2.2.1. Neural Tissue Flashcards Preview

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Flashcards in 2.2.1. Neural Tissue Deck (57)
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parts of CNS

brain and spinal cord

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parts of PNS

cranial, spinal, and peripheral nerves

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afferent neurons function

sensory and receptor neurons. Carry nerve impulse from receptors or sense organs toward CNS

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efferent neurons function

motor or effector neurons that carry nerve impulses away from CNS to effectors such as muscles or glands

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somatic nervous system function

regulates voluntary body movements

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autonomic nervous system

regulates involuntary body movements

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sympathetic nervous system

part of autonomic nervous system and stimulates fight or flight response as well as homeostasis

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parasympathetic nervous system

part of autonomic nervous system and responsible for rest and digest or regulation of internal organs and glands

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Neuron components

1. cell body (soma)
2. axon (transmit)
3. dendrites (receive)
4. nerve terminals

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astrocyte (astroglia)

star shaped glial cell in CNS that provide mechanical/structural support

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oligodendrocyte

type of neuroglia. Function is to support and insulate axons of CNS via myelin sheet

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glial cells

non-neural cells that maintain homeostasis, form myelin, and provide support and protection for CNS and PNS

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steps of neurotransmission

1. depolarization of presynaptic membrane which induces opening of calcium channels
2. Influx of calcium into presynaptic neuron causes vesicles in presynaptic neuron to release neurotransmitters into synapse
3. Neurotransmitters in synapse bind to receptors in postsynaptic region which causes depolarization in postsynaptic membrane
4. membrane retrieval occurs by coated vesicles

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gray matter composition

mostly cellular elements: cell bodies of neurons and astroglia with dendrites covered by synapses

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white matter composition

mostly axons covered by myelin sheet (oligodendrocytes)

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Ectoderm is source for this tissue

1. epithelial
2. neural

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neuron cell body characteristics

1. large nucleus
2. light cytoplasm with high transcription rate
3. contains nissl bodies (granules of RER)

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dendrite characteristics

1. multiple per neuron and vary in shape
2. receptive surface of neurons and form dendritic spines at the postsynaptic element
3. motile
4. dendrites are extensions of neuronal perikaryon (bulbous part of the neuron with the nucleus)

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axon characteristics

1. one per neuron but may branch
2. thin (.1 to 25 micron) but long (up to several feet)
3. highway for neurons: massive macromolecular and organelle movement (axonal transport)
4. contain neurofilaments, microtubules, mitochondria
5. do not contain ribosomes or golgi

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synapse definition

specialized junction enabling communication between pre and postsynaptic neuron

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nerve terminal characteristics

1. precede a synapse
2. communication is chemical and electrical in nature
3. presynaptic nerve terminal contain synaptic vesicles that store and release chemical messenger molecules (neurotransmitters)

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types of neurotransmitters

1. classical
2. peptide
3. other

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classic neurotransmitter

1. acetylcholine
2. epinephrine
3. norepinephrine
4. dopamine
5. serotonin
6. glutamate
7. aspartate
8. GABA

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peptide neurotransmitter

1. encephalin
2. VIP
3. neurotensin
4. substance P
5. CGRP

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other type neurotransmitter

1. NO
2. CO
3. adenosine
4. growth factors

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Types of neurons

1. sensory
2. motor
3. intermediate

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classification of neuron

1. unipolar: one dendrite OR one axon
2. pseudounipolar: one process that branches into a dendrite AND an axon
3. bipolar: one dendrite and one axon
4. multipolar: many dendrites and one axon

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supporting cells

1. astroglia
2. oligodendrocytes
3. microglial cells
4. ependymal cells

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function of astroglia

1. mechanical/structural support
2. react to injuries (gliosis - proliferation of more glial cells)
3. metabolic support via nourishing neurons with glucose, taking up toxic metabolites, and regulating access to brain parenchyma

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function of oligodendrocyte

wrap axons in the CNS with multiple processes that form multilayer myelin sheets (insulation for fast transmission)

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node of Ranvier structure and function

structure: gap between myelin segments that contains a high density of Na ion channels
function: permits signal transduction. Also allows fast efficient travel of impulses via saltatory conduction

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saltatory conduction

propagation of action potentials of myelin axons from one node of Ranvier to the next increasing the conduction velocity of action potentials

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microglial cell function

resident immune cell of CNS which phagocytose cellular debris. They are of monocytic origin

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What makes up a peripheral nerve?

Endoneurium (inner)
Perineurium (around)
Epineurium(outer)

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What part of the peripheral nerve must be rejoined in microsurgery for limb reattachment?

Perineurium (permeability barrier): surrounds a fascicle of nerve fibers

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Blood-Brain Barrier (BBB)

Prevents circulating blood substances from reaching the CSF/CNS
Formed by 3 structures:
1. Tight junctions b/w non-fenestrated capillary endothelial cells
2. Basement membrane
3. Astrocyte foot processes

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What can rapidly diffuse through the BBB?

Non-polar/lipid-soluble substances
(glucose and amino acids cross slowly)

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Histologically, how to distinguish b/w the cell body and the axon?

Axons do not have RER and, therefore, will not stain with the Nissl substance like cell bodies and dendrites will

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Wallerian degeneration

If an axon is injured it will undergo degeneration distal to the injury and axonal retraction proximally (allows for potential regeneration of axon if injury occurs in the PNS)

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"Fried egg" appearance on H&E stain

Oligodendrocytes (smaller than astrocytes with shorter and fewer processes)

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Reactive gliosis

Proliferation/hypertrophy of astrocytes in response to neural injury

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Multiple sclerosis, progressive multifocal leukoencephalopathy (PML), and leukodystrophies

Central myelinating diseases that destroy oligodendrocytes

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Ependymal cells

Line the cerebral ventricles and central canal; also involved in CSF production and circulation (lined with stereocilia)

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Schwann Cells

Derived from the neural crest, myelinate one and only one PNS axon leading to increased conduction velocity via saltatory conduction b/w nodes of Ranvier; also promote axonal regeneration

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Guillain-Barre Syndrome

Consequence is schwann cell destruction

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Acoustic neuroma

Type of schwannoma (tumor); typically located in internal acoustic meatus (CN VII); if bilateral, strongly associated with neurofibromatosis type 2

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Vasogenic edema

infarction and/or neoplasm that destroys endothelial cell tight junctions

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Neural Tube

Where neurons and glia of the CNS develop

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Neural Crest

Where neurons and glia of the PNS develop

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Kinesins and dyneins

Kinesins: involved in the movement of organelles and vesicles down the axon

Dyneins: movement of organelles, vesicles, and possibly microtubule fragments towards the cell body

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Neural Development of the Neural Plate

Notochord induces the ectoderm to differentiate into neuroectoderm and form the neural plate, then the notochord becomes the nucleus pulposus of the intervertebral disc

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What does the neural plate give rise to?

Neural Tube and Neural Crest cells

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Alar plate

Dorsal (sensory)

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Basal Plate

Ventral (motor)

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What does the neuroectoderm give rise to?

CNS, ependymal cells, oligodendroglia, and astrocytes

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What does the neural crest give rise to?

PNS neurons, Schwann cells

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What does the mesoderm give rise to?

FIRST AID: Microglia (like Macrophages, originate from Mesoderm)