Lecture 3- Induction of the Nervous System I Flashcards
What is the polarity in the 8-cell human embryo?
- none apparent pre-implantation
- after 3 divisions
What is the polarity in a 3 week old human embryo?
-post-implantation, axis apparent but shifted when compared to an adult
What are the axes like in an adult human brain?
-
What are the 7 stages of neural development (in order)?
- Neural induction
- Neurulation
- Morphogenesis and patterning of the neural tube
- Neurogenesis
- Neuronal migration
- Axon growth and pathfinding
- Synaptogenesis
What is neural induction (stage 1 of neural development)?
-assigning neural potential to a region of early embryo
What is neuralation (stage 2 of neural development)?
-forming the rudimentary nervous system
What is neurogenesis (stage 4 of neural development)?
-productions of neurons and glia from precursor cells
What is neuronal migration (stage 5 of neural development)?
-neurons move from sites of production to their position in the mature brain
What is axon growth and pathfinding (stage 6 of neural development)?
-axons grow and find appropriate target and dendritic arborization takes place
What is synaptogenesis (stage 7 of neural development)?
-making and refining connections
Why are amphibians good models to study early neural development?
- have large eggs (1mm diameter)
- develop externally of the mother so can work on them more easily
- see-through embryo and egg
What is a blastula and when is the developing embryo called blastula?
- a hollow sphere of cells, referred to as blastomeres, surrounding an inner fluid-filled cavity called the blastocoele formed during an early stage of embryonic development in animals
- embryo development begins with a sperm fertilizing an egg to become a zygote which undergoes many cleavages to develop into a ball of cells called a morula. Only when the blastocoele is formed does the early embryo become a blastula.
What is a blastocoele?
the fluid-filled central region of a blastula and mammalian blastocyst (same as blastula but specific to mammals)
What is a gastrula?
-the stage in the embryo development in which the three germ layers are established after involution of blastula cells
What is involution?
- process in the early development of an embryo at the beginning of gastrulation (so shoft from blastula to gastrula) where a sheet of cells moves into the interior of the embryo by rolling in under itself
- creation of the germ layers
What does the nervous system arise from?
- region of the dorsal ectoderm
- called the neuroectoderm or neurogenic region
What is a blastopore?
- an opening into the archenteron during the embryonic stages of an organism
- will become the anus (or mouth, depends if protostome= mouth first or deuterostome= anus first, humans= anus first)
What is the archenteron?
-the primitive gut, blastopore is its opening
What does the ectoderm that won’t be part of the nervous system become?
-the epidermis of the skin
What is the IMZ (Involuting Marginal Zone)/ DLB (dorsal lip of blastopore)?
- region of cells immediately above the blastopore lip which narrows and lengthens internally during gastrulation
- creates mesoderm
What is a neurula?
-the stage of vertebrate development at the end of gastrulation when the neural tube is forming
What is the notochord?
- in vertebrate embryos it is a rod-like structure that runs from head to tail and lies centrally beneath the future central bervous system
- it is derived from dorsal mesoderm
- it plays an important role in patterning the overlying neural tube
What happens to neuroectoderm at the beginning of neuralation?
- it spreads anteriorly and becomes the neural plate
- the anterior part will become the brain, posterior will become the spinal cord
What does the notochord develop from?
-from a region of the mesoderm underlying the neural plate
