Final Exam Flashcards
Function of Tanycytes
Line the 3rd ventricle and extend to the hypothalamus (signal from CSF to CNS)
What are the 4 types of glial cells?
- Microglia
- Oligodendrocytes/Schwann Cells
- Astrocytes
- Ependymal (including radial glia)
What kind of cell acts as a stem cells? What does this mean?
Radial glia. They produce neuronal progenitors that become astrocytes during development.
What glial cells are phagocytotic?
Microglia
What glia cells act as scaffold for neurons to migrate along during brain development?
Radial glia
Blood flow regulation with astrocytes vs pericytes.
Astrocytes - regulate blood flow by controlling arteriole diameter
Pericytes - regulate blood flow by controlling capillary diameter
Key functions of astrocytes.
K+ regulation
Removal of glutamate/GABA
Blood brain barrier
Key function of ependymal cells.
Line ventricles
Key function of microglia.
Immune function
Sense injury and clear debris
How do glial cells act in a coordinated fashion?
Astrocytes are connected by gap junctions and by diffusion of gliotransmitters released in a calcium dependent manner can act in a coordinated fashion.
What are the 4 regions of a neuron with distinct roles in the generation and communication of signals between neurons?
- Soma
- Axon (and axon collaterals)
- Dendrites
- Presynaptic release sites
What is the significance of afterhyperpolarization?
Action potential is below normal resting potential, therefore there is a refractory period where it is hard/impossible to fire another action potential.
Key features of dendrites.
Contain ribosomes - can make proteins/peptides locally
Varying diameter - thick proximal and thin distal
Actin filaments - can grow and shrink
What are the two ways thalamic relay neurons can fire?
Tonic - follow sensory input/pass input along
Burst - ignores input and fires rhythmically
Key features of the soma.
Metabolic center
Lots of ER - protein production
Lots of mitochondria - energy
Key features of axons.
Contain microtubules and microtubule binding proteins - anterograde and retrograde transport
No actin
Where can axon-axonic signaling occur?
At places where there is no myelin, but not at the Nodes of Ranvier because there aren’t any receptor sites.
What controls the about of signal released?
Calcium influx into the presynaptic terminal
How does fluorescence work?
Photon moved to an excited state
Slightly lower energy release when photon leaves excited state
Ex. blue can send a photon to excited state and green can be released when photon is released from excited state
What is the relationship between mitral cells and granule cells?
Mitral cell dendrites release glutamate that activate the receptors on the granule cell spines, which release GABA onto the mitral cells.
Convergence vs Divergence
Convergence - the number of neuronal inputs converging to a single neuron
Divergence - number of neurons on to which one neuron synapses
Cephalization
Concentration of neurons at the anterior of the brain
Neural “Plexi”
Loose collection of neurons analogous to the enteric nervous system in vertebrates
What kind of symmetry do flatworms, segmented worms, arthropods and mollusks have?
Bilateral symmetry
Central pattern generators
Network of neurons that produce rhythmic output in the absence of rhythmic input
What leads to cephalization?
Bilateral symmetry with concurrent concentration of sensory structures at one end.
What area of the brain experienced the most expansion during evolution?
The association cortices expanded more than the primary sensory and motor areas
Key features of interneurons.
Mainly local connections - don’t “project”
Some excitatory, but most are inhibitory
What parts of the brain increase/decrease during evolution?
Increase - forebrain (cerebellum)
Decrease - midbrain
What is special about photoreceptor potentials?
No action potentials, only graded potentials
How is the non-zero voltage difference (membrane potential) produced?
Produced by processes that maintain different concentrations of charged molecules inside and outside a selectively permeable cell surface membrane.
How are changes in voltage across the membrane produced?
By changing the selective permeability of the membrane for different ions - opening of channels that are permeable to some but not all ions.
What direction will ions move across the membrane?
In whatever direction brings the membrane potential towards the equilibrium for that ion
Ex. If membrane potential is –40 and equilibrium potential is –58, then net flux of K+ would be out (positive out)
What is important to balance ionic pressure?
Ionic and non-ionic compounds like amino acids and proteins that don’t diffuse across the membrane.
What is the importance of permeability?
Needed to harvest the energy stored in the concentration gradient (no permeability = no voltage generated)
What three things determine the electrochemical “equilibrium condition”?
- Concentration
- Charge
- Voltage differences
What are the two energy storage mechanisms that make up an electrochemical gradient?
- Voltage difference
- Concentration differences
What happens with conductance of the membrane for an ion increases?
Current will flow and the membrane potential will change so that it is closer to equilibrium for that ion.
What is ionic current for a given ion proportional to?
The permeability (conductance) x the force driving it across the membrane.
What happens to cations if the electrochemical driving force is negative?
Cations more into the membrane (anions move out)
How is the length constant calculated?
Rm x Cm
How does capacitance allow integration?
It makes voltage last longer than current, allowing voltage to build up from added current and leads to action potentials.
What happens to the time constant and the length constant with an axon get larger?
Time constant -
Length constant - gets larger
Why is valence important in membrane potential?
Important because force against charge needs to be doubled if the charge of the ion is 2. The ion needs half as much voltage to oppose force if the change of the ion is 2.
What happens to R and C with myelination?
R - increases because axon is insulated
C - decreases because membrane is thicker
What happens with multiple sclerosis?
Oligodendrocytes demyelination - decreased ability to sustain firing
How does olfactory receptor excitation occur?
cAMP gated Na/Ca channels and Ca-gated Cl channels. Cl reversal potential must be depolarized relative to the threshold (high Cl inside the cell).
What is the function of L-DOPA?
Increases the amount of dopamine synthesis for treatment of Parkinson’s?
What are the active peptides of Proenkephalin A?
Met-enkephalin and Leu-enkephalin
What are advantages of storing transmitters in vesicles for release?
Speed - rapid delivery
Osmolarity - high concentration of transmitter stored in terminal without affecting osmolarity
Protects transmitter from degradation
What are the effects of binding 2 ligands instead of 1?
Probability of release is more dependent on concentration
Do peptide hormones have ionotropic or metabotropic receptor?
Only metabotropic
