NERVOUS SYSTEM

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• NERVOUS SYSTEM

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Nervous System Overview

• Role Maintain homeostasis
• Sense changes (____ neurons)
• Integrate information (_______)
• Respond (______ neurons)
• Basic Anatomy
• Mass ____ lbs 3 total body mass
• Main Subdivisions
• Central Nervous System (CNS)
• Peripheral Nervous System (PNS)

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CELLS OF THE NERVOUS SYSTEM

• 2 Types of cells found in the N S
• 1. NEURONS nerve cells
• 2.NEUROGLIA (Glia) specialized connective tissue

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NEURONS

• Motor neurons
• Also called ________ neurons.
• Interneurons
• Also called _______neurons.
• Sensory neurons
• Also called _______neurons.

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STRUCTURE OF NEURON

• AXON is surrounded by segmented wrapping called
  _______.
• - It is

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Axon - long section, transmits impulses Dendrite
- small extensions from the cell body receive
information Neurofibrils - fibers within the axon
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Interesting Facts about the Neuron

• Longevity can live and function for a lifetime
• Do not divide fetal neurons lose their ability
  to undergo mitosis neural stem cells are an
  exception
• High metabolic rate require abundant oxygen and
  glucose

The nerve fibers of newborns are unmyelinated -
this causes their responses to stimuli to be
course and sometimes involve the whole body.  Try
surprising a baby!
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GLIA

• Glia or neuroglia They are special types of
  supporting cells
• - Function is to
• Large cells look like stars astrocytes
• Smaller cells are Microglia
• Example Oligodendrocytes helps hold fibers
  together, produce the fatty myelin sheath that
  envelops nerve fibers in the brain and spinal cord

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NERVES

• Nerve is a group of peripheral nerve fibers
  (axons) bundled together like the strands of a
  cable.
• Myelin is found on nerves and is white.
• Nerves are referred to as _____ matter of the PNS
  and also the CNS.
• Unmyelinated axons and dendrites are called
  ________. (because of their color)

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Brain Gray over White
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Spinal Cord White over Gray
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REFLEX ARC

• Nerve impulses are conducted from receptors to
  effectors over neuron pathways known as
  ___________
• This results in a _______. (a contracted muscle
  or secretion from a gland)
• 2 types of reflex arcs
• - two-neuron arcs spinal cord and motor neuron
• - three-neuron arcs sensory neurons,
  interneurons and motor neurons

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Animation

• http//www.youtube.com/watch?vY5nj3ZfeYDQ
• http//bcs.whfreeman.com/thelifewire/content/chp46
  /46020.html

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RECEPTORS

• Impulse conduction normally starts in the_______.
• Found at the beginning of the dendrites of
  sensory neurons
• Location

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MS (MULTIPLE Sclerosis) DAMAGE TO MYELIN

• Hard lesions replace the destroyed Myelin
• As the myelin is lost, nerve conduction is ______
• Causing weakness, loss in coordination, visual
  impairment, speech disturbances
• No known cure, occurs most in women ages 20-40.

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Synapse

• A microscopic space from the axon ending of one
  neuron to the dendrite of another neuron.
• The nerve impulse stops, chemicals are sent
  across the gap, the impulse continues alone the
  dendrites.

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Neurotransmitters

• Chemicals by which neurons communicate
• Some help us sleep, inhibit pain, make us
  energetic
• Examples
• Acetylcholine-
• Norepinephrine and Dopamine-
• Serotonin-
• Endorphins-

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Neurotransmitters
Excitatory - increase membrane permeability,
increases chance for threshold to be
achieved Inhibitory - decrease membrane
permeability, decrease chance for threshold to be
achieved
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The Action Potential- an All-or-None Electrical
Signal
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Cell Membrane Potential
At rest, the inside of a neuron's membrane has a
negative charge. As the figure shows, a Na / K
pump in the cell membrane pumps sodium out of the
cell and potassium into it. However,  more
potassium ions leak out of the cell. As a result,
the inside of the membrane builds up a net
negative charge relative to the outside.
Animations of Nerve Impulses http//highered.mcgr
aw-hill.com/sites/0072495855/student_view0/chapte
r14/animation__the_nerve_impulse.html
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Action Potential Overview

• Signals or impulses of communication
• Travel along axons
• Are all-or-none events
• Threshold must be reached
• Two phases
• Depolarization
• Repolarization

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Axon Diameter and Action Potentials

• Recall that axons are also called nerve fibers
• Larger fibers propagate impulses faster
• Larger fibers usually myelinated
• Smallest fibers are unmyelinated and therefore
  propagate impulses slower

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Resting Membrane Potential

• Recall that there is a separation of charges
  across the membrane of excitable cells.
• Extracellular fluid contains more sodium ions
  than are found inside a cell
• Cytosol contains more anions and negatively
  charged proteins
• Thus sodium ions cling to the outside cell surface

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Resting Membrane Potential

• Cell somewhat permeable to potassium
• Much less permeable to sodium
• Sodium quick to rush in when gates open
• following both electrical and concentration
  gradients
• Potassium not quick to rush out
• only has concentration gradient to drive flow

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Resting Membrane Potential

• small build-up of anions in cytosol
• equal build-up of cations in extracellular fluid

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Change in Membrane Potential

• Na channels open
• Fast Na influx
• Inside of cell becomes less negative
• If change is 15mV action potential occurs

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Ongoing Research

• Improve environment for spinal cord axons to
  bridge injury gap
• Find ways to stimulate dormant stem cells to
  replace lost, damaged, or diseased neurons
• Develop tissue cultured neurons that can be used
  for transplantation purposes.

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Drugs that Affect Synapses and Neurotransmitters
Strychnine poisoning can be fatal to humans and
animals and can occur by inhalation, swallowing
or absorption through eyes or mouth Strychnine
is a neurotoxin which acts as an antagonist of
acetylcholine receptors. It primarily affects the
motor nerves in the spinal cord which control
muscle contraction. An impulse is triggered at
one end of a nerve by the binding of
neurotransmitters to the receptors.
   Strychnine use by athletes?  
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Drugs that Affect Synapses and Neurotransmitters

• Cocaine, morphine, alcohol, ether and chloroform
• Ecstasy

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LSD  (hallucinogen)
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Dangers of Ecstasy (MDMA)

• The most common cause of Ecstasy-related death is
  overheating (hyperthermia). MDMA interferes with
  the body's ability to regulate its own body
  temperature and to see other warning signs
  allowing the body to overheat without discomfort
  especially when dancing for hours in hot clubs.

The neurotransmitter serotonin is vital in
regulating many of our basic functions. Serotonin
is, among other things, the feel good
neurotransmitter and helps to regulate body
temp. Our brain cells are constantly trying to
bring some amount of serotonin back into the
cells and out of the synapse using serotonin
reuptake transporters.    Ecstasy essentially
takes these upkeep transporters and reverses
their roles. This causes a massive flood of
serotonin from the brain cells into the synapse. 
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LSD lysergic acid diethylamide

• Actions/Effects LSD alters the action of the
  neurotransmitters serotonin, norepinephrine, and
  dopamine, triggering extreme changes in brain
  function. Physical effects include increased body
  temperature, heart rate, and blood pressure.
  Psychological effects include perceptual and
  thought distortions, hallucinations, delusions,
  and rapid mood swings.
•  
•  

Cocaine blocks reuptake of dopamine
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Central Nervous System

• Integrates and correlates incoming sensory
  information
• Source of thoughts, emotions, memories
• Most motor signals originate in CNS

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CNS (CENTRAL NERVOUS SYSTEM)Spinal Cord and Brain

• 4 Divisions of the brain
• Brainstem
• Cerebellum
• Diencephalon
• Cerebrum

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BRAINSTEM

• Medulla Oblongata largest part of the
  brainstem.
• - extension of the _________
• - Location lies below the _______
• - Functions reflex center
• -It controls

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DIENCEPHALON

• Hypothalamus
• - Structure
• - Function Acts as the major center for
• controlling the _____. (function of internal
  
• organs)
• - Controls _____________
• - Centers for controlling

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DIENCEPHALON

• THALAMUS
• - Structure dumbbell shaped mass of gray
  matter in each cerebral hemisphere
• - Function
• - Produces emotions of pleasantness and
  unpleasantness associated with sensation

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CEREBELLUM

• Second largest part of the brain
• Structure
• - composed of _____in outer layer and
  _______in the inner layer
• Function

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CEREBRUM

• Largest part of the brain
• Structure Structures Series of ridges and
  grooves
• -Ridges are called convolutions or ____
• -Grooves are called _____ (deepest sulci
  are called fissures)
• -Divided into two halves- ________
• -Hemispheres connected by the _________

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CEREBRUM

• HEMISPHERES Divided into lobes
• Lobes are named after bones that lie over them.

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CEREBRUM

• Function mental process of all types
• Sensations
• Consciousness
• Thinking
• Memory
• Willed Movements

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Cerebrum

• Specific areas have specific functions
• Temporal lobes auditory areas interpret incoming
  nervous signals as specific sounds
• Visual area of the occipital lobe helps you
  understand and identify images
• If a specific part of the brain is damaged, for
  example the Primary Taste Area, you would not be
  able to taste things.

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__________CEREBRUM
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SPINAL CORD

• Structure Outer part composed of white matter
• - Interior part composed of gray matter
• Function center of all spinal cord reflexes
• - sensory tracts conduct impulses ___ the
  brain.
• - motor tracts conducts impulses ____ the
  brain

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Cutting the Cord

• Completely severing the spinal cord produces a
  loss of sensation for all areas below the cut,
  called anesthesia.
• It also produces a loss of the ability to make
  voluntary movements, called paralysis.

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Peripheral Nervous System (PNS)Cranial and
Spinal Nerves

• Function
• Cranial Nerves
• - 12 pairs of cranial nerves
• - Functions vary

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SPINAL NERVES

• Structure contain dendrites of sensory neurons
  and axons of motor neurons
• Function conduct impulses necessary for
  sensations and voluntary movements

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Autonomic Nervous System (ANS)

• Structure Consists of motor neurons that conduct
  impulses from spinal cord or brainstem to
• 1. Cardiac Muscle tissue
• 2. Smooth muscle tissue
• 3. Glandular epithelial tissue
• Function

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2 Divisions of ANS

• 1. Sympathetic nervous system
• -Structure
• -Function

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2 Divisions of ANS

• 2. Parasympathetic Nervous System
• Structure
• Function

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Autonomic Neurotransmitters

• Each division of the ANS signals its effectors
  with a different neurotransmitter.
• This is how an organ can tell which division is
  stimulating it.
• Ex. The heart responds to acetylcholine from the
  parasympathetic division by slowing down. If
  norepinephrine, from the sympathetic division, is
  present, the heart speeds up.

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ANS as a Whole

• Regulates the bodys autonomic functions in ways
  that maintain HOMEOSTASIS