The Nervous System

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The Nervous System

• Anatomy Physiology 2

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Organization of the nervous System

• Central nervous system (CNS) the brain and
  spinal cord
• Interprets incoming sensory information and
  issues instructions based on past experiences and
  current conditions
• Peripheral nervous system (PNS) the nerves that
  extend from the brain and spinal cord
• Link and carry all the information to the CNS

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Organization of the nervous System

• The PNS is divided into 2 subdivisions
• Sensory division keeps the CNS informed of
  events going on both inside and outside the body
• Motor division activates muscles and glands

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Organization of the nervous System

• The motor division has two subdivisions
• Somatic nervous system voluntary controls the
  body
• Autonomic nervous system regulates involuntary
  activities

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Nervous Tissue

• Nerve Cells
• The main part of the nervous system
• The human body contains numerous nerve cells
• Nerve cells are called neurons
• Neurons are similar to electrical wires and carry
  messages along long, thin strands
• They can reach up to a meter in length
• A nerve is a bunch of neurons bunched together

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Nervous Tissue

• Nerve Cells
• Have all the organelles that other cells have,
  but look very different
• Dendrites receive information from other neurons
• Axons sends information to other neurons
• A synapse is a connection between 2 neurons

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Nervous Tissue

• Nerve fibers are covered with a whitish, fatty
  material called myelin
• When the myelin completely cover the nerve cells
  it called the myelin sheath
• Its function is to make nerve cells faster

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Nervous Tissue

• Not all cells are mylinated
• In the brain there are dense collections of
  myelinated regions called white matter and dense
  collections of unmyelinated regions called gray
  matter

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Pathway of Messages

• Information is sent on 2 different pathways it
  is not the same pathway
• For example if you touch something hot the
  information is sent to your brain on one pathway
  and the result of touching something hot (it
  burns) is sent on another pathway
• Nerve cells do not touch one another the
  information skips across the synapse

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Nervous System Parts

• Nerve cells are important parts of the nervous
  system, but others include
• The brain
• The organ that sends, receives and processes
  information from all body parts
• It is made of billons of neurons
• Spinal cord
• Carries information from the brain to the body
• All information from the body is first sent to
  the spinal cord, then to the brain

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The Brain
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The Brain

• Parts
• Cerebrum
• Diencephalon (interbrain)
• Brain stem
• Cerebellum

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The Brain

• Cerebrum
• The cerebrum has two cerebral hemispheres
• Has elevated ridges of tissue called gyri and
  shallow grooves called sulci which provide
  landmarks
• Controls thought, reason, senses, speech, memory,
  consciousness, interpretation of sensation and
  voluntary movement

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The Brain

• Cerebrum
• Occipital lobe visual area
• Temporal lobe auditory area
• primary motor area controls movement
• Brocas area involved in speech
• Frontal lobe intellectual reasoning and
  socially acceptable behavior

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The Brain

• Cerebrum
• Corpus callosum connects the cerebral
  hemispheres
• Diencephalon
• Sits atop the brain stem
• Contains the thalamus, hypothalamus and
  epithalamus

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The Brain

• Diencephalon
• Thalamus quickly recognizes pleasant or
  unpleasant sensations
• Hypothalamus controls body temp, water balance
  and metabolism also drives emotions
• Epithalamus important to the endocrine system

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The Brain

• Brain stem
• About the size of a human thumb
• 3 parts midbrain, pons, medulla oblongata
• Midbrain controls and directs incoming impulses
• Pons helps control breathing
• Medulla oblongata controls heart rate, blood
  pressue, breathing, swallowing and digestion

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The Brain

• Cerebellum
• Has two hemispheres
• Large cauliflower-like structure under the
  occipital lobe
• Helps make movement smooth and not robot-like and
  controls balance

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Nervous System Parts

• Spinal Cord
• About 17 inches long
• Can be thought of as the power lines from the
  power plant
• Spinal cord is protected by vertebrae (series of
  bones)
• Is a two-way passage system
• All the nerves that extend from the spinal cord
  are called body nerves

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Reflexes

• Reflexes are reactions that are quick and
  protective
• During a reflex the message does not reach the
  brain first, but reacts, then tells the brain the
  information
• How a reflex works
• If you put your hand on a hot stove the
  information is sent to your spinal cord through
  one pathway, through another pathway information
  is sent back to your hand to move, along yet
  another pathway information is sent to your brain
  and finally through another pathway information
  is sent to your hand that it hurts