1. Neurons and glia

Question 1

Cell theory

Answer 1

Individual cell = elementary functional unit of all animal tissue

Question 2

Staining to study neuron

Question 3

Which protein provides the “legs” for retrograde transport?

Answer 3

Dynein

Question 4

Functions of neuron

Answer 4

Process info
Sense environment
Communicate internal info
Command body responses

Question 5

Functions of glia

Answer 5

Insulate
Nourish neurons
Support
Immune cells

Question 6

Reticular theory

Answer 6

Neurites of different cells fuse together to form a continuous network

Question 7

Soma

Answer 7

~ 20 micrometer diameter
Includes:
- Cytosol: salty, K-rich fluid inside the cell
- Organelles: membrane-enclosed structure within soma
- Cytoplasm: contents within cell membrane (include organelles but not nucleus)

Question 8

Nucleus

Answer 8

5-10 micrometer diameter
Includes:
- Chromosomes: contain DNA
- DNA molecules
- Gene expression: read out of DNA to synthesize proteins in cytosol
- Central dogma of molecular biology: DNA transcripes into mRA which translates into protein

Question 9

Transcription

Answer 9

DNA contains protein-coding genes (exons) and non-coding regions (introns)
DNA is the same in every somatic cell of the body
RNA polymerase binds to promotors to initiate transcription and ends at terminator
Regulations of gene expression (gene regulation) happens at all stages of gene expression

Question 10

Ribosomes and the rough endoplasmatic reticulum (ER)

Answer 10

Ribosomes synthesize protein (building blocks: amino acids, 20 kinds)
Attach to (rough) ER or free ribosomes
In neurons, many ribosomes attach to rough ER

Question 11

Difference between proteins synthesized on free ribosomes or rough ER?

Answer 11

Proteins synthesized on free ribosomes are for cytosol while on rough ER are inserted in membrane

Answer 12

Neurons: more rough ER than glia or other non-neuronal cells; a lot of special membrane proteins for information processing

Question 13

Functions of smooth endoplasmatic reticulum

Answer 13

Very diverse
Important for folding proteins (3D structure)
Regulate internal Ca (sarcoplasmatic reticulum in muscles)

Question 14

Functions of golgi apparatus

Answer 14

Package proteins into vesicles
Sort proteins for delivery to different cell regions (trafficking)

Question 15

Mitochondria

Answer 15

Site of cellular respiration, responsible for aerobic respiration (i.e. O2 dependent)
“Inhalation”: pyruvic acid (derived from sugars, digested proteins,
fat) & O2: Krebs cycle
Product of Krebs cycle provides energy for another series of
reactions (electron transport chain): ADP -> ATP
“Exhalation”: 17 ATP molecules for 1 pyruvic acid molecule (ATP =
cell’s energy source)

Question 16

Central dogma of molecular biology

Question 17

Membrane

Answer 17

~ 5 nanometer thick barrier that encloses cytoplasm
With protein in membrane. The concentration of protein varies which influences the function of the neuron

Question 18

Cytoskeleton

Answer 18

Internal scaffolding of neuronal membrane
Important for structural integrity
Three bones: microtubules, microfilaments, neurofilaments
Not static (polymerization) -> important for motility

Question 19

Microtubules

Answer 19

20 nanometers
Tubulin molecules
Run longitudinally
Wall of pipe composed of smaller strands braided like rope
Theses strands composed of tubulin protein
The process of joining tubulin molecules is called polymerization
Microtubule-associated proteins (MAPs) regulate polymerization and anchor microtubules
Pathological changes in an axonal MAP is tau

Question 20

Microfilaments (F-actin)

Answer 20

5 nanometers
Actin molecules
Distributed near plasma membrane throughout neuron but enriched in dendritic spines and presynaptic terminals
Braids of two thin strands (polymers of actin protein)
Critical role in changing cell shape (e.g. mechanisms for muscle contraction)

Question 21

Neurofilaments

Answer 21

10 nanometers
Provide stability to axon

Question 22

Axon

Answer 22

Only present in neurons
Includes:
- Axon hillock - beginning
- Axon proper - middle
- Axon terminal - end
- Axon collateral - branches

Diameters: less than 1 micrometer to 25 micrometers

Question 23

Differences between axon and soma

Answer 23

• Rough ER and Golgi do not extend into axon - no protein synthesis
• Axons contain a diverse set of localized mRNAs
• Unique protein composition (in axon?)

Question 24

Differences between cytoplasm of axon terminal vs of axon

Answer 24

• No microtubules in axon terminal
• Presence of synaptic vesicles in axon terminal
• Abundance of membrane proteins in axon terminal
• Large number of mitochondria in axon terminal

Question 25

Synapse

Answer 25

Pre and post
Synaptic cleft
Synaptic transmission
- Electrical to chemical to electrical transformation
- Learning and memory
- Synaptic transmission dysfunction
- Site of action for toxins and psychoactive drugs

Question 26

Axoplasmic transport

Answer 26

Slow: 0.2-8mm/day
- Cytosolic (soluble) proteins
- Cytoskeletal components

Fast: 0-400nm/day (0.5-6micrometer/s)
- Material enclosed within vesicles, walk along microtubules (transmembrane proteins, secreted proteins)
- Anterograde: soma -> terminal, leg = kinesin
- Retrograde: terminal -> soma, leg = dyein
- Fueled by ATP

Question 27

Cytoskeleton and intracellular tracfficking

Answer 27

Microfilaments (actin, periphery), microtubules (tubulin, axonal and dendritic processes)

Polar:
- Dynamic plus ends, often points towards periphery
- Stable minus end, often anchored at cell center

Microtubules: long distance transport

Dynein: (-) end-directed motor in axon. From axon terminal -> cell body

Kinesin: (+)-end-directed motor in axon. From cell body -> axon terminal

K1Fa: kinesin transporting vesicle precursors

F-actins direct local traffic utilizing myosin proteins as molecular motors

Question 28

Dendrites

Answer 28

Dendritic trees and dendritic spines
local protein synthesis at spines

Receive (+) inputs

Site of plasticity

Question 29

Classifying neurons (how many ways, what are they)

Answer 29

Number of neurites: unipolar, bipolar, multipolar

Dendritic and somatic morphologies
- Stellate cells (start-shaped)
Pyramidal cells (pyramid-shaped)
- Spiny
- Aspinous

Firing patterns

Transcriptome: single cell RNA sequence

Expression of calcium-biding proteins or neuropeptides

Neurotransmitters

Question 30

Types of gial in CNS

Answer 30

Astrocytes: end-feed wrap around blood vessles (blood-brain barrier)

Oligldendrocytes: wrap axons of CNS neurons for insulation
Microglia: immune cells of NS

Question 31

Astrocytes

Answer 31

Most glias in the brain are astrocytes

Fill spaces between neurons

Influence neurite growth

Contact with blood vessles (blood-brain barrier)

Processes surrounding synapes

Regulate chemical content of extracellular space

Question 32

Myelinating glial

Answer 32

Oligodendroglia: in CNS, several axons

Schwann cells: in PNS, 1 axon

Insulate axons

Node of ranvier

Question 33

What are three physical characteristics that distinguish axons from dendrites?

Question 34

Colchicine is a drug that causes microtubules to break apart (depolymerize). What effect would this drug have on anterograde transport? What would happen in the axon terminal?