the spinal cord. protection vertebrae spinal meninges three layers of connective tissue – dura...

The Spinal Cord

Protection

VertebraeSpinal meninges• Three layers of connective tissue– Dura mater– Arachnoid mater– Pia mater

• Continuous with cranial meningesCerebrospinal 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 stimulus2. Sensory neuron: through dorsal root ganglion

and root posterior horn 3. Integrating center: single synapse between

sensory and motor neurons4. Motor neuron: from anterior horn ventral

root spinal nerve 5. Effector: muscle or gland responds

The Reflex Arc