Download Lecture PNS

PNS Terminology
• Ganglia – neuron cell
bodies & dendrites
• Nerves – bundles o
myelinated axons
• PNS neuroglia
– Satellite cells
• Enclose neuron cell bodies in
ganglia
– Schwann cells
• Cover peripheral axons
I - Olfactory
II - Optic
III - Oculomotor
IV-Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII – Acoustic/Vestibulocochlear
IX - Glossopharyngeal
X - Vagus
XI – Accessory/Spinal Accessory
XII - Hypoglossal
-cranial nerves – 12 pairs
-olfactory, optic & acoustic contain only sensory axons = sensory nerves
- oculomotor, trochlear, abducens, accessory & hypoglossal carry only motor
information = motor nerves
-remaining are mixed nerves – both motor and sensory axons
“some say my mother bought my brother some bitter beer – my, my”
Optic Chiasma
I
III
II
V
VI
VII
IX
VIII
X
XI
The Olfactory Nerve (I)
• Sensory Nerve
• Carries sensory information
– Sense of smell
• Synapse within olfactory bulbs
• Sensory Nerve
• The optic nerve (II)
– carries visual information to
occipital lobe
The Vestibulocochlear Nerve (VIII)
• Sensory Nerve
• also called the Acoustic nerve
• Vestibular nerve
– Monitors sense of balance, position and movement
• Cochlear nerve
– Monitors hearing
•The oculomotor nerve (III)
–Primary source of innervation for
extra-ocular muscles
•The abducens nerve (VI)
–Innervates lateral rectus muscle of
eye
•Move the eyeball
•The trochlear nerve (IV)
–Smallest cranial nerve
–Innervates superior oblique eye
muscle
Motor Cranial Nerves
• The accessory nerve (XI) – Motor nerve
• innervates swallowing muscles & controls
sternocleidomastoid and trapezius muscles and other
muscles of pectoral girdle
• two branches: cranial part (internal branch) & spinal part
(external branch)
•The hypoglossal
nerve (XII) – motor
nerve
–voluntary motor
control over tongue
movements
The Trigeminal Nerve (V)
• Largest cranial nerve
• Mixed nerve
• Ophthalmic branch
– sensory – upper eyelid, eyeball
lacrimal glands, side of nose, forehead
and scalp
• Maxillary branch
– sensory – nose, palate, part
of pharynx, upper teeth, upper
lip and lower eyelid
• Mandibular branch
– sensory – tongue, cheek,
lower teeth, skin over mandible
and side of head anterior to ear
-motor – muscles of chewing
The Facial Nerve (VII)
– Mixed nerve
– controls muscles of scalp
and facial expression
– transmits pressure
sensations from face &
taste sensations from
tongue
– major branches:
•
•
•
•
•
Temporal
Zygomatic
Buccal
Mandibular
Cervical
The Glossopharyngeal Nerve (IX)
• Mixed nerve
• Innervates the
tongue & controls
swallowing
The Vagus Nerve (NX)
• Mixed nerve
• vital to autonomic
control of visceral
function
• major nerve of the
ANS/parasympathetic
system
31 Pairs of Spinal Nerves
• Ensheathed by three connective tissue
layers
– Outermost epineurium
• dense network of collagen fibers around
the peripheral nerve
– Middle perineurium
• partitions nerve into fascicles
– Inner endoneurium
• delicate connective tissue fibers
surrounding each axon
• under the endoneurium is the myelin
sheath
• outer layer of the myelin sheath is called
the neurilemma
• neurilemma covers the myelin sheath
and Schwann cells
• myelin sheath covers the axon
Spinal Nerves
• connected to the spinal cord via roots (bundles of axons)
• Posterior root = sensory axons into the posterior gray horn
• Anterior root = motor axons from the anterior gray horn
Spinal Nerves
• before the posterior root is the dorsal root ganglion = cell bodies
of incoming sensory neurons (axons continue on to form the root)
Spinal Nerve
•spinal nerves emerge from
intervertebral foramina as mixed
nerves
•after passing through
intervertebral foramina the spinal
nerve branches into three rami
•Dorsal ramus
•Ventral ramus
•Rami communicantes
•Dorsal ramus
-sensory/motor innervation to and
from skin and muscles of back
•Ventral ramus
- sensory/motor innervation
to and from skin and
structures of ventral and
lateral body wall, muscles of
the upper and lower limbs
Spinal Nerve
Epidural space
Dura and
Arachnoid
maters
Dorsal
Ramus
Dorsal
Root
Dorsal Root
Ganglion
Ventral
Root
•rami communicantes
-carries nerves of the ANS
Ventral
Ramus
Rami
Communicantes
Dorsal Root of SN
Ventral Root of SN
SPINAL NERVE
Dorsal
Ramus
Ventral
Ramus
Rami
Communicantes
Sensory – IN
Motor – OUT
Sensory – IN
Motor – OUT
Signals to and from the
ANS
SKIN
BACK MUSCLES
TRUNK
LIMBs
VISCERA – cardiac and
Smooth muscle
Nerve Plexuses
• Four major plexuses
–
–
–
–
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
• nerve networks formed by
the ventral rami of spinal
nerves
• found in neck, arm, low
back & sacral regions
• no plexus in thoracic region
– intercostal nerves this region
Cervical Plexus
• C1-C4 ventral rami
• Some fibers from C5
• Innervates muscles of the
neck and diaphragm
– major nerve from plexus =
Phrenic nerve
Brachial Plexus
• Ventral rami of C5-T1
• Innervates pectoral girdle and upper limbs
Brachial Plexus
•
nerves arise from cords & trunks
– Superior, middle and inferior trunks
– Lateral, medial and posterior cords
– musculocutaneous, radial, median and ulnar nerves arise from these cords
• Lateral cord: musculocutaneous, median nerves
• Medial cord: ulnar, median nerves
• Posterior cord: radial, axillary nerves
Lumbar Plexus
•
•
•
•
ventral rami of T12–L4
Innervate pelvic girdle and lower limbs
femoral nerve gives off many muscular branches
posterior segment gives off branches to the quads and
branches to the knee + large saphenous nerve
Sacral Plexus
• ventral rami of L4–S4
• innervates pelvic girdle and lower limbs
• sciatic nerve becomes the tibial nerve, sural nerves & common
fibular nerve in the leg