The Peripheral Nervous System

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The PeripheralNervous System

• Lecture 12

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Peripheral N. S.

• Cranial Nerves - 12 pair
• Optic is CNS
• Spinal Nerves - 31 pair
• Somatic Division
• Sensory info
• Body Movement
• Autonomic division - Homeostasis
• regulation

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Cranial Nerves

• From ventral surface
• numbered anterior ---gt posterior
• Sensory, motor, or mixed
• Mnemonic

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Oh Oh Oh To Touch And Feel Very Green Vegetables
A H
Olfactory Optic Oculomotor Trochlear
Trigeminal Abducens Facial Vestibulococlear Gloss
opharangeal Vagus Accessory Hypoglossal
I II III IV V VI VII VIII IX X XI XII
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Cranial Nerves

• I. olfactory frontal lobe
• smell
• II. optic nerve - diencephalon
• visual sensory
• All others arise from brainstem

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Cranial Nerves

• III, IV, VI - eye movement
• primarily motor, but also proprioceptive
• III. Occulomotor
• mesencephalon
• IV. Trochlear
• mesencephalon
• VI. abducens
• pons

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Cranial Nerves

• V. Trigeminal - 3 branches, pons
• ophthalmic - sensory, eyes forehead
• maxillary - sensory, nasal cavity to mouth
• mandibular - mixed
• sensory lower face
• motor mastication

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Cranial Nerves

• VII. Facial - pons/medulla mixed
• sensory taste
• motor facial expressions
• VIII. Vestibulocochlear - pons/medulla
• sensory auditory equilibrium
• IX. Glossopharangeal - medulla
• sensory taste
• motor pharangeal muscles

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Cranial Nerves

• X. Vagus - medulla mixed
• sensory viscera of thorax / abdomen
• motor larynx/pharnyx, parasympathetic nervous
  system
• XI. Accessory - medulla/super, spinal cord
• motor neck, upper back
• XII. Hypoglossal - medulla
• motor tongue

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Spinal Nerves

• 1 pair for each vertebral segment
• 8 pr. cervical (C1-C8)
• 12 pr. thoracic (T1-T12)
• 5 pr. lumbar (L1-L5)
• 5 pr. sacral (S1-S5)
• 1 pr coccygeal

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Spinal Nerves

• Thoracic nerves relatively small
• back ribs
• Cervical, lumbar, sacral large nerves
• rest of the body
• All Interconnect
• after leaving vertebral canal
• form 4 major plexuses

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Cervical Plexus

• C1 - C5
• neck, back of head, shoulders, diaphragm
• Phrenic nerve
• principal nerve respiration control
• diaphragm
• quadriplegia if crush C5 - C7 phrenic intact

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Brachial Plexus

• C5 - T1
• arms hands, most of shoulder
• Musculocutaneous nerve
• sensory lateral arm
• motor biceps, anterior muscles
• Radial nerve
• motor posterior arm dorsolateral forearm and
  hand

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Brachial Plexus

• Median nerve
• motor anterolateral forearm hand
• opponent motion of thumb
• Ulnar nerve
• motor anteromedidal forearm hand
• opponent motion of little finger

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Lumbar Plexus

• L1 - L4
• lower back abdomen
• Major nerves
• lateral femoral cutaneous
• obturator
• femoral

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Sacral Plexus

• L4 - S5
• motor gluteal region, posterior lateral thigh,
  leg foot
• Selected nerves
• Pelvic parasympathetic (S2 - S4)
• elimination, sexual function
• Sciatic nerve
• largest nerve of body
• hamstring superior foot

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Dermatomes

• Sensory innervation
• each spinal nerve has segmental field
• (receptive field)
• Overlap at distal branches
• redundancy
• retain some sensation even if a complete spinal
  nerve destroyed

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Somatic N. S.
Effector
Motor Neuron

Spinal Cord

• Striate muscle
• nerve-dependent
• uninterrupted neuron
• excitatory only
• Cholinergic - ACh
• Nicotinic

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Autonomic N. S.

• Homeostasis
• Effectors
• Smooth Muscle
• Cardiac Muscle
• Glands

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Autonomic Subdivisions

• NOT nerve-dependent
• Sympathetic
• Emergency, flight/fight
• Parasympathetic
• Conservation / vegetative

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Autonomic N. S. General Features
Preganglionic neuron
Effector
Spinal Cord
Postganglionic neuron
Ganglion
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Autonomic N. S. General Features
Effector
ACh
Spinal Cord

• Different NT at effectors
• Symp. NE
• Parasymp. ACh

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Sympathetic vs. Parasympathetic

• Sympathetic
• ganglia near spinal cord
• interconnected ---gt active together
• long-lasting fx
• Parasympathetic
• ganglia near effector
• discrete ---gt active independently
• transient fx
• Antagonistic regulation

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Parasympathetic
Sympathetic
Spinal Cord
Smooth muscle
Glands
NE
ACh
Adrenal Glands
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Sympathetic Arousal Syndrome

• Emergency
• Sympathetic ganglia connected
• 1 part active ---gt all active
• Adrenal glands
• releases NE into blood
• maintains sympathetic arousal

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Sympathetic - Thoracolumbar outflowParasympatheti
c - Craniosacral outflow
Brain
Thoracic Lumbar
Sacral