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Neuro Exam 2 > 15 CNS Histology - A > Flashcards

15 CNS Histology - A Flashcards

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1
Q

What are neurons?

A

cells that respond to stimuli through electrochemical mechanisms

– Excitable or inhibitory

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2
Q

What are Glia?

A

support cells involved in conduction speed, repair, neurotransmitter maintenance

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3
Q

Describe the cell body of a “Typical” neuron.

A

Cell body is large & has a large, euchromatic nucleus with a well-developed nucleolus

  • Nissl substance/bodies
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4
Q

What happens to a neuron, when you increase the amount of dendritic spines?

A

it increases receptive area

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5
Q

Where does the long axon of a “Typical” neuron emerge from?

A

emerges from an axon hillock

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6
Q

What are Nissl substances/bodies of a “Typical” neuron?

A

large, basophilic masses of free polysomes & RER

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7
Q

What is the distal end of an axon called?

A

Terminal arborization

  • some have branching, collateral branches
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8
Q

Ends of axons usually have small what?

A

telodendria

  • dilation of branch ends & contact postsynaptic cell
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9
Q

Describe a multipolar neuron.

A
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10
Q

Describe bipolar neuron.

A
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11
Q

Describe unipolar neuron.

A
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12
Q

Describe anaxonic neuron.

A
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13
Q

For neuronal synapse communication, is the transmission unidirectional or bidirectional?

A

synaptic transmission is unidirectional

Synapses = Sites where nerve impulses are transmitted from one neuron to another, or from neurons and other effector cells

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14
Q

Synapses convert an electrical signal (nerve impulse) from the _____________ into a chemical signal that affects the ___________.

A
  1. presynaptic cell
  2. postsynaptic cell
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15
Q

Most synapse communication between nerves act by releasing what?

A

Neurotransmitters - small molecules that bind receptor proteins

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16
Q

Describe what the presynaptic terminal bouton of a chemical synapse contains.

A

mitochondria & synaptic vesicles –> release NT via exocytosis

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17
Q

Describe what the postsynaptic cell membrane of a chemical synapse contains.

A

receptors for the neurotransmitter

ion channels to initiate a new impulse

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18
Q

What is a 20- to 30-nm-wide intercellular space that separates pre- & postsynaptic membranes in a chemical synapse?

A

synaptic cleft

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19
Q

Describe the electrical synapse of a neuron.

A

Permit direct, passive flow of electrical current from one neuron to another

  • potential difference (voltage) generated locally by presynaptic action potential
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20
Q

How does current flow occur and links pre- & postsynaptic membranes (2nm) in electrical synapses of neurons?

A

Gap junctions

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21
Q

What proteins permit diffusion of small molecules & electric current flow in an electrical synapse of neurons?

A

Connexon

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22
Q

What are the five (5) types of Glial cells?

A
  1. Neuropil
  2. Astrocyte
  3. Ependymal cell
  4. Microglial cell
  5. Oligodendrocyte
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23
Q

What is a neuropil?

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A

type of Glial cell

fibrous intercellular network of cellular processes emerging from neurons & glial cells

24
Q

What are characteristics of Astrocytes?

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A
  • large number of long, branching processes
  • proximal regions are reinforced with intermediate filaments made of glial fibrillary acid protein (GFAP)

They form a vast network of delicate terminals contacting synapses & other structures

Terminal processes of a single astrocyte typically associate 1M+ synaptic sites

25
What are characteristics of Oligodendrocytes?
Type of Glial cell. - Extend many processes that wrap repeatedly around a portion of a nearby axon - Cytoplasm gradually moves out: leaves compacted layers of cell membrane, collectively termed **myelin**. Forms a **myelin sheath**. Will enwrap axons from multiple neurons - a given axon is covered by many oligodendrocytes Usually appear as small cells with rounded, condensed nuclei & unstained cytoplasm
26
What are characteristics of Ependymal cells?
* Columnar or cuboidal cells that line the fluid-filled ventricles of the brain & the central canal of the spinal cord * Apical end may cilia & long microvilli – Facilitate movement of CSF – Likely involved in absorption • Joined apically by apical junctional complexes & there is no basal lamina
27
What are characteristics of Microglia?
A type of Glial cell. * Less numerous than oligodendrocytes or astrocytes * Migratory, will remove damaged or unactive synapses or other fibrous components * Major mechanism of immune defense in the CNS, removing any microbial invaders * Originate from monocytes
28
What has a central mass of grey matter that has the shape of a butterfly?
**- Ventral, dorsal, & lateral horns**
29
What lies in the **central commisure** of grey matter of a spinal cord?
**Central canal** - lined by ependymal cells and contains CSF
30
What does white matter consist of for a spinal cord?
White matter consists of ascending tracts of sensory fibers & descending motor tracts
31
The sharply folded **cerebellar cortex** is organized with three (3) layers. What are they?
1. Molecular layer 2. Purkinje cells 3. Granular layer
32
Describe the **molecular layer** of the cerebellar cortex.
has much neuropil & scattered neuronal cell bodies
33
Describe **Purkinje cells** of the cerebellar cortex.
extend dendrites throughout the molecular layer as a branching basket of nerve fibers - Conspicuous in H&E-stained sections
34
Describe the **granular layer** of the cerebellar cortex.
contains various very small, densely packed neurons (i.e., granule cells) & little neuropil
35
What is organized into folia with the _______ **medulla** located deep?
The cerebellar cortex!! 1. **cerebellar**
36
Biologically, older parts of the cerebral cortex are arranged into three layers. What is this called?
**Archicortex**
37
What is the majority of the cerebral cortex (about 90%) called? How many layers does it consist of?
**neocortex** consists of **6 layers**
38
The neocortex has a variety of cells, divided into five (5) different morphological types. What are they?
1. Pyramidal cells 2. Stellate (granule) cells 3. Cells of Martinotti 4. Fusiform cells 5. Horizontal cells of Cajal
39
Describe pyramidal cells of the neocortex.
pyramid-shaped cell bodies with the apex directed towards the cortical surface • Huge upper motor neurons of the motor cortex (Betz cells), are the largest pyramidal cells
40
Describe stellate (granule cells) of the neocortex.
small neurons with a cell body the shape of a star (look like granules in micrographs)
41
Describe cells of Martinotti of the neocortex.
small polygonal cells with a few short dendrites
42
Describe fusiform cells of the neocortex.
spindle-shaped cells oriented at right angles to the surface of the cerebral cortex
43
Describe horizontal cells of Cajal of the neocortex.
small & spindle-shaped but oriented parallel to the surface (least common)
44
What are the 6 cortical layers of the neocortex?
1. Molecular (plexiform) layer 2. Outer/external granular layer 3. Pyramidal cell layer 4. Inner/internal granular layer 5. Ganglionic layer 6. Multiform cell layer
45
Here are more examples of the 6 cortical layers of the neocortex.
46
Describe and name the first cortical layer of the neocortex.
Molecular (plexiform) layer superficial layer containing dendrites & axons of cortical neurons; sparse neuroglia & horizontal cells of Cajal
47
Describe and name the second cortical layer of the neocortex.
Outer/external granular layer dense population of small pyramidal cells & stellate cells, mixed with axons & dendrites from deeper layers
48
Describe and name the third cortical layer of the neocortex.
Pyramidal cell layer pyramidal cells of moderate size predominate, Martinotti cells are also present
49
Describe and name the fourth cortical layer of the neocortex.
Inner/internal granular layer consists mainly of densely packed stellate cells
50
Describe and name the fifth cortical layer of the neocortex.
Ganglionic layer large pyramidal cells & smaller numbers of stellate cells & cells of Martinotti make up this layer
51
Describe and name the sixth cortical layer of the neocortex.
Multiform cell layer wide variety of cell types (small pyramidal cells, cells of Martinotti, stellate cells & fusiform cells in the deeper part)
52
What is the choroid plexus and what support cell type are associated with it?
Elaborately folded & highly vascular tissue, found in the roofs of the 3rd & 4th ventricles, & in parts of lateral ventricular walls • Contains a thin layer of well-vascularized pia mater covered by **_cuboidal ependymal cells_**
53
What is the choroid plexus responsible for?
Removes H2O from blood & releases it as CSF – Contains Na+, K+, & Cl– ions – Very little protein – Only cells include sparse lymphocytes * Completely fills ventricles, central canal of SC, subarachnoid & perivascular spaces * Arachnoid villi provide absorption pathway for CSF back into the venous circulation
54
Histologically speaking, how do Choroid plexus' look like? Cell type, structure, etc.
Branching system of blood vessels which run in fronds composed of a fibrous core covered by cuboidal/columnar epithelium → villous structure * Capillaries & vessels are large, thin-walled * Epithelial cells rest on a basal lamina * Long bulbous microvilli project from the epithelial cells * Tight junctions (zonula occludens) between epithelial cells contribute to a blood-CSF barrier
55
Describe what a "Typical" neuron looks like.
1. Cell body - **Nissl substance/bodies** 2. Numerous dendrites 3. Long **axon** covered by myelin
56
Describe the **dendrites** of a "Typical" neuron.
Numerous **dendrites** extend from the perikaryon * Extensive branching/arborization * Numerous **dendritic spines** ↑↑ receptive area * Spines are **plastic**
57
Where is the site where excitatory or inhibitory stimuli are initiated on a neuron?
The **initial segment** of an axon (which originates from the axon hillock)

Neuro Exam 2 (21 decks)

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