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
are myelinated nerves segmentally arranged along the spinal cord.
Spinal
nerves
The is the pathway for sensory (afferent) nerve fibers and the
ventral root for motor (efferent) nerve fibers.
dorsal root
The
unite outside and lateral to the spinal cord to form a spinal nerve
dorsal and ventral roots
Twelve (12) Cranial Nerves
Olfactory Nerve (
Optic Nerve
Oculomotor Nerve
Trochlear Nerve
Trigeminal Nerve
Abducens Nerve
Facial Nerve
Auditory Nerve
Glossopharyngeal Nerve
Vagus Nerve
Accessory Nerve
Hypoglossal Nerve
(1) – SVA (sensory); nonmyelinated; lacks a ganglion.
➢ Arise from olfactory hair cells and terminate in the rhinencephalon.
Olfactory Nerve
(II) – SVA (sensory) nerve.
➢ Arise from sensory neurons in retina and terminate in the superior colliculus of
corpora quadrigemina in the brainstem.
Optic Nerve
(III) – motor
➢ Arise from the basal plate of mesencephalon and terminate in the inferior
oblique and the superior, inferior and internal rectus muscles of the eyeball
Oculomotor Nerve
(IV) - motor
➢ Arise from the basal plate of mesencephalon and terminate in the superior
oblique muscle of the eye.
Trochlear Nerve
(V) – mixed (sensory and motor)
➢ Three main divisions that arise from the semilunar ganglion: a. Opthalmic, b.
Maxillary, and c. Mandibular divisions.
Trigeminal Nerve
, (VI) – motor
➢ Arise from the basal plate of myelencephalon and terminate in the external rectus
muscle of the eyeball. When it contracts it rotates the eyeball outward (abduction).
Abducens Nerve
(VII) – mixed (motor and sensory)
Facial Nerve
(VIII) - sensory; presents an acoustic ganglion beneath the auditory
vesicle, caudal to the geniculate ganglion of CN VII.
Auditory Nerve
(IX) - mixed (sensory and motor)
Glossopharyngeal Nerve
(x) - mixed (motor and sensory) nerve
Vagus Nerve
(XI) - motor nerve. It has a commissural ganglion, which is a
continuation of the jugular ganglion
Accessory Nerve
(XII) - predominantly motor nerve fibers that arise separately
from the posterior myelencephalon and form a single trunk to supply the skeletal
muscles of tongue.
Hypoglossal Nerve
- The GSA cranial nerves are similar to the GSA
spinal nerves except that the point of termination is the alar plate of the brain
General Somatic Afferent (GSA)
- The GVA cranial nerves are similar to the GVA
spinal nerves except that the point of termination is the alar plate of the brain.
General Visceral Afferent (GVA)
) - The GSE cranial nerves are similar to the GSE
spinal nerves except that the point of origin is the basal plate of the brain.
General Somatic Efferent (GSE
) - The GVE cranial nerves are similar to the GVE
spinal nerves except that the point of origin is the basal plate of the brain.
General Visceral Efferent (GVE
- The SSA cranial nerves carry impulses from the
eye and ear (involved in the relationship of the animal to external environment) to the alar
plate of the brain.
Special Somatic Afferent (SSA)
- The SVA cranial nerves carry impulses from the
chemoreceptors in the olfactory epithelium and taste buds to the alar plate of brain
Special Visceral Afferent (SVA)
) - The SVE cranial nerves conduct impulses from the
basal plate of the brain to skeletal muscles w/ visceral functions.
Special Visceral Efferent (SVE
