1. Week 11
The Spinal Cord

2. Activity 1: The Spinal Cord

3. The Spinal Cord Cervical spinal nerves Cervical enlargement Thoracic
Lumbar
enlargement
Lumbar
spinal nerves
Conus
medullaris
Sacral
spinal nerves
Cauda
equina

4. L2
Conus Medullaris L3 L4
Cauda Equina
(horse’s tail) L5

5. Lumbar Tap
T12
Cauda equina
Subarachnoid space L5 L4 L5

6. Cross Section of SC Between C2 and C3
Pia mater
Spinous process
Subarachnoid
space
Arachnoid mater
Dura mater
Body of vertebra
Vertebral vein & artery
Which is the dorsal side?

7. Physiology
Dorsal
In 
Ventral
 Out

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

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

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

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

12. Cross sectional anatomy of the spinal cord
A visual analogy?
Dorsal horns
sensory neurons
Dorsal
horn?
Ventral
horn?
Gray commissure
Ventral horns
motor neurons

13. PMS
AMF

14. Regional Differences Cervical Thoracic Sacral Lumbar Cervical
enlargement
Lateral
horn
Lumbar
enlargement
Sacral
Lumbar

15. White Matter fiber tracts for transmission of information
ascending (sensory) tracts
descending (motor) tracts
Posterior funiculus
Lateral funiculus
Anterior funiculus

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

17. Anatomy of a Spinal Nerve
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

18. Dorsal root ganglion Pseudounipolar neuron cell bodies
What is the structural classification of these neurons?

19. Activity 2: Nerve Plexi & Peripheral Nerves

20. There are 31 pairs of spinal nerves

21. Cervical Plexus The phrenic nerve innervates the respiratory diaphragm
“ C3,4,5 keeps the diaphragm alive!

22. Brachial Plexus

24. Lumbar Plexus

25. Sacral Plexus

26. Activity 2: Human Reflex Physiology

27. Structural Organization of the Nervous System
Central Nervous System
Peripheral Nervous System

28. 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

29. Sensory Receptors
Soma
Receptors
Axon
Receptive Endings

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

31. Therefore, for a Reflex Arc:
1) Receptor = Proprioceptors of ?? muscle
2) Sensory Neuron - ?? Nerve holding the sensory neurons
3) Integration centers – which CNS organ?
4) Motor Neurons - ?? Nerve holding the motor neurons
5) Effector - ?? Muscle

32. Effector is the muscle group that contracts to extend the leg
Patellar Reflex
Receptor is the proprioceptors of the muscle group associated with the tendon being tapped
Effector is the muscle group that contracts to extend the leg
Note that the Afferent & Efferent neurons can travel through the same peripheral nerve

33. Will the velocity increase or decrease from baseline?
Patellar Reflex
3 Tests
Simultaneous muscle activity
Mental distraction
Fatigue
Will the velocity increase or decrease from baseline?

34. Pupillary Reflex
Contralateral?
– or -
Ipsilateral?