Chapter 31 Notes The Nervous System

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Chapter 31 NotesThe Nervous System
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The Nervous System

• is a rapid communication system using electrical
  signals.
• enables movement, perception, thought, emotion
  and learning.
• consists of a network of specialized cells called
  neurons.

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Neuron structure

• Cell Body central part of neuron, maintains cell
  function, relays signals from one part of cell to
  another.
• Dendrites extend from cell body, receive
  information from other cells.

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• Axon long extension from the cell body,
  transmits signals to other neurons, ends in an
  axon terminal. Many axons are insulated with
  myelin which improves the efficiency of signal
  transmission.
• Synapse where the axon terminal connects with
  another neuron, separated by a gap called the
  synaptic cleft.

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Axon terminal
axon
Cell body
dendrites
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• Neuron function
• Neurons transmit signals down axons by altering
  the flow of sodium and potassium ions across
  their membranes in response to chemical signals.
  The resulting imbalance of electrical charges
  inside vs. outside the axon creates an electrical
  voltage potential (an action potential) that is
  propagated down the length of the axon.

• Nerve A bundle of several neurons and supporting
  cells.

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• When an electrical impulse reaches the axon
  terminal, it stimulates the release of
  neurotransmitters from the pre-synaptic neuron
  into the synaptic cleft. These chemical
  messengers bind receptors on the surface of the
  post-synaptic neuron and either stimulate or
  inhibit an action potential in it.

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• Most psychoactive drugs function by mimicking or
  interfering with the function of
  neurotransmitters and/or their receptors.

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Structure of the Nervous System

• Divided into two parts
• Central Nervous System (CNS)
• Interprets and responds to information
• Consists of the Brain Spinal Cord

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• Peripheral Nervous System (PNS), which contains
• Sensory neurons that send info (sight, smell,
  touch, sound, taste, pain) to the CNS.
• Motor neurons that send commands from CNS to
  muscles and other organs. Divided into
• Somatic nervous system controls skeletal muscles
  that are under conscious control
• Autonomic nervous system controls smooth muscles
  that are not under conscious control (i.e. the
  heart, diaphragm, digestive system)

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• Parts of the Brain
• Cerebrum (green)
• Largest part of the brain, divided into two
  hemispheres.
• Handles learning, memory, perception and
  intellectual functions.
• Left hemisphere processes sensations from and
  controls movement on the right side of the body,
  the right hemisphere does the same for the left
  side of the body.

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• Cerebellum (blue)
• Regulates balance, posture and movement
• coordinates the moving of several muscles
  together (i.e. for walking)

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• Brain Stem a collection of several structures at
  the base of the brain. (yellow)
• Midbrain, pons and medulla oblongata relays
  information and regulates homeostasis and vital
  body functions.
• Thalamus central relay center for all sensory
  information traveling from the body to the brain.
• Hypothalamus regulates homeostasis and the
  endocrine system.

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