DEV2022 – Lecture 18
Neural tube is the source of everything in the nervous system because although
the neural crest does give rise to some components, the neural crest is derived
from the neural tube. Almost all of the cells found in the brain and spinal cord
(CNS) is derived from a common neural stem cell.
Neural epithelium ectodermally derived forms a neural tube (hollow cylinder).
At the cranial end, it differentiates into 3 major parts, and one of the 3 major
parts form the brain, which are connected to the brainstem.
The brain winds up being composed of 3 components (forebrain, midbrain,
hindbrain). These parts of the brain are programmed such that the part in the
front, middle or back are responsible for those parts of the brain.
A transplant experiment:
Transplant of hindbrain into forebrain becomes a part of the hindbrain in the
Most neurons are:
Nerve tissues consists of 3 components: nerves, cells that support the nerves
(neuroglial cells), and connective tissue.
Lots of cell processes coming from the cell body, and a single axon (multipolar).
Occurs in places like retina (bipolar)
It has no dendrites or processes coming from the cell body (pseudounipolar).
Tangled web of dendrites, synapses (nerve cell processes) – so much of it, that
theres hardly any extracellular space = neuropil.
Central canal of neural tube becomes brain ventricles:
There are spaces inside of the brain = ventricles.
Spinal cord and spinal nerves:
Extension of CNS at the spinal cord ends at L1.
Neural crests contribute to the development of glial cells and sensory nerves.
Glial cells = supporting non-neural cells found in CNS and PNS.
Dorsal root ganglion = derived from neural crest.
The motor component of the spinal nerve develops from the neural tube.
A typical myelinated peripheral nerve:
Nerves that are myelinated. They have a central dot (axon) and a donut ring
Schwann cells are the myelinate nerves of the PNS.
More myelin = bigger the nerve = more insulation