Week 2: Neurons & Embryology Flashcards
Unipolar Neuron
1 cell process bc the sensory portion of cell is in the soma
Bipolar Neuron
2 cell processes; Dendrite tree is outside the soma
Multipolar Neuron
2 dendrites that transmit sensory & motor impulses; Makes up most of the CNS & PNS
*Typical neuron that we think of
Pseudopolar Neuron
When an axon from a unipolar neuron splits so there’s myelinization on the dendritic side
Nissl Bodies
Rough ER
Synthesizes & transports proteins
Neurofibrils, Microfibrils, & Neurotubules
Help maintain cell’s shape
Golgi Apparatus
Further processes protein compounds from ribosomes
Packages neurotransmitters to protect them from enzymes in cytoplasm
Packages lysosomes
Mitochondria
Converts nutrients to energy
Inclusions
Anything w/in the cell
Axon Hillock
AP trigger zone
Collateral Axon
Splits off the main axon to go to a slightly different target
Telodendria
Very ends, right before the terminal buttons
Schwann Cells
Myelin in the PNS; Multiple on 1 axon
Oligodendrocytes
Myelin in the CNS; Multiple axons for 1 cell
Glial Cells
Scaffolding & support cells & communication facilitators; Also help enhance flow of ECF (nutrient transport) & scar formation
Include astrocytes, oligodendrocytes, microglia, & ependymal cells
Astrocytes
- Star-shaped cytoskeletal cells in the CNS
* Provide structural support, form BBB, facilitate nutrient transport, & release glutamate
Protoplasmic Astrocytes
Gray Matter
Fibrous Astrocytes
White Matter
Radial Astrocytes
Guide Development
Microglia
Phagocytes
Ependymal Cells
Specialized microglia that line the ventricles & CNS cavities
Type of Axoplasmic Transport
Anterograde & Retrograde
Anterograde Transport
Moves neurotransmitters & other substances from the soma & down the axon towards the pre-synaptic terminal
Retrograde Transport
Moves substances from the synapse towards the soma
Resting Membrane Potential
-65mV
Depolarization
Cell is becoming positively charged
Afferent Transmission
Towards the CNS (sensory)
Efferent
To the PNS (muscles)
What are the events that lead up to an AP?
1) Cell is at RMP. Voltage-gated Na+ & K+ channels are closed.
2) Membrane gets subjected to a stimulus so Na+ channels open & Na+ begins to flow in & the cell starts to become more (+).
3) Threshold. Na+ channels continue to open so inflow of Na+ increases. Cell’s charge is at least -55mV.
4) Interior of the cell continues to become more (+). At this point, the Na+ concentration is almost equal so Na+ channels begin to close.
5) AP. Charge of the neuron is about +30mV.
6) Voltage-gated K+ channels open & K+ begins to flow out of the cell so the neuron is starting to become (-).
7) K+ channels are still open so the cell continues become more negatively charged & the cell hyperpolarizes.
What part of the neuron does GBS effect?
Myelin
What are the stages of development in days 1-14?
Mature Follicle–>Oocyte–>Fertilized Zygote–>2-cell Stage–>4-cell Stage–>8-cell Stage–>Morula–>Blastocyst
What forms during the 2nd-8th week?
Bilaminar Embryo Hypoblast Epiblast Primitive Knot Notochord
Primitive Knot
Directs the movement of the devo of the primitive streak
Notochord
Becomes the nucleus pulposus
What forms on days 16?
Ectoderm, Mesoderm, & Endoderm (Trilaminar Layer)
What does the ectoderm become?
The neural plate, which eventually becomes the epidermis & nervous system
What does the mesoderm become?
Dermatomes (skin), Myotomes (muscle), & Sclerotome (Axial Skeleton)
What does the endoderm become?
Smooth muscle in internal organs
Neural Plate
Where the groove forms
What happens on day 18?
Neural groove & folds form
What happens on day 21?
Neural tube starts to form
What forms on days 26-28?
Scleroderm, Mytomes, & Dermatomes
What does the scleroderm become?
Axial Skeleton
What does the mytome become?
Muscle
What does the dermatome become?
Skin
Ependymal Layers
Line ventricles & secrete CSF
Mantle Layers
Becomes grey matter
Marginal Layers
Becomes white matter
Sulcus Limitans
Imaginary line that separates motor & sensory fxns
Dorsal Alar Plate
Sensory Fxn
Ventral Basal Plate
Motor Fxn
What does the prosencephalon become?
Telencephalon & Diencephalon
Prosencephalon–>Telencephalon–>?
Cerebral hemispheres
Corpus Striatum
Cortex + Medullary Center of White Matter
Prosencephalon–>Diencephalon–>?
Thalamus, Epithalamus, & Subthalamus
What does the mesencephalon become?
Midbrain
What does the rhombencephalon become?
Metencephalon & Myelencephalon
Rhombencephalon–>Metencephalon–>?
Pons & Midbrain
Rhombencephalon–>Myelencephalon–>?
Medulla
When does prosencephalon development start?
5th Week
Anencephaly
Rudimentary brainstem w/out cerebral & cerebellar hemispheres.
“Cephalic neuropore doesn’t close in the 4th wk so development essentially stops at the midbrain level”
Arnold-Chiari Deformity
Inferior cerebellum & medulla are elongated, protruding into the vertebral canal; Malformation of the medulla & pons happens as well.
Spina Bifida
Developmental defect when the inferior part of the neural tubes fails to close so vertebral arches don’t fuse
CP
Motor disorder caused by permanent, nonprogressive damage to the developing brain
Tethered-Cord Syndrome
End of the spinal cord adheres to one of the lower vertebrae
What are the parts of the trilaminar layer?
Endoderm, Mesoderm, & Ectoderm
What form of spina bifida is associated w/more impairments & why?
Myelomeningocele bc the spinal cord is outside of the dural sac.
When do we start looking human-ish?
5th week
Projection Fibers
Axons that travel up & down the CNS
Association Fibers
Axons that connect one lobe or ipsilateral fibers to another
Commissural Fibers
Axons that run between the hemispheres or contralateral fibers
*Always cross midline
Temporal Summation
1 nerve sends neurotransmitter that bombards the same dendrite.
Meningocele
Dural sac extrudes beyond the back; Does not involve spinal nerves
Meningomyelocele
Portions of the spinal cord get displaced into the extruding dural sack so nerve roots get stretched.
Cleft Palate
Suture of the palatine bone doesn’t fuse properly in the 6th-12th week
Microcephaly
Underdevo of brain tissue
Myeloschisis
Neural tube doesn’t devo so baby will have paralysis-No dural container
Plagiocephaly
Asymmetrical skull shape
*Flattening on one side will cause overgrowth on the opposite side.