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Nervous System Communication. Kid Concussions In The News. Neurons . Nerve cells Parts of neurons Cell body Long extensions (fibers=dendrites or axons) Message = nerve impulse. Animal Nervous Systems. Sponges – no nervous system Other animals all have neurons in systems. Nerve Net.

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Kid ConcussionsIn The News


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Neurons

  • Nerve cells

  • Parts of neurons

    • Cell body

    • Long extensions (fibers=dendrites or axons)

  • Message = nerve impulse


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Animal Nervous Systems

  • Sponges – no nervous system

  • Other animals all have neurons in systems


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Nerve Net

  • In all cnidarians

  • Interconnected nerve cells

  • No brain


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Ringlike Nervous System

  • In echinoderms

  • Ring with 5 radiating nerves


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Ladderlike Nervous System

  • In many Platyhelminthes

  • Some have distinct brain (ganglia)


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Annelid Nervous System

  • Segmental ganglia

    • Ganglia = aggregations of nervous tissue

  • Ventral nerve cord & brain

    Arthropod

    Mollusks(depends

    level of activity) some have

    giant fibers


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Vertebrate Nervous System

  • Central nervous system

    • Brain & spinal cord

  • Peripheral nervous system

    • Nerves to & from CNS


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Nerve Cells(Neurons)

  • Cell body

    • Contains nucleus and organelles

    • Produces substances necessary for cell to live & function

  • Axon (conducts or passes on impulse)

    • Long cell extension

    • May have myelin covering

  • Dendrites (receive impulse)

    • Usually short cell extensions

    • No myelin covering

    • most neurons have multiple dendrites


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Sensory Neurons

  • Receive information from sense organ receptors

  • Transmit to the central nervous system

  • Cell bodies of sensory neurons lie near the CNS


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Motor Neurons

  • Transmit commands away from CNS to effector (muscle or gland)

  • Each neuron has one long axon

  • Cell bodies on most motor neurons lie in or near CNS


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Interneurons

  • Located within brain & spinal cord

  • Integrate information

  • Axons may or may not be myelinated

  • usually axons are shorter than those in PNS


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Neuroglia

  • Nerve support cells

  • Provide support, protection, & nutritional stability

  • Schwann cells (special neuroglial cells)

    • Found around axons

    • Produce myelin sheath

  • Oligodendrocytes – produce myelin sheath around some CNS axons


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Myelin Sheath

  • Insulates axon

  • Nodes of Ranvier-allows impulse to move at a greater speed along axon

  • Uninsulated areas- no myelin sheath


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Nerve Impulses

  • Electrical signals transmitted along membranes of nerves


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Resting Potential

  • Neuron is electrically charged at rest

  • Outside is positively charged

  • Inside is negatively charged


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Sodium-Potassium Pump

  • Proteins embedded within cell membrane

  • Moves sodium to the outside

  • Moves potassium to the inside

  • Maintains resting potential

  • Requires energy (ATP)


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Action Potential

  • Nerve impulse is started by a stimulus

  • Stimuli cause movements of ions through membrane

  • Threshold potential

    • Sufficient stimulation to depolarize membrane

  • Action potential

    • Rapid reversal of membrane electric potential


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Nerve Transmission

  • Action potential at one point depolarizes next area

  • Depolarization moves in self-propagating wave


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Saltatory Conduction

  • Nerve impulse jumps & moves faster along myelinated axon


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Synapse

  • Area where nerve communicates

  • Transfers message

    • Another neuron

    • An effector


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Synaptic Cleft

  • Neurons do not touch other neurons or effector cells

  • Nerve impulse must cross gap (electrical signal is changed to a chemical signal)


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Neurotransmitters

  • Organic molecules (> 60 different chemicals)

  • Transfer message across synaptic cleft

  • Attach to receptors on target cell


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Neuromuscular Junctions

  • Synapse between neuron & skeletal muscle

  • Neurotransmitter is aceytylcholine


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Neuron to Neuron Connections

  • Uses many different neurotransmitters

    (such as dopamine, norepinephrine, serotonin)

  • Some cause different effects

    • Excitatory synapse – continuation of impulse

    • Inhibitory synapse – reduce ability to depolarize


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Integration of Nerve Impulses

  • Summed impulses determine if postsynaptic neuron will depolarize


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Human Nervous System

  • Central nervous system

    • Brain

    • Spinal cord

  • Peripheral nervous system

    • Brings messages to & from CNS

    • Somatic nervous system – voluntary

    • Autonomic nervous system - involuntary


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Central Nervous System

  • Integrates sensory & motor impulses


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Spinal Cord

  • Connects peripheral nervous system with brain

  • Receives information via spinal nerves

  • Includes reflex arcs


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CNS Protection - Meninges

  • Layers of membranes

    • Dura mater

    • Arachnoid

    • Pia mater


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Peripheral Nervous System

  • Sensory & motor impulses

  • Cranial nerves communicate directly with brain,

    some are strictly sensory or motor, some are mixed.


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Spinal Nerves

  • Sensory & motor nerve fibers

  • 31 pairs and all are mixed nerves

  • Travel directly to spinal cord

  • Nerves are bundled to form mixed nerves


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Motor Neuron Systems

  • Somatic nervous system, part of PNS

    • Voluntary

    • Movements of skeletal muscles

    • requires a single motor neuron

    • Reflex = automatic response to nerve stimulation

  • Autonomic nervous system, part of PNS

    • Involuntary motor pathways

    • requires two motor neurons


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Divisions of the Autonomic Nervous System

  • Parasympathetic

    • Acetylcholine is the neurotransmitter

    • Prevails during periods of inactivity

    • Housekeeping

  • Sympathetic

    • Norepinephrine is the neurotransmitter

    • “fight or flight”

    • Responds to stress

    • Prepares body for action

  • Parasympathetic & sympathetic together help to maintain homeostasis


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Psychoactive Drugs

  • Affect action of neurotransmitters

    In specific parts of the brain

  • Some are abused


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Drug Addiction

  • Chronic use (or abuse) of psychoactive drugs

  • Person becomes physically dependant

  • Drug use tends to increase due to drug tolerance



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