The Nervous system

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I can not remember to forget you!
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Who is Lenny and what is his condition?

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What was Lenny like before the accident?

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Will Lenny ever go back to normal?
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The Nervous system

• The Bodys Control Center

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What is the function of the nervous system?

• Input stimulus coming from the environment
  Sensory System
• Respond to stimulus with an output Motor System

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1st Part Central Nervous system (CNS)
How is the nervous system organized?

• Composed of the brain and spinal cord

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2nd Part Peripheral nervous system (PNS)

• Part of nervous system that exists outside CNS
• Connects the CNS to the limbs and organs
• Divided into two branches
• Somatic nervous system (voluntary)
• Autonomic nervous system (involuntary)

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The somatic and autonomic systems are both motor
systems?

• 1. Somatic controls skeletal muscle (voluntary)
• 2. Autonomic controls involuntary muscles and
  glands
• 2a. Parasympathetic normal state
• 2b. Sympathetic alert state

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Nervous Tissue
What is the anatomy of the nervous system?
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What is the nervous tissue made up of?

• Composed of 2 types of cells
• 1. Neuroglia/glial cells
• 2. Neurons

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What are the different types of glial cells in
the CNS?

• Astrocytes metabolic structural support
• Microglia remove debris
• Ependymal cells cover and line cavities
• Oligodendrocytes make insulation myelin.

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What are the different types of glial cells in
the PNS?

• Schwann cells make myelin
• Satellite cells support cells

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What does a neuron look like?
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How are neurons classified?
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Puffer Fish-FUGU

• Delicacy in Japan
• Can die from eating it if not prepared by
  specially certified chefs
• Contain a poison, tetrodotoxin (TTX), that blocks
  NA channels
• How would this cause muscle paralysis?
• Cells cannot depolarize if exposed to TTX, cannot
  fire action potentials, thus, paralysis

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How do neurons work?

• Neurons are excitable cells that can send
  electrical impulses over long distances when
  stimulated via action potentials.

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Electrocution
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How do action potentials work?

• 1. Polarization State cell is resting (high
  negative charge inside cell compared to outside)
• 2. Depolarization State cell is excited,
  channels open up and Na come rushing in (pos.
  inside).
• 3. Repolarization State within milliseconds Na
  gates close K gates open (neg. inside)

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Depolarization
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Repolarization
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Once a nerve fires can it fire again?

• Refractory Period during repolarization
  stimulus can not occur.

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Does every stimulus cause the neuron to respond?

• Stimulus is sent to soma through local
  potentials. If threshold is met action potential
  will occur completely and at the same strength.
  All or None

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How do action potential happen so fast?

• Impulses are conducted from dendrite to axon.
• Speed is determined by diameter of axon and
  presence of myelin.

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Myelin vs. Unmyelinated Axons

• Small, unmyelinated axons have speeds as low as
  0.5 meters/sec while larger, myelinated axons
  have speeds as fast as 100 meters/sec

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What do neurons look like that are myelinated and
unmyelinated?

• In the brain, myelinated axons appear white and
  unmyelinated axons appear gray

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How do neurons communicate between neurons?

• Synapses dendrite/axon connection.

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How do chemical synapses work?

• Impulse arrives at axon terminal causing Ca
  gates to open.
• Influx of Ca causes the release of
  neurotransmitters from the terminal, which will
  then attach to receptors on the dendrite and
  excite the neuron.
• Enzyme will break down nts and stop transmission.

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Types of NTs

• Acetylcholine excitatory to voluntary muscles
  and nerve impulses.
• Norepinephrine excitatory or inhibitory to
  involuntary muscles.
• Epinehrine excitatory or inhibitory for
  behavior and mood pathways.
• Serotonin inhibitory to regulate temp, mood,
  sleep and sensory perception.
• Endorphins inhibitory to sensory pain nts.

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Do all stimulus travel to the brain for
processing?
Reflexes
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What is a reflex?

• Automatic motor response to a specific stimulus.
• Rapid, predictable and involuntary
• Response is often proportionate to stimulus
• Autonomic Reflexes vs. Somatic Reflexes

Function maintain homeostasis by making quick
adjustments
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How does a reflex differ from a cognitive neural
pathway?
Stimulus Spinal Cord -Brain Spinal Cord
-Motor Response
Stimulus Spinal Cord Motor Response
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How does a reflex arc work?
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3
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What is the spinal cord?

• Neural super highway
• Ascending Descending nerves
• Nerve bundles of neuron pathways

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Spinal Cord vs. Vertebral Column

• Total of 31 segments each with a pair of
  nerves.
• Each named based off of location in vertebral
  column (C1, T3, L2, S1 etc.)

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How is the spinal cord protected and nourished?
Meninges
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Whats the difference between a fissure and a
sulcus?
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White vs. Grey Mater Roles
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How does the right side of the body know what the
left side is doing?
Commissure
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How does the spinal cord differentiate between
sensory and motor responses?
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What are some common reflexes?

• Withdrawal reflex
• Startle reflex

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Stretch Reflexes
Prevent overstretching of muscle Important for
posture Equipment Reflex hammer Patellar
reflex assesses L2 to L4 level of spinal
cord Achilles reflex assesses first 2 sacral
segments
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Stretch Reflexes Continued
Bicep reflex assesses C5 and C6 level of spinal
cord Tricep reflex assesses C6 and C7 level of
spinal cord
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Plantar ReflexBabinski
Common in children under 2. If positive after
age 2 damage to spinal cord/brain
connection. Equipment Reflex hammer
handle Normal response--toes curl Positive
Babinski--toes flare Uncoordinated, weakness and
difficulty with muscle control.
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Cranial Nerve Reflexes/Pupillary Reflexes
Absence of normal reflexes severe trauma
deterioration of vital brain tissue due to
metabolic imbalance Equipment Flashlight, dark
room Pupillary light reflex pupil constricts
in response to light
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How do medications work?

• Many medications are designed to modify synapses
• ex Selective serotonin reuptake inhibitors
  (SSRI)
• antidepressants/antianxiety
• prevent cleanup of neurotransmitter, serotonin,
  thus increasing its effects on the receiving cell

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If you wanted to paralyze someone, which NT would
you play with?

• Acetylcholine
• Certain insecticides and terrorist nerve-gases
  are acetylcholinesterase inhibitors
• Paralysis of skeletal muscles, diaphragm, etc.ce

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