1.1 Flashcards
Describe the organization of the nervous system.
Describe the autonomic nervous system.
It works with somatic.
It acts on smooth muscle (blood vessels, GI tract), cardiac muscle, and glands.
Embryology
Embryogenesis begins with the fusion (fertilization) of male and female gametes. These 2 cells will eventually become all the different kinds of cells in the body.
Mechanisms underlying embryogenesis
- Induction of cell differentiation
- Neuron generation and apoptosis
- Neuronal guidance
- Synapse formation
Cell differentiation
Cells are targeted so they differentiate into different types of cells. Before induction begins, every daughter cell is identical.
Trilaminar germ disc develops.
- ectoderm: nervous system and skin
- mesoderm: muscle, skeleton, kidneys, and reproductive system
- endoderm: endocrine glands, lungs, digestive tract, and liver
Neurulation
Neurulation
The folding process that transforms a disc into a 3D neural tube. The notochord develops within the mesoderm and triggers neurulation.
Steps:
1. Neural plate thickens
2. Neural groove forms
3. Neural fold closes, forming neural crest (becomes PNS ganglia) and neural tube (becomes CNS).
Somites form skeleton and musculature.
Pharyngeal arches form the skeleton and muscles of the head and back.
Development of somites leads to segmental innervation.
Cell differentiation: brain and spinal cord
The neural tube develops 3 layers of cells.
- ependymal: line the fluid filled canal
- mantle: future grey mater
* alar and basal plates that are separated by the sulcus limitans
- marginal: future white matter
Cell differentiation: spinal cord
Alar plate becomes dorsal horn (sensory).
Basal plate becomes ventral horn (motor).
In the thoracic and upper lumbar areas, the basal plate also gives rise to lateral horn (ANS neurons).
Cell differentiation: brain
Develops at the cranial end of the neural tube with 3 divisions.
- prosencephalon
- mesencephalon
- rhombencephalon
The adult brain arises out of the primary brain vesicles to assume final form.
One of the most common groups of congenital defects involves abnormal tube closure.
Neuron generation and apoptosis
Neurogenesis - billions of cells that develop throughout life
Apoptosis - programmed cell death
Driven by proteins acting on specific cells
When neurotrophic factors are present, neurons grow. When absent, neurons die.
- EX: huntington’s disease
Neuronal guidance: neurochemical specificity
The axon grows are the cytoskeleton expands.
Growth cone: cytoskeleton responds to cues and changes direction of growth/
- attractive or repellant
Synapse formation
Growth cone contacts a muscle fiber and forms a neuromuscular junction.
Involves the trigger of acetylcholine production, which is attractive.
CNS
The adult brain arises out of the primary brain vesicles to assume the final form.
The spinal cord arises out of the caudal end of the neural tube.
Function:
- detects internal and external stimuli
- integrates stimuli and relates to previous experiences
- acts/reacts to maintain homeostasis
CNS: Brain
BRAINSTEM
3 divisions: midbrain, pons, medulla oblongata
- hub for connection
* cranial nerves
* ascending (sensory) and descending (motor) pathways
* reticular formation
DIENCEPHALON
Hypothalamus: survival and reproduction
Thalamus: process motor and sensory information, gateway to cerebral cortex
CEREBRAL CORTEX
Input integration
Orientation
Executive function
CNS: Spinal cord
Connects CNS to PNS
Carries signals to and from CNS
Mediates reflexes
