Exam #1: Histology Review--Self Study Flashcards
What is the Perikaryon?
Cell body of a neuron, also known as the some
List the histological characteristics the perikaryon.
- Prominent round to oval euchromatic nucleus (protein synthesis is constant)
- Rich in free ribosomes & rER–> contains nissil bodies
- Dark nucleolus
- Rich in mitochondria to meet high energy requirements
*Remember that euchromatic= loosely packed & active
What are nissil bodies?
Stacks of rER that stain dark blue with acidophilic stains
What are microtubules? What is the function of microtubules?
- Long, rigid, & flexible structures that form the skeleton of the neuron
- Also aid in transport of materials to & from the soma
What are neurofilaments?
- Intermediate filaments of neurons
- “Muscles” of the neuron b/c of contractile properties
What is the axon hillock?
- Proximal end of the axon
- Funnel-shaped
- Pale staining b/c lacking rER
- Contains microtubules & microfilaments
What is lipofuscin?
- Old degenerated plasma membrane that cannot be fully degraded by lysosomes & accumulates in the cytoplasm
- Accumulates with age; thus, commonly called the “age pigment”
What is neuromelanin?
Byproduct of DA synthesis that commonly accumulates in the Substantia Nigra
What is the function of dendrites?
Increase the receptive surface area of the neuron
What is the initial segment of a neuron?
Part of the axon where the nerve terminal is generated (proximal)
What are the function of myelin?
- Increases conduction velocity
- Insulates axons
Does the axon contain rER?
NO!
What is Anterograde Transport? What facilitates anterograde transport?
- Flow of substances away from the cell body
- Kinesin micotubule motor protein
- Slow= No ATP
- Fast= ATP
What substances are transported via slow anterograde transport?
- Tubulin
- Actin
- Neurofilament proteins
What is Retrograde Transport? What facilitates retrograde transport?
- Flow of substances from the axon terminal to the cell body
- Dynein mitrotubule motor protein
- Fast Transport only (ATP)
- Viruses & toxins
What substances are transported via fast retorgrade transport?
- sER
- Vesicles
- Mitochondria
- Amino Acids
- Sugars
- Nucleotides
- Ca++
List the characteristics of bipolar neurons.
- Associated with the special senses (vision, hearing, balance, smell)
- Dendrite in the periphery
- Axon terminates in brainstem
List the characteristics of pseudo-unipolar neurons.
- Cell body is located in sensory ganglia
- Axon terminal is in the brainstem
- E.g. Cranial Nerves
List the characteristics of astrocytes.
- Star shaped with astrocytic feet that cover the surface of capillaries
- Form the BBB
- Form scar tissue in response to a lesion
- Monitor ionic & chemical composition of the CSF
What is microglia?
- Phagocytic cells of the nervous system
- Derived from monocytes
What is an astrocytoma?
- Most common type of brain tumor
- Arises from astrocytes
- Deforms ventricles
What are ependymal cells?
Type of neuroglia that lines the ventricles
What is an Ependymoma?
- Tumor of the 4th ventricle that compresses the surrounding structures
- Rare type of tumor that arises from ependymal cells
What is the difference between an unmyelinated axon in the CNS vs. PNS?
- “naked” in the CNS
- Sit in a Schwann cell groove in PNS
What are the differences between Schwann cells & Oligodendrocytes?
Oligodendrocytes
- Myelinate axons in the CNS
- 3 foot-like processes myeliante 3 axons
Schwann Cells
- Myelinate axons in the PNS
- Myelinate 1-to-1
What is myelin?
- Fatty & white b/c of lipid content (Lipoprotein)
- NOT secreted; rather, wraps around the axons
What is the difference between an internode and a Node of Ranvier?
Internode= myelinated portion of an axons
Node of Ranvier= gap between two internodes
What are Clefts of Schmidt-Lanterman?
Schwann cell cytoplasm that gets trapped in the concentric layers of the call membrane myelinating the axon
What is the difference between: endonerium, perineurium, & epineurium?
Endonerium=
- Connective tissue surrounding individual axons in the PNS
- Contains collagen
Perineurium= connective tissue surrounding a fascile in the PNS
Epineurium
- Connective tissue surrounding an entire nerve in the PNS
- Dense irregular collagenous tissue sleeve
- Contains blood & lymphatic vessels
What is Multiple Sclerosis (MS)?
- Autoantibodies generated against oligodendrocytes
- Triggered by oligodendrogliopathy
What is Optic Neuritis?
Inflammation of the optic nerve
- Presents with papilledema
- Most common cause is MS
What is papilledema?
Swelling of the optic disc
Outline the different locations of Gray & White Matter.
Gray
- Cerebellar Cortex & Cerebral Cortex
- Nuclei deep to Cerebral Cortex
- Nerve cell bodies
White
- Myelinated axons
- Tracts
- Nerve cell axons
How many cranial nerves are there? What about spinal nerve?
12 & 31
What is the difference between the voluntary nervous system & involuntary nervous system?
Voluntary= brain, spinal cord, & motor neurons in peripheral nerves
Involuntary= ANS
What is “craniosacral outflow” referring to? What about “thoracolumbar outflow?”
PNS vs. SNS
What is an axodendritic synapse?
- most common type of synapse
- axon terminal & dendrite
What is an axosomatic synapse?
Synapse between an axon terminal & membrane of a cell body
What is an axoaxonic synapse?
- Least frequent type of synapse
- Synapse between two axon terminals
What is the difference between collapse & “kiss & run” neurotransmission?
Kiss & Run= Brief attachment & release of only a portion of the contents of a vesicle
Collapse= Vesicle attaches & completely empties all of its contents into the synaptic cleft
Describe the flow of CSF.
1) Choroid Plexus
2) 2x lateral ventricles
3) 3rd Ventricle
4) Cerebral Aqueduct of Sylvius
5) 4th Ventricle
6) Most leaks into the subarachnoid space
7) Remainder goes into the central canal of the spinal cord
Outline the anterograde changes that occur in response to injury.
- Distal segment of axon degenerates
- Elimination of debris by phagocytic cells (Schwann cells & macrophages)
- Schwann cells form tunnels for the axon sprouts to go through
Outline the reterograde changes that occur in response to injury.
- Swelling of the cell body
- Chromatolysis (Nissil bodies & rER breakdown/ nucleus moves aside)
- Protein synthesis
- Nucleus moves back
- Axon sprouts
What is the difference between a fibrous & a protoplasmic astrocyte?
Fibrous= white matter Protoplasmic= gray matter
