Topic 6 Flashcards
is derived from neural crest cells. It consists of
cranial and spinal nerves and their ganglia
Peripheral Nervous System (PNS) -
The cranial and spinal nerves are
composed of (nerve fibers) of neurons whose cell bodies are located within the
CNS (for cranial nerves) or in ganglia (for spinal nerves
axons
Classification of Neurons Based on the Number of Processes
Unipolar Neuron
Pseudounipolar Neuron
Bipolar Neuron
Multipolar Neuron
- has only one process, the axon. All afferent neurons are
unipolar and have their cell bodies in sensory ganglia (spinal or dorsal root
ganglia and cranial ganglia).
Unipolar Neuron
- has two (2) processes that arise separately from the cell
body, fuse for a while to form 1 process and divide shortly thereafter into
axon and dendrite.
Pseudounipolar Neuron
- has two (2) processes, 1 axon and 1 dendrite
Bipolar Neuron
- has three (3) or more processes: one (1) axon and 2 or more
dendrites.
Multipolar Neuron
– conduct impulses from the receptor organs to
the CNS.
Sensory or afferent neurons
– conduct impulses from the CNS to target
organs.
Motor or efferent neurons
- transfer sensory impulses from
sensory neurons to efferent neurons.
Association neurons or interneurons
innervate voluntary muscles and structures w/ epithelia
derived from ectoderm like skin.
Somatic neurons –
innervate involuntary muscles and structures derived
from splanchnopleure like blood vessels and visceral organs.
Visceral neurons -
is an axon of neuron and its sheath that connects peripheral structures w/
the brain or spinal cord
nerve fiber
Majority of the nerves in the PNS end and begin in the spinal cord and are therefore called
spinal nerves.
A few (12) end and begin w/ brain and are called
cranial nerves