1. Unit 2 Notes: Neurons & Nervous System Organization

2. (1) Neurons
Neuron: Nervous System cells found individually in the brain and spinal cord, and peripheral tissue.
There are 2 Types of Neurons: Multipolar and Unipolar
Every Neuron has the same structural parts:
Dendrites  Receive incoming messages.
Cell Body  Integrate and process incoming messages.
Axon  Send outgoing messages.
Myelin Sheath  Increases the rate of nerve impulses.
Axon Terminal  Releases neurotransmitters.

6. (2) Unipolar Neurons
Used to transmit “afferent” / “sensory” input messages TO the central nervous system.
Do NOT process incoming messages, therefore dendrites do not need to be next to the cell body.

7. (3) Multipolar Neurons
Used to transmit “efferent” / “motor” output messages FROM the central nervous system.
They DO process incoming messages, so their dendrites ARE next to the cell body.

8. (4) Nervous System Organization
Your nervous system is organized into different levels of communicative neurons.
All stimuli messages going to the brain are transmitted through the Sensory / Afferent Division of your nervous system.
Outgoing messages travel either through the:
Autonomic or Somatic Division
Sympathetic or Parasympathetic Division

10. (5) Defining The Levels
Sensory = Afferent = Going TO the central nervous system
Motor = Efferent = Going AWAY from the central nervous system
Somatic = Voluntary
Autonomic = Involuntary
Sympathetic = Emotional
Parasympathetic = Non-Emotional

11. (6) Other Terms to Know
Central Nervous System: Brain, Brain Stem, Spinal Cord
Stimuli / Stimulus = Something that triggers a response