Ch. 4 - Development & Growth Of The Nervous System Flashcards
Nearly all new neurons are generated by when?
The end of fetal period and early neonatal period
What are the first two organ systems to function?
- Cardiovascular
2. Nervous
When does the development in the form of new neural connections occur?
T/o the growth ages
Can synaptic developments occur in old age?
Yes, with appropriate environmental stimuli
Do neural cells regenerate?
No, they are specialized cells that cannot regenerate
When does the total number of neurons start diminishing? Where?
Age 20, especially from the cerebral cortex.
Total brain weight decreases:
___% from age 20 - 90
10%
How much does nerve conduction velocity decrease?
10%
What are the 3 layers of the embryonic disc?
- Endoderm
- Mesoderm
- Ectoderm
When does the neural plate form?
18 days after conception
What does the neural plate form from?
Ectoderm
The neural plate elongates and the lateral edges fold outward to form what?
Neural folds
The rostral end of the neural plate enlarges and will later develop into what?
The brain
The neural folds continue to grow and eventually meet in the midline beginning in the ________ region to form the ___________ which progresses cephalically and caudally
Cervical; neural tube
The entire length of the neural tube is closed by when?
25 days
What develops as a bilateral column of cells from the neural ectoderm?
Neural crest
What 9 things do neural crest cells develop into?
- Sensory ganglia
- Autonomic ganglia
- Enteric ganglia
- Pia mater
- Arachnoid mater
- Sclera of the eye
- Neurolemma
- Adrenal medullary cells
- Carotid body receptors
What are the 4 basic zones (layers) of the neural tube from inside out?
- Ventricular zone
- Subventricular zone
- Intermediate (mantle) zone
- Marginal zone
Neurons which migrate here will become the gray matter of CNS
Intermediate (mantle) zone
Layer of small proliferative cells dividing as primitive neuro lasts which can migrate. Spongioblasts will become astrocytes and oliogodendroglia (myelin makers)
Subventricular zone
The most central layer consists of dividing cells which then move out to the next two layers as precursor cells. The cells that remain in this layer are called ependymal cells
Ventricular zone
Very few cells; distant axons migrate in /c macroglia to form the white matter
Marginal zone
What 2 things are structural organization and function of cells determined by?
- Intrinsic influences (mostly genetic)
2. Extrinsic influences (mostly environmental)
The predictability of the form and connections of a neuron, and therefore its function; probably genetically determined (including destination of migration, structural characteristics of the cell, characteristic physiological properties of the cell)
Neural specificity
Variation from the predictable pattern; probably the result of environmental factors as new synapses and interconnections are established
Neural plasticity