Topic 2 Flashcards
Electrical signalling
Action potenital
Chemical signalling
Occurs at the synapse with neurotransmitters
Axon hillock
Where AP are generated from, must be of a certain magnitude/ reach electrical threshold for it to occur
Resting membrane potential
-65 mv
Depolarisation
influx of Na+
Hyperpolaristaion
efflux of K+
electrical differnce
resting membrane potential - the electrical difference outside the cell compared to the inside
Factors to generate the resting membrane potential
1) Concentration of ions in the cytoplasm and in the ECF
2) permeability of membrane
3) Transporters present
Neurotransmitter in lipid bilayer
they can not cross, hence why they need a transporter
ion channels
Made of protein
will open and close to allow passage of ions
uncharged solutes
pass through passively
charged solutes
require energy as they are going against the concentration gradient
this creates an eletrical gradient
Gradient
is magnitude and direction of flow
determine by electro-chemical gradient
Membrane is most permeable to
K+ ions, usually as more potassium channels are present
also taking in more k+ reduces likelihood of firing an AP
Selectivity of channels
dependant on:
pore size
what amino acid lines the channel
Transportes
are embedded in the membrane
have 2 separate gates at both ends of the membrane
coupled transport
when a transporter moves 2 molecules at a time, the first one provides the second one with ATP to move
Symporters
type of transporter
moves soltes in the same direction
Antiporters
type of transporter
moves solutes in opposite directions
ATPase
3 Na+ OUT
2 K+ IN
Leaky k+ channels
always open k+ channels
passive
allows k+ to leave the cell
makes resting mebrane potential more negative
Na+ leak
At rest there is an inward leak of sodium, this pushes the extra k+ out thats being brought in by ATPase
volatge gated k+ channels states
open an closed
volatage gated Na+ channel states
activation, inactivation , resting state
Axon with shorter refractory period
can conduct faster
conduction velocity
10 m/s
Gap junctions
Made of 6 proteins called conexons
basically a bridge between the two neurons
Synaptic intergration
when multiple signals come up at the same time
summation occurs
a stronger signal is then made
types of synpases
axodendritic
axoaxonal
axosomatic
Gray’s type 1 synpase
synapses are asymmetrical
post synaptic side is thicker
Gray’s type 2 synapse
symmetrical
usually inhibtory
types of neurotransmitter based on chemical structure
Amino acid NT
Amine NT
Peptide NT
all synapses in cns release amino and amine but not all can release peptide
Peptide NT
made in rough ER, then packaged in Golgi apparatus and then into vesicles
EPSP
Excitatory post synaptic potential
when an influx of cations come in, making the membrane more positive and causing an AP
will hit at dendrite
IPSP
Inhibitory postsynaptic response
influx of anions preventing an AP from occurring
while hit at soma
Synaptic intergration
multiple IPSP and EPSP are fired together and summed up to determine whether an AP will occur
spatial summation
1 neuron receives multiple inputs
temporal summation
1 presynaptic neuron fires multiple inputs to create more magnitude
Shunting inhibtion
Lowers resting membrane potential to ensure an AP isn’t fired regardless if the EPSP is large enough or not
located at the start of the axon hillock
Toxin
are produced by a biological mechanism
usually causes an immune response
Poison
Causes metabolic or other changes to an organism
venom
is a toxin that is injected
Puffer fish
tetrodotoxin
bind to and blocks Na+ channels
therefore no AP can occur
tingling of mouth, numbess, paralysis
Poison dart frog
batrachotoxin
lowers the membrane potential, making it harder for AP to fire
muscle paralysis
also causes channels to remain open causing muscle tremors
Black Mamba
dendroxtin
blocks voltage gated k+ channels
AP essentially keeps firing
causes muscle tremors and sezure
also a cardiotoxin
Cone Snails
contains a cocktail of toxins
that essentially affects every part of action potential
