Week 6 Flashcards
Vm
voltage across the membrane
Vm of most cells at rest
-70 mV
what causes cells to be -70 mV at rest?
movement of charged components (Na+, K+)
graded potential
change in Vm
depolarized (stimulatory stimulus)
moving towards 0 mV
hyperpolarized (inhibitory stimulus)
moving away from 0 mV
repolarization
returning towards resting potential
why do graded potentials vary in size?
differences in the change in the number of ions present
as distance increases
graded potentials decrease (diffusion has a distance problem)
what causes an action potential?
graded potentials
what types of cells generate action potentials?
excitable cells
are action potentials also graded potentials?
yes
what characteristic of graded potentials do action potentials not have?
variable size
why is an action potential an “all or none event?”
all requirements must be met for action potential to occur, if not just a graded potential
what are the important parts for an action potential to occur?
Vg Na+ channels with inactivation gate and K+ Vg channels
what are the three possible states for a Na+ channel with an inactivation gate?
open, closed, inactivated
does inactivated mean closed?
no
what triggers the Na+ and K+ channels?
change in Vm
what is threshold potential?
potential needed to reach to trigger action potential
what is a subthreshold potential?
depolarization without reaching threshold potential (no AP)
why are action potentials the same every time?
it takes the same amount of time to open/close channels
how do action potentials travel?
a new one is propagated at each axon section, AP before triggers the next one
why do action potentials not form in the myelin parts of the axon?
ions cant move through that many layers of plasma membrane
where do the ions enter/exit the axon?
nodes of ranvier
how does electrical signal travel through myelinated axons?
AP occurs in the node of ranvier, graded potential travels quickly through the myelinated section to the next node
what are the two types of input?
excitatory presynaptic and inhibitory presynaptic
excitatory presynaptic input (EPSP)
stimulatory, increases likelihood of AP occurring
inhibitory presynaptic input
inhibitory, decreases likelihood of AP occurring
what are the two types of summations?
temporal and spatial
temporal summation
same presynaptic synapse sending multiple messages close in time (build on each other)
spatial summation
different presynaptic synapses impacting the same postsynaptic at the same time
greater # of synapses ->
increased likelihood for summation to reach threshold
presynaptic factors
Ca2+, NT availability, receptor availability and Vm
postsynaptic factors
receptor availability, Vm, other presynaptic inputs
what is the role of Ca2+ in synapse strength?
needed to exocytose NT
brain stem
controls most vital pieces
what are the three parts of the brain stem?
medulla, pons, midbrain
what are the functions of the brain stem?
respiration, circulation and digestion (swallowing)
cerebellum
movement, balance and coordination, muscle tone
saltatory conduction
process of an AP traveling through a myelinated axon
