1 Flashcards
Describe the euglena animal model for the nervous system
- flagella enables movement
- eyespot responds to light as it contains pigments transducing photons from light. triggers more movement.
- receptive and responsive
How did the primordial nervous system arise?
Stretch-receptive myocytes spanning the outer ectoderm/epidermis proliferated and gave rise to an identical daughter cell and a non-identical sensorimotor cell with a more complex shape
DEFINE: neurosecretory cells
cells that secrete peptide hormones that are 9-12 amino acids long e.g. insulin, glucagon and somatostatin
Somatostatin
hormone that regulates myocytes
Hydra Nervous System
- sensory neurons span the ectoderm
- motor neurons located beneath the ectoderm. they receive input from sensory neurons and output to effector cells and other motor neurons
- neurosecretory cells
- 2 layered nervous system - information flows backwards and forwards between sensory and motor cells
- interneurons between sensory neurons and myocytes/motor neurons
- interneurons between neurosecretory cells and myocytes/motor neurons
- diffuse nerve net
- radial symmetry
flatworm nervous system
- more clustering and organisation of neurons
- bilateral symmetry
- non-segmented worm
What is the purpose of gangliation?
Clustering the same neurons together produces a larger response
support for nervous system evolution theory using c.elegans
- trace progeny of P cell = single cell
- P cell forms AB cell and P cell
- neurons and hypodermis are derived from AB cell so they share lineage
so nerve cells derived through specialisation of epidermis cells
Neurogenic
region of cells that will become the nervous system
Neuroblasts
dividing progenitors whose descendants will be neurons
How does the nervous system develop in the Drosophila embryo?
- layer of ectoderm lies next to neurogenic region
- gastrulation - migration of neurogenic region downwards. neurogenic region joins there as development proceeds
- neuroblasts delaminate and migrate inwards
- neuroblasts coalesce and form the ventral nerve cord
What do neuroblasts divide into?
- 2nd neuroblast - maintained as multipotent cell
- ganglion mother cell - gives rise to neurons and glia
Where does the hypothalamus develop in the early nervous system?
ventral forebrain
How long does it take for the chick embryo to form?
21 days
When are the first signs of neural differentiation seen in human embryos?
2 weeks
How does the nervous system end up inside in vertebrates?
- neural plate is a sheet of neural precursors
- neural plate is bounded by ectoderm on either side
- neural plate rolls up into neural tube
- layers of ectoderm are brought together and fuse above the neural tube
results in layer of skin overlying neural tube and encasing it
How are BMPs made?
made as long prodomain proteins that are cleaved by BMP1 into their active components
What is the vertebrate homolog of Screw
BMP7
What is the vertebrate homolog of Dpp
BMP4
What is the vertebrate homolog of tolloid
BMP1
What is the vertebrate homolog of Sog?
Chordin
Spina bifida
neural tube defect - neural tube does not close properly