P215 Fall 2006 Nervous System: Development and Spinal Cord

Fox, Eighth Edition: Chapter 8, pages 190 - 192; 209 - 211, 213 - 214
Fox, Ninth Edition: Chapter 8, pages 194 - 196; 216 - 219, 221 - 222


I. EMBRYONIC DEVELOPMENT
A. Normal Pattern
1. neurulation of embryo's neuroectoderm
a. neural plate
b. neural groove
c. neural tube
1) nervous tissue walls
2) central fluid-filled space


Click to see neurulation in cross-section through part of embryo (flash format)



2. early neural tube differentiation
a. front portion develops into brain
b. rear portion develops into spinal cord
B. Some Developmental Problems
1. neural tube defects (NTDs)
2. two common kinds of NTDs
a. spina bifida


b. anencephaly


3. prevention of NTDs



II. SPINAL CORD
A. Review of Structure
1. central canal
2. gray matter
3. white matter
4. spinal nerves
a. dorsal spinal roots with dorsal root ganglia
c. ventral spinal roots



B. Functional Organization
1. sensory afferent neurons
a. carry in sensory information to CNS
b. via spinal nerves and dorsal spinal roots and ganglia
2. interneurons
a. in CNS
b. help process information, analyze, decide
3. motor efferent neurons
a. carry motor commands out from CNS
b. via ventral spinal roots and spinal nerves



C. Spinal Reflexes
1. reflex arcs
2. examples
a. withdrawal reflex

1) stimulus -
2) events -


3) response -
b. muscle stretch reflex

1) stimulus -
2) events -


3) response -
2. differences between these two kinds of reflexes



(Click for Spinal Reflex Arcs)
(Click for Muscle Stretch Reflex)
D. Spinal Pathways
1. connections between different levels of CNS
a. short pathways in spinal cord
b. long pathways between spinal cord and brain
c. axons of interneurons
2. major kinds of long pathways
1) ascending

2) descending

2. organization
a. precise location in white matter for each pathway
b. particular origin and termination for each pathway
c. specific functions of different pathways



3. damage of long spinal pathways
a. affects conduction of action potentials
b. losses

c. what remains




OBJECTIVES: NERVOUS SYSTEM


1) Explain the general pattern of central nervous system development.
From what embryonic tissue does the nervous system develop?
What is the neural plate? What is the neural groove? What is the neural tube?
How are the neural plate, neural groove and neural tube related?
What are some common problem in nervous system development?
How common and how serious are these problems?

2) Describe the functional organization of the spinal cord.
What is the difference between gray matter and white matter?
Where are gray and white matter located in the cord?
How does sensory information enter the spinal cord?
How do commands exit the spinal cord?
What happens in between (in the cord itself)?

3) Describe the workings of a spinal reflex.
What is meant by a "reflex arc"?
What is a withdrawal reflex? Why is it "useful"?
What is a stretch reflex? What are two reasons is it so fast?
Do reflexes vanish after spinal injuries?

4) Describe the way neural impulses pass between the brain and spinal cord.
Axons of what neurons make up many of the pathways?
Where are these pathways located?
Are they well-organized or just jumbled together?
What is the difference between ascending and descending spinal pathways?
What kind of information do these pathways carry?
What can happen to sensory and movement functions after damage to the cord?
What sort of sensory and movement loss is experienced and where in
relation to the point of spinal damage?