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Nervous System Organization
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Development of nervous system:
Gastrulation
Formation of 3 germ layers
1. Ectoderm (epidermis / neural tissue)
2. Mesoderm (muscle / CT)
3. Endoderm (epithelium of GI & resp. tracts)
Neural plate formation
Beginning of 3rd week
notochord induces overlying ectoderm to form neural plate
End of 3rd week
lateral edges of neural plate form neural folds
(depressed mid-region = neural groove)
What is neurulation?
Neural tube formation
by fusion of neural folds (rostro-caudal direction)
Rostral neuropore (cranial opening) & caudal neuropore are open to amniotic fluid
When does closure of neuropores occur?
Coincides with establishment of blood supply to the neural tube
Where is the spinal cord derived from?
neural tube (caudal to 4
th
pair of somites)
What does the alar plate become?
Dorsal horn of spinal cord
Sensory (afferent)
What does the basal plate become?
Ventral horn of spinal cord
Motor (efferent)
3 zones of spinal cord development
Ventricular zone:
cell proliferation into neurons / macroglia
Intermediate zone
: neurons differentiate / form axons and dendrites
(a.k.a mantle layer)
Marginal zone:
edge of cord where longitudinal axon fasicles grow
Where is the brain derived from?
neural tube (rostral to 4th pair of somites)
Outline brain development from primary vesicles
Forebrain
- Prosencephalon
- Telencephalon
- Diencephalon
Midbrain
- Mesencephalon
- Mesencephalon
Hindbrain
- Rhombencephalon
- Metencephalon
- Myelencephalon
Differential growth in brain development
Causes folding / bending of developing brain
3 main flexures (folds)
:
- midbrain flexure
- pontine flexure
- cervical flexure
CNS Gray Matter
Neuron cell bodies in nuclei
Astrocytes
Microglia
Some oligodendroglia
CNS White Matter
Myelinated axons
(myelin formed by oligodendroglia)
Where is the PNS derived from?
Neural crest
Peripheral nerve components
Myelinated axons (covered by endoneurium)
Fascicles (covered by perineurium)
Nerves (covered by epineurium)
Where are peripheral ganglia of the ANS derived from?
Neural crest
Purpose of ANS
Visceral innervation
Components of ANS
3 Components
- sympathetic
- parasympathetic
- enteric
Neuron systems in ANS
Preganglionic neuron
- gray matter of CNS
Postganglionic neuron
- sympathetic = autonomic ganglia
- parasympathetic = visceral wall / ganglia close to organ
Origins of parasympathetic fibers
CN III, VII, IX, X
Spinal nerves C1 - S2/S4
Origins of sympathetic fibers
Spinal nerves T1 - L2
Sympathetic Preganglionic Neurons
Neurons in the spinal cord lateral horn from T1-L2 or 3
Some synapse in paravertebral ganglia
Others travel via splanchnic nerves to prevertebral ganglia
cholinergic
Sympathetic Postganglionic Neurons
Neurons in paravertebral (sympathetic chain) or some prevertebral (collateral) ganglia
adrenergic (except to eccrine sweat glands = cholinergic)
Parasympathetic Preganglionic Neurons
Neurons in brainstem nuclei or sacral spinal cord
Cholinergic
Parasympathetic Postganglionic Neurons
Neurons in wall of viscera
Cholinergic
Author
mnm2186
ID
30591
Card Set
Nervous System Organization
Description
Exam 2
Updated
2010-08-20T17:40:49Z
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