The Nervous System

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The Nervous System
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• The NERVOUS SYSTEM controls and coordinates
  functions throughout the body and responds to
  internal and external stimuli

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The Nervous System can be broken into two parts

• The CENTRAL NERVOUS SYSTEM composed of the brain
  and the spinal cord
• The PERIPHERAL NERVOUS SYSTEM composed of all
  the nerves that arent part of the brain or
  spinal cord

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Central Nervous System

• The skull and vertebral column protect the brain
  and spinal cord
• The brain and spinal cord are protected in three
  layers of tissue called MENINGES
• The space between the meninges and the brain and
  spinal cord is filled with CEREBROSPINAL FLUID,
  which acts as a shock absorber and helps protect
  the central nervous system.

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Parts of the Brain

• CEREBRUM contains the frontal, parietal,
  occipital, and temporal lobes
• CEREBELLUM
• BRAIN STEM
• THALAMUS and HYPOTHALAMUS

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The Cerebrum

• Folds in the Cerebrum increase the surface area
  of the brain
• Responsible for voluntary actions, intelligence,
  learning, and judgment
• Divided into two hemispheres, left and right
• Outer Layer Gray matter composed of nerve cell
  bodies
• Inner Layer White matter composed of bundles of
  axons with myelin sheaths

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• The Cerebellum
• Second largest region of the brain
• Located in the back of the skull
• Responsible for balance and muscle coordination
• The Brain Stem
• Connects the brain to the spinal cord
• Regulates the flow of information from the brain
  to the rest of the body
• Controls basic life functions, such as heartbeat,
  breathing, swallowing, etc

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Thalamus and Hypothalamus

• Located between the brain stem and the cerebellum
• The THALAMUS receives signals from the body and
  sends them to the cerebrum to be processed
• The HYPOTHALAMUS recognizes and analyzes hunger,
  thirst, fatigue, anger, and body temperature.

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The Spinal Cord

• Communication line between the brain and the rest
  of the body
• Made up of bundles of nerves that branch out into
  the rest of the body
• Processes REFLEXES, quick responses to stimuli

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Peripheral Nervous System

• SENSORY DIVISION transmits impulses from the
  sense organs to the brain
• MOTOR DIVISION transmits impulses from the brain
  to the muscles or glands

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Peripheral Nervous System

• SOMATIC regulates voluntary impulses
• AUTONOMIC - regulates the involuntary body
  functions

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SIGHT
Light is focused through the LENS onto the
RETINA. Images are transmitted from the retina to
the brain through the OPTIC NERVE
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HEARING vibrations from noise in the air are
sensed by three tiny bones in the ear, the
HAMMER, ANVIL, and STIRRUP. These create pressure
waves in the fluid of the COCHLEA, which contains
tiny hairs that wave back and forth. The motion
of these hairs produce the nerve impulses that
are sent to the brain
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SMELL

• SCENT is the detecting of trace amounts of
  chemicals
• CHEMORECEPTORS in the lining of the nasal
  passages detect these chemicals and send an
  impulse to the brain
• Smell is closely tied to memory and feeling, and
  can generate responses in people almost
  immediately

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Taste

• Taste is closely related to smell, and taste is
  the detection of chemicals by chemoreceptors on
  the tongue
• Tastes are classified as bitter, sour, salty, and
  sweet
• The human mouth has over 10,000 taste buds, even
  on the roof!

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TOUCH

• Nerve endings in the skin respond to temperature,
  touch and pain
• The areas that are most sensitive to touch have
  the highest concentration of nerve endings the
  feet, hands, and face

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How are messages moved in the nervous system?
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NEURONS are cells that transmit messages, called
IMPULSES, through the nervous system
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The CELL BODY contains the NUCLEUS and most of
the cytoplasm, metabolic activity of the cell
takes place here
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DENDRITES branch out from the cell body, and they
carry impulses from the environment or from other
neurons toward the cell body
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The AXON carries impulses away from the cell
body. The axon is covered in a membrane called
the MYELIN SHEATH. There are gaps in the myelin
sheath, called NODES. The signal can jump from
node to node, increasing the speed of the impulse.
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• http//animations.3d4medical.com/Nerve-impulse-ani
  mation_AN2162.html

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A RESTING NEURON is one that is not transmitting
an impulse.
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A neuron can transfer a signal to another cell at
locations called SYNAPSES. At the synapse,
chemicals called NEUROTRANSMITTERS are released,
which sends the impulse to receptors in an
adjacent cell.