Dont get Nervous

1
Dont get Nervous!

• An Intro to the Human Nervous System and Neuron
  Structure

2
Overview the Brain as a Control Center

• The human brain contains about 100 billion nerve
  cells, or neurons
• Each neuron may communicate with thousands of
  other neurons
• Functional magnetic
• resonance imaging (MRI) is a
• technology that can reconstruct
• a three-dimensional map of
• brain activity

3
Organization of Nervous Systems

• All animals except sponges have
• a nervous system
• What distinguishes nervous systems of different
  animal groups is how neurons are organized into
  circuits
• The simplest animals with nervous systems, the
  cnidarians, have neurons arranged in nerve nets

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Invertebrate Nervous Systems
LE 48-2a
Radial nerve
Nerve ring
Nerve net
Hydra (cnidarian)
Sea star (echinoderm)
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LE 48-2d
Brain
Spinal cord (dorsal nerve cord)
Brain
Sensory ganglion
Ganglia
Squid (mollusc)
Salamander (chordate)
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Vertebrate Nervous Systems

• In vertebrates, the central nervous system
  consists of a brain and dorsal spinal cord
• All other parts of the nervous system which relay
  information between the central nervous system
  and other parts of the body peripheral nervous
  system
• The peripheral nervous system (PNS) connects to
  the central nervous system (CNS)

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Central nervous system (CNS)
Peripheral nervous system (PNS)
Brain
Cranial nerves
Spinal cord
Ganglia outside CNS
Spinal nerves
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Nervous systems process information in three
stages sensory input, integration, and motor
output
Sensory input
Sensor
Integration
Motor output
Effector
Central nervous system (CNS)
Peripheral nervous system (PNS)
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Neuron Types

• Sensory neurons transmit information from sensors
  that detect external stimuli and internal
  conditions carry impulses from receptors to the
  CNS
• Sensory information is sent to the CNS, where
  interneurons integrate the information
• Motor output leaves the CNS via motor neurons,
  which communicate with effector cells to produce
  responses
• The three stages of information processing are
  illustrated in the knee-jerk reflex

10
Gray matter
Cell body of sensory neuron in dorsal
root ganglion
Quadriceps muscle
White matter
Hamstring muscle
Spinal cord (cross section)
Sensory neuron
Motor neuron
Interneuron
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Reflex Arc

• The simplest nerve pathway
• A neural circuit that travels only through the
  spinal cord, not the brain
• Provides a framework for a reflex action
• Stimulus is detected by sensory neuron ?
• relayed to the inter- or motor neuron in the
  spinal cord ? a response is transmitted via the
  motor neuron ? the effector cell responds

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Neuron Structure

• Most of a neurons organelles are in the cell
  body
• Most neurons have dendrites, highly branched
  extensions that receive signals from other
  neurons
• The axon is typically a much longer extension
  that transmits signals to other cells at synapses
• Many axons are covered with a fatty protein for
  insulation myelin sheath

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Neuron Structure
Dendrites
Cell body
Nucleus
Synapse
Signal direction
Axon hillock
Axon
Presynaptic cell
Synaptic terminals
Myelin sheath
Postsynaptic cell
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Now YOU get to Build a Neuron

• In your lab groups, build a neuron
• Use the materials at your lab bench however you
  want to make a sensory or a motor neuron (see p.
  413)
• Mount your representation onto a piece of paper
  and label the parts OR use pins to label
• - Dendrites - Myelin Sheath
• - Synapse - Axon hillock
• Axon - Cell body
• Pre-synaptic cell - Post-synaptic cell
• Schwann cell - Node of Ranvier
• Be creative and have fun!