Lecture 8 - Neurohistology

Question 1

Fast axonal transport occurs in both _____ and _____ directions, and it requires ATP, Dynein, and Kinesin. Slow Axonal transport ONLY occurs in a(n) _______ direction and does not require ATP or use Dynein/Kinesin.

Answer 1

Anterograde and Retrograde

Anterograde (toward axon terminal)

Question 2

Dendrites contain mitochondria and RER. The latter has been found necessary for formation and retention of ____ ____ ____.

Answer 2

Long Term Memories (LTM)

Question 3

3 types of Synapses:

1. Axosomatic –> _______ (Excitatory, Inhibitory, or Both?)
2. Axodendritic –> _______ (Excitatory, Inhibitory, or Both?)
3. Axo-axonic –> (Excitatory, Inhibitory, or Both?)

Answer 3

1. Inhibitory
2. Excitatory
3. Both

Question 4

Chandelier Cells (ChCs - a type of interneuron) synapse at the initial segment of other cells’ Axons and are ALWAYS _______ (excitatory, inhibitory, or both?)

Answer 4

Inhibitory

Question 5

What are the 3 layers of the Cerebellum in this Micrograph? How do the Purkinge and Granular layers differ in the Cerebellum vs other neuronal tissue?

Answer 5

From out to in: Molecular layer, Purkinge layer, Granular layer.

The Purkinge neurons are arranged in a single-cell layer and are very large. Typically, large neurons are excitatory, but these are Inhibitory (GABA).

The Granular cells in the cerebellum are small. Typically, small neurons are inhibitory, but these are Excitatory (Glutamate).

Question 6

Granular cell neurons in the Cerebellum extend their processes to the ______ layer and form horizontal connections that connect up to thousands of _____ cell neurons via ____ ______-type synapses.

Answer 6

Molecular layer (all the way up)

Purkinge cell neurons

En Passant-type synapses

Question 7

Cortical Pyramidal neurons are considered Projection neurons bc they have ______ (short or long?) axons that extend from the Cortex and synapse with _______ neurons. Cortical Non-pyramidal neurons are considered ______ circuit neurons –> So what is true of their projection lengths?

Also, based on the size and connections of Pyramidal vs non-pyramidal cortical neurons, which are likely excitatory and which are likely inhibitory?

Answer 7

Long

Motor neurons

Local circuit neurons

Their projections are short (hence local)

Pyramidal –> Excitatory

Non-pyramidal –> inhibitory

Question 8

How does the complexity and recency (evolutionarily new vs old) of cortical regions correlate to the number of layers they have?

Answer 8

More recent –> typically more complex –> more layers

Question 9

In the Neocortical regions (6 layers), Inputs from the Thalamus come into Layer ______, which is comprised mostly of ______ neurons. Outputs from Superficial layers (layers II and III), which are comprised mostly of ______ neurons, project locally within the neocortex or through the _____ _____ (bridge to the other side) and to the Neocortex in the opposite hemisphere.

Deep layers (V and VI) are also comprised of ______ neurons that project to _______ structures.

Answer 9

Layer IV

Granular neurons

Pyramidal neurons

Corpus Collosum

Pyramidal neurons

Subcortical structures

Question 10

Oligodendrocytes and Astrocytes are considered _______.

Answer 10

Macroglial cells

Question 11

P0 and PLP are distinct among CNS and PNS myelin. Which protein belongs to which myelin?

Answer 11

PLP –> CNS (Oligodendrocytes)

P0 –> PNS (Schwann cells)

Question 12

Keep in mind there are two types of Oligodendrocytes, 1 that myelinates and 1 that does not. Which are the Intrafasicular and which are the grey matter Satellite Oligodendrocytes?

Answer 12

Myelinating –> Intrafasicular

Non-myelinating –> Grey Matter Satellite

Question 13

What is the relationship between axon diameter and myelination?

Answer 13

Thickness of myelin is directly correlated to Axon diameter. Axons smaller than 0.8microns are not myelinated.

Question 14

Because Astrocytes regulate ____, ____, and water balance in their local environment (about 50 micron radius), they are the first cells to become edematous when something causes edema (e.g. hydrocephalus).

Answer 14

pH, [K+], and water balance

Question 15

Astrocytes have a variety of functions including _____ and _____ of neurotransmitters. There are specifically responsible for recycling ______.

Neurons do not store energy. Though they can take up glucose, in times of high activity Astrocytes store energy as ______ and metabolize it to ______, which can also be taken up by Neurons as a source of energy.

Answer 15

Degrading and Inactivating

Glutamate

Glycogen

Lactate

Question 16

Keep in mind Astrocytes can also regulate blod flow via ______ (causes constriction of blood vessel) and ______ (causes dilation).

It’s important to remember they help form the _____. In fact, they have been shown to convert Fenestrated liver capillaries to non-fenestrated capillaries in an experiment.

Answer 16

AA –> constriction

PGE2 –> dilation

BBB

Question 17

______ Astrocytes are those found in White matter, while _______ Astrocytes are those found in Grey matter.

Which are richer in GFAP?

Answer 17

Fibrous

Protoplasmic

Fibrous (white matter) are richer in GFAP

Question 18

In response to injury, Astrocytes can be divided into two types: Active and Reactive. Which promote regeneration and which block it via scar formation and chemical signaling?

Answer 18

Active –> regen

Reactive –> block regen

Question 19

NG2 cells are ________ progenitor cells. They can be induced to divide and differentiate via activity of neurons they synapse with –> this would increase the myelination of the adjacent, active neurons –> increasing conduction speed. This process is termed _______ Myelination (basically practice makes perfect –> the more you use it, the more efficient it becomes).

Answer 19

Oligodendrocyte progenitor cells

Adaptive Myelination

Question 20

Microglia in the brain are hematopoetically derived from monocytes that migrate from the ____ ____, fetal ______, and fetal ____ _____.

Answer 20

Yolk sac

Fetal Liver

Fetal Bone Marrow

Question 21

Microglia are considered _______ when they are quiescent. They are like Dendritic cells of the immune system, and when they become activated, they can upregulate _____ to co-stimulate T-cells.

Answer 21

Ramified

MHC II