Download BN07 PNS Anatomy

The Peripheral
Nervous System
Lecture 7
Peripheral N. S.
Cranial Nerves - 12 pair
 Spinal Nerves - 31 pair
 Somatic Division
 Sensory info
 Body Movement
 Autonomic division - Homeostasis
 regulation ~

Cranial Nerves
From ventral surface
 numbered anterior  posterior
 Sensory, motor, or mixed
 Mnemonic ~

I
Oh
Olfactory
On
II
Oh
Optic
Old
III
Oh
Oculomotor
Olympus
IV
To
Trochlear
Towering
V
Touch
Trigeminal
Top
VI
And
Abducens
A
VII
Feel
Facial
Famous
VIII
Very
Vestibulococlear
Vocal
IX
Green
Glossopharangeal
German
X
Vegetables
Vagus
Viewed
XI
A
Accessory (Spinal)
Some
XII
H
Hypoglossal
Hops
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 ~

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
cervical, brachial, lumbar, sacral ~
Somatic Nervous System

Sensory input




receptors  DRG  dorsal SC
Dorsal column-medial lemniscal pathway
Spinolthalamic tract
Motor output



Lateral SC  ventral horns  muscles
Corticospinal tract
Rubrospinal tract ~
Dermatomes


Sensory innervation
each spinal nerve has
receptive field
Overlap at distal branches
redundancy
retain some sensation
even if a complete spinal
nerve destroyed ~
Somatic N.S.:
Motor Output
The Lateral Pathway
Voluntary movement
 distal limbs
 2 tracts
 Corticospinal tract
about 1 million axons
 Rubrospinal tract
small part of pathway ~

Motor N.S.

Striate muscle
 uninterrupted neuron
a motor neuron
nerve-dependent
 Excitatory only at neuroeffector synapse
 NT is acetylcholine (ACh)

cholinergic


Nicotine = direct agonist (AG)
Curare = direct antagonist (ANT) ~
Somatic Motor N. S.
Effector
Motor Neuron
ACh
Spinal
Cord
Autonomic N. S.
Homeostasis
 Effectors
 Smooth Muscle
 Cardiac Muscle
 Glands ~

Autonomic Subdivisions
Not nerve-dependent
 Sympathetic
 Emergency, flight/fight
 Parasympathetic
 Conservation / vegetative ~

Autonomic N. S.: General Features
Preganglionic
neuron
Ganglion
Effector
Postganglionic
neuron
Autonomic N. S.: General Features
Effector
ACh

Nicotinic
 different R-subtype than
neuromuscular ~
Autonomic N. S.: General Features
Effector
ACh

Neuroeffector junction
 Different NT for each
division ~
Pharmacology of Autonomic NS

Preganglionic neuron
releases ACh

Different NT at effectors
 sympathetic division: NE
Norepinephrine (or noradrenaline)

parasympathetic division: ACh ~
Sympathetic vs. Parasympathetic
Sympathetic
 ganglia near spinal cord
 interconnected ---> active together
 long-lasting effects
 Parasympathetic
 ganglia near effector
 discrete ---> active independently
 transient effects
 Antagonistic regulation ~

Effector Responses
Effector
Sympathetic Parasympathetic
Heart
+
Respiration
+
GI
+
Immune system +
Sweat glands
+
no input
Iris
+ (radial) + (sphincter) ~
Parasympathetic
Sympathetic
Pre-
Post-
Smooth
muscle
Glands
ACh
NE
Adrenal Glands
Sympathetic Arousal Syndrome
Fight or flight situations
 Diffuse sympathetic activation
 Adrenal glands
 releases NE into blood
 maintains sympathetic arousal
 Parasympathetic rebound
 antagonistic regulation ~
