Nervous%20System

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Nervous System

• By Daniel Aleynick

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What does it do?

• Responsibilities
• Receive signal
• Interpret signal
• Send signal to do an action

The Nervous System control most of the actions
your body performs
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Organization of Nervous System

• Nervous System
• Central Nervous System (CNS) Consists of the
  brain and spinal cord.
• Peripheral Nervous System (PNS) Are the nerves
  that connect the CNS to the rest of the body

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Information Processing

• A sensor (example eye or skin) picks up a
  signal, which is sends to the brain.
• The CNS processes the information, and sends
  another signal to a specific effector (example
  muscle)
• Effector proceeds with an action, such as a
  movement.

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Neuron Structure

• Composed of
• Cell Body
• Dendrites
• Axon
• Synaptic terminals

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Supporting Cells

• Supporting cells are known as Glia.
• Astrocytes provide support for neurons and
  control concentration of ion levels
• The blood-brain barrier is formed by astrocytes
  creating a very tightly controlled extracelluar
  chemical environment.
• Radial Glia Form tracks that newly formed
  neurons can travel. Also act as stems cells and
  can generated new neurons.

Astrocytes
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Surrporting Cells Cont

• Schwann Cells They make up the myelin sheath
  which covers the axon of neurons. They act as an
  insulator and increase the speed of the action
  potentials.

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Resting Potential

• Membrane potential The electrical difference
  between the inside and outside of a cell.
• Resting potential The membrane potential when a
  cell is not transmitting a signal.

Membrane Potential
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Gated Ion Channels

• There are three types ion channels
• Stretch-gated ion channels
• Ligand-gated ion channels
• Voltage-gated ion channels

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Voltage and Lignad Ion Channels

• Voltage-gated Ion Channels
• Are found in axons and open and close when the
  membrane potential changes.
• Stretch-gated Ion Channels
• Open and close when the cells sense it is being
  stretch. This occurs when the cell becomes
  mechanically deformed.

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Ligand-gated Ion Channels

• Ligand-gated Ion Channels Are ion channels that
  open and close when a specific molecule binds to
  the channel. This molecule is usually a
  neurotransmitter.

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Action Potential Useful Terms

• Hyperpolarization An increase of the magnitude
  of membrane potential by becoming more negative.
  This is caused by K channels to opening up.
• Depolarization A reducation in the magnitude of
  membrane potential. This occurred when Na
  channels open up.
• The changes in the membrane potential are called
  graded potentials.

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Production of Action Potentials
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Action Potentials

• What is an action potential?
• An action potential is a stimulus strong enough
  to produce depolarization past the threshold
• The threshold is the membrane potential limit
  that must be reached for an action to occur. This
  is a all or nothing event so nothing occur unless
  the limit is reached. Once reached, the whole
  action takes place.

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Conduction of Action Potentials

• An action potential starts in the axon hillock.
• From there a cascade effect takes place
• As the axon hillock is depolarized, it
  depolarizes a neighboring region of axon
  membrane.
• This next region than depolarizes another nearby
  region until the action potential reaches the
  synaptic terminals

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Conduction Speed

• The faster the body can send out signals, the
  faster one can react. But how does the body
  increase the speed of conduction?
• The axon of some neurons is covered by Schwann
  cells. Since these cells are made from lipids,
  they are insulators. This causes the electrical
  signal to jump over the Schwann cells increase
  the speed of the signal. This is known as
  salutatory conduction.

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Neuron Communication

• A neuron pass a signal to another neuron by
  chemical synapses.
• Synaptic terminals produce a neurotransmitter and
  package then in synaptic vesicles.
• The neurotransmitter move across the synaptic
  cleft and active the ligand-gated ion channels on
  the nearby neuron.

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Neurotransmitters

• Acetylcholine
• Is one of the most common neurotransmitters.
• Functional Class Is an excitatory in vertebrate
  skeletal muscles and an inhibitory at other
  sites.
• It is secreted by the CNS, PNS, and neuromuscular
  junctions.

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Neurotransmitters Cont

• The next group of neurotransmitters are the
  Biogenic Amines
• Norepinephrine Can be an excitatory or
  inhibitory and is produced in the CNS and PNS
• Dopamine Is both an excitatory and inhibitory
  and is produced in the CNS and PNS
• Serotonin Is generally a inhibitory and is
  produced by the CNS

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Neurotransmitters Cont

• Amino Acids can also be used as
  neurotransmitters
• Gamma Aminobutyric Acid Is an inhibitory and is
  made in the CNS and neuromuscular junctions.
• Glycine It is an inhibitory neurotransmitter and
  is created in the CNS
• Glutamate Is an excitatory and is produced in
  the CNS and neuromuscular junction.
• Aspartate An excitatory that is made in the CNS

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Neurotransmitters Final

• The last group of major neurotransmitters are
  Neuropeptides
• Substance P (not a creative name) is an
  excitatory that is produce in both the CNS and
  PNS
• Met-enkephalin Is generally an inhibitory that
  is made in the CNS

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Gases as Neurotransmitters

• Gases can be dissolved in fluids of the body and
  used as neurotransmitters as well.
• Common examples are
• NO and CO

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Regions of the Nervous System

• The peripheral nervous system is made up of all
  the nerves connect the brain and spine to the
  rest of the body
• Cranial nerves extend from the brain and spread
  to organs of the head and upper body
• Spinal Nerves originate in the spinal cord and
  extend to parts of the body below the head.

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PNS

• The PNS can be divided into two functional
  components
• The Somatic Nervous System (SNS)
• The Autonomic Nervous System (ANS)
• The Autonomic Nervous System can then be divided
  further into 3 more division
• Sympathetic division
• Parasympathetic division
• Enteric division

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Somatic Nervous System

• Is considered voluntary because it is subject to
  conscious control.
• Sends signals to and from the skeletal muscles of
  the body.

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ANS Sympathetic

• The sympathetic division deals with arousal and
  energy generation of the body
• The Fight or Flight response
• Digestions stops
• Energy production increases
• Adrenaline is released
• Faster Heart Rate

Adrenaline RUSH
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ANS Parasympathetic

• Self-maintenance functions known as Rest and
  Digest
• Digetionenchanced
• Heart Rated Slowed
• Glycogen production

Resting and Digesting
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ANS Enteric Division

• Is a network of neurons in the digestive tract,
  pancreas and gallbladder.
• They control the secretions and smooth muscle
  activities of the body, such as peristalsis, the
  uncontrolled movement of food through the body.

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Brain Structure

• In adults the brain consists of 5 structures
• Cerebrum
• Dienceohalon
• Midbrain
• Cerebellum
• Medulla Oblongata

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Cerebrum

• Is divided into two different regions
• The Right Cerebral Hemisphere
• The Left Cerebral Hemisphere
• Each Hemisphere has an other cover of gray brain
  matter and an inner region, the cerebral cortex,
  that is white brain matter.
• Basal Nuclei are groups of neurons in the
  cerebrum that are centers for planning and
  learning movement
• A think band of axons known as the corpus
  callosum always the right and left hemisphere to
  communicate.

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Diencephalon

• Is divided into 3 regions
• The Epithalamus
• The Thalamus
• The Hypothalamus
• The Epithalamus consists of the pineal gland and
  choroid plexus that produces cerebrospinal fluid.
• The Thalamus is the sensory center. All incoming
  information from sense is sorted here
• The Hypothalamus produced vital hormones and is
  the bodys thermostat, control temperature as
  well as hunger, thirst, and other survival
  mechanisms.

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Midbrain

• Acts as the rely stations for all auditory and
  visual information that brain receives.
• It also controls the eyes and how they move

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Cerebellum

• The cerebellum is important for coordination and
  error checking during motor, perceptual, and
  cognitive functions
• Is responsible for hand-eye coordination and
  balance.
• Good way to remember its function is
  Cere-balance.

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Medulla Oblongata

• Is the control central for some of the most vital
  body processes
• It controls automatic and homeostatic functions
  such as
• Breathing
• Heart Beats
• Blood Vessel Activity
• Swallowing
• Vomiting
• Digestion

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Circadian Rhythms

• The biological clock of the body controlling
  cycles such as the sleep/wake cycle
• Uses cues from the environment to change cycles.
• Examples of cues are light intensity and hunger.
• Paired up with the hypothalamic structures call
  the Superchiasmatic nuclei, clusters of neurons
  in the CNS.

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Laterlization

• During brain development, different function
  segregate to either the left or the right
  cerebral hemisphere
• The Left side is more adept to language, math,
  logical operations, etc
• The Right side is stronger at pattern
  recognition, nonverbal thinking and emotion
  processes.
• Left side is factual information while right side
  is creativity.

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Memory and Learning

• The body is constantly making connection between
  what is happening to what has already happen.
• Short-term Memory is stored in the frontal lobe
  and are memories of what has recently happened.
  When these memories become irrelevant, the brain
  forgets them.
• Long-term Memory is aided by the hippocampus.
  These are short-term memories that were stored
  for later use. The more a memory is used the
  easier it is to remember, hence practice makes
  perfect

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Disease/Nervous Problems

• Schizophrenia
• A mental disturbance where the patient can no
  longer distinguish between reality and
  imagination.
• Bipolar Disorder
• Involves swings of mood from high to low and
  affects 1 of the population
• Alzheimer's Disease
• Mental deterioration which results in confusion,
  memory loss, and other variable symptoms. Usually
  the results of old age