the need to continue obtaining and
  using a substance no free choice
• Withdrawal physical symptoms that occur upon
  stopping the drug

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Disorders of the Nervous System

• Autoimmune Disorders
• Multiple Sclerosis (MS)
• An autoimmune disease that mainly affects young
  adults
• The sheaths of myelinated neurons in the brain
  and spinal cord degenerate and form hardened
  (sclerotic) scar tissue. These areas cant
  effectively insulate the neurons and so impulse
  transmission is slowed and disrupted and the
  nerves are also damaged.
• People with MS experience a variety of symptoms
  depending on which areas of the CNS are damaged.
• Symptoms include visual disturbances, weakness,
  loss of muscular control and sensation, and
  urinary incontinence

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Multiple Sclerosis

• Cause unknown. Thought to be disorder of the
  immune system or genetic tendency
• Thought that a virus attacks immune system so it
  perceives myelin as a threat
• Course can be mild to severe
• Diagnosed MRI, Evoked Potential nerve test to
  determine the speed of impulses traveling through
  nerves examine CSF to see if any cell
  abnormalities
• Disease-modifying drugs Interferons or Copazone
  to reduce frequency of relapses, Avonex or
  Betaseran to help decrease disability

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• Amyotrophic Lateral Sclerosis (ALS)
• Similar to MS but the sclerotic areas begin in
  areas of the spinal cord involved in the motor
  control of skeletal muscles
• Primary symptom is progressive weakening and
  wasting of skeletal muscles, especially those
  responsible for breathing

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• Trauma
• Concussion caused by a violent blow to the head
  or neck
• Usually see a short loss of consciousness due to
  a disruption of the electrical activity of brain
  neurons.
• After regaining consciousness, person may have
  blurred vision, confusion, nausea and vomiting
• Typically concussions dont have permanent damage
  unless there is a subdural hematoma bleeding
  into the space between the meninges

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• Bleeding increases pressure within
  head?compresses brain tissue and disrupts
  function of brain
• Symptoms drowsiness, headache and weakness of 1
  side of body
• Treatment surgery for immediate relief of
  pressure and repair of bleeding blood vessels

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• Spinal cord injuries will impair sensation and
  function below the level of injury
• Paraplegia or quadriplegia can be fatal will
  always cause problems with bladder and bowel
  control
• Infections Brain and spinal cord typically do
  not get infected due to the blood-brain barrier
• Encephalitis inflammation of the brain
  typically caused by a virus
• Causes breathing in respiratory droplets,
  contaminated food, insect bite, skin contact
• Symptoms inflammation of brain tissue?cerebral
  edema, headache, fever, fatigue, hallucinations,
  confusion, disturbances in speech, memory or
  behavior, epileptic seizures

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• Treatment Hospitalization with intravenous
  medications antiviral or antibiotics,
  anti-seizure to prevent seizures, steroids to
  reduce brain swelling
• Acute phase usually lasts for 1-2 weeks fever
  and symptoms may gradually or suddenly disappear
  some people may take several months to recover
  although in severe cases there may be residual
  disabilities
• Meningitis Inflammation of the meninges can be
  viral or bacterial
• Symptoms headache, fever, nausea and vomiting,
  light sensitivity, stiff neck
• Treatment hospitalization. If viral, mild
  symptoms and will improve in few weeks
• If bacterial, can be fatal IV antibiotics needed
  ASAP

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• Rabies infectious viral brain disease
• Transmitted to humans by direct contact, either
  bite or lick over broken skin
• Virus attacks the sensory neurons in the bite
  region then travels to the spinal cord, then to
  the brain where it multiplies and kills cells
• Symptoms swollen lymph glands, painful
  swallowing, vomiting, choking, spasms of throat
  and chest muscles, fever, becomes irrational.
  Death within 2-20 days
• Treatment wash wound thoroughly ASAP, go to
  emergency room or doctor, have animal tested,
  receive rabies immunization ASAP

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• Neural and synaptic transmission disorders
  action potentials cant be properly sent.
  Symptoms depend on which nerves are affected
• Epilepsy recurring episodes of abnormal
  electrical activity in brain
• Seizure triggers fatigue, stress, flashing
  lights
• Seizures vary widely due to which part of brain
  is affected
• Treatment EEG, medications

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• Parkinsons disease progressive degenerative
  illness loss of dopamine releasing neurons in
  the area of the midbrain that coordinates muscle
  movements cant perform smooth, coordinated
  movement
• Symptoms stiff joints, muscle tremors in hand,
  loss of mobility, depression and other mental
  impairments
• Treatment L-dopa, a drug which the body
  converts to dopamine.

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• Dementia
• Loss of mental functions that is severe enough to
  interfere with a persons daily life
• Is not a disease itself but is a group of
  symptoms
• Alzheimers disease is a common cause of dementia

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• Alzheimers disease disorder of mental
  impairment, especially memory due to a shortage
  of the neurotransmitter acetylcholine. Primarily
  affects neurons in the limbic system and frontal
  lobe. See plaques in brain tissue and abnormal,
  tangled neurons.
• Symptoms Progresses from memory lapses to
  severe memory loss, especially of STM. LTM
  affected very slowly. Disorientation, dementia,
  personality changes, loss of ability to function
  independently
• Treatment medications which increase the
  brains production of acetylcholine

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• Brain tumors abnormal growth in or on the brain
• Can be cancerous or benign
• Problems due to increased pressure within the
  brain
• Symptoms headache, vomiting, visual impairment,
  confusion, muscle weakness, difficulty speaking,
  seizures
• Treatment Surgical removal, radiation and
  chemotherapy.