Spinal Cord, Spinal Nerves, and Somatic Reflexes

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

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

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

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

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).

2 TYPES OF MATTER WITHIN SPINAL CORD Gray Matter and White Matter

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

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

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

Reflex Arc