1. The Spinal Cord & Peripheral Nervous System Lecture 4

2. Spinal Cord n Dorsal root ganglion l sensory input n ventral root l motor output n Caudal spinal cord l Cauda equina ~

3. n Clinically important anatomy l Descending & ascending tracts n Motor 1. corticospinal tract distal muscles l only descending tract with overt effects ~ Spinal Cord Tracts

4. n Sensory 2. Dorsal column-medial lemniscal tract l touch, vibration, & proprioception l axons ascend ipsilaterally l synapse then decussate at medulla 3. Spinothalamic tract (lateral) l pain & temperature l decussate at SC entry level l ascends contralaterally ~

5. Spinal Cord Tracts 4. Spinocerebellar tract l position of body in space & relative position of limbs l affected in hereditary ataxias no symptoms in other diseases ~

6. Medulla Dorsal column-medial lemniscal path Spinothalamic path Corticospinal trct

7. Dorsal Ventral Dorsal columns Spinal Cord anterolateral columns Corticospinal tract Rubrospinal tract

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

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

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

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

12. 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 ~

13. Somatic Nervous System n Sensory input l sensory receptors ---> l dorsal root ganglion (DRG) ---> l dorsal horns n Motor output l ventral horns ---> muscles ~

14. Dorsal column-medial lemniscal pathway n Dorsal Columns n Submodalities l Touch l vibration l 2 point discrimination l proprioception ~

15. Touch R Spinal Cord Thalamus - VP Medulla S1 R Dorsal Column DRG Medial lemniscus Dorsal column-medial lemniscal pathway

16. Spinothalamic Tract n Anterolateral Columns n Sensory neuron l NT = Substance P l gray matter n 2d order neuron crosses midline at spinal cord ~

17. Pain R Spinal Cord DRG Reticular Formation Spinothalamic Tract Thalamus - VPL & intralaminar S1 Spinoreticular Tract

18. Dermatomes n Sensory innervation l each spinal nerve has segmental field (receptive field) n Overlap at distal branches l redundancy l retain some sensation even if a complete spinal nerve destroyed ~

19. The Lateral Pathway n Voluntary movement l distal limbs l 2 tracts n Corticospinal tract about 1 million axons n Rubrospinal tract small part of pathway ~ Somatic N.S.: Motor Output

20. Motor N.S. n Striate muscle l uninterrupted neuron l * nerve-dependent n Excitatory only at neuroeffector synapse n Cholinergic - ACh l Nicotine = direct AG l Curare = direct ANT ~

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

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

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

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

25. Effector Autonomic N. S.: General Features ACh n Nicotinic l different than neuromuscular l antagonist: hexamethonium ~

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

27. Pharmacology of Autonomic NS n Preganglionic neuron releases ACh n Different NT at effectors l sympathetic division: NE l parasympathetic division: ACh ~

28. Sympathetic vs. Parasympathetic n 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 ~

29. Parasympathetic Post- Pre- Sympathetic Adrenal Glands ACh Glands Smooth muscle NE

30. Sympathetic Arousal Syndrome n Fight or flight situations l Diffuse sympathetic activation n Adrenal glands l releases NE into blood l maintains sympathetic arousal n Parasympathetic rebound n Emotional experience l depends on set & setting ~