Module 7 notes

Question 1

What are the two types of brain cells?

Answer 1

neurons and glia.

Question 2

We used to believe the brain had about 100 billion neurons, but now we know the number is closer to…

Answer 2

86 billion.

Question 3

How many neural cell bodies can fit across the tip of a new number 2 pencil?

Answer 3

50-200.

Question 4

Why is neuroscience still fairly new compared to other disciplines?

Answer 4

original brain matter has the consistency of yogurt, so it was hard to slice. They had to develop “fixing” which is a way of hardening the brain.
Fixing hardened the brain, but the chemicals used destroyed cellular structures. Fermeldahyde was working but also toxic.
With fixation, another problem rose, which was the size of neurons. In order to put them on a slide, it must be one layer thick, and they are incredibly small. Then a microtome was developed, which can slice brain tissue that thin.
The next issue was the lack of pigmentation in the brain. It would look like creamy, white field. There was need of a stain that only sticks to certain molecules, because a stain that stains everything would lack contrast to determine structures.
Franz Nissl created Nissl stain. which adheres to material inside of cell bodies. This allowed us to discern of cell patterns and we were able to see the 6 layers of the cortex. Then Golgi stain was developed, and was great because it only stained 5% of cells. (100 percent wouldn’t allow us to see much.)
We were able to see axons and dendrites and Ramon y Cajal used the Golgi stain to realize neurons are in circuits.

Question 5

Cytoarchitectonics is what?

Answer 5

the study of CNS tissues under a microscope.

Question 6

Describe the axon of a neuron.

Answer 6

only one, doesn’t taper, doesn’t branch as much as dendrites, and is smaller in diameter than dendrites.

Question 7

Describe the dendrites of a neuron.

Answer 7

6-18 per cell, taper down, branch, at the end of the dendritic field, you can have 100’s of thousands of branches.

Question 8

What are the four morphological regions of neural structure and their functions?

Answer 8

the soma (integrator)
Dendrites (input unit)
axon (propagation structure) 
synaptic knobs (output portion.)

Question 9

What are the parts of the soma (9)?

Answer 9

cell body made up of nucleus and porous nuclear membrane made of a lipid bilayer, endoplasmic reticulum (rough and smooth) in the cytoplasm, the Golgi apparatus, lysosomes, mitochondria, peroxisomes, and external membrane.

Question 10

How are the two layers of the lipid bilayer different?

Answer 10

the outside is hydrophilic, and the inside is hydrophobic.

Question 11

What is the difference between rough and smooth endoplasmic reticulum?

Answer 11

rough ER has ribosomes, whereas smooth ER does not.

Question 12

what is the function of er?

Answer 12

receives messenger RNA and is responsible for construction of proteins and enzymes.

Question 13

the golgi apparatus is responsible for…

Answer 13

packaging, and the creation of synaptic vesicles.

Question 14

What is the function of lysosomes?

Answer 14

to break down waste.

Question 15

What is the function of Mitochondria?

Answer 15

energy and calcium processing.

Question 16

What is the function of peroxisomes?

Answer 16

detox of hydrogen peroxide.

Question 17

What structures have a lipid bilayer?

Answer 17

the nuclear membrane, ER, golgi apparatus, lysosomes and external membrane.

Question 18

Which structures lack a lipid bylayer?

Answer 18

Mitochondria and peroxisomes.

Question 19

Which two structures were originally parasitic but where engulfed by cells, creating their function within the cell?

Answer 19

the mitochondria and peroxisomes.

Question 20

What percentage of the total volume of the cell is the soma?

Answer 20

10%

Question 21

What are the two types of axons?

Answer 21

myelinated or unmyelinated.

Question 22

What is the benefit of having a myelinated axon?

Answer 22

the action potential travels much faster.

Question 23

What is saltatory conduction?

Answer 23

the rapid propulsion of an action potential down myelinated axons.

Question 24

what are the three cytoskeletal systems used to keep the shape of the cell and transport local materials?

Answer 24

the microtubules, the neurofilaments and the microfilaments.

Question 25

What are the three components of the axoplasmic transport system?

Answer 25

anterograde (fast and slow) and retrograde (fast). They are for recycling and neurotrophic hormones.

Question 26

What are MAPS?

Answer 26

microtubule assisting proteins (ex: tau and kinesins) that are hormones gained from other cells and glia and go back to the cell body. They can be hijacked by viruses that present at the synaptic knob and move through the retrograde system back to the soma to cause damage, leading to a variety of disorders. Herpes simplex 1 is one of these, which attacks the mesial temporal and basal frontal lobes.

Question 27

Neurofilaments are…

Answer 27

coiled wires, made of tetrameric twisting protofilaments. smaller than neurotransmitters, and add shape and stability to the cell.

Question 28

Microfilaments act as what?

Answer 28

local roads of the cell that get material to their final destination.

Question 29

What two structure make up the trigger zone?

Answer 29

the axon hillock and the initial segment of the axon.

Question 30

Where is the only place an action potential can be generated?

Answer 30

the trigger zone.

Question 31

What are the classes of neurons by processes in the cell body?

Answer 31

unipolar (one process), bipolar (2), multi-polar (2+) and pseudopolar (side soma.)

Question 32

What are the classifications of neurons by shape?

Answer 32

pyramidal, basket, stellate, and spindle.

Question 33

What are the classifications of neurons by size, specifically axon length?

Answer 33

Golgi type 1 (long) includes: pyramidal tract, motor cortex, corpus callosum, and projection neurons. Golgi type 2 are short and connect only to direct neighboring neurons.

Question 34

What are the classifications of neurons by function?

Answer 34

sensory, motor, association.

Question 35

Glial cells form what in which the neurons sit?

Answer 35

a matrix for structural support.

Question 36

What are the functions of glial cells other than providing a matrix

Answer 36

essential for myelination, deliver neurotrophic hormones, act as scavengers using phagocytes, mop up or absorb ions, and are involved in nervous system development.

Question 37

How are glial cells involved in nervous system development?

Answer 37

it starts as single layer of nervous system cells, then migrates up to form the 6 layers. The neurons and cortex build circuits and must wire together in a specific way. Glial cells direct neurons to appropriate connections. A thin cortex can be a sign this process didn’t complete. (Dyslexia, seizure disorder.) They play a role in autoregulation of cerebral blood flow by causing arteries to dilate or constrict. They are involved in sugar processing, and may be involved in processing information, reasoning, judgement, and decision-making.

Question 38

Explain the role of glial cells with the blood-brain barrier.

Answer 38

the walls of capillaries are permeable, so the glial cells for around them creating tight junctions that only allow certain molecules to pass from the capillaries into the brain.

Question 39

Name the types of glial cells mentioned in lecture.

Answer 39

oligodendrocytes produce myelin in the CNS. Schwann cells produce myelin in the PNS. Astrocytes are the glial cells involved in the blood-brain barrier, microglial play an acidic role, and ependymal cells keep CSF in.