Embryology: Neurulation & Neural Crest, Histology: Nervous Tissue Flashcards
What is the somatic nervous system
the nervous system that innervates the skin and most skeletal muscle
what is the visceral (autonomic) nervous system
the nervous system that innervates the viscera, smooth muscle, and glands
what are the divisions of the visceral/autonomic nervous system
sympathetic and parasympathetic
What are the steps in the formation of the neural tube
- thickening of neural plate
- elongation of neural plate
- lateral folding
- fusion of opposing neural folds
- separation from overlying ectoderm
what is the role of each of these structures in neural tube formation: notochord neural groove neural crest median hinge point lateral hinge point neural crest cells
notochord - lies below the neural groove and signals the formation of the following structures
neural groove - cells that form the first invagination of the neural tube
neural crest - cells that come together to complete the tube formation (remain as free cells outside of tube)
median hinge point - first fold point of the tube
lateral hinge point - two lateral points of folding that bring the neural crests together
What are the different primary CNS segments
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
spinal cord
how many folds are there in the primary CNS
2 (cephalic and cervical)
what are rhombomeres
different segments of the hindbrain caused by HOX genes
What are the secondary CNS segments
Prosencephalon 1. telencephalon 2. diencephalon 3. Mesencephalon Rhombencephalon 4. metencephalon 5. myelencephalon spinal cord
how many folds are there in the secondary CNS
3 (mesencephalic, cervical, pontine)
What does the telencephalon develop into (and the neural canal in that area)
cerebral hemispheres (lateral ventricles)
What does the diencephalon develop into (and the neural canal in that area)
Thalamus, hypothalamus, pituitary gland, eyes (3rd ventricle)
what does the mesencephalon develop into (and the neural canal in that area)
anterior (visual) and posterior (auditory) colliculi (cerebral aquedcut
What does the metencephalon develop into
cerebellum, pons
what does the myelencephalon develop into
medulla oblongata
What happens at the external limiting membrane of the neural tube, and what happens at the lumen side of the neural tube
DNA synthesis occurs at the external limiting membrane
mitotic division occurs at the lumen side
What is the first progenitor cell in the CNS
neuroepithelium
what are the steps of differentiation of CNS cells
- neuroepithelium
- multipotential stem cell
- Bipotential progenitor cell
4a. neuronal lineage progenitor cell
- mature neuron
- microglial cell
4b. Glial lineage progenitor cell
- oligodendrocyte
- type 2 astrocyte
- type 1 astrocyte
- special glial cells
- ependymal cells
What happens in the development of mature neuron
they have outgrowths called filopodia that extend and retract (testing the environment) that develop into axons and dendrites
what are the two divisions of the brain
brain stem = myelencephalon, pons, and mesencephalon
higher centers = cerebellum and forebrain
what are the steps in the development of the thalamus and hypothalamus (pineal gland)
- swellings on the inner diencephalon with the hypothalamic sulcus between them
- sulcus dorsus separates the thalamus from the epithalamic swelling
- thalamic swellings grow and connect via interthalamic adhesions
- pineal gland forms from a midline diverticulum off of the epithalamic roof plate
what are the steps in the development of the pituitary gland
- infundibulum develops from the floor of the 3rd ventricle
- Rathkes pouch forms from the ectoderm lined space near future mouth
- move toward each other. and join
- rathkes pouch breaks off
- both move into the sella turcica
what forms the anterior pituitary, and what forms the posterior pituitary
infundibulum turns into posterior pit
rathkes pouch turns into anterior pit
what is the mesencephalon largely made up of
white matter, tracts that connect the forebrain and hindbrain
What does the lumen of the neural tube associated with the mesencephalon develop into
the cerebral aqueduct
what happens if the cerebral aqueduct becomes blocked
hydrocephalus (fluid accumulation in the brain)
what things develop into the pons
rhabdomeres 1 and 2 and cerebellum
what is the function of the pons
relay signals linking the spinal cord with the cerebral cortex and cerebellum
what are the pontine nuclei
the part of the pons that relays input from the cerebrum to the cerebellum
What things develop into the cerebellum
metencephalon and the adjacent rhombic lips
what is the function of the cerebellum
center for balance and posture
what are the steps in formation of the cerebellum
- paired cerebellar plates form
- cranial portions meet and cover 4th ventricle
- dumbell shaped swelling forms
- cranial and caudal portions are separated by posterolateral fissure
- fissures, folding = lobes with transverse fissures and vermis
what develops into the medulla oblongata
the myelencephalon (rhabdomeres 3-8)
what is the function of the medulla oblongata
it is the relay center between the spinal cord and higher brain centers
what does the medulla oblongata regulate
respiration, heartbeat, reflex movements
What are the steps in formation of the peripheral nerves
- outgrowth of axons from motor neuroblasts in the basal plate
- neural crest cells form the spinal ganlion with their axons growing toward the dorsal horn and their dendrites growing toward periphery
- interneurons grow between sensory nerve termination and motor neurons
- reflex arc forms (sensory information leading strait into motor response)
what forms all sympathetic and parasympathetic ganglia
neural crest cells
What is hirschsprungs disease
when NCC’s fail to colonize in the wall of lower colon (parasympathtic) which means there is no parasympathetic innervation which means no peristalsis which means constipation
What is myelination and how does it happen
it is when a schwann cell (NCC derivative) wraps around the nerve and insulates it
what happens with unmyelinated cells
they are embedded in non-spiral schwann cells
what are the two main kinds of peripheral neuropathies
axonal degeneration and demyelination
what type of peripheral neuropathy is charcot-marie-tooth
demyelinating (slows nerve conduction)
what is a neurite
an outgrowth, axon or dendrite
what are the steps in the growth of an axon
- pioneering axon grows to a target
- other axons follow
- a bundle of axons form (fascicles)
Where do NCC’s originate from
the lateral margins of the neural plate
How do NCC’s migrate?
as mesenchymal cells, they change their shape, lose CAMS, and gain integrins. they travel through well defined pathways (CAMS come back upon destination)
what determines differentiation of NCC’s
environment determined upon arrival, internal factors before migration
what are the three main divisions of NCCS
- crainial
- circumpharyngeal
- Trunk
what are the things to remember about cranial NCC’s
they leave before the neural tube closes
the origin specifies the destination
they are responsible for the tissues of the facial region
what are the things to remember about circumpharyngeal NCC’s
they migrate in two groups (vagal and cardiac)
Vagal - migrate into gut and are precursors to parasympathetic innervation
Cardiac - outflow of the heart and great vessels, associate with thymus, thyroid and parathyroid
what are the things to remember about trunk NCC’s
they leave after the neural tube closes
they migrate in three pathways (dorsolateral, ventrolateral, ventral)
dorsolateral - melanocytes
ventrolateral - sensory ganglia
ventral - adrenal chromaffin cells, sympathetic ganglia and neurons
what are neurocristopathies
defects of NCC development
what is neurofibromatosis
peripheral nerve tumors
what is albinism
pigmentation defect
what is diGeorge syndrome
defects in development of craniofacial and cardiovascular system
what causes the nervous system to work
action potentials send messages to the body
what are the components of the nervous system
brain, spinal cord, nerves, supporting cells
what are the divisions of the Nervous system
CNS PNS - sensory - somatic - visceral - motor - somatic - autonomic - para, and sympathetic
what do neuroglial cells do
provide neuronal support and nutrition
maintain homeostasis
forms myelin
participates in transmission
what are the 4 neuron characteristics
conducting potential
longevity
amitotic
high metabolic rate
What is the soma
cell body (nucleus and organelles), they make up the gray matter
what are clusters of cell bodies called in the CNS and PNS
CNS = nuclei PNS = ganglia
what is a synapse
the junction where an axon bulb interacts with another neuron or effector organ
what are the three main parts of a synapse
presynaptic neuron
synaptic cleft
postsynaptic neuron
what is the resting potential of a neuron
-70 mV
What are bipolar neurons for
special senses
what are unipolar neurons for
sensory PNS, taste
what are multipolar neurons for
motor neurons and interneurons
what are the 6 types of glial cells
astrocytes - most common (blood brain barrier, assists in migration)
oligodendrocytes (produce myelin for many neurons)
microglia (macrophages of the CNS)
ependymal cells (line the fluid filled ventricles, create CSF, move it with cilia)
schwann cells (PNS myelination)
satellite cells (surrounds cells in the ganglia, stucture and metabolic help)
what are the layers of PNS connective tissue coverings
endoneurium (surrounds axons)
perineurium (holds groups of fibers into fascicles)
epineurium (holds the fascicles together)
What are the three meningous layers
Dura mater - dense simple squamous epithelium
Arachnoid mater - trabeculae attach to pia, create space, hydraulic cushion, no Blood vessels
Pia mater - many blood vessels
What are the layers of the cerebrum from superficial to deep
molecular external granular outer pyrimidal inner granular inner pyrimidal multiform
what are the two layers of the cerebellum
cortex - outer molecular - inner granular
medulla - white matter and glial cells
where does the spinal cord end
between the 1st and 2nd lumbar vertebrae
what are PNS nerve fibers, nerves,
nerve fibers are individual cell axons
nerves are bundles of nerve fibers
how many peripheral nerves are there
12 cranial nerve pairs
31 spinal nerve pairs