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 ~