Download Neural Development - Peoria Public Schools

Neural Development
Option A.1
The neural tube of embryonic chordates is formed by
the infolding of ectoderm followed by elongation of
the tube.
• Neurulation- the development of a dorsal nerve cord .
a. Occurs in the first month of gestation for humans.
• Steps:
1. Part of the ectoderm, the outer germ layer in an early
embryo, becomes the nerve plate.
2. The nerve plate folds in to form the neural groove.
3. This then separates from the ectoderm to form the
neural tube.
a. The neural tube will elongate as the embryo
grows.
4. Neural crest cells are formed.
a. Can become many cells including: pigment
cells, nerve cells, skeleton and connective tissue parts.
Neurons are initially produced by
differentiation in the neural tube
• Neuro-ectodermal cells- cells from the neural plate that
become the nervous system.
Annotation of a diagram of
embryonic tissues in Xenopus p.
515
• Draw, color and annotate the diagrams.
Incomplete closure of the
embryonic neural tube can cause
spina
bifida
• Vertebral arch- thin section of the spine that encloses the
spinal cord.
• Spina bifida- the two parts of the vertebral arch never fuse
leaving a gap.
a. Most common in the lower back.
b. Can be mild to severe.
1. Severe can cause damage to spinal cord and
nerves.
Immature neurons migrate to a
final location
• Nerve cells migrate to their final position with amoeba like
movement
a. Once in their final position, mature neurons do not
normally move.
An axon grows from each
immature neuron in response to
chemical
stimuli
• Immature neurons have only the cell body and nucleus.
• One axon develops on each neuron.
a. Axon- outgrowth from the cell body that carries
signals to another neuron.
b. Chemical stimuli determine when they grow and
which direction it grows in the embryo.
Some axons extend beyond the
neural tube to reach other parts of
the
body.
• Axons can be up to one meter long in human.
• Axon Regrowth:
a. Damaged or severed axons can be regrown as long as
the cell body is intact.
A developing neuron forms
multiple synapses
• Axons and dendrites grow in the direction of other cells.
• Synapse- gap between two neurons.
• A synapse develops between the neuron and the other cell.
a. Ex. Motor neuron and a muscle cell
• Most neurons develop multiple synapses.
a. Some neurons in the brain develop hundreds.
Synapses that are not used do not
persist
• Synapses can be formed at any stage in life.
• When used:
a. Chemical markers are left that strengthen a synapse.
• When not used:
a. Synapse is weak due to no chemical markers.
Neural pruning involves the loss of
unused neurons
• Neural pruning- the elimination of part or all of a neuron cell.
a. Destroyed by apoptosis- programmed cell death.
The plasticity of the nervous
system allows it to change with
experience
• Plasticity- ability of the nervous system to rewire itself.
a. Higher before the age of six.
b. Basis for new memories.
Events such as strokes may
promote reorganization of brain
function
• Stroke- disruption of blood supply to the brain.
a. Parts of the brain take on new functions to
supplement damaged parts.