The Spinal Cord
Protection
Vertebrae
Spinal meninges
• Three layers of connective tissue
– Dura mater
– Arachnoid mater
– Pia mater
• Continuous with cranial meninges
Cerebrospinal fluid (CSF)
Spinal Meninges
• Epidural space: between vertebrae and dura
mater
• Dura mater- tough, dense connective tissue
• Arachnoid mater: resembles spider’s web
– Extends into subarachnoid space
• Subarachnoid space
– CSF circulates in this space
• Pia mater: thin, delicate layer
– Adheres to surface of spinal cord (and
brain)
– Contains blood vessels
Spinal Meninges
Spinal Meninges
Structure of the Spinal Cord
Structure of the Spinal Cord
Spinal Nerves
Nerves attached to spinal cord by 2 roots
• Dorsal root: made of axons of sensory neurons
– Dorsal root ganglion: swelling containing cell
bodies of sensory neurons
• Ventral root: composed of axons of motor
neurons
– Both somatic motor and autonomic motor
Spinal Cord Functions
Pathways for nerve impulses within tracts
• Ascending (sensory)
• Descending (motor)
Reflexes: fast, involuntary sequences of actions
in response to stimuli
• Can be simple (withdrawal) or complex
(learned sequence such as driving car)
The Reflex Arc
1. Sensory receptor: responds to stimulus
2. Sensory neuron: through dorsal root ganglion
and root  posterior horn
3. Integrating center: single synapse between
sensory and motor neurons
4. Motor neuron: from anterior horn  ventral
root  spinal nerve 
5. Effector: muscle or gland responds
The Reflex Arc