Chap 14 Flashcards
Nervous system
all nervous tissue in the body
central nervous system
brain and spinal cord
peripheral nervous system
cranial nerves, spinal nerves, and ganglia
Functionally divided:
sensory and motor nervous systems
sensory nervous system
conveys sensory information to the CNS
motor nervous system
conducts motor commands to the muscles and glands
neuron characteristics
excitable
transmit nerve impulses
non mitotic
glial cells
completley surround and support neurons
generally neurons have:
a cell body, dendrites and an axon
classified structurally as
unipolar, bipolar, or multipolar depending on the number of attachments to the cell body.
classified functionally as
sensory, motor or interneurons
CNS glial cells:
astrocytes, ependymal cells, microglial cells, and oligodendrocytes
astrocytes
help form the blood brain barrier and regulate tissue fluid composition
ependymal cells
line CNS cavities and produce cerebrospinal fluid
microglial cells
act as phagocytes in nervous tissue
oligodendrocytes
mylinate CNS axons
PNS glial cells
satellite cells and nerolemmocytes
satellite cells
support neurons cell bodies in ganglia
nerolemmocytes
mylinate PNS axons
Nerve impulse:
a rapid movement of a charge along a neurons plasma membrane
Mylination
oligodendrocytes (CNS) and nerolemmocytes (PNS) form a discontinuous mylin sheath along the axon, with small gaps (neurofibril nodes)
neurofibril nodes
small gaps between mylin sheath help conduct impulses faster
unmylinated axons
associated with a neurolemmocyte but not ensheathed by it.
Wallerian degeneration
regeneration of damaged neurons
limited to PNS axons that are able to regrow under certain conditions
Epineurium
surrouds fascicles
perineurium
surrounds individual fasicles
endoneurium
surrounds individual axons
synapse
a specialized junction between two excitable cells where a nerve impulse is transmitted
synaptic knobs
swellings of axons at their end branches
synaptic cleft
space between the presynaptic and postsynaptic cells
classification of synapses
axodendritic, axosomatic or axoaxonic
axodendritic
most common: presynaptic knobs synapse with postsynaptic dendrites (standard delivery)
axosomatic
between synaptic knobs and the cell body of postsynaptic neuron (express delivery)
axoaxonic
least common: presynaptic knob with postsynaptic knob (first class delivery) *usually overides brains orders
electrical synapses
a flow of ions pass from presynaptic cell to postsynaptic cell through gap junctions
chemical synapses
nerve impulse causes a release of a chemical neurotransmitter from presynaptic cell that induces response in the postsynaptic cell.
what increases rate of conduction?
presence of a myelin sheath, larger the axon diameter.
neuronal pools
groups of interneurons- cordinate and integrate nervous activity.
converging circuit
neurons synapse at a single postsynaptic neuron
>—-
diverging circuit
spreads information to several neurons
—–<
reverberating circuit
neurons continue to restimulate presynaptic neurons in the circuit.
-0
Parallel after discharge circuit
involves parallel pathways that process the same information over different amounts of time and deliver that information to the same output cell.
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