Neurons and Glia

Question 1

Anterograde transport

Answer 1

A cellular process responsible for the movement of substance from the cell body to the distal parts of a cell

Question 2

Aspinous neuron

Answer 2

A neuron lacking dendritic spines

Question 3

Astrocyte

Answer 3

A star-shaped glial cell of the central nervous system

Question 4

Axon

Answer 4

The long thread-like part of a neuron along which impulses are conducted from the cell body to other cells

Question 5

Axon collateral

Answer 5

Branches off a neuron’s main axon

Question 6

Axon hillock

Answer 6

The site in the soma where membrane potentials propagated from synaptic inputs are summated before being transmitted to the axon

Question 7

Axon terminal (bouton)

Answer 7

The enlarged club-shaped endings by which axons make synaptic connections with other neurons or effector cells

Question 8

Axoplasmic transport

Answer 8

A cellular process responsible for the movement of substances from the soma down the axon

Question 9

Bipolar neuron

Answer 9

A neuron with two neurites extending from the soma

Question 10

(“Reticular theory”) by Camillo Golgi (1843-1926)

Answer 10

Golgi proposed that neurons were fused together to form a continuous reticulum (or network)

Question 11

(“Neuron doctrine”) by Santiago Ramon y Cajal (1852-1934)

Answer 11

Cajal proposed that neurons were not continuous but communicated by neuron-neuron contact

Question 12

Nissl stain

Answer 12

comprised of a basic dye (e.g. cresyl violet) – stains the nuclei and Nissl bodies of neurons

Question 13

Golgi stain

Answer 13

comprised of a silver chromate solution – stains neurons and their projections

Question 14

Light microscopy

Answer 14

• Standard light microscopy has a limit of resolution of 0.1 𝝻M
• Space between neurons approximately 0.02 𝝻M (or 20 nM)

Question 15

Electron microscopy

Answer 15

• Electron microscopy has a limit of resolution of 0.1 nM

* Our insights into the fine structure of neurons have come from electron microscopy

Question 16

Structure of simple prototypical neuron

Answer 16

1. Cell body (soma)
2. Axon
3. Dendrites

Question 17

Cell body organelles

Answer 17

• Nucleus
• Rough endoplasmic reticulum (RER)
• Smooth endoplasmic reticulum (SER)
• Golgi apparatus
• Mitochondrion

Question 18

Microtubules

Answer 18

• A polymer of the protein tubulin – located in axons and dendrites and important in axoplasmic transport

Question 19

Microfilaments

Answer 19

• A polymer of the protein actin – found throughout the neuron but particularly abundant in axons and dendrites

Question 20

Neurofilaments

Answer 20

• A type of intermediate filament – particularly abundant in axons and important in regulating axonal shape
• Promising biomarker for neurodegenerative disorders (e.g. Alzheimer’s)

Question 21

What are axons?

Answer 21

Axons are highly specialised neuronal projections that conduct nerve impulses (or action potentials) within the nervous system

Question 22

What are axons comprised of?

Answer 22

• Axon hillock – tapers away from the soma to form the initial segment of the axon
• Axon ‘proper’ – axon can branch to form axon collaterals (and recurrent collaterals)
• Axon terminal – site at which the axon meets other neurons at a synapse

Question 23

Glial cells

Answer 23

• Myelin is a membranous sheath that wraps around and insulates axons
• Gaps in myelin sheath are Nodes of Ranvier – highly enriched in voltage-gated Na+ ion channels

Question 24

What are dendrites?

Answer 24

• Dendrites are highly specialised neuronal projections that receive synaptic inputs from other neurons
• Dendritic spine structure is sensitive to type and amount of synaptic activity

Question 25

Different dendrites?

Answer 25

Stellate | Pyramidal

Question 26

Neuron projects

Answer 26

Unipolar Bipolar Multipolar

Question 27

Connections

Answer 27

Sensory Motor Interneurons

Question 28

Axon length

Answer 28

Golgi type I and Golgi type II

Question 29

What are astrocytes

Answer 29

Astrocytes are star-shaped glial cells that function to regulate – in a number of ways – the extracellular environment of the brain.

Question 30

Astrocytes

Answer 30

• Astrocytes regulate the extracellular environment in the brain by, for example, enclosing synaptic junctions and actively removing neurotransmitters from the synaptic cleft

Question 31

Microglia

Answer 31

Phagocytosis of neuronal and glial debris (e.g. sites of injury) • Synaptic connection remodelling • Directing neuronal migration during brain development

Question 32

Ependymal cells

Answer 32

* Osmotic regulation of cerebrospinal fluid * Flow of cerebrospinal fluid * Directing cell migration during brain development

Question 33

What are ependymal cells?

Answer 33

Ependymal cells are a type of glial cell that provides the lining of the ventricular system of both the brain and spinal cord. Ependymal cells line the ventricular system and act as a physical barrier separating brain tissue from cerebrospinal fluid (CSF)

Question 34

What are microglia?

Answer 34

Microglia are a type of glial cell that function as phagocytes within the nervous system to remove neuronal and glial debris. Microglia – which account for approximately 5-15% of total CNS cell number depending on anatomical region – are broadly distributed in the brain and spinal cord

Question 35

4 types of glial cells

Answer 35

``` Astrocytes Microglia Ependymal cells Oligodendrocytes/Schwann cells Glial cells are the “support cells” within the nervous system and can be classified into four categories based on structure and function. ```

Question 36

Oligodendrocytes

Answer 36

Oligodendrocytes (pictured) are situated in the central nervous system (CNS)

Question 37

Schwann cells

Answer 37

Schwann cells are situated in the peripheral nervous system (PNS)