​​​​​​​ The Nervous System

By: Mackenzie Keogh and Seth Brown



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Neuron


The Nervous System

  • The role of the nervous system is to monitor changes inside and outside of the body, also to process and interpret sensory input and cause a response by activating muscles or glands.
  • Functions:
    • Sensory Input: Gathered information for sensing changes inside and outside the body.
    • Integration: Process and interpretations of sensory input to make decisions about what response should be made.
    • Motor Output: Affecting a response by activating muscles and glands.

Peripheral Nervous System

  • The peripheral nervous system carries impulses to and from the stem and spinal cord.
  • Neurons
    • Function of Neurons: Transmit messages throughout the body.
    • Structure of a Neuron:
      • Dendrites: Convey incoming messages towards the cell body.
      • Axons: generate nerve impulses and conduct them away from the cell body.
      • Cell Body: Metabolic center of the neuron.
      • Axon Terminals: contains vesicles that hold neurotransmitters.
      • Synaptic Cleft: Gap that seperates axon terminal from next neuron.
      • Myelin: Protects and insulates fibers and increases the transmission rate of nerve impulses.
      • Schwann Cells: Specialized supporting cells that wrap themselves tightly around the axon like a jelly-roll.
      • Myelin Sheath: Tight coil of wrapped membranes that enclose the axon when the wrapping process is done.
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Neuron

  • Three Types of Neurons
    • Functional: Groups neurons according to the direction of the nerve impulse is traveling relative to the Central Nervous System.
      • Sensory: Neurons carrying impulses from sensory receptors.
      • Motor: Neurons carrying impulses from the Central Nervous System to the visceral and muscles and glands.
      • Association: Located in the Central Nervous System. Connect the motor and sensory neurons in neural pathways.
    • Structural: Based on the number of processes extending from the cell body.
      • Multipolar: Several process extending from cell body. Motor and association are the most common structural type.
      • Bipolar: Nerons with two processes: axon and dendrite.
      • Unipolar: Single process emergency from the cell body.
  • A receptor is a peripheral nerve ending specialized for response to particular types of stimuli. Molecule that binds specifically with other molecules (hormones and neurotransmitters).
  • Nerves are essential to functioning. Nerve pain and damage can affect quality of life and can cause serious problems such as muscle atropy, twitching, paralysis, etc.
  • Nerve Stimulants:
    • Light
    • Sound
    • Pressure
    • Neurotransmitters
Action Potential
  • All or nothing: According to the action potential theory an action potential either happens or it simply doesn't. An action potential is illustrated in the following graph. If you would like to see an action potential in motion click here
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Action Potential Graph

    • Resting Potential: Non-conducting, excitable cell, with the inside of the cell more negative than the outside.
    • Threshold Level: Point after which radical changes are likely to occur
    • Refectory Period: Short time immediately after an action potential in which the neuron cannot respond to another stimulus.

    • Polarization
      • Polarized: Plasma membrane of ar resting or inactive neruro, there are fewer positive ions sitting on the inner face of the neurons plasma membrane than there are on its outer face in the tissue fluid that surrounds it.
      • Depolarization: inward rush of sodium ions changes the polarity of the neurons membrane of the site.
      • R​epolarization: Out flow of positive ions from the cell restores the electrical conditions at the membrane to be polarized or resting state.
Central Nervous System
    • Protection for the Central Nervous System:
      • Meninges: Three connective tissue membranes covering and protecting the central nervous system. Double layered membrane surrounding the brain.
      • Cerebrospinal fluid: In and around the brain and spinal cord; forms a watery cushion that protects he fragile nervous tissue from blows and other trauma.
      • Skull: The hard covering surrounding the barin to protect it from blows to the head or trama.
    • The brain in compossed of four seperate regions, all serving different purposes
      • Cerebrum: Controls movement, balance, and equilibrium in the body.
      • Diencephalon: Contols vital functions in the body such as swallowing, visions and hearing.
      • Brain Stem: Controls breathing, heartbeat, and blood pressure.
      • Cerebellum: Provices precise timing for skeletal muscle activity and controls balance and equilibrium within the body.
    • Right Brain vs. Left Brain
      • Right Brain: The right brain controls the emotions and artisitc creativity.
        • emotional feelings
        • imagination
        • symbols and images
        • present and future
        • religion and philosophy
        • appreciates
        • fantasy based
        • risk taking
        • spatial preception
        • impetuous
      • Left Brain: The left brain controls logical, mathematical, and realistic functions.
        • logic
        • detail oriented
        • fact rules
        • language
        • present and past
        • math and science
        • comprehension
        • acknowledgment
        • pattern preception
        • reality based
        • forms strategies
        • practical
        • safe
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If the woman appears to be spinning clockwise, then you use more the right side of your brain and vice versa.

  • Corpus Callosum: Connects the cerebral hemispheres. Allows the cerebral hemespheres to communicate with one another. It's a very large fiber tract of cerebral white matter.
  • Four Lobes of Cerebral Hemispheres
    • Occipital Lobe: Visual impulses
    • Temproal Lobe: Auditory and olfactory impulses
    • Parietal Lobe: Process information from skin receptors (pain, heat, pressure, etc.)
    • Frontal Lobe: Oversees control of skeletal muscles
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Four Lobes of Cerebral Hemispheres

  • Major Structures of Diencephalon
    • Thalamus: Relay station for sensory impulses passing upward to the sensory cortex.
    • Hypothalamus: Regulates body temperature, water balance, and metabolism.
    • Pituitary Gland: Regulates the glands, thyroid, adrenal cortex, water balance, and lactation.
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Major Structures of Diencephalon

  • Major Structures of Brain Stem
    • Midbrain: Convery ascending and descending impulses. Reflex centers involved with vision and hearing.
    • Pons: Hold important nulei involved in the control of breathing.
    • Medulla Oblongata: Contains nuclei that control heart rate, blood pressure, breathing, swallowing, and vomitting.
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Ma jor Structures of Brain Stem

  • Cerebellum: Provides the precise timing for skeletal muscle activity and controls our balance and equilibrium throughout the body.
  • Making Memories: Memory is a complex system that follows through many different steps. The process of memory begins with encoding, then proceeds to storage until it need to be retrieves. Memory goes through three different stages before it stored into the brain as a long-term memory. The sensory stage, lasting only a split second, the sensory stage allows visuals, sounds, and a touch to last briefly after a stimulation is over. Short-term memory, which can retain roughly seven items no longer than 20-30 seconds. Then, finally, long-term memory, which can store unlimited amounts of information.

Neural Disorders

Some very common neural disorders include Multiple Sclerosis and Alzheimer's disease.
Multiple Sclerosis is the breakdown of the fatty layer that surrounds the Schwann cells of axons called the myelin sheath. The myelin sheath conducts nerve impulses down the length of the axon. So if the myelin sheath has been broken down or removed an action potential cannot be conducted down the length of the axon. This means that Multiple Sclerosis, or the breakdown of the myelin sheath, can cause paralysis. To learn more about Multiple Sclerosis click here.
Alzheimer's is the buildup of a protein called beta amyloid around the synaptic clefts of the neurons in the brains that control memory. This buildup of protein means that memory impulses cannot be transmitted through the brain, this leads to degenrative memory loss, and potentially death as the victim forgets how to feed themselves. Teatment or prevention of Alzheimer's can iclude but are not limited to, a better diet and more excercise. To learn more about Alzheimer's disease click here.

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