BMS2011 Lecture Notes - Lecture 13: Facial Nerve, Trochlear Nerve, Sternocleidomastoid Muscle
30 May 2018
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Week 6. PNS & ANS vessels, Brain and Cranial
nerves
PERIPHERAL NERVOUS SYSTEM
• Cranial and spinal nerves
• Corresponding nerve with each vertebra
o Major dividing line: coronal; dorsal = sensory, ventral = motor
o Grey matter = soma, dendrites (unmyelinated)
o Anterior horns: motor dedicated
o Lateral horns: autonomic nervous system
o Posterior, dorsal horn: sensory
-dorsal root ganglion: where we have first cell bodies
o Root level = sensory or motor
Dorsal root = only sensory
Ventral root = only motor
o Dedicated roots together = true mixed spinal nerve (only exists for limited time)
-> rami
Ramus = mixed sensory and motor
Dorsal ramus: much smaller
Ventral ramus: innervates hypaxial -> dermis/dermatome of that segment
• Epaxial (dorsal) are much smaller -> dorsal ramus much smaller -> goes to less content
• Peripheral nervous system = ventral rami
• Hypaxial and Epaxial are roughly distributed the same in fish
find more resources at oneclass.com
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• Major change from fins -> limbs:
o Shift in HOX genes for limb bud
-from occipital to distal region of spinal cord
-fish dot eed to look aroud
-driven by having a neck (we need to look around independent of positioning of
limbs
• Decoupling limb, upper limbs are separate
• Modified segments: Limbs and plexuses
Nerve plexus = interwoven network of mixed spinal nerves
-ventral ramus derived structures
-ventral rami -> merge together -> complex patterns
Impacting factors
o Limb bud only develops from ventral hypaxial mesoderm
o Limb has a front and back (dorsal and ventral parts)
-need to divide nerve, anterior and posterior portion
o >1 segment of embryo contributes to limb
-somites migrate out
-each has a ventral rami
-each has anterior and posterior part
o Limb rotation:
Cellular division and cell death -> shapes limb
More rotation in mammals than in reptiles
-dropping elbows to side (face posteriorly)
-different for upper and lower limbs (knee anterior)
Innervation of
upper limbs
Brachial plexus:
o Ventral ramus derived (C5-T, reeer theres C8)
-merge together -> divide out
o Ventral ramus = roots of brachial plexus
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o Provides all innervation (motor, sensory) to upper limbs
o Stretches through root of neck to axillar
-> as we leave axillar, no longer plexus -> terminal nerves:
Musculocutaneous (proximal):
-anterior muscles of arm (flexor groups eg. bicep)
Axillary:
-shoulder
Radial:
-posterior muscles of arm and forearm (extensors)
-most widely distributed of these nerves
-damage has profound effects on overall function of forelimb
Ulnar and median (distal):
-pass through arm without innervating anything
-innervates muscles of forearm anteriorly and hand
-ulnar = primary hand nerve
**know compartmentalisation: different nerves going to particular region of
arm/forearm, anteriorly and posteriorly, proximal vs distal
Innervation of
lower limbs
Two plexi:
Lumbar (L1-L5)
o Main branches:
1. Femoral nerve: anterior muscles in thigh
2. Obturator nerve: medial muscles in thigh
Sacral (L4-S3)
o Sciatic nerve:
not really a nerve
always 2 separate nerves that share a common epineurium
(fibrous connective tissue layer that binds them together)
nothing is innervated by this nerve
nerve components that span posterior thigh, leg and foot
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Pns & ans vessels, brain and cranial nerves. Dorsal root ganglion: where we have first cell bodies: root level = sensory or motor. Ventral root = only motor: dedicated roots together = true mixed spinal nerve (only exists for limited time) From occipital to distal region of spinal cord. Driven by having a neck (we need to look around independent of positioning of limbs: decoupling limb, upper limbs are separate, modified segments: limbs and plexuses. Nerve plexus = interwoven network of mixed spinal nerves. Ventral rami -> merge together -> complex patterns. Impacting factors: limb bud only develops from ventral hypaxial mesoderm, limb has a front and back (dorsal and ventral parts) Need to divide nerve, anterior and posterior portion: >1 segment of embryo contributes to limb. Each has anterior and posterior part: limb rotation: Cellular division and cell death -> shapes limb. More rotation in mammals than in reptiles. Different for upper and lower limbs (knee anterior)
