A.1 neural development Flashcards
two types of neural cells that differentiate from multipotent stem cells
Neurons (aka: nerve cells)
- Process and transmit information
Glia (aka: glial cells)
- To support neurons in a variety of ways (providing structure, insulation, nutrients, supporting the formation of new neurons/synapse for example)
causes, consequences, treatment of spina bifida
Potential causes: Unknown but attributed to folate deficiency during pregnancy. Genetics, diabetes, obesity, some medicines.
Consequences: may cause paralysis
Treatment: Surgery
spina bifida
a birth defect resulting in the incomplete closure of the neural tube (and associated vertebrae). The vertebral processes do not fuse, leaving the spinal cord nerves exposed and prone to damage
embryogenesis
The development of a fully-formed organism from a fertilised egg
gastrulation
All tissues are derived from three initial germ layers (ectoderm, mesoderm, endoderm) formed via gastrulation
neurulation
The formation of a neural tube in embryonic chordate
describe the process of neurulation
- Cells located in the outer germ layer (ectoderm) differentiate to form a neural plate
- The neural plate then bends dorsally, folding inwards to form a groove flanked by a neural crest
- The infolded groove closes off and separates from the neural crest to form the neural tube
- The neural tube will elongate as the embryo develops and form the central nervous system (brain and spinal cord)
- The cells of the neural crest will differentiate to form the components of the peripheral nervous system
label Neurulation in a Xenopus Embryo
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types of spina bifida
spina bifida occulta: the splits in the vertebrae are so small that the spinal cord does not protrude
spina bifida cystica: a meningeal cyst forms (meningocele) which may include the spinal elements (myelomeningocele)
nerve cell types
There are two types of neural cells that differentiate from multipotent stem cells:
- Neurons (aka: nerve cells) Process and transmit information
- Glia (aka: glial cells) To support neurons in a variety of ways (providing structure, insulation, nutrients, supporting the formation of new neurons/synapse for example)
neuronal migration
Immature neurons must migrate to precise locations so that they can form the neural networks.
There are two ways by which neurons migrate:
Glia-guidaded (radial migration)
Glia-independent (tangential migration)
An axon grows from each immature neuron in response to chemical stimuli
Immature neurons consist of a nucleated cell body (soma).
Axons and dendrites will form as a result of chemical signals (ex: Nerve Growth Factor).
Neurons originating from the neural tube can stay within the region and form the CNS or they can extend away from the region and form parts of the PNS
Some axons extend beyond the neural tube to reach other parts of the body
Axons grow to very specific parts of the body, following precise paths.
At the tip, growing axons have a structure called the growth cone.
The growth cone has receptors that respond to chemical signals (called guidance cues) in the environment. These “instruct” the axon where to grow.
The guidance cues either 1) attract the axon or 2) repel the axon
So, depending on the guidance cue, the axon will either grow towards or grow away from a certain area.
A developing neuron forms multiple synapses
Recall: The synapse is the junction between a neuron and a target cell (effector cell). Chemical messengers (such as acetylcholine (ACh)) travel across the synapse.
Although mature neurons general form one synapse with its effector cell, developing neurons form multiple synapses with its effector cell.
In the CNS, synapses can be formed with the cell body (soma), dendrites of the cell body, or the axon.
In the PNS, synapses are formed with muscle fibres or glands
The interactions of the neurons with the effector cells influence the development of these cells.
