1.2.1 Neurohistology Flashcards
What is a multipolar neuron?
Multipolar: Majority of neurons are this type.
They have a single axon and many dendrites. Described as fusiform, stellate, pyramidal, granule, polyhedron, and spherical based on the morphology of the soma and the arrangement of their processes
What is this an image of and what is the importance?
Node of Ranvier – small unmyelinated spot of axon, concentrated of Na channels, allows saltatory conduction of APs
What is the role of microglia?
Microglia – activated during injury to phagocytose debris
What is the importance of the CSF?
removes waste products/drugs, cushions brain, carries hormones and neurotransmitters
Describe the endoplasmic reticulums of neurons.
Neurons have elaborate ER containing both smooth and rough ER
What are astrocytes and what is their importance?
Astrocytes – CNS, fibrous (white matter tracts, lipid), protoplasmic (grey matter)
Functions – BBB, structural support, insulation of synapses, electrolyte (K+) and pH balance, sequesters neurotransmitters, immune system and phagocytosis
What is a pseudo-unipolar neuron?
single process extends from soma, but may give rise to multiple branches function as dendrites or an axon. Pseudounipolar neurons are found in ganglia of cranial nerves and dorsal root ganglia. They originate as bipolar neurons in which axon/dendrite fuse to form a single T-shaped process extending from soma.
What is the arrow pointing at and what is the importance?
Nissl Substance or Nissl Bodies
Alanine stains the RER that is often aggregated in large clusters, known as Nissl bodies. The ER is well developed since neurons produce many molecules
What are the characteristics of the Pia Mater?
single cell thick, intimate with brain and spinal tissue, denticulate ligaments in the spinal cord
What is neuromelanin?
metabolic byproduct that is dark in fresh tissue, located in substantia nigra (tegmentum) and in noradernergic neurons in the locus coeruleus
What is a dendritic spine?
Dendritic spines – increases surface area of dendrite, increase then decreases with age
What is a neurofilament?
Neurofilaments – intermediate filaments unique to neurons
What is a bipolar neuron?
Bipolar – one axon with single axon and single dendrite on the opposite side, many neurons are bipolar before fully differentiating
What is the role of microtubules?
Microtubules – maintain cellular structure integrity, axon growth, and vesicle transport
What are the characteristics of the arachnoid mater?
thin and web-like, heavy vasculature, subarachnoid space contains the CSF
What are the three layers of the meninges?
Most outside: Dura mater
Arachnoid mater
Most inside: Pia Mater
What is the role of a schwann cell?
Schwann cells – myelin formation in Peripheral NS, only one internode, neural crest derived
What is an internode?
Internode – axon segment under myelin sheath
What is the soma of a neuron?
cell body of the neuron
What is the role of an ependymal cell?
single layer to separate neural tissue and ventricle cavities, cuboidal with cilia
What is the role of an oligodendrocyte?
Oligodendrocytes – myelin formation in CNS, up to 50 internodes
What are some characteristics of the blood brain barrier?
Blood-brain barrier: separates the brain tissue from the rest of the body and environment
Specialized endothelial cells with super tight junctions
Outer surface surrounded by end-feet of astrocytes to help maintain the BBB
Describe axonal transport and the difference between anterograde vs retrograde transportation.
Transport – proteins synthesized in the soma are sent up and down the axon
- Anterograde* – toward the + end (synapse), uses kinesin
- Retrograde* – toward the – end (soma), dynein
What is this an image of and describe the characteristics.
Neuronal nuclei – large and round located in the center of soma, lack of chromatin → looks clear, prominent nucleololus
What are the characteristics of the Dura Mater?
attached to skull, tough due to collagen, contains fibroblasts, vessels, lymphatics
What is an axon and what is the importance of them?
Axon – transmission of action potential to the next cell, usually covered with myelin sheath
What is the Choroid plexus?
cells in lateral ventricle that produce CSF
What is a synapse and what is the importance?
Synapses are highly specialized intercellular junctions that allow neurons to communicate with other neurons or effector cells. Action potentials cause the release of chemical neurotransmitters (housed in synaptic vesicles) that diffuse across the synaptic cleft to affect the postsynaptic cell. Synapses on other neurons can be axodendritic, axosomatic, or axoaxonic.
The synapse between motor neurons and muscle are highly specialized synapses and are one of the most intensely studied synapses. Acetylcholine is the neurotransmitter released by motor neurons. Several neuromuscular diseases affect this important synapse.
How do these two images compare to each other?
Top - Normal
Bottom - Parkinsons
Depigmentation of the substantia nigra is the main macroscopic neuropath hallmark of Parkinson’s Disease.
What is an axon hillock and what is the importance?
Hillock – cone shaped and is faint staining (few organelles), origin of the axon from the soma
This is also the site where the action potential is generated
What is a dendrite and how does it relate to cellular activity?
Dendrite – arise from the soma, spines seen, receives synaptic input from other cells, more dendrites = more activity
