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Neurology > Cellular Neuroanatomy > Flashcards

Cellular Neuroanatomy Flashcards

1
Q

2 Principle Cells Types of Neuroanatomy

A

1) Neurons & their unique morphology
- cell bodies (soma) & Nissl bodies
- morphology & function of dendrites & axons
- axonal transport
2) Neuroglia: function & morphology of different glia cells
- astrocytes & satellite cells
- Schwann cells, oligodendrocytes, & meylin

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2
Q

Connections b/w Neurons

A
  • Chemical synapses: Morphology, function, & neurotransmitters
  • Electrical Synapses
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3
Q

The Neurons

A
  • structural & functional unit of the NS
  • electrically excitable
  • collects sensory information
  • integrated information
  • controls effector organs like muscles & glands
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4
Q

Supporting Cells (glia)

A
  • glia = glue
  • provide physical support (protection)
  • electrical insulation for impulse conductance
  • metabolic exchange between the vascular system and the NS
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5
Q

The Cell Body (Soma)

A
  • cell’s supply station
  • produces proteins & provides metabolic function
  • houses cell nucleus (light area) & machinery for metabolic functions and the production of proteins
  • has nucleoulus (dark spot)
  • cytoplasm that contains all cell organelles like rER, Golgi, lysosomes, & mitochondria
  • soma in neurons is rich in rER (it produces a large amount of proteins, large stacks appear as islands in Nissl stain)
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6
Q

Dendrites

A
  • cell’s receiver: imputs
  • receives electrical impulses from other neurons
  • neuron may have one or many
  • synaptic inputs on most cells (especially excitatory synaptic input) are preferentially on to dendrites & dendritic spins
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7
Q

Axon

A
  • output for the cell
  • sends electrical impulses to other neurons
  • each neuron has a single axon, originates at soma where it forms an axon hillock (free of cell organelles)
  • electrical signals are initiated in axon & travel down the axon to terminal, where neurotransmitters are released for chemical neurotransmission
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8
Q

Dendritic Spines

A
  • small, membranous protrusions from the dendrite
  • receive synaptic inputs (excitatory)
  • transmit electrical signals to the dentrite
  • serve as anatomical substrate for synaptic transmission
  • synaptic plasticity
  • memory storage
  • hundreds of thousands per dendrites
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9
Q

Gray Matter

A

-unmyelinated tissue-primarily somas & dendrites

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10
Q

White Matter

A

-tissue containing myelinated axons (myelin = lipid wrapping on axons, appearance is white in unstained tissue)

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11
Q

Nissl Stain

A
  • stains neuronal somas

- primarily indicates cell bodies & proximal dendrites (not axons)

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12
Q

Nissl Bodies

A
  • basophilic masses, primarily rough endoplasmic reticulum (rER) and ribosomes
  • masses are concerned with protein synthesis, much of which occurs in cell bodies of neurons
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13
Q

Nissl Substance Extends into?

A

-proximal dendrites but not into the axon hillock, which gives rise to the axon

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14
Q

Pyramidal neuron

A
  • pear-shaped soma & prominent apical dendrite (shown extending upwards from soma)
  • typically have a group of basal dendrites as well as the apical dendrite & its branches
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15
Q

Initial Segment

A
  • portion of axon from the hillock to the beginning of myelination
  • site of action potential initiation
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16
Q

Motoneuron

A

-when axon connects to a effector organ (muscle, gland)

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17
Q

Long axons are myelinated because?

A

electrical insulation resulting in faster nerve impulses conduction

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18
Q

Collaterals

A

-major branches of an axon

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19
Q

Neuron Types

A
  • unipolar (pseudo)
  • bipolar
  • multipolar
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20
Q

Unipolar Neurons

A
  • have a single neurite (process - axon or dendrite)

- do not exist in mature vertebrate nervous system

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21
Q

Pseudounipolar Neurons

A
  • sensory neurons with cell bodies in the dorsal root ganglia
  • peripheral & central processes of a single axon mostly bypass the soma
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22
Q

Bipolar Neurons

A
  • mostly local circuit interneurons
  • 2 primary neurites (dendrites)
  • leave the soma at opposite ends of the cell
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23
Q

Multipolar Neurons

A
  • several primary dendrites leaving the soma

- Ex: pyramidal neurons of cortical regions, Purkinje cells of cerebellum, or motoneurons (spinal cord & brain stem)

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24
Q

Silver Stain

A

(Golgi-stained cells)

-stain random subset of cells but show entire morphology of those cells

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25
Q

Principle Cells

A
  • are projection neurons
  • integrate information & send axons to other brain areas (path of an axon from one brain area to another)
  • Golgi Type I cells (long projection axon)
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26
Q

Interneurons

A
  • cells that do not send their axon out of the local brain area
  • Ex: chandelier cells, basket cells, double bouquet cells (in cortex)
  • local circuit neurons
  • Golgi Type II cells (either no axon or short, local axon)
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27
Q

Synapses

A

-specialized junctions that allow neural signals to be communicated from one cell to another (or from neuron to another effector)

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28
Q

2 Types of synaptic transmission?

A

1) Chemical

2) Electrical: form direct electrical connections b/w neurons, called gap junctions

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29
Q

Electrical Synapses

A
  • formed as direct connections from one cell to another via gap junctions
  • electrical signals & small molecules can pass directly b/w the pre-and-postsynaptic cell at an electrical synapse
  • close appositions of the pre/post synaptic membranes
30
Q

Chemical Synapses

A

-electrical signal in the presynaptic neuron is transduced into release of a chemical transmitter that traverse a synaptic cleft w/w cells to bind to receptors on the postsynaptic neuron (or effector)

31
Q

Location of most excitatory synapse in the brain?

A

dendritic spines

32
Q

Neuromuscular Junction

A

-when a synapse is formed b/w a neuron and a muscle

33
Q

Axosomatic Synapse

A

contact from an axon to a soma

34
Q

Axodendritic Synapse

A

axon contacting a dendrite (spine or shaft)

35
Q

Most excitatory synapses are formed on?

A

dendritic spines (axospinous = subset of axodendritic)

36
Q

Axoaxonic Synapse

A

axon to axon synaptic contact

37
Q

Dendrodendritic Synapse

A

dendrite to dendrite

38
Q

Vertebrate Chemical Synapses

A

-unidirectional

only transmit information from the presynaptic neuron to the postsynaptic neuron

39
Q

Steps of Chemical Synapse

A

1) Presynaptic bouton (axonal varicosity) contains membranous synaptic vesicles called synaptic vesicles that contain neurotransmitter
2) On an incoming nerve impulse, entry of Ca2+ causes synaptic vesicles to release their contents into the synaptic cleft
3) Specialized receptor proteins located in the postsynaptic density bind the neurotransmitter & generate another electrical signal in the postsynaptic cell

40
Q

3 Types of neurotransmitters?

A
  • Excitatory
  • Inhibitory
  • Modulatory
41
Q

Excitatory Neurotransmitters

A
  • increases the probability that the postsynaptic neuron will fire a nerve impulse
  • Ex: synapses containing ACh (at nicotinic receptors) or glutamate (AMPA, NMDA receptors)
42
Q

Inhibitory Neurotransmitters

A
  • reduces the probability that the postsynaptic neuron will fire a nerve impulse
  • Ex: synapses with glycine or gamma-aminobutyric acid (GABA - at GABAa receptors)
43
Q

Modulatory Neurotransmitters

A
  • influences how excitatory and inhibitory signals are integrated
  • Ex: synapses using dopamine or norepinephrine (also acetylcholine at muscarinic receptors & GABA at GABA b receptors)
44
Q

Type I Synapse

A

-Excitatory (excitatory amino acids)
-Asymmetric - pronounced postsynaptic density (denser that presynaptic membrane)
(Gray’s type 1)

45
Q

Type II Synapse

A

-Inhibitory (GABA, Glycine)
-Symmetrical (thin postsynaptic density - same density as presynaptic membrane)
(Gray’s type 2)

46
Q

Excitatory

A

something that increases the probability for an action potential

47
Q

Inhibitory

A

something that decreases the probability for an action potential

48
Q

Where are type I synapses found?

A

mainly on dendrites & result in an excitatory response in the post-synaptic cell

49
Q

Where are type II synapses found?

A

on the soma & inhibit the receiving cell’s activity

50
Q

Connexons

A

(large channels)

  • direct, passive flow of electrical current from one cell to the next is achieved by these
  • made up of molecules called connexins (6 form a connexon)
51
Q

Electrical synapses

A

bi-directional, either cell can be both pre- and postsynaptic

52
Q

Gap Junctions are made up of?

A

-a connexon from each cell

53
Q

Axonal Transport

A
  • proteins synthesized in the soma are packed into cargo vesicles & transported along microtubules toward their destination (ratchet-like action)
  • kinesin
  • dynesin
54
Q

Kinesin

A

-moves cargo vesicles anterograde (away from soma)

55
Q

Dynein

A

-moves cargo vesicle retrograde (toward soma)

56
Q

Supporting Cells

A
  • neuroglia (glia: Schwann cells, Oligodendrocytes, Astrocytes) as well as other cell types (microglia, satellite cells, ependymal cells)
  • not “excitable cells” do not generate action potentials
  • structural support
  • facilitating electrical signaling
  • isolating cells electrically & biochemically
  • assisting in repair in response to injury
  • producing cerebrospinal fluid
57
Q

Schwann Cells

A
  • provide myelination in the peripheral nervous system
  • improves electrical insulation, which increases conductance velocity for action potentials
  • individual cells wrap around an axon
  • where 2 cells touch, form “node of Ranvier” (unmyelinated area), site where action potentials regenerate
  • synapses are not myelinated
58
Q

Oligodendrocytes

A
  • provide myelination in the central nervous system
  • each process provides myelination for one axon, therefore one oligodendrocte myelinates several axons
  • neighboring internodes originate from different oligodendrocytes
  • many axons in the CNS are not myelinated
  • one forms 30-50 internodes (many different axons, 1 internode per axon)
59
Q

Astrocytes

A
  • there are 2 types: fibrous (white matter)& protoplasmic (grey matter), radial astrocytes “servants of CNS”
  • general support
  • blood brain barrier
  • move metabolites to & from neurons = metabolic exchange
  • maintain constant ionic conc. for optimal neuronal function
  • radiating processes (astrocyte), contact neurons (perineural feet), endothelial cells of blood vessels (perivascular feet), and myelin
60
Q

Satellite Cells

A
  • function as astrocytes in the autonomic NS/ peripheral ganglia
  • small, cubodial cells of neural crest origin
  • modified Schwann cells (PNS) or oligodendrocytes (CNS)
  • surround the entire soma of ganglion cels, but only their nucleus is visible in H&E stains
61
Q

Microglia

A
  • phagocytosis, inflammation

- “immune cells of the CNS”

62
Q

Polydendrocytes

A

stem cells within the brain

63
Q

Ependymal Cells

A
  • ventricles of the brain and the central canal of the spinal cord are lined with ependymal cells
  • form a cuboidal to columnar epithelium, ciliated
  • lack tight junctions b/w ependymal cells allows a free exchange b/w cerebrospinal fluid and nervous tissue
  • apical surface covered with cilia and microvilli
  • basal surface is in close contact with astrocytes
64
Q

Neuroglia

A
  • “GLUE”

- outnumber neurons 10 to 1, make up 50% brain volume

65
Q

Schmidt-Lanterman Clefts

A

-small folds of cytosol remain to support the myelin

66
Q

Each Schwann Cell forms how many internodes?

A

1

67
Q

Osmium Stain

A

-stains individual myelinated axons black

68
Q

Endoneurium

A

thin layer of connective tissue (stain brownish), that surrounds each nerv fiber

69
Q

Perineurium

A

-delimits the fascicle

70
Q

Fibrous Astrocytes

A

-have vascular feet that physically connect them to the outside capillary walls

71
Q

Radial Astrocytes

A
  • oriented in a plane perpendicular to the axis of the ventricles, with one axis towards the pia and the other near the vnetricle
  • mostly present during dev. and play a role in neuron migration
72
Q 
Mueller Cells (retina)
Bergmann Glia (cerebellum)
A

-examples of radial glia that persist into adulthood

Neurology (18 decks)

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