Lecture 16: Development Of Nervous System Flashcards
At approximately what week of development does development of the peripheral nervous system begin?
Week 4 (day 28-33)
Beginning at day 28 of development, motor neurons appear in the ______ column of the neural tube, starting in the _______ region
By day 29, ________ root ganglia are present at most levels. ______ root ganglia begin to form at day 30, starting in the________ region.
Ventral; cervical
Dorsal; ventral; cervical
At day 31 of development, spinal nerves sprout and grow into ________, starting in the cervical region
At day 33, ______ trunks form, starting in the cervical region
Myotomes
Sympathetic
The CNS is comprised of brain and spinal cord, and derivatives are formed from _______ ______
Neural tube
If the CNS is brain and spinal cord, what is the PNS?
All components of nervous system outside the CNS:
Cranial nerves and ganglia
Spinal nerves and ganglia
Autonomic nerves and ganglia
Enteric nervous system
The PNS develops primarily from ________ _______, with some aspects of neural crest, neuroectoderm, and ectodermal placodes
Neural tube
What are the 2 primary divisions of PNS?
Sensory (afferent) division
Motor (efferent) division
What are the 2 modalities of the sensory (afferent) division of the PNS?
Somatic sensory
Visceral sensory
What are the 2 modalities of the motor (efferent) division of PNS?
Somatic motor
Visceral motor
What modality of the PNS is responsible for motor innervation of all skeletal muscles?
Somatic motor (voluntary motor)
What modality of the PNS is responsible for motor innervation of smooth muscle, cardiac muscle, and glands, and is equivalent to the ANS?
Visceral motor (involuntary motor)
What modality of the PNS is responsible for touch, pain, pressure, vibration, temperature and proprioception in the skin, body wall, and limbs?
Somatic sensory
What special senses are associated with somatic sensory modality of the PNS?
Hearing, equilibrium, and vision
What modality of the PNS is associated with stretch, pain, temperature, chemical changes, and irritation in the viscera; nausea and hunger?
Visceral sensory
What special senses are associated with visceral sensory modality of the PNS?
Taste and smell
Motor function is associated with what anatomical region of the spinal cord?
Anterior region
Autonomic function is associated with what anatomical region of the spinal cord?
Lateral regions
Sensory information is associated with what anatomical region of the spinal cord?
Posterior region
Which type of matter, gray or white, makes up the “H” shaped region of the spinal cord?
Gray
What is the gray matter of the spinal cord made up of?
Neurons and glial cells
What is the white matter of the spinal cord made up of?
Myelinated axons
Does not contain many neuron cell bodies
The gray matter of the spinal cord has posterior, lateral, and anterior horns, what function does each of these pertain to?
Posterior = sensory
Lateral = visceromotor
Anterior = motor
The developing neural tube is divided into dorsal and ventral regions, separated by what named component that will become the regions of the spinal cord?
Sulcus limitans
The neural tube is divided into dorsal and ventral regions, separated by the sulcus limitans and is comprised of a germinal _____________.
It spans the full width of the NT from lumen/canal to the outer surface. It will give rise to a range of cell types in the brain and spinal cord
Neuroepithelium
What are the 3 primary cell types derived from the germinal neuroepithelium?
Neuroblasts
Glioblasts (spongioblasts)
Ependymal cells
Germinal neuroepithelium gives rise to apolar neuroblasts, glioblasts (spongioblasts), and ependymal cells.
What is the fate of the apolar neuroblasts?
Become neurons, complete with axon + cell body + dendrites
Germinal neuroepithelium gives rise to apolar neuroblasts, glioblasts (spongioblasts), and ependymal cells.
What is the fate of glioblasts?
Become astrocytes (protoplasmic or fibrous)
OR
Become oligodendrocytes
Germinal neuroepithelium gives rise to apolar neuroblasts, glioblasts (spongioblasts), and ependymal cells.
What is the fate of the ependymal cells?
Become epithelium of the choroid plexus
Germinal neuroepithelium gives rise to apolar neuroblasts, glioblasts (spongioblasts), and ependymal cells.
What is an additional cell type not derived from neuroepithelium, but derived from mesenchymal cells?
Microglial cells (have macrophage-like activity)
During neural tube differentiation, it is separated into 3 zones.
Which zone has stem cells positioned closest to the lumen that are mitotically active and will migrate?
Ventricular zone
During neural tube differentiation, it is separated into 3 zones.
Which zone contains migrating cells that undergo differentiation into neurons and/or glia and extend axons away from the lumen toward the outer surface?
Mantle/intermediate zone
During neural tube differentiation, it is separated into 3 zones.
Which zone is poor in neuronal cell bodies and contains axons that will eventually be myelinated?
Marginal zone
By the end of the 4th week of development, the mantle layer of the spinal cord reorganizes into what 2 regions?
Alar (dorsal) columns
Basal (ventral) columns
By the end of the 4th week of development, the mantle layer of the spinal cord reorganizes into the alar columns and basal columns. These are connected by the ______ ______ and the ______ ______
Roof plate; floor plate
T/F: the roof plate and floor plate that join the alar and basal columns of the developing spinal cord have their own distinct populations of neurons
False! The roof and floor plate contain no direct populations of neurons
T/F: plates/columns extend the entire length of the developing spinal cord and cells will undergo continued differentiation due to signaling from the plates
True
The alar plate is made up of _______ horns which carry ________ information
Dorsal; sensory
The basal plate is made up of ______ horns which carry ______ information
Ventral; motor
Which of the following cell types are found in the neural tube?
A. Motor neurons B. Sensory neurons C. Interneurons D. A and C only E. All of the above
D. A and C only
You do not directly form sensory neurons in your neural tube or spinal cord, you will find sensory neurons in the dorsal root ganglion – cell body is positioned there and the other end is generally in the periphery like the skin
Neuron types are determined based on their position in dorsal-ventral progenitor domains. What type of neurons are derived from dorsally positioned cells?
Interneurons
Neuron types are determined based on their position in dorsal-ventral progenitor domains. What type of neurons are derived from ventrally positioned cells?
Interneurons
Motor neurons
[remember that sensory neurons do not form in the neural tube or spinal cord!]
What signaling factor, member of the TGF-B superfamily, is found in the ROOF PLATE of the neural tube and forms a gradient counteracting SHH so that dorsal/ventral axis can be established?
BMP
BMP goes on to activate what 2 signal factors in order to establish neuronal identity?
PAX3 and PAX7
What signaling factor, found in the FLOOR PLATE of the neural tube helps establish a gradient so that dorsal/ventral axis can be established?
SHH
A high concentration of SHH is found in the floor plate of the NT, and it contributes to the differentiation of ______ neurons
Motor
What is the result of a low concentration of SHH on the neural tube?
Multiple interneurons are induced, depending on the decrease in SHH
What are the 2 primary downstream targets of SHH for ventral neuron formation?
NKX2.2 and NKX6.1
T/F: in general, sensory neurons form before the motor neurons
False! Motor neurons form before sensory
_____________ columns form when the dorsalmost cells of the basal plate undergo segregation. These will form the ______ horns, which are only found in some areas of the spinal cord
Intermediolateral; lateral
Only some areas of the spinal cord have lateral columns: T1-L3 and S2-S4.
What type of neurons are found in T1-L3 lateral horns?
Visceral motor neurons of SYMPATHETIC division (fight or flight)
Only some areas of the spinal cord have lateral columns: T1-L3 and S2-S4.
What type of neurons are found in S2-S4 lateral horns?
Visceral motor neurons of PARASYMPATHETIC division (rest and digest)
The peripheral nervous system is derived from what 2 major progenitors?
Neural crest cells Ectodermal placodes (cranial PNS only)
What do neural crest cells give rise to in the trunk?
Sensory neurons in DRG
Schwann cells
Sympathetic ganglia
Enteric nervous system
Axons of the PNS exiting the ventral horn pass through the cranial _________, forming the ventral root
The ventral root is then joined by axons from the _______ horn. Neural crest cells form DRG _______ neurons.
Axons from the DRG extend to the _____ horn
Sclerotome
Lateral; sensory
Dorsal
What remnant of the lumen of the neural tube remains in the mature spinal cord?
Central canal
T/F: spinal nerves contain 2-3 components each, so each spinal nerve carries both sensory and motor modalities (sometimes visceral MNs as well)
True
The posterior root of spinal nerves consist of axons from ______ _____ _____
The ventral root of spinal nerves contain axons from ________ ______ ________
The ventral root of spinal nerves may also contain axons from _____ _______ ________in the intermediolateral cell columns/lateral horn
Dorsal root ganglion (sensory)
Somatic motor neurons
Visceral motor neurons
What are the 4 types of neurons that may be found as components of a typical spinal nerve?
Somatic sensory neuron
Visceral sensory neuron
Autonomic motor neuron
Somatic motor neuron
What type of nerve supplies somatic muscle?
General somatic efferent (GSE)
What type of nerve supplies autonomics to smooth and cardiac muscle and glands?
General visceral efferent (GVE)
What type of nerve supplies the muscles derived from the pharyngeal arches?
Branchial or Special Visceral Efferent (SVE)
What type of nerve supplies sensation in the skin, joint capsule, tendon, and muscle?
General somatic afferent (GSA)
What type of nerve supplies sensation of visceral structures?
General visceral afferent
What type of nerve supplies senses of hearing, balance, and sight?
Special somatic afferent (SSA)
What type of nerve supplies senses of taste and smell?
Special visceral afferent (SVA)
The autonomic nervous system consists of a 2-chain system. What are the 2 chains?
Chain 1: Preganglionic neuron and fibers
Chain 2: Ganglionic neuron and postganglionic fibers
[recall that somatics have 1-neuron chain]
What are some differences between sympathetic and parasympathetic
Sympathetic = fairly short preganglionic fiber with numerous long branches, fight or flight, utilize ACh and NE as NT’s
Parasympathetic = long preganglionic fibers that extend out to ganglia that are positioned in the organs themselves, there is minimal branching compared to sympathetics, slower activation, utilize ACh as NT
Preganglionic neurons of the ANS are derived from __________
Neuroectoderm
What are the NCC derived sympathetics?
Trunk and collateral ganglia
Ganglionic neurons
What are the NCC derived parasympathetics?
CN ganglia in the head and neck
Terminal ganglia in trunk
Ganglionic neurons
What cell type is responsible for the myelination in the CNS?
Oligodendrocytes
[glial cells derived from neuroepithelium, begins in lower brain stem, older tracts first, 6th months through puberty
What cell type is responsible for the myelination in the PNS?
Schwann cells
[NCC derived, motor roots myelinated before sensory roots, 4th month]
