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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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neurons
Neurons
  • Nerve cells
  • Parts of neurons
    • Cell body
    • Long extensions (fibers=dendrites or axons)
  • Message = nerve impulse
animal nervous systems
Animal Nervous Systems
  • Sponges – no nervous system
  • Other animals all have neurons in systems
nerve net
Nerve Net
  • In all cnidarians
  • Interconnected nerve cells
  • No brain
ringlike nervous system
Ringlike Nervous System
  • In echinoderms
  • Ring with 5 radiating nerves
ladderlike nervous system
Ladderlike Nervous System
  • In many Platyhelminthes
  • Some have distinct brain (ganglia)
annelid nervous system
Annelid Nervous System
  • Segmental ganglia
    • Ganglia = aggregations of nervous tissue
  • Ventral nerve cord & brain

Arthropod

Mollusks(depends

level of activity) some have

giant fibers

vertebrate nervous system
Vertebrate Nervous System
  • Central nervous system
    • Brain & spinal cord
  • Peripheral nervous system
    • Nerves to & from CNS
nerve cells neurons
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
sensory neurons
Sensory Neurons
  • Receive information from sense organ receptors
  • Transmit to the central nervous system
  • Cell bodies of sensory neurons lie near the CNS
motor neurons
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
interneurons
Interneurons
  • Located within brain & spinal cord
  • Integrate information
  • Axons may or may not be myelinated
  • usually axons are shorter than those in PNS
neuroglia
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
myelin sheath
Myelin Sheath
  • Insulates axon
  • Nodes of Ranvier-allows impulse to move at a greater speed along axon
  • Uninsulated areas- no myelin sheath
nerve impulses
Nerve Impulses
  • Electrical signals transmitted along membranes of nerves
resting potential
Resting Potential
  • Neuron is electrically charged at rest
  • Outside is positively charged
  • Inside is negatively charged
sodium potassium pump
Sodium-Potassium Pump
  • Proteins embedded within cell membrane
  • Moves sodium to the outside
  • Moves potassium to the inside
  • Maintains resting potential
  • Requires energy (ATP)
action potential
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
nerve transmission
Nerve Transmission
  • Action potential at one point depolarizes next area
  • Depolarization moves in self-propagating wave
saltatory conduction
Saltatory Conduction
  • Nerve impulse jumps & moves faster along myelinated axon
synapse
Synapse
  • Area where nerve communicates
  • Transfers message
    • Another neuron
    • An effector
synaptic cleft
Synaptic Cleft
  • Neurons do not touch other neurons or effector cells
  • Nerve impulse must cross gap (electrical signal is changed to a chemical signal)
neurotransmitters
Neurotransmitters
  • Organic molecules (> 60 different chemicals)
  • Transfer message across synaptic cleft
  • Attach to receptors on target cell
neuromuscular junctions
Neuromuscular Junctions
  • Synapse between neuron & skeletal muscle
  • Neurotransmitter is aceytylcholine
neuron to neuron connections
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
integration of nerve impulses
Integration of Nerve Impulses
  • Summed impulses determine if postsynaptic neuron will depolarize
human nervous system
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
central nervous system
Central Nervous System
  • Integrates sensory & motor impulses
spinal cord
Spinal Cord
  • Connects peripheral nervous system with brain
  • Receives information via spinal nerves
  • Includes reflex arcs
cns protection meninges
CNS Protection - Meninges
  • Layers of membranes
    • Dura mater
    • Arachnoid
    • Pia mater
peripheral nervous system
Peripheral Nervous System
  • Sensory & motor impulses
  • Cranial nerves communicate directly with brain,

some are strictly sensory or motor, some are mixed.

spinal nerves
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
motor neuron systems
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
divisions of the autonomic nervous system
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
psychoactive drugs
Psychoactive Drugs
  • Affect action of neurotransmitters

In specific parts of the brain

  • Some are abused
drug addiction
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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