Neuroscience Final Flashcards
How thick is the neuronal membrane?
5 nanometers
How large is a neuronal soma?
5-50 micrometers
Describe the scaffolding of a neuron?
Microtubules —tublin based molecules with diameters of 20 nanometers— are present everywhere except axon terminals. Neurofilaments (10 nm). Microfilaments —actin based molecules with diameters of 5 nm — are present throughout the membrane.
Describr the differences brtween the cytoplasm of axon terminal and axon
Axon terminals require lots of energy to send out neurotransmitters. As a result, they contain more mitochondria. They have no microtubules. There are more proteins. And there are synaptic vesicles.
Describe voltage gated sodium channels?
These channels open and close fast. They inactivate after closing to prevent back-flow from triggering another action potential.
Describe voltage-gated potassium channels
These open slow and shut slow. They do not inactivate. They open slow to allow for sodium channels to depolarize the cell before they depolarize it.
Which neurotransmitters do ionotropic receptors respond to?
Small molecule neurotransmitters
Which neurotransmitters do metabotropic receptors respond to?
Neuropeptides
GABA receptors
Gaba gated anion channels are inhibitory. The receptors also respond to modulators that enhance the function of GABA in its presence.
How do GPCRs work?
When a GPCR is activated, the gprotein splits into two parts which activate ion channels and enzymes
Describe signal amplification by GPCRs
G-protein stimulates a structure to convert ATP to CAMP. Increased CAMP levels activate protein kinases which add phosphate groups to AMPA receptors making them more conductive to sodium. It also causes the insertion of additional AMAPR.
Describe synaptic integration
Synapses receive thousands of EPSPs and IPSPs. Synaptic integration is the summation of these inputs within the postsynaptic cell. This process allows for complex computations
Describe long term potentiation?
Synapses that activate concurrently are strengthened. An inactive synapse will not be strengthened.
Describe AMPAR and NMDAR
Glutamatergic cation channels. NMDA id voltage gated. When there is sufficient depolarization, owing to current from AMPA receptors, NMDA opens. Ca2+ enters —if there is a high level within the cell, LTP takes place.
What happens when there is substantial Ca+ increase?
Kinases activate and add phosphate groups to AMPA receptors, making them more conducive to Na+. They also cause the insertion of additional AMPA receptors.
How can LTP activate “silent stnapses”
If the cell is sufficiently depolarized, then AMPA receptors will insert themselves in the cell membrane.
Describe long term changes during LTP
There are changes in gene expression that cause the growth of additional dendrites to form new synapses.
Describe the molecular mechanisms of LTD
- Moderate Ca2+ -> phosphorylates
- Remove phosphate groups from AMPAR and internalize AMPAR
Protoplasmic astrocytes
Exist in the gray matter. Shorter, highly complex, arborized processes
Fiborous astrocytes
Less complex, elongated processes. Exist in white matter
Morphogenesis of astrocytes
Tiling feature: little to no overlap between processes. Astrocyte differentiation results in this tiling, as cells show decreasing overlap during development.
How do astrocytes communicate with each other?
Gap junctions
Potassium Spatial Buffering
Normal and pathological conditions increase extracellular potassium concentration. Astrocytes uptake potassium through reuptake channels and redistribute it to maintain concentration graduents.
Astrocyte-neuron lactate shuttle hypothesis
The uptake of glutamate triggers glycolis which produces lactate for neurons. Possible mechanism for coupling lactate production with neuronal activity
Astrocyte functions
- Synapse maturation and removal
- Neurotransmitter reuptake
- Metabolic support
- Potassium homeostasis
- Synaptogenesis
How do astrocytes regulate neurons?
Ca+ dependent signaling
Reactive astrocytes
Swollen shorter morphology during injurious conditions
Changes in gene expression for reactive astrocytes
Gain new functions or loss homestatic ones
Moderate resctivity
Swollen, shorter morphology. Tiling property retained.
Severe reactivity
Glial scar tissue, overlap between processes
Reactive astrocyte pros
- Growth factors
- Phagocytosis of debris
- Homeostatic support
Reactive astrocyte cons
- Release of cytokines
- Oxidative stress
- Synaptic damage
Type 1 Oligodendrocyte
Small rounded body, white and gray matter, many fine processes
Type 2 Oligodendrocytes
Polygonal shape, fewer thicker processes, white matter
Type 3
Bulky cell body, white matter, one to four processes
Type four
Elongated cell body, white matter, attach to and envelop medium to large axons
Myelin composition
Lipids, proteins, and water
functions of oligodendrocytes
- Regulate expression of ion channels on nodes of ranvier
- Myelinatiom of axons
3 maturation and maintenance of the node of ranvier - Modulation of neuronal excitability and neurotransmitter release
- Metabolic support to axons and ion homeostatic maintenance
Microglia origin
Progenitor cells in the yolk sac
Resting microglia
Ramified morphology, found under physiological conditions
Activated microglia
Swollen morphology, larger cell body and smaller processes. Present during development and pathological conditions
Microglia delf renewel
During physiological conditions, microglia stay within a region of the brain. When there is a deficit of microglia, they self-renew by division.
Synaptic pruning
A process during postnatal development in which synapses are eliminated
Synaptic pruning
Microglia phagocytose inactive synapses using the complement system
