Spinal Cord, Spinal Nerves, and Somatic Reflexes

1. Spinal Cord, Spinal Nerves, and Somatic Reflexes

2. Functions of the Spinal Cord • Conduction – sends information up and down the cord • Locomotion • Reflexes – involuntary responses to stimuli

3. The Spinal Cord is continuous with the brain and emerges from the foramen magnum at the base of the skull stretches downward for approx.  42 - 45 cm through the vertebral foramen there are 31 pairs of spinal nerves that emerge from the spinal cord through the intervertebralforamen 

4. Reflexes: the simplest responses to a stimulus Ex. Sneezing and Blinking produces a rapid motor response to a stimulus because the Sensory Neuron synapses directly with a motor neuron in the Spinal Cord. are very fast and most never reach the brain

5. Meninges • Enclose the spinal cord • Three layers • Dura mater – superficial • Arachnoid mater • Pia mater – deep • Space between • Epidural – between dura mater and vertebral bone • Subarachnoid – between arachnoid and pia mater

6. 2 Types of Nerves Radiating from Spinal Cord the dorsal roots contain Neurons that carry signals to the CNS from various kinds of Sensory Neurons (Affectors). the ventral roots contain the Axons of Motor Neurons, which are neurons that contact and carry information to the Muscles and Glands (Effectors).

8. Gray Matter and White Matter 2 Types of Matter within Spinal Cord

9. Gray Matter • Site of information processing • Contains primarily unmyelinated structures • Dendrites • Synapses • Looks like a butterfly • 2 dorsal horns • 2 ventral horns • Central canal

10. White Matter • Carry signals fromone aprt of CNS to another • Contains myelinated structures • Primarily axons • Surrounds the gray matter • Bundles of axons that provide avenues of communication up and down the spinal cord

11. Reflexes • What is a reflex? • Four properties of a reflex • Stimulation – response to sensory input • Quick • Involuntary • Sterotyped (predictable response)

12. Reflex Arc