Chapter 14: The nervous system: the spinal cord and spinal nerves

CNS

consist of the spinal cord and brain

spinal cord

integrates and processes information

spinal meninges

provide protection, physical stability, and shock absorption

the three meningeal layer

dura mater- tough, fibrous outermost layer

arachnoid mater-middle layer

pia mater- innermost layer

gray matter

surrounds central canal and contains cell bodies of neuron and glial cells

posterior gray horn

contains somatic and visceral sensory nuclei

anterior gray horns

contains somatic motor nuclei

lateral gray horns

contains visceral motor neurons

gray commissures

contain the axons of interneurons that cross from one side of the cord to the other

ascending tracts

relay information from spinal cord to brain

descending tracts

carry information from brain to spinal cord

reflex

immediate involuntary response to a specific stimulus

reflex arc

the neural "writing" of a single reflex

Reflex arc example

step one-arrival of stimulus and activation of receptor

step two- activation of a sensory neuron

step three- information processing in CNS

step four- activation of a motor neuron

step five- response by effector

cranial reflex

processing of the brain

spinal reflex

processing of the spinal cord

innate reflex

genetically determined

acquired reflex

learned

somatic reflex

control skeletal muscle contractions

include superficial and stretch reflexes

visceral(autonomic reflexes)

control actions of smooth and cardiac muscles glands

monosynaptic

one synaspe

polysnaptic

multiple synaspes(two to several hundred)

stretch reflexes

step 1- stimulus stretching of muscle stimulus muscles spindles

step 2- activation of a sensory neuron

step 3- information processing at motor neuron

step4 - activation of motor neuron

step 5- response contraction of muscle