Chapter 2 - Neurons and Glia

Question 1

Challenges to study of brain?

Answer 1

Size 0.01mm across
Jelly consistency
Development of microtome to slice
Uniform colour spawned stains

Question 2

Wha tis histology?

Answer 2

Microscopic study of structure of tissues

Question 3

What did Nissl create?

Answer 3

Nissl stain
Some dyes stain nuclei of all cells plus clumps of material surrounding nuclei of neurons known as Nissl bodies are Rough ER

Nissl stain differentiates between neurons and glia, and allows study of cytoarchitecture of neurons in different parts of brain
We know now that each region performs different function

Question 4

Whst did Golgi do?

Answer 4

Golgi stain
Makes small number of neurons become darkly coloured in entirety
Showed neuronal body, region of neuron around nucleus, only small fraction of structure of neuron

Question 5

What are names for body containing nucleus?

Answer 5

Soma, cell body, perikaryon

Question 6

What are axons, dendrites?

Answer 6

Output (length)

Input

Question 7

What did Cajal say?

Answer 7

Neuron doctrine.

Neurons communicate by contact not continuity

Question 8

What’s in soma?

Answer 8

Cytosol: potassium fluid with salt
Organelles
Cytoplasm
Nucleus

Question 9

How are mistakes made in DNA?

Answer 9

Gene copy number variations - overcopying
Mutations
Single nucleotide polymorphisms - minor misspelling

Question 10

What is:
Knockout mice
Transgenic mice
Knock-in mice

Answer 10

1. One gene deleted
2. Genes introduced and overexpressed
3. Native gene replaced by modified gene

Question 11

What distinguishes the axon from soma?

Answer 11

1. No rough ER extends into axon
2. Few free ribosomes in mature axons
3. Protein composition of axon membrane fundamentally different from soma membrane
4. No protein synthesis in axon. All originate in soma

Question 12

What is axon collateral?

Answer 12

Branches

Question 13

Does speed depend on diameter?

Answer 13

Yes

Question 14

Where does axon begin? End?

Answer 14

Hillock

Terminal bouton

Question 15

How does cytoplasm of axon terminal differ from axon’s?

Answer 15

1. Microtubules don’t extend into terminal
2. Terminal contains numerous small bubbles of membrane called synaptic vesicles
3. Inside surface of membrane facing synapse has dense protein covering
4. Axon terminal cytoplasm has many mitochondria (high energy demand)

Question 16

What moves material from soma to terminal in anterograde axoplasmic transport? Back to soma in retrograde transport?

Answer 16

Kinesin, dynein

Question 17

What do dendritic spines do?

Answer 17

Punching bags hanging off dendrite
Believed to isolate various chemical reactions triggered by some types of synaptic activation
Unusual changes have been shown to occur in brains of individuals with cognitive impairments

Question 18

How are neurons classified?

Answer 18

1. Number of neurites (axons and dendrites). Neurons with single neurite unipolar, two bipolar, more multipolar
2. Dendrites. In cerebral cortex are stellate and pyramidal cells. Also spiny and aspinous. Pyramids are all spiny, stellates either
3. Connections. Primary sensory neurons, motor neurons, interneurons (most)
4. Axon length. Golgi type 1 stay in brain (projection). Golgi type 2 stay local (local circuit). Pyramidal long 1, stellate short 2.

Question 19

What are cholinergic cells?

Answer 19

Motor neurons releasing acetylcholine

Question 20

What are glial types?

Answer 20

1. Astrocytes. Most numerous. Between neurons. Influence whether neurite can grow or retract. Restrict spread of neurotransmitters. Proteins removes neurotransmitters from cleft. NT receptors can trigger bio and electric events inside glial cell. Regulate concentration of extracellular substances
2. Myelinating glia. Oligodendroglial and Schwanns. Insulate axons. Space is node of Ranvier. Oligs only in CNS and contribute to several axons.
3. Ependymal cells line ventricles
4. Microglia are phagocytes. Eat synaptic connctions