Chapter 1 Flashcards
ion channels…
passive transport, selectively permeable, can be gated, Na+, K+, Ca2+, Cl-
ion pumps…
active transport, require ATP, Na+/K+, Ca2+
resting membrane potential
-70mV
hyperpolarization
change in membrane potential, IPSPs
depolarization
change in membrane potential, EPSPs
action potential
rapid depolarization and depolarization, occurs at ~55mV
Action potential events (5)
- at threshold, voltage gated Na+ channels open and Na+ flows into cell
- more Na+ flows into cell increasing depolarization
- voltage gated K+ channels open, K+ flows OUT of cell
- Na+ channels close, K+ channels still open. during hyper polarization, another AP cannot be generated
- K+ channels close when membrane is hyper polarized, membrane potential returns to steady state
absolute refractory period
period following the firing of an action potential when it cannot be stimulated no matter how great the stimulus is
relative refractory period
period shortly after the firing of a nerve finer when partial depolarization has occurred and a greater than normal stimulus can stimulate a second response
hodgkin-huxley model
mathematical model of action potentials
electrotonic conduction
fast, passive, short distances
self-propogating conduction
action potential ripples down axon, keeps regenerating new signals, slow, long distances
saltatory conduction
relatively fast, self-regenerating, long distances, myelinated sections are insulated (where electronic conduction occurs)
speed of propogation
depends on axon diameter, myelination, temp, etc.
slow as <1m/s, fast as >120m/s
neural coding (AP signals)
neural coding depends on rate, duration and timing
synaptic vesicle cycle
Ca+ entering the pre-synaptic cell causes vesicle to fuse with the membrane, causing ion channels to open allowing NT to release and cross synaptic cleft
inhibitory PSPs (4)
- prevent runaway firing of APs
- help control the energy consumption of the brain
- contribute to important oscillatory patterns of neural activity
- provide basis for negation as a computational primitive
7 major NTs
glutamate, GABA, acetylcholine, dopamine, serotonin, noradrenaline (norepinephrine), histamine
5 biochemical NT classifications
amino acids, monoamines, peptides, gases, other
Neurotransmitter characteristics
synthesized by & localized within presynaptic neurons, stored in terminal bouton, released by presynaptic neurons during APs, postsynaptic neutrons contain receptors specific to it, a mechanism exists to remove it after release
3 ways of NT reuptake
active reuptake : pumped back into presynaptic neuron
enzymatic breakdown
diffusion out though extracellular membrane
metabotropic receptor
work through 2nd messenger cascade
ei. G-protein coupled receptors
gap junction
direct electrical and chemical conduction, fast, low plasticity, no amplification
post synaptic potential
travels from synapse to axon hillock by electrochemical conduction (all PSPs converge at the axon hillock)
PSPs at the trigger zone
strength depends on strength of PSP at synapse, time course of the PSP, distance to the synapse, time since the AP
summation of PSPs
EPSPs add to the membrane potential, IPSPs subtract from the membrane potential. trigger zone starts at the resting potential (-70mv), AP fires if sum exceeds threshold
spatial summation
PSPs from different synapses (locations) sum together
temporal summation
PSPs from same synapse (different points in time) sum together
synaptic integration as computation
at each point in time, neutron sums all of its inputs which are then graded, output is all or none depending if threshold is exceeded
church-turing thesis
every effectively calculable function is a computable function
computational universality
all turing complete systems are computationally equivalent
Alan Turing (1912-1954)
turing test, universal turin machine, helped break the german enigma code in WWII
reflex circuit
inhibitory interneuron: out the ventral root, along the axon to the muscle, causing contraction
sensory input on knee, down the axon into dorsal root
artificial neural network (ANN)
understanding brain function by allowing stimulation & prediction.
artificial intelligence: program to control computer, robot or machine
Green fluorescent protein
inserted into DNA to target protein, when protein is expressed, so is the fluorescence
brainbow
a single rainbow transgene expresses red, cyan, or yellow. multiple rainbow transgress can express more colours
