a bundle of axons
outside the brain and spinal
cord
Nerve
originate
from the brain; 12 pairs.
Cranial nerves
originate from
spinal cord; 31 pairs.
Spinal nerves
collection of neuron
cell bodies outside the brain
and spinal cord.
Ganglion
extensive network of
axons, and sometimes neuron
cell bodies, located outside
CNS.
Plexus
supportive cells
with many functions.
Glial cells
transmits action
potentials from receptors
toward the CNS.
SENSORY DIVISION
(AFFERENT)
transmits action
potentials from CNS to
effectors (muscles,
glands).
MOTOR DIVISION
(EFFERENT)
from CNS to skeletal muscles.
Voluntary; single neuron system.
Somatic NS
from CNS to smooth muscle,
cardiac muscle and certain glands.
Subconscious or involuntary
control.
Autonomic NS
Prepares body
for physical activity.
Sympathetic
Regulates
resting functions.
Parasympathetic
plexuses within the
wall of the digestive tract
Enteric
or soma: typical cell
functions such as protein
synthesis and house
keeping; contain Nissl
bodies (rough E R).
Cell body
cell extensions of the
cell body that receive
information from other
neurons or sensory
receptors
Dendrites
arises from axon hillock
of the cell body then
becomes the initial
segment; part of trigger
zone where action
potentials are generated
Axon
has many dendrites and an axon
Multipolar neuron
has a dendrite and an axon
Bipolar neuron
appears to have an axon and no dendrites
Pseudo-unipolar neuron
has multiple dendrites but no axon
Anaxonic neuron
Secrete cerebrospinal
fluid (CSF)
Choroid plexus
Input travels along one pathway.
SERIAL PATHWAY
many converge and synapse with smaller
number of neurons.
CONVERGENT PATHWAY
small number of presynaptic neurons synapse
with large number of postsynaptic neurons.
DIVERGENT PATHWAY
outputs cause reciprocal activation.
REVERBERATING CIRCUIT
neurons stimulate several
neurons in parallel organization, which converge upon a common output
cell. for example, complex data processing in brain.
PARALLEL AFTER-DISCHARGE CIRCUIT