Nervous System Components Flashcards
What are the non-neural cells and the excitable cells in the brain?
Glia and neurons
What makes the nervous system special?
~ 6000 genes expressed in brain only
~ 8000 ubiquitois genes
What are gating properties?
conditions that open gated channels (ex. amount of calcium required)
How are glial cells essential elements for neural electrical functions?
1) modulate synaptic function
2) role in brain metabolism
3) maintain chemical homeostasis
4) regulate blood flow through capillary beds
5) provide “immune” type functions
6) provide a scaffold for neuronal migration during development
How do glial cells differ from neurons?
They are non-excitable, have different functions and are replaced by precursors throughout adulthood
What classes of glial cells are there?
1) astrocytes
2) oligodendrocyte or schwann cell
3) microglial cells
4) ependymal cells (includes radial glia)
What is the difference between vertebrate and invertebrate?
Invertebrates have less glial cells that are not as specialized
What/where are ependymal cells?
endothelial cells that line the ventricles
What can ependymal cells produce?
some can produce cerebrospinal fluid
What are ependymal cells derived from?
radial glia which are present during development
What are tanycytes?
a subtype of ependymal cell that lines the third ventricle to the hypothalamus and is involved in transferring signals from CSF to the CNS
How does brain development occur?
cell surface proteins act as signals to attract and motivate neurons to migrate along the surface of radial glial cells
What do schwann and oligodendrocytes do?
myelinate neurons by wrapping around them and increasing electical resistance by insulating
What are the key differences between schwann and oligodendrocytes?
schwann cells wrap around a single motor neuron axon in peripheral nerve whereas oligodendrocytes wrap around multiple neurons each in CNS
What functions do microglia serve?
1) main elements of intrinsic immune system
2) sense brain injury and clear cellular debris
3) implicated in brain inflammatory responses, cognitive deficits, percussive brain injury, stroke damage
How do microglia work?
check the environment by redistributing membrane (filpodia) and engulf and digest damaged tissue (phagocytotic)
What are microglial derived from?
hemopoetic stem cells in bone marrow
What are some of the functions of an astrocyte?
1) influencing integrity of BBB
2) removal of glutamate and GABA at synapses
3) synthesis of precursor for glutamate and GABA production
4) and more…
How do astrocytes maintain the BBB?
form tight junctions with foot processes so that proteins, drugs and charged molecules cannot diffuse
How is synaptic activity coupled to glucose usage?
astrocytes do this by coupling glutamate upatke with glucose utilization
How do astrocytes help to regulate blood flow to active brain regions?
they control the arteriole diameter (as calcium concentration increases they signal arterioles to contract and vice versa)
How close are neurons to capillaries? Why?
they are 10-20 micrometers to decrease diffusion time
Why does oxygenated and de-oxygenated blood appear to be different colours?
deoxygenated: blue (absorbs red and reflects blue)
can be used to measure brain activity
What are the differences between MRI and fMRI?
MRI: static image, based on water distribution
fMRI: dnamic, based on paramagnetic properties of oxy and deoxy hemoglobin
both: poor spatial resolution but can image through skull
What is a CT scan good for imaging?
structure (not activity) and often used for confirmation of problem and viewing areas before surgery
How does a CT work?
x-ray based
What does PET stand for?
positron emission tomography
What does PET measure?
metabolic activity in biochemically specific neurons (using short-lived isotopes)
What did Golgi do?
developed a technique for staining neurons and interpreted what he saw
What are the signaling units of a neuron?
1) soma (cell body)
2) axon and axon collaterals (not always)
3) dendrites (spiny or smooth)
4) presynaptic release sites (terminals, boutons, and non-localized release sites)
What does the size of dendritic arbor indicate?
the amount of convergence on to a neuron and allows different sets of signals to come in
How many inputs can a purkinje cell receive?
100, 000
What types of neurons are there?
1) pyramidal
2) bipolar
3) ganglion
4) amacrine
5) purkinje
What does the cell body do and what does it contain?
it is the main metabloic centre of neuron and site of protein synthesis
it contains lots of mitochondria and endoplasmic reticulum
How large are cell bodies?
vertebrates: 8-200 micrometers
invertebrates: 8-600 micrometers
What is the function of the dendrites and what organelles do they contain?
they are the primary site of input and can release neurotransmitter
they contain ribosomes to make local proteins and lots of actin
What are the physical features of dendrites?
they vary in size and complexity and are generally think proximally and thinner distally
What are the functions of the axons?
specialized in relaying electrical signals
What physical features do axons have?
they vary in length and have a constant diameter along length with specialized areas (terminal or en passant)
What are the primary functions of a neuron?
they generate, send, receive, and integrate electro-chemical signals that encode information
How do neurons communicate with one another?
via synapses and neurotransmitters
What are “directed” synapses?
the transmitter is released onto receptors less thn 15 nm away across synaptic cleft
What are “non-directed” hormonal/neuromodulatory synapses?
the transmitter is released onto receptors many micrometers away
What is submicron scale?
higher resolution than micron scale (ex. electron microscopy)
What is micron scale?
confocal, muliphoton, widefield microscopy
How does multiphoton imaging work?
it uses fluorescence (for example: high energy (blue light) causes electrons to go from ground state to excited state and a photon (green) is released when energy comes down and stops at a different level
What are the features of spines on dendrites?
always protruding and collapsing looking for connection (shapes: mushroom, stubby, filiform)
What are the cons of dendrite spines?
cost of more membrane and increase in surface area unhelpful
What are the 2 pros of dendrite spines?
1) compartmentalization of calcium
2) high resistance of thin neck increases the proportion of synaptic current that flows across the spine head membrane PROVIDED that there are voltage gated channels in spine
What are circuits?
they are made from neurons connected via synapses
What is convergence?
defined by number of inputs to a single neuron
What is divergence?
number of targets innervated by one neuron
What is genetic heterogeneity?
can be defined as mutations at two or more genetic loci that produce same or similar phenotypes
