1. Use the diagram to label:
Sensory (afferent) neuron
Motor (efferent) neuron
CNS
PNS
Interneuron

2. Spinal cord and spinal nerves
spinal cord anatomy
spinal meninges
where to put that needle
spinal cord terminology
spinal nerves
ascending and descending tracts
where do spinal nerves go?
dermatomes
nerves plexuses
cervical plexus
brachial plexus
simple reflexes
anatomy of spinal cord injuries

3. 31 PAIR of spinal nerves 8 cervical 12 thoracic 5 lumbar 5 sacral
1 coccygeal
Spinal cord levels
Spinal nerves
Vertebral levels T1 T1
Medullary cone T1 T1
Cauda equina T2

4. adult
infant

6. Meninges of the spinal cord
Dura mater (pink)
Pia mater
Subarachnoid
space
Arachnoid mater (blue)

7. Dura mater is continuous with epineurium of nerve fibers

8. Denticulate ligament
Coccygeal ligament

9. From which space is a spinal tap taken from?
Into which space is spinal anesthetic injected?
Into which space is an epidural anesthetic injected?
Dura mater and
arachnoid
Pia mater
Subarachnoid space

10. Epidural anesthesia
Spinal anesthesia & spinal tap

11. Anatomy of the spinal cord
Posterior (dorsal) sulcus
Posterior (dorsal) horn
Central canal
(CSF)
Spinal nerve
Anterior (ventral) horn
Nerve roots
Anterior (ventral) fissure
Fissure >> sulcus

12. Gray and White Matter White matter = myelinated nerve fibers
Gray matter = nerve cell bodies, dendrites, neuroglia & unmyelinated axons

13. Nerve Fiber = nerve process (axon or dendrite)
Nerve = bundle of nerve fibers in PNS (mixed)
Tract = bundle of nerve fibers in the CNS (mixed)
Ganglion = cluster of neuronal cell bodies in PNS
Nucleus = cluster of neuronal cell bodies in the CNS

14. Label anterior and posterior.
Label a nerve root and a spinal nerve.
What is in the central canal?
Label the posterior (dorsal) horn.
What is it composed of?

16. ** Don’t need the brain to have
A simple reflex arc
Information relayed
to brain - slower
Sensory neuron
Info processing
in CNS
Motor neuron
** Don’t need the brain to have
a reflex **

17. The Stretch Reflex Too much stretch, too fast
Contract muscles to protect them

18. Sensory or ascending tracts
Motor or descending tracts
The spinal cord is very organized – anatomically & functionally

19. brain
midbrain
medulla
Ipsilateral
Contralateral
Decussation
spinal cord

20. Ascending tract (Sensory info) Midbrain Medulla Thalamus
3rd order neuron
Thalamus
Midbrain
2nd order neuron
Medulla
Decussation in medulla
1st order neuron L R

21. Fig. 14.4(TE Art) Gracile fasciculus Below T6 (legs)
Somatosensory cortex
Fig. 14.4(TE Art)
Thalamus
Midbrain
Midbrain
Gracile fasciculus
Below T6 (legs)
Cuneate fasciculus
Above T6 (arms)
Spinothalamic
tract
Medulla
Fine touch, proprioception, pressure
pain, heat, and cold

22. Ascending tract summary

23. Descending tracts Motor info Corticospinal tract Midbrain Medulla
Motor cortex
Upper motor neurons
Midbrain
Medulla
Lateral corticospinal tract
Ventral corticospinal tract
Lower motor neurons
To skeletal muscles

24. Damage to motor neurons…..
Paralysis
loss of muscle function
causes?
para, quad, hemi – plegia
flaccid = no reflexes
spastic = exaggerated reflexes
no inhibitory control from UMN
hyperreflexia
Upper motor neurons
Spastic paralysis
Lower motor neurons
Flaccid paralysis

25. Diseases that damage motor neurons…..
Upper motor neurons
Amyotrophic Lateral Sclerosis
degeneration of upper and lower motor neurons
paralysis of voluntary muscles
Lou Gehrig & Stephen Hawking 1942-
Poliomyelitis
degeneration of lower motor neurons
occurs in ventral horn
caused by polio virus
Lower motor neurons

26. Spinal nerves 31 PAIR of spinal nerves Vertebral level vs spinal level
8 cervical (C1 is different)
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Vertebral level vs
spinal level

27. Spinal nerve anatomy
Dorsal root ganglion

28. Thoracic cavity Dorsal ramus Ventral ramus Spinal nerve
Spinal nerve = mixed
Ramus = mixed

29. Spinal Nerves
dermatomes
plexuses

30. Each spinal nerve innervates 1 somite
Somite = skin, muscles, bones

31. Dermatome
area of skin supplied by the sensory nerve fibers of one spinal nerve
Characteristic pattern
No dermatome for C1 (motor only)
Use dermatomes to assess spinal nerve damage

32. You are an EMT
Frank dove into shallow end
you evaluate him and find:
his neck hurts
he can breath well on his own
he can’t feel or move his legs
he can’t feel his pinky
he can feel his thumb
Where is his injury??
Will he be paraplegic or quadriplegic?

33. Ventral rami traveling together
Nerve Plexuses:
Ventral rami traveling
together
Cervical plexus (C1 –C5)
Brachial plexus (C5–T1)
Thoracic nerves (12 pairs)
No plexus in thoracic region
Lumbar plexus (L1–L4)
Sacral plexus (L4 –S4)
Sciatic
nerve
sciatica

34. Fig. 14.13(TE Art) Cervical plexus C1-C5 ventral rami neck & shoulder
phrenic nerve C3 C4 C5
Phrenic nerve C3-C5

35. Phrenic nerve
C3-5
motor to diaphragm
skeletal muscles

36. Brachial plexus
C5-T1
ventral rami
arm & shoulder

37. Brachial plexus passes deep to the clavicle
Damage to brachial plexus (upper or lower motor neuron lesion?)

38. Brachial plexus damage
Lower motor neuron lesion = flaccid paralysis

39. Ventral rami traveling together
Nerve Plexuses:
Ventral rami traveling
together
Cervical plexus (C1 –C5)
Brachial plexus (C5–T1)
Thoracic nerves (12 pairs)
No plexus in thoracic region
Lumbar plexus (L1–L4)
Sacral plexus (L4 –S4)
Sciatic
nerve
sciatica

40. Spinal cord injuries (SCI)
SCI’s are damage to the spinal
cord (vs vertebral column)
damage occurs from severing,
stretching or compression
result in loss of motor & sensory
function below injury site – why?
can be complete or incomplete
flaccid paralysis immediately after
injury (due to spinal shock)
spastic paralysis after spinal shock
subsides

41. Back to Frank….. Can he breath on his own?
2. Will he be able to move/feel his legs? His arms?
3. Upper or lower motor neuron lesion?
4. What kind of paralysis will Frank have?
- during spinal shock = flaccid paralysis, no reflexes
- after spinal shock = spastic paralysis, uncontrolled reflexes