2. cellular organisation of the nervous system

Question 1

1. describe the hierarchical structure of the brain. 3

Answer 1

1. reductionist approach - cells communicate with each other
2. systems communicate with each other
3. it is an integrated mechanism.

Question 2

do the brain hierarchy diagram

Answer 2

:)

Question 3

what was golgi’s reticular theory? 5

Answer 3

1. 1800s, brain sructure and nerve cells explored
2. golgi invented the golgi stain - reduced silver salts
3. picks out seemingly random individual cells and stains them in great detail
4. golgi saw that cells appeared to be fused together in a network - he called the cells neurites
5. this was called reticular theory

Question 4

What was cajal’s neuronal doctrine? 6

Answer 4

1. he adapted golgi’s stain so fewer cells were labelled at a time
2. found that each neurone was a discrete cell, therefore cells are the smallest functional unit of the brain - neurone doctrine
3. principle of dynamic polarization - electrical signals in the brain only flow in one direction down a neurone
4. principle of connectional specificity - specific connections at specific parts with specific parts of other neurones
5. never got along with golgi, who rejected principle of dynamic polarization
6. they won a joint nobel prize anyway

Question 5

How did microscopes and brain microscopy contribute to our understanding of the brain? 5

Answer 5

1. electron microscope developed
2. in thin tissue specimens, electrons are absorbed differently by different organelles
3. allows examination of cell ultrastructure
4. confirmed existence of synapses
5. however, all cells must be fixed, therefore dead.

Question 6

What role did fluorescent labeling play in brain microscopy? 6

Answer 6

1. development of fluorescent labeling methods allowed a powerful way of determining protein distribution in cells
2. selective antibody/drug is prepared and tagged with fluorescent label
3. added to tissue and binds strongly
4. any free labelled antibody/drug washed away
5. left with image distribution of fluorescence which corresponds with target protein’s distribution
6. however, limited by range of antibodies available

Question 7

What marker proteins are used for different types of neuronal cell? 4

Answer 7

1. Glial cells have glial fibrillary acidic protein
2. neurons have neurofilament proteins
3. axons have tau
4. dendrites have MAP-2

Question 8

What is immunofluorescence? 3

Answer 8

1. tissues are dead
2. lots of light needed
3. very pretty, resulting in images from above

Question 9

What are confocal microscopes? 4

Answer 9

1. Like light microscopes but use a laser
2. also require high sensitivity cameras and imaging software
3. can examine live cells and their physiology
4. modest resolution, 0.1micron

Question 10

What are glia?6

Answer 10

1. neurones are the excitable cells and glia support them
2. outnumber neurones 10:1
3. May mediate some signalling in brain, could play important emotional role
4. can divide, unlike neurones
5. ectoderm leads to macroglia and neuroglia
6. mesoderm leads to microglia

Question 11

Do you know the glia hierarchy?

Answer 11

Draw it out!

Question 12

What are astrocytes? 5

Answer 12

1. majority of glia
2. star shaped and fill spaces between neurons
3. regulate ecf composition by taking up excess NETS and K+ and dissipating it, diluting their conc.
4. Can’t create an electrical signal but can respond with other types of signal
5. New research suggests they can play an important role in directing the proliferation and differentiation of neuronal stem cells

Question 13

What are oligodendrocytes and schwann cells? 6

Answer 13

1. make myelin to myelinate axons of neurons
2. oligodendrocytes are part of the cns
3. they wrap myelin around several axons
4. schwann cells are a part of the cns
5. they myelinate a single axon
6. gaps in the myelin sheath are called the nodes of ranvier

Question 14

What are microglia and ependymal cells? 5

Answer 14

1. microglia act as brain scavengers
2. they have phagocytic/immune functions
3. they can migrate
4. ependymal cells line ventrivles
5. they also direct cell migration during brain development

Question 15

Describe the prototypical neurone. 5

Answer 15

1. simple, non-polarized cells have a plasma membrane and a nucleus eg. kidney cell, HEK293
2. a simple polarized cell has an apical and basolateral surface eg. epithelial cells
3. a highly polarized cell may have dendrites, a soma (cell body) and an axon eg. neuron
4. There are 50+ types of neuron
5. Usually, dendrites are basal and axons apical

Question 16

Do you know the differences between axons and dendrites? Do the table

Answer 16

Yay :)

Question 17

Describe neuronal structure. 6

Answer 17

1. Neurites/axons are specialised for transmission of information
2. Dendrites are specialied for receipt of info
3. cell body (soma/perikaryon) with cytosol and organelles including nucleus
4. cell membrane called plasmolemma
5. Can’t reproduce, but glia can
6. cells can trigger action potentials

Question 18

Describe the neuronal cytoplasm. 4

Answer 18

1. Contains peroxisomes and mitochondria for energy metabolism
2. ribosomes
3. vacuolar apparatus - secretory pathway/endocytic pathway contains:
   - endoplasmic reticulum
   - secretory vesicles
   - golgi complex
   - endosomes and lysosomes
4. some organelles are also found in the dendrites

Question 19

What is the axon hillock? 4

Answer 19

1. Division between soma and axon
2. Synaptic vesicles
3. Mitochondria
4. Smooth endoplasmic reticulum

Question 20

What’s the difference between axons and dendrites? 4

Answer 20

1. differences in cell membrane
2. different receptors and proteins in them
3. dendrites have:
   - ca2+ channels
   - ligand gated ion channels (glutamate receptors)
   - GPCRS
4. axons have:
   - GPCRS at terminals
   - ca2+ channels at terminals
   - na+ and k+ channels (axon shafts)

Question 21

what is the role of the neuronal cytoskeleton? 5

Answer 21

1. there are no ribosomes in axons so proteins must be transported to axon terminal
2. cytoskeleton provides structural support, shape and flibre of axons and dendrites
3. Transports cargo eg. proteins to and from axons and dendrites
4. tethering of components at membrane surface
5. runs down neuron and dendrites

Question 22

What are microtubules? 6

Answer 22

1. run longitudinally down axons and dendrites
2. big, 20nm wide tubulin polymers
3. polymerisation and depolymerisation - shape and length changed easily
4. microtubule associated proteins eg. MAP-2, tau
5. structural and transport roles
6. proteins include kinesin and dynein

Question 23

What are neurofilaments? 4

Answer 23

1. 10nm wide filamentous protein threads
2. protein strands are woven
3. prove mechanical strength
4. related to intermediate cells in rest of body

Question 24

What are microfilaments? 4

Answer 24

1. 5nm wide actin polymers
2. capable of depolarization and repolarization
3. found tethered to membrane in dendritic spines
4. mediate shape change

Question 25

Describe structural forms of neuronal classificaiton. 5

Answer 25

1. pseudounipolar is sensory, paert of cns, has a line and a blob coming from middle of line
2. bipolar, blob in middle of line, many in eyes
3. multipolar, several dendrites and one axon
4. structural neuronal classification is based on morphology or number os prcesses coming from cell body
5. multipolar cells include the motor neurones of the spinal cord and pyramidal cells of hippocampus and purkinje cells of cerebellum

Question 26

How are neurones classified functionally? 5

Answer 26

1. based on the direction of conducted impulses
2. sensory (afferent eg stomach, visceral) neurones go to sensory receptor, then to processor
3. Motor (efferent eg. somatic, visceral) conduct signals originating in cns
4. interneurons are between sensory and motor neurons
5. also many neuronal types on molecular level based on main net types

Question 27

how are dendritic spines linked to mental retardation? 3

Answer 27

1. proximal dendrite malformation correlates well with severity of retardation
2. dendritic spines compartmentalize chemicals which may help synapses to function better
3. Malformation may be due to impoverished environment during a critical period of brain development

Question 28

What happens in the brain during alzhiemer’s? 6

Answer 28

1. 80% of 80 year olds show symptoms
2. mental ampairment - irritability and forgetfulness
3. has genetic and familial origins
4. characterized by nerofibrils - dead and dying neurons
5. filaments become tangled and are destroyed, forming neurofibrillary plaques full of cytoskeletal junk
6. neurons no longer function