The PeripheralNervous 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 ~
Oh
Oh
Oh
To
Touch
And
Feel
Very
Green
Vegetables
A
H
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulococlear
Glossopharangeal
Vagus
Accessory (Spinal)
Hypoglossal
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
On
Old
Olympus
Towering
Top
A
Famous
Vocal
German
Viewed
Some
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 smallback & ribs
Cervical, lumbar, & sacral: large nervesrest 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 Receptors ventral horns muscles Corticospinal tract Rubrospinal tract ~
Dermatomes
Sensory innervationeach spinal nerve has receptive field
Overlap at distal branchesredundancyretain 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 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.
Spinal Cord
Motor Neuron
Effector
ACh
Homeostasis Effectors
Smooth Muscle Cardiac Muscle Glands ~
Autonomic N. S.
Not nerve-dependent Sympathetic
Emergency, flight/fight Parasympathetic
Conservation / vegetative ~
Autonomic Subdivisions
Effector
Ganglion
Preganglionic neuron
Postganglionic neuron
Autonomic N. S.: General Features
Effector
Autonomic N. S.: General Features
ACh
Nicotinic different R-subtype than
neuromuscular ~
Effector
Autonomic N. S.: General Features
ACh
Neuroeffector junction Different NT for each
division ~
Pharmacology of Autonomic NS
Preganglionic neuronreleases 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
Post-Pre-
Sympathetic
Adrenal Glands
ACh
Glands
Smooth muscle
NE
Sympathetic Arousal Syndrome
Fight or flight situations Diffuse sympathetic activation
Adrenal glands releases NE into blood maintains sympathetic arousal
Parasympathetic rebound antagonistic regulation ~