Cell Specialization and the Nervous System

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Cell Specialization and the Nervous System
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One or Many???

• A single-celled organism is called unicellular.
• Examples bacteria, algae (plant), yeasts (fungi)
• These organisms perform ALL of their functions in
  ONLY ONE CELL!!!
• Multicellular organisms are made up of MANY
  cells.
• These organisms have cell specializationdifferent
  types of cells for different jobs/purposes.
• As cells specialize, only DNA related to the
  functions of a particular cell remains active.

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Stem Cells

• All cells in your body came from a single
  fertilized cell.
• Most cells become specialized before birth. Once
  a cell becomes specialized, it cannot be changed
  into another type of cell.
• Stem cells are cells that have not become
  specialized.
• Stem cells can be found in
• developing embryos
• Adult bone marrow

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Levels of Organization

• Cells Example Neuron
• Tissuesa group of similar cells working together
• Example Nervous Tissue
• Organsa group of similar tissues working
  together
• Example Brain, Spinal Cord, Eye
• Organ Systemsa group of organs working together
• Example nervous system

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Cells What Do They Really Look Like?
Muscle cells
Kidney cell
Nucleus
Cells have dramatically different shapes and
sizes.
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Human Nervous System

• Controls and coordinates body activities
• Nervous System of complex animals
• Brain
• Spinal Cord
• Neurons

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Human Neuron Diagram
Dendrite
Cell body
Myelin sheath
Axon
Node of Ranvier
Axon terminals
Neurons are specialized cells that transmit
impulses throughout the body.
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Neuron Structure

• 3 Main Parts
• Cell Bodycontains nucleus and organelles
• Axonsingle long projection that extends from the
  cell body usually has a branched end
• Carries messages away from the cell body
• Dendritesshort, slender branches that extend
  from the cell body
• Carry messages toward the cell body

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Neuron Communication

• Neurons communicate with other neurons and organs
  using an electrical signal called nerve impulse.
• Nerve impulsedifference in the number of sodium
  and potassium ions inside and outside of the
  nerve cell this creates a difference in
  electrical charge.
• Action Potentiala sudden change in the
  electrical charge of a neuron
• Neurons communicate with each other and with the
  tissues and organs they affect, but they do not
  touch.

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Synapse

• Synapsethe axon of one neuron, a dendrite of
  another and the space between them
• Neurons communicate chemically across the
  synaptic gap.
• Neurotransmittersmolecules that carry the nerve
  impulse across the synaptic gap usually proteins
• As long as neurotransmitters are bound to the
  receptor site, the neuron will continue
  generating impulses.
• Neurotransmission Animation

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Sense Organs

• Animals have sense organs that enable them to
  monitor what is happening in their surroundings.
• Sense Organs Eyes, Ears, Mouth, Nose, and Skin
• Each organ detects a different type of stimulus
  through sensory receptors.
• Sensory receptors are specialized structures at
  the ends of sensory neurons that respond to
  specific types of stimuli.
• These receptors convert the stimuli to nerve
  impulses that are carried by neurons to the
  brain, where the impulses are interpreted.