2. cellular organisation of the nervous system Flashcards
1
Q
- describe the hierarchical structure of the brain. 3
A
- reductionist approach - cells communicate with each other
- systems communicate with each other
- it is an integrated mechanism.
2
Q
do the brain hierarchy diagram
A
:)
3
Q
what was golgi’s reticular theory? 5
A
- 1800s, brain sructure and nerve cells explored
- golgi invented the golgi stain - reduced silver salts
- picks out seemingly random individual cells and stains them in great detail
- golgi saw that cells appeared to be fused together in a network - he called the cells neurites
- this was called reticular theory
4
Q
What was cajal’s neuronal doctrine? 6
A
- he adapted golgi’s stain so fewer cells were labelled at a time
- found that each neurone was a discrete cell, therefore cells are the smallest functional unit of the brain - neurone doctrine
- principle of dynamic polarization - electrical signals in the brain only flow in one direction down a neurone
- principle of connectional specificity - specific connections at specific parts with specific parts of other neurones
- never got along with golgi, who rejected principle of dynamic polarization
- they won a joint nobel prize anyway
5
Q
How did microscopes and brain microscopy contribute to our understanding of the brain? 5
A
- electron microscope developed
- in thin tissue specimens, electrons are absorbed differently by different organelles
- allows examination of cell ultrastructure
- confirmed existence of synapses
- however, all cells must be fixed, therefore dead.
6
Q
What role did fluorescent labeling play in brain microscopy? 6
A
- development of fluorescent labeling methods allowed a powerful way of determining protein distribution in cells
- selective antibody/drug is prepared and tagged with fluorescent label
- added to tissue and binds strongly
- any free labelled antibody/drug washed away
- left with image distribution of fluorescence which corresponds with target protein’s distribution
- however, limited by range of antibodies available
7
Q
What marker proteins are used for different types of neuronal cell? 4
A
- Glial cells have glial fibrillary acidic protein
- neurons have neurofilament proteins
- axons have tau
- dendrites have MAP-2
8
Q
What is immunofluorescence? 3
A
- tissues are dead
- lots of light needed
- very pretty, resulting in images from above
9
Q
What are confocal microscopes? 4
A
- Like light microscopes but use a laser
- also require high sensitivity cameras and imaging software
- can examine live cells and their physiology
- modest resolution, 0.1micron
10
Q
What are glia?6
A
- neurones are the excitable cells and glia support them
- outnumber neurones 10:1
- May mediate some signalling in brain, could play important emotional role
- can divide, unlike neurones
- ectoderm leads to macroglia and neuroglia
- mesoderm leads to microglia
11
Q
Do you know the glia hierarchy?
A
Draw it out!
12
Q
What are astrocytes? 5
A
- majority of glia
- star shaped and fill spaces between neurons
- regulate ecf composition by taking up excess NETS and K+ and dissipating it, diluting their conc.
- Can’t create an electrical signal but can respond with other types of signal
- New research suggests they can play an important role in directing the proliferation and differentiation of neuronal stem cells
13
Q
What are oligodendrocytes and schwann cells? 6
A
- make myelin to myelinate axons of neurons
- oligodendrocytes are part of the cns
- they wrap myelin around several axons
- schwann cells are a part of the cns
- they myelinate a single axon
- gaps in the myelin sheath are called the nodes of ranvier
14
Q
What are microglia and ependymal cells? 5
A
- microglia act as brain scavengers
- they have phagocytic/immune functions
- they can migrate
- ependymal cells line ventrivles
- they also direct cell migration during brain development
15
Q
Describe the prototypical neurone. 5
A
- simple, non-polarized cells have a plasma membrane and a nucleus eg. kidney cell, HEK293
- a simple polarized cell has an apical and basolateral surface eg. epithelial cells
- a highly polarized cell may have dendrites, a soma (cell body) and an axon eg. neuron
- There are 50+ types of neuron
- Usually, dendrites are basal and axons apical
16
Q
Do you know the differences between axons and dendrites? Do the table
A
Yay :)
17
Q
Describe neuronal structure. 6
A
- Neurites/axons are specialised for transmission of information
- Dendrites are specialied for receipt of info
- cell body (soma/perikaryon) with cytosol and organelles including nucleus
- cell membrane called plasmolemma
- Can’t reproduce, but glia can
- cells can trigger action potentials
18
Q
Describe the neuronal cytoplasm. 4
A
- Contains peroxisomes and mitochondria for energy metabolism
- ribosomes
- vacuolar apparatus - secretory pathway/endocytic pathway contains:
- endoplasmic reticulum
- secretory vesicles
- golgi complex
- endosomes and lysosomes - some organelles are also found in the dendrites
19
Q
What is the axon hillock? 4
A
- Division between soma and axon
- Synaptic vesicles
- Mitochondria
- Smooth endoplasmic reticulum
20
Q
What’s the difference between axons and dendrites? 4
A
- differences in cell membrane
- different receptors and proteins in them
- dendrites have:
- ca2+ channels
- ligand gated ion channels (glutamate receptors)
- GPCRS - axons have:
- GPCRS at terminals
- ca2+ channels at terminals
- na+ and k+ channels (axon shafts)
21
Q
what is the role of the neuronal cytoskeleton? 5
A
- there are no ribosomes in axons so proteins must be transported to axon terminal
- cytoskeleton provides structural support, shape and flibre of axons and dendrites
- Transports cargo eg. proteins to and from axons and dendrites
- tethering of components at membrane surface
- runs down neuron and dendrites
22
Q
What are microtubules? 6
A
- run longitudinally down axons and dendrites
- big, 20nm wide tubulin polymers
- polymerisation and depolymerisation - shape and length changed easily
- microtubule associated proteins eg. MAP-2, tau
- structural and transport roles
- proteins include kinesin and dynein
23
Q
What are neurofilaments? 4
A
- 10nm wide filamentous protein threads
- protein strands are woven
- prove mechanical strength
- related to intermediate cells in rest of body
24
Q
What are microfilaments? 4
A
- 5nm wide actin polymers
- capable of depolarization and repolarization
- found tethered to membrane in dendritic spines
- mediate shape change
25
Q
Describe structural forms of neuronal classificaiton. 5
A
- pseudounipolar is sensory, paert of cns, has a line and a blob coming from middle of line
- bipolar, blob in middle of line, many in eyes
- multipolar, several dendrites and one axon
- structural neuronal classification is based on morphology or number os prcesses coming from cell body
- multipolar cells include the motor neurones of the spinal cord and pyramidal cells of hippocampus and purkinje cells of cerebellum
26
Q
How are neurones classified functionally? 5
A
- based on the direction of conducted impulses
- sensory (afferent eg stomach, visceral) neurones go to sensory receptor, then to processor
- Motor (efferent eg. somatic, visceral) conduct signals originating in cns
- interneurons are between sensory and motor neurons
- also many neuronal types on molecular level based on main net types
27
Q
how are dendritic spines linked to mental retardation? 3
A
- proximal dendrite malformation correlates well with severity of retardation
- dendritic spines compartmentalize chemicals which may help synapses to function better
- Malformation may be due to impoverished environment during a critical period of brain development
28
Q
What happens in the brain during alzhiemer’s? 6
A
- 80% of 80 year olds show symptoms
- mental ampairment - irritability and forgetfulness
- has genetic and familial origins
- characterized by nerofibrils - dead and dying neurons
- filaments become tangled and are destroyed, forming neurofibrillary plaques full of cytoskeletal junk
- neurons no longer function
