The Peripheral Nervous System Lecture 7 Peripheral N

The Peripheral Nervous System Lecture 7

Peripheral N. S. Cranial Nerves - 12 pair n Spinal Nerves - 31 pair n Somatic Division l Sensory info l Body Movement n Autonomic division - Homeostasis l regulation ~ n

Cranial Nerves From ventral surface l numbered anterior posterior n Sensory, motor, or mixed n Mnemonic ~ n

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 n 8 pr. cervical (C 1 -C 8) n 12 pr. thoracic (T 1 -T 12) n 5 pr. lumbar (L 1 -L 5) n 5 pr. sacral (S 1 -S 5) n 1 pr coccygeal ~ n

Spinal Nerves n Thoracic nerves relatively small back & ribs n Cervical, lumbar, & sacral: large nerves rest of the body n All Interconnect l after leaving vertebral canal l form 4 major plexuses cervical, brachial, lumbar, sacral ~

Somatic Nervous System n Sensory input l l l n receptors DRG dorsal SC Dorsal column-medial lemniscal pathway Spinolthalamic tract Motor output l l l Lateral SC ventral horns muscles Corticospinal tract Rubrospinal tract ~

Dermatomes n n Sensory innervation leach spinal nerve has receptive field Overlap at distal branches lredundancy lretain some sensation even if a complete spinal nerve destroyed ~

Somatic N. S. : Motor Output

The Lateral Pathway Voluntary movement l distal limbs l 2 tracts n Corticospinal tract about 1 million axons n Rubrospinal tract small part of pathway ~ n

Motor N. S. n Striate muscle l uninterrupted neuron a motor neuron nerve-dependent n Excitatory only at neuroeffector synapse l NT is acetylcholine (ACh) l cholinergic l l Nicotine = direct agonist (AG) Curare = direct antagonist (ANT) ~

Somatic Motor N. S. Effector Motor Neuron ACh Spinal Cord

Autonomic N. S. Homeostasis n Effectors l Smooth Muscle l Cardiac Muscle l Glands ~ n

Autonomic Subdivisions Not nerve-dependent n Sympathetic l Emergency, flight/fight n Parasympathetic l Conservation / vegetative ~ n

Autonomic N. S. : General Features Preganglionic neuron Ganglion Effector Postganglionic neuron

Autonomic N. S. : General Features Effector ACh n Nicotinic l different R-subtype than neuromuscular ~

Autonomic N. S. : General Features Effector ACh n Neuroeffector junction l Different NT for each division ~

Pharmacology of Autonomic NS n Preganglionic neuron releases ACh n Different NT at effectors l sympathetic division: NE Norepinephrine (or noradrenaline) l parasympathetic division: ACh ~

Sympathetic vs. Parasympathetic Sympathetic l ganglia near spinal cord l interconnected ---> active together l long-lasting effects n Parasympathetic l ganglia near effector l discrete ---> active independently l transient effects n Antagonistic regulation ~ n

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 l Diffuse sympathetic activation n Adrenal glands l releases NE into blood l maintains sympathetic arousal n Parasympathetic rebound l antagonistic regulation ~ n