Neuroanatomy
Difference between afferent and efferent
afferent="arriving" sensory
efferent="exiting" motor
what 3 forces work to generate resting membrane potential in neuron at rest?
1. Na/K pump: neurons use ATP to pump 3 Na+ out and 2K+ in the cell
2. facilitated diffusion of K+: neurons have membrane proteins that are always open and allow for the free movement of K+ only
3. electrostatic pressure: deals with movement of ions based on charge, not conc.
all or none principle
a neuron will either fire or will not
what are gap junctions compared to chemical synapses? which is more common in the nervous system?
gap junctions allow for the direct transfer of currents between cells
most connections between neurons are chemical synapses and are most common in nervous system
what are the common amino acid NTs? how are amino acid NTs inactivated and what is the role of astrocytes?
glutamate, glycerine, GABA
inactivated by reuptake in both neurons and astrocytes
astrocytes regulate ECF, remove K+ and NTs, metabolism and guiding, and formulate tight junctions (blood brain barrier)
Where does CSF flow in the meninges?
Subarachnoid space then circulates around brain
what are the 3 ways substances move across a cell membrane
1. simple diffusion- substances go from high to low conc., no membrane protein or energy used (passive transport)
2. facilitated diffusion- high to low conc., uses membrane proteins, no energy used (passive transport)
3. active transport- low to high conc., uses membrane proteins and energy (ATP)
how are scientists able to generate APs with light?
optogenetics: shine light on membrane protein channel rhodopsin (foreign gene introduced to brain cells- virus)
allows Na+ to enter when stimulated with light
what are the 4 types of NTs?
where are they synthesized in the neuron and what is the exception to this rule?
amines, amino acids, neuropeptides, "special" (gases, Ach...)
synthesized in synaptic terminal except neuropeptides (made in cell body because they go through translation and transcription)
what is special about lipid and gaseous NTs? what type of signaling can they do?
they are able to diffuse without the use of vesicles
these NTs signal via metabotropic receptors
white vs grey matter
what parts of neurons are found in each type of matter
white matter= myelin/axons
grey= soma with dendrites
what is resting membrane potential
(about -60mv) no polarization occurs within cell
what causes brief hyperpolarization in resting membrane potential at the end of an AP
the greater efflux of K+ during an AP when voltage K+ channels are open and K+ leaves causes brief hyperpolarization
what protein is responsible for making empty vesicles during endocytosis?
clathrin protein
what does a typical ionotropic receptor look like?
formed from several proteins subunits to make an ion channel
in development, what are the 3 embryonic layers and what does each turn into as adults?
1. endoderm- deepest layer, gives rise to organs
2. mesoderm- middle layer, gives rise to bones and muscles
3. ectoderm- outermost layer, gives rise to entire nervous system and skin
when at rest, what ions have higher conc. inside the cell and outside the cell
inside=potassium (K+)
outside= sodium (Na+)
how are APs propagated in one direction along the axon? does the AP change amplitude as it moves?
once an AP starts,it moves in a chain reaction from cell body to axon terminal, does not change amplitude
moves only in one direction
- along axon when a region is at threshold, voltage gated Na+ channels open which spreads and depolarizes adjacent segments of axons
- adj segments are at threshold and more Na+ channels open and works its way down the entire axon
- does not move up (towards soma) due to refractory period (inactive Na+ channels)
what are the two types of NT receptors and how are they different
ionotropic: ion channels that open in response to NT binding, less selective than voltage gated channels, results are fast in post synaptic neuron
metabotropic: integral membrane protein that activates messengers inside cell (G-proteins) slower than ionotropic, secondary messengers lead to changes in post synaptic neuron
what is the ionotropic GABA receptor? what type of response does it initiate? what moves through it?
initiates IPSPs and form Cl- channels
What 3 developmental structures come from the prosencephalon?
telencephalon, optic vesicle, diencephalon
what things can move through a cell membrane without membrane proteins
fats, O2, CO2, uncharged gases
how do the size of an axon and myelination affect conduction speed of an AP? what are the two ways that signals can move down an axon and what are the differences between them?
bigger axon= better conduction
- glia cells (oligodendrocytes and schwann cells) help make neurons' myelin
saltatory= myelinated, signals jump between nodes of ranvier (spaces between myelin sheaths) fast conduction
continuous= non-myelinated axon, slow conduction
how do IPSPs inhibit/hyperpolarize and what ion channel do they typically target?
usually generated by transmitters that activate Cl- channels (iontropic), Cl- rushes into cell, hyperpolarizes cell, moves away from threshold and decrease chance of AP
why does the brain need a balance of glutamate/GABA signaling?
glutamate is excitatory and GABA is inhibitory
too much of one can lead to seizures