enteric nervous system gutgut central nervous system (cns) brainbrain spinal cordspinal cord...
Post on 21-Dec-2015
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Enteric Nervous System
• gutgut
Central Nervous System (CNS)
• brainbrain
• spinal cordspinal cord
Peripheral Nervous System (PNS)
• cranial nerves (12 pr)cranial nerves (12 pr)
• spinal nerves (31 pr)spinal nerves (31 pr)
• Acetylcholine- slows heart rate; PNS • Glutamate- most prevalent neurotransmitter in the brain• Aspartate- in CNS• GABA- inhibitory neurotransmitter• Glycine- inhibitory neurotransmitter• Norepinephrine- awakening from deep sleep• Epinephrine- increase heart rate• Dopamine- movement of skeletal muscles• Seratonin- sensory perception, temp regulation, mood,
sleep• Nitric oxide- may play a role in memory and learning• Enkephalin- inhibit pain impulses by suppressing release
of substance P• Substance P- enhances perception of pain
tyrosine
Converging circuit• same source• Pacinian corpuscles -- pressure• different sources• control of respiration
Diverging Circuit• permits broad distribution of a specific
input typesA. amplificationB. divergence into multiple tracts
Parallel after-charge circuit• several neurons process same
information at one time• each chain has a different number of
synapses, but eventually they all reconverge on a single output
• output neuron may go on firing for some time after input has ceased
• important in withdrawal reflexes• longer-lasting output from small period of
pain
Reverberating Circuit• axons extend back toward the sources of
an impulse and further stimulate the presynaptic neuron
• helps maintain consciousness, muscular coordination, normal breathing, short term memory...
• Mature neurons are amitotic• If the soma of a damaged nerve is intact, axon
will regenerate• Involves coordinated activity among:
– Macrophages—remove debris– Schwann cells—form regeneration tube and
secrete growth factors– Axons—regenerate damaged part
• CNS oligodendrocytes bear growth-inhibiting proteins that prevent CNS fiber regeneration
Figure 13.4 (1 of 4)
Endoneurium
Dropletsof myelin
Fragmentedaxon
Schwann cells
Site of nerve damage
The axonbecomesfragmented atthe injury site.
1
Figure 13.4 (2 of 4)
Schwann cell Macrophage Macrophagesclean out thedead axon distalto the injury.
2
Figure 13.4 (3 of 4)
Fine axon sproutsor filaments
Aligning Schwann cellsform regeneration tube
3 Axon sprouts,or filaments,grow through aregeneration tubeformed bySchwann cells.
Figure 13.4 (4 of 4)
Schwann cell Site of newmyelin sheathformation
4 The axonregenerates anda new myelinsheath forms.
Single enlargingaxon filament
INQUIRY
1. What voltage is the threshold potential?
2. Describe depolarization, repolarization and hyperpolarization.
3. Which ion causes the neurotransmitters to be released across the synapse?
4. Name 2 instances that you can stimulate a neuron to depolarize.
5. What disease is characterized by myelin sheath degeneration?
6. Can all parts of the CNS regenerate if damaged?