Development of the Nervous system Flashcards
What does the myotome and splanchnic form?
Myotome forms the skeletal muscle only, splanchnic forms the smooth and cardiac muscle (visceral)
What is made above the 4th somite before neurulation and below the 5th somite?
Above the 4th is the brain, below the 5th is the spinal cord
What is considered to be part of the central nervous system (CNS)?
Anything enclosed within the brain/vertebral column, including brain and spinal cord
What is considered to be part of the peripheral nervous system (PNS) and what are some examples?
Starts in spinal cord/brain, but goes outside of it to muscle or skin, or a sensory nerve on the muscle or skin that goes back to the brain.
Cranial nerves, spinal nerves, ganglia (collection of cell bodies), enteric plexus, sensory receptors (finger tips/skin)
What are the two categories of the peripheral nervous system?
Somatic Autonomic
What is important of the somatic nervous system?
Means body… has motor and sensory portions which are voluntary/you are conscious of (medial, radial ulnar N.)
What is important of the autonomic system?
Has motor and sensory neurons (ignored)
Parasympathetic and Sympathetic
unconscious and involuntary (heart beat)
What is grey matter of the adult spinal cord and what is it made up of?
It is the location of cell bodies of neurons and is made up of dorsal (posterior) horns: sensory neurons, lateral horns: autonomics, anterior (ventral) horns: motor neurons
Where do you see lateral horns mostly (vertebrae wise)?
T1 to L2
What is white matter of the adult spinal cord and what does it consist of?
White matter is where axons are located and they are myelinated (unlike grey matter).
Dorsal (post) funiculus: sensory
Lateral funiculus: sensory and motor
Anterior (ventral) funiculus: motor
The neural plate/tube is divided into two different parts, A and B. What are they and what do they become?
A is Alar plate, becomes sensory neurons that stay in the CNS and never leave (remember neural crest cells are sensory at distance, not inside CNS)
B is Basal plate, becomes motor neurons, lower skeletal and pre-ganglionic/synaptic
how are the alar and basal plate divided?
Sulcus limitans
Afferent vs. Efferent?
Afferent are sensory neurons
Efferent are motor neurons
What does the neural canal/ central canal become?
Ventricular system (in future)
What are the 3 different zones of the spinal cord?
Ventricular zone, closest to the central canal
intermediate zone/matle layer, becomes grey matter
Marginal zone, becomes white matter
The ventricular zone gives rise to stems cells. What are the options for the development of the stem cells?
The can rise up to the intermediate zone or they will stay in the ventricular zone and give rise to ependymoblast to ependymal cell (line ventricular and cell) to the choroid plexus cell which makes cerebral spinal fluid (CSF) derived from neural tube
What does the intermediate zone of the spinal cord contain?
GREY MATTER Astrocytes (regulate microenvironment), neurons
What does the marginal zone of the spinal cord contain?
WHITE MATTER: Oligodendrocytes myelinate cells/axons in the CNS (schwaan from crest myelinate cells in PNS)
What does the neural tube (nueroectoderm) give rise to?
Axons, astrocytes, oligodendrocytes, ependyma cells and choroid plexus (CFS!!)
Where do microglial cells come from?
From mesoderm/mesenchymal cells
monocytes from brain become microglial
The vertebral column and spinal cord are the same length at month 3, where can the spinal cord of a newborn and adult be found out?
Newborn at L2/L3
Adult at L1/L2
because the vertebrae increases in size
If you have a premature infant in the ICU, where do you do the lumbar puncture?
Much lower, between L3 and L4 to make sure you do not hit spinal cord
The sensory neurons in the periphery and the spinal ganglion cells are made from what?
Nueral crest cells
What is at the dorsal end of the neural tube and what does it release?
The roof plate (organization center) that releases BMP to make the dorsal end (BMP also released by surface ectoderm)
What is at the ventral end of the neural tube and what does it release?
The floor plate (organization center) that releases sonic hedgehog (SHH) to make the ventral end (as well as the notochord)
What does high BMP levels activate and what do those do?
It activates PAX3 and PAX7 which are genes that will turn on sensory neurons to make the alar plate
What does high SHH levels activate and what do those do?
It activates NKX2.2 and NKX6.1 which are genes that turn on the neuron formation to make basal plate (ventral)
What happens when there are lower SSH and higher BMP levels?
It will activate NKX6.1 and PAX6 which will form the ventral motor neurons all depending on the CONCENTRATION GRADIENT!!!
What develops from the neural tube?
motor neurons and pre-ganglionic autonomic neurons
What develops from the neural crest?
neurons of dorsal root ganglia, sensory ganglia of cranial nerves, schwaan cells, sympatheic and parasympathetic ganglia (autonomic)
What are dorsal root (sensory) and ventral root(motor) of the spinal cord derived from?
Dorsal: nueral crest cells
Ventral: neuroectoderm (basilar plate-tube)
Mixed spinal nerves such as dorsal ramus (epimere/epaxial) and ventral ramus (hypomere/hypaxial) have nueral crest or neural tube cells?
They have both!
How do you get into and out of the spinal ganglia?
Ramus communicantes (motory/sensory to viscera)
General somatic efferent (GSE) from neuroectoderm
motor neurons that innervate muscles that came from the somites (somatic mucle–biceps/latissimus)
General visceral efferent (GVE) from neuroectoderm
motor neurons that innervate autonomics to smooth and cardial muscle
Brachial or Special visceral efferent (SVE) from neuroectoderm
motor neurons that innervateds muscles from pharyngeal arches (face and neck muscles)
General somatic afferent(sensory) (GSA) from neural crest cells
sensory neruons that Innervate skin, joints, muscle (mesoderm near ectoderm)
General visceral afferent (sensory) GVA from neural crest cells
sensory nerons that innervate structures from endoderm or mesoderm that developed adjacent to endoderm (organs)
What is the difference between sympathetic and parasympathetic?
Symp: Fight or flight
Para: rest and digest
What develops ganglion and post ganglion cells?
Nueral crest
What develops pre-ganglion cells?
Neuroectoderm
where is the sympathetic system located?
in the spinal cord T1-L2
What are the differences between pre and post ganglion in sympathetic system?
preganglion (lateral horn) (NE) are myelinated and short, while postganglion (NC) are unmyelinated and long
Where is the parasympathetic system located?
in the cranial nerves (4 there) and S2-S4 (innervate pelvic organs)
Where do preganglionic region come from in parasympathetic?
lateral horn of spinal cord, myelinated and long
Where do postganglionic region come from in parasympathetic?
Nueral crest, short and not myelinated
Where are the parasympathetic ganglia usually located?
wall of the viscera/organs (hirsprung’s disease lack postganglionic which are neural crest cells)
four cranial ganglia
When does myelinationg of the axons occur?
during the late fetal period and continues into first postnatal year (why we cant walk), completely myelinated by 22/23!
What myelinates the CNS?
Oligodendrocytes from neuralectoderm, 6months through puberty (frontal lobe is last)
What myelinates the PNS?
Schwann cells from neural crest, motor roots before sensory roots during the 4th month (baby kicks).
