Neurobiology 1: Bioelectricity & Synapses Flashcards
What are the 3 main types of neurons?
sensory(bring info into CNS), motor (send info out from CNS),and interneurons (connects those two, most brain neurons)
function of glial cells in CNS?
- supporting cells that are not excitable (no rapid change in mem pot), but do have a resting potential (ALL CELLS HAVE A RESTING POT. ALL)
- provide nutrient support (glucose, lactose)
- In CNs: (blood brain barrier): astrocytes (type of glial cell) that filter toxic compounds flowing through blood…lay in between blood and neurons
- glia are all around neurons
- NT reuptake
- K+ homeostasis
- in PNS: oligodendrocytes (another kind of glial cell) wrap myelin around axon
function of glial cells in PNS?
- provides insulation by wrapping myelin sheaths around axons
- myelin is composed of FA
- comprises grey matter–> where most of neuronal cell bodies are outside brain
- white matter in the middle is composed of axons that connect the cell bodies in grey matter
- reverse in spinal cord: white matter outside, grey matter in middle
why is there a resting potential (Vm)?
1) conc diff of ions across mem
2) diff permeability to ions of K+, Na+2, Cl-, Ca+2
what molecules have a negative charge in the cell
proteins and nucleic acids
Which ions are abundant in cytoplasm vs extracellular?
High anions in cytosol
High K+ in cytosol
Low Na+ in cytosol
Low Cl- in cytosol
why is there a membrane pot in a cell
high permeability to K+ and low permeability to Na+ and Cl-
If the mem was 100% permeable to K+, what would the Ek be?
-92 mV
If the membrane was 100% permeable to Na+ what would the ENa be?
+62 mV
What is the driving force?
Difference between E and resting mem pot
What is the driving force for K+?
Since Ek = -92 but resting mv is -60, wants to make cell more neg so pushes K+ out but is WEAK
What is the driving force for Na+?
Both conc gradient and E wants to pull Na+ in so STRONG…opposite direction with K+
What is the driving force for Cl-?
high conc of Cl- outside, so wants to go in but the - charge clashes with an alr neg cytosol so WEAK
What is the driving force for Ca+2?
LOTS of Ca+2 outside so conc gradient drives, in and +2 outside attracted to neg cytosol so STRONG
What happens if inc permeability to Na+?
Na+ comes in–> depolarize
what happens if inc permeability to K+
K+ leaves–> hyperpolarize
what happens if inc permeability to Cl-
Ca+2 comes in–> STRONG depolarization
How does the Na+/K+ pump work?
- uses ATP
- keeps Na+ low and K+ high inside to maintain Vm
- Na+ enters from inside
- ATP, conformational change to open
- releases Na+ and K+ enters from outside
detail an axon potential
at rest, K+ ion channels alr open, Na+ voltage act gate is closed, inact is open
When threshold is reached, activ gate opens, transient influx of Na+ inside, inact closes
As inside of cell gets more (+), K+ voltage gate opens so mem is 100% permeable to K+
K+ leaves, so mem is less (+) which brings depolarization down
what is the mem threshold
mV that opens Na+ activ gate
detail the propagation of an action potential
spreads to one direction down axoplasm… first area that got depolarized before it is repolarized to resting b/c of Na+ inact gate closing and K+ opening so the once super (+) inside is now less (+)
how is the duration the action potential determined?
kinetics of opening of Na+, and K+ channels and inactiv of Na+ channel
how is the direction of the action potential determined?
can’t go backwards b/c inact gate closes…can only go forward to Na+ channels available for depolarization
What is the significance of the diameter of axons in invertebrates?
small diameter= slow AP, high resistance to current flow, frequent voltage gates along axon
large diameter = fast AP, less resistance, travel farther, fewer voltage gates required
