2. Week 12 The Spinal Cord & PNS

3. What’s ahead Identify structures of the spinal cord Identify peripheral nerves Identify components of the reflex arc

4. Activity 1:The Spinal Cord

5. The Spinal Cord Cervical enlargement Lumbar enlargement Conus medullaris Cauda equina Cervicalspinalnerves Thoracicspinalnerves Lumbar spinal nerves Sacral

6. Conus Medullaris Cauda Equina (horse’s tail) L5L5L5L5 L4L4L4L4 L3L3L3L3 L2L2L2L2

7. L4L4 L5L5 T 12 L5L5 Cauda equina Lumbar Tap Subarachnoid space

8. Spinal Cord Anatomy Spinal meninges Pia mater Arachnoid mater Dura mater Subarachnoid space

9. Spinal Cord Anatomy Posterior median sulcus Anterior median fissure Central canal

10. Spinal Cord Anatomy Dura mater Arachnoid mater Pia mater Gray matter Dorsal horn Lateral horn Ventral horn White matter Posterior funiculus Lateral funiculus Anterior funiculus Gray commisure Gray matter = Inside, cell bodies & unmyelinated fiber tracts White matter = Outside, myelinated fiber tracts

11. Spinal Cord / Spinal Nerve Anatomy Dorsal Root Dorsal Root Ganglion Ventral Root Spinal Nerve

12. Spinal Cord / Spinal Nerve Anatomy Dorsal root ganglion Ventral root Dorsal ramus Spinal nerve Ventral ramus to Plexus

13. Arachnoid mater Dura mater Dorsal root Posteriormediansulcus Denticulate ligament Posterior Spinal Cord Dorsal root ganglion Ventral root What do you suppose this is?

14. How can you tell the Ventral side from the Dorsal side?

15. PMS vs. AMF Posterior Median Sulcus Anterior Median Fissure AMF

16. Cross sectional anatomy of the spinal cord Gray Matter Ventral horns motor neurons Dorsal horns Sensory/inter neurons A visual analogy Dorsal horn Ventral horn

17. 1a ? Posterior median sulcus 1b ? Anterior median fissure 2a ? 2b ? 2c ? Dorsal horn Lateral horn Vental horn

18. CervicalThoracic Lumbar Sacral Regional DifferencesCervicalenlargement Lumbarenlargement Lateralhorn

19. fiber tracts for transmission of information ascending (sensory) tracts descending (motor) tracts Posterior funiculus Lateral funiculus Anterior funiculus Cross sectional anatomy of the spinal cord White Matter

20. Some fiber tracts in the different funiculi Posterior funiculus: Faciculus cuneatus and gracilis Ascending sensory Lateral funiculus Spinothalamic tract Ascending sensory Corticospinal tract Descending motor Anterior funiculus Spinothalamic tract Ascending sensory Corticospinal tract Descending motor

21. Spinal cord c.s. microscopic view Dorsal root ganglion Ventral root Central canal Gray commissure Dorsal root Dura mater

22. Dorsal root ganglion Pseudounipolar neuron cell bodies Identify the structural classification of these neurons

23. Physiology Posterior In  Anterior  Out

24. Dorsal root: afferent, sensory Ventral root: efferent, motor Dorsal ramus: mixed, motor and sensory to trunk Ventral ramus: mixed motor and sensory form nerve plexi

25. Activity 2: Nerve Plexi & Peripheral Nerves

26. Ventral Rami  Plexus  Peripheral Nerve

27. There are 31 pairs of spinal nerves & 4 nerve plexi

28. Cervical Plexus The phrenic nerve innervates the respiratory diaphragm “ C 3,4,5 keeps the diaphragm alive!

29. Brachial Plexus

31. Nerves Arising from Thoracic Ventral Rami

32. Lumbar Plexus

33. Sacral Plexus

34. Activity 3:Human Reflex Physiology

35. Reflex Terminologies Reflex: Reflex Arc: Autonomic (Visceral) Reflex: Somatic Reflex: A rapid, predictable, involuntary motor response to a stimulus that acts to return the body to homeostasis Mediated by the spinal cord The neural pathway a nerve impulse follows that mediates a reflex (from sensory receptor  effector organ) Mediated through the ANS Not subject to conscious control Vasoconstriction/dilation, sweating, salivation, digestion, heart rate, pupil dilation/constriction Involve stimulation of skeletal muscles by the somatic division of the nervous system Subject to conscious interference

36. Reflex Arc (1) Receptor - reacts to stimulus (2) Sensory Neurons - afferent impulses to CNS (3) Integration centers - synapses in CNS (4) Motor Neurons - efferent impulses from Integration centers to effector (5) Effector - muscle or glands

37. Exteroceptors * Interoceptors Proprioceptors * Respond to stimuli arising outside the body: Touch Pain Temperature Pressure Detect stretch Respond to stimuli inside the body (viscera, vessels) Classifications of Sensory Receptors by Location

38. Proprioceptors Stretch Reflexes Receptor = Proprioceptor of the muscle

39. Patellar Reflex Receptor = Proprioceptors of (?) muscle Afferent Neuron = Afferent fibers of (?) nerve Integration Center = Efferent Neuron = Efferent fibers of (?) nerve ? Effector= (?) muscle

40. Patellar Reflex

41. 3 Tests 1.Simultaneous muscle activity 2.Mental distraction 3.Fatigue Is the response greater or less than baseline?

42. Pupillary Reflex Contralateral? – or - Ipsilateral?

43. On the Practical: Identify the structures of the Spinal Cord from models and slides Identify the Peripheral Nerves and Nerve Plexi from models Identify the components of the Reflex Arc Lab Activity: Study Spinal Cord & Peripheral Nerves Perform Reflex experiments & analyze