The Nervous System

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The Nervous System
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I. The Nervous System

• A. The Nervous system controls coordinates
  functions throughout the body and responds to
  internal external stimuli.
• Choreographing a dance, Writing a song,
  Practicing lines in a play.have one thing in
  common.

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II. Neurons

• A. Messages that are carried by the nervous
  system are called impulses and travel along
  neurons.
• B. Neurons can either be a sensory, motor or
  interneurons but all have the same structures
  including
• 1. Cell Body contains nucleus, most of
  cytoplasm most metabolic activity takes place
  here.
• 2. Dendrites branched extensions, receive
  signals
• 3. Axon carries impulses across neuron to
  another (covered by myelin)

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III. Nerve Impulse

• A. An impulse begins when a neuron is stimulated
  by another neuron or by the environment.
• B. The flow of an impulse is similar to an
  electrical current through a wire as charged ions
  move along ion pumps across the neuron membrane
  changing the energy potential.

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IV. The Synapse

• A. The synapse is where one neuron transmits the
  impulse to another neuron. (synaptic terminal)
• Ex. Motor neuron pass impulse to muscle cell
• B. The synaptic cleft is the space between
  neurons where neurotransmitters (chemicals used
  by neurons) to transmit an impulse.

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V. Ion Pumps Membrane Potential

• A. All neurons have a membrane potential. A
  difference between the inside of the cell
  (negative) and extracellular fluid (positive).
• 1. Polarized state resting potential (-70mV)
• B. Sodium-Potassium pump maintains the
  polarization by pumping ions that leak across the
  membrane
• 1. In order for the nerve to fire a stimulus it
  must be strong enough to overcome the resting
  potential (threshold)

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V. Ion Pumps Membrane Potential

• C. Neurons have gated-ion channels that
  open/close in response to a stimulus.
• 1. Only allowing one kind of ion to flow through
• D. If a stimulus triggers a sodium-ion gated
  channel to open sodium flows into the cytoplasm
  resulting in a decrease in polarization, becoming
  somewhat depolarized (making it easier for the
  nerve to fire). The opposite occurs if
  potassium-ion channel is stimulated and membrane
  is hyperpolarized.

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V. Ion Pumps Membrane Potential

• E. An action potential, impulse, can only be
  generated in an axon of a neuron.
• 1. When this occurs and the axon is stimulated
  the sodium channels open and sodium ions flood in
  the cell, potassium channels open and flood
  potassium out as a response causing a wave of
  depolarization reversing the action potential
  which only lasts a short time.
• F. The sodium-potassium pump restores the
  membrane to the original polarized condition
  (repolarization) or refractory period

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VI. Division of the Nervous System

• A. The human nervous system can be divided into
  2 parts
• 1. Central nervous system relays messages,
  processes analyzes information
• 2. Peripheral nervous system transmits impulses
  from sense organs to central nervous system
  vice-versa

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VII. Central Nervous System

• A. Central nervous system includes the brain
  spinal cord.
• 1. These are surrounded by meninges
  cerebrospinal fluid to not only act as a shock
  absorber but also allows exchange of nutrients
  and waste products

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VII. Central Nervous System

• B. The Brain (consists of over 100 bill neurons)
• 1. Cerebrum largest most prominent region of
  brain
• a. Responsible for voluntary activities, site for
  intelligence/learning judgment
• b. Divided into regions called lobes based off
  the skull bones that surround the lobe (frontal,
  temporal, parietal, occipital)

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• 2. Cerebellum second largest region of brain,
  located at the back of the skull.
• a. coordinates balances actions of the muscles
• 3. Brain stem located below cerebellum
  connecting brain to spinal cord consists of the
  pons medulla oblongata
• a. control blood pressure, heart rate, breathing
  swallowing

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• 4. Thalamus found between brain stem
  cerebrum,
• a. receives messages from sensory receptors
  relays message to cerebrum
• 5. Hypothalamus control/analyze hunger, thirst,
  fatigue, anger body temp. works with endocrine
  as well.
• 6. Spinal Cord communication between brain
  rest of body (31 pairs of nerve branches).
  Processes reflexes directly.

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IIX. Peripheral Nervous System

• A. Peripheral nervous system consist of all the
  nerves, ganglia associated cells that are not
  part of the brain spinal cord.
• B. The peripheral is divided further into 2
  systems
• 1. Somatic nervous system
• 2. Autonomic nervous system

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• 1. Somatic nervous system regulates activities
  that are under conscious control
• a. allow quick reflex movement due to reflex
  arcs inborn, automatic protective. Only goes
  to spinal cord

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• 2. Autonomic nervous system regulates
  activities that are automatic, or involuntary
  movement
• a. Divided into 2 parts farther that oppose one
  another actions sympathetic parasympathetic
• Ex. Sympathetic speed up heart rate during a run
  while the parasympathetic will decrease the heart
  rate when you finish