Shared Flashcard Set

Details

neurophysiology
lecture chapter 12
56
Anatomy
Undergraduate 1
05/06/2010

Additional Anatomy Flashcards

 


 

Cards

Term
neuron communication
Definition
since neurons are excitable cells, they communicate with one another by using electrical potential and currents
Term
electrical potential
Definition
the difference in concentration of charges particles on either side of membrane of neuron
Term
electical current
Definition
involves flow of charges particles from one point to another
Term
what happens when a neuron is stimulated?
Definition
electrical potential can chage suddenly to produce local potentials and/or action potentials
Term
why do local potentials and action potential occur?
Definition
due to ion flow through channels in membrane
Term
ion channels
Definition
allow electrocytes to flow across membrane, which establishes a current
Term
leakage channels
Definition
are always open and allow Na+1, and K+1 to move
Term
gated channels
Definition
open and close in response to stimuli
Term

voltage-gated channels

 

Definition
open in response to change in electical potential
Term
ligand-gated channels
Definition
open and close in respinse to specific chemical stimulus (acetylcholine)
Term
mechanically gated channels
Definition
open or close in response to vibration or pressure or tissue stretching
Term
why is there difference in electrial charges between ECF and ICF of a neuron?
Definition
because of unequal distribution of ions on either side of plasma membrane
Term
the plasma membrane is most permeable to what ion?
Definition
potassium
Term
concentration of K+
Definition
is higher in ICF than in ECF, so K+1 diffuse out of neuron along their concentration gradient
Term
where are the large organic anion and what do they do?
Definition
trapped inside neuron and tend to draw K+1 back into neuron along electrial gradient
Term
Concentration of Na+
Definition
is higher in ECF than in ICF, so Na+1 tend to diffuse into neuron along their concentration and electrial gradients
Term
consequences of differences in K+ and Na+
Definition
inside of neuron is negative with respect to outside and neuron is polarized
Term
Rest membrane potential (RMP)
Definition
potential difference of -70mv is established with inside of neuron 70mv more negative than outside of neuron
Term
what happens when there is diffusion of sodium ions into the neuron and diffusion of potassium ion out of neuron?
Definition
this will eventually eliminate resting membrane potential (RMP)
Term
what is the role of ATP-driven membrane pump?
Definition
actively transports 3 Na+1 out of neuron and 2 K+1 into neuron per molecule of ATP spent to maintain electrochemical gradient  nd keep RMP at -70mv
Term
local potential
Definition
small change in RMP caused by stimulus that opens ligand-regulate sodium gate in plasma membrane of a neuron
Term
cause of local potential
Definition
Na+1 rush into neuron causing membrane to depolarize
Term
what is the pathway of a local potential?
Definition
local potential typocally beings al dendrite, spread through soma, then travels from axonal trigger zone to synaptic knob
Term
what kind of communication is local potentials used for?
Definition
only short distance communication
Term
why are local potentials graded?
Definition

they vary is size according to stimulus strength

-strong stimulus causes grater change in membrane potential and gates open, which allows current to flow farther

Term
where do local potential become weaker?
Definition

as they spread away from the point of stimulation

-plasma membrane is permeable to ions, so charge is lost and current dies out

Term
when would local potential be reversed?
Definition
RMP gets restored if stimulation ceases prematurely
Term
local potential is excitatory if..
Definition
it depolarized plasma membrane of neuron to make potential defferences less negative
Term
local potential in inhibitory if...
Definition
it hyperpolarizes plasma membrane of neuron to make potential differences more negative
Term
action potentials are..
Definition
a dramatic change in membrane potential resulting from opening and closing voltage-gates ion channels during interval of about 1msec
Term
excitatory stimulus applied to neuron generates what?
Definition
excitatory local potential that depolarizes membrane causing RMP to be less negative
Term
what happens if excitatory local potential spreads to "trigger zone"?
Definition
if it remains strong enough, it opens enough voltage-regualted gates to generate action potential
Term
what is the threshold voltage? (#)
Definition
-55mv
Term
what happens if membrane reaches critical threshold voltage?
Definition
voltage-gated sodium channels open
Term
at threshold voltage, what happens with sodium ions?
Definition
they rush into neuron and establish positive feedback that depolarizes membrane from -55mv to 0mv to +35mv
Term
what does depolarization trigger?
Definition

slow sodium inactivation gates to close, which prevents and more Na+1 from entering neuron

-membrane is now positive and negative outside

Term
what happens at peak depolarization?
Definition
slow volatage-gated potassium channels open and K+ rushes out of neuron to repolarize membrane from +30mv to 0mv to -70mv
Term
what do voltage-regulated potassium channels do the restore RMP?
Definition
remain oen longer that voltage-gated sodium channels, so loss of K+1 may cause after-hyperpoalization, making membrane potential more negative that RMP until voltage-gates potassium channels close to restore RMP
Term
3 characteristics of an action potential
Definition

-they follow all-or-nothing principle because any stimulus that depolarizes membrane to threshold will generate action potential

-they do not become weaker as the spread away from point of stimulation

-they are irreversible

Term
refractory period
Definition
brief period of time during which meuron may not be able to generate another action potential
Term
how long does absolute refractory period last?
Definition
last from threshold until repolarization is complete
Term
neuron restimulation during absolute refractory period?
Definition
neuron can't be restimulated by stimulus of any strength because voltage-gated sodium channels open and then are inactivated
Term
how long does relative refractatory period last?
Definition
last until hyperpolarization ends
Term
neuron restimulation in relative refractory period?
Definition
neuron can be restimulated if stimulus is larger than threshold
Term
how can a neuron communicate with another neuron?
Definition
for communication a nerve signal mush travel length of the axon
Term
nerve signal
Definition
traveling wave of excitation produced by self-propagating chian of action potentials moving in only one direction (dominoes)
Term
continuous conduction
Definition
produced in unmyelinated fibers where there is a step-by-step depolaritation of each adjacent area of plasma membrane
Term
propagation in unmyelinated fibers?
Definition
is slow but does not lose power because last action potential generated at synaptic knob has same voltage as first action potential generated at trigger zone
Term
nerve signals in myelinated fibers
Definition
seem to 'leap' along neuron from one node of ranvier to next node of ranvier by saltatory conduction
Term
propagation in myelinated fibers
Definition
much faster, but does lose power (is decremental)
Term
why is propagtion in myelinated fibers decremantal?
Definition
signal gets weaker, but reaches next node of ranvier just in time to open voltage-gated sodium channels to generat new action potential
Term
how is propagation speed determined?
Definition
is determined by presence or absence of myelin, diameter of fiber, temperater and not determined by strength of stimuli
Term
propagation speed and large diameter fibers..
Definition

conduct signals faster than small ones because:

-they tend to be myelinated and small fibers tend to be unmyelinated

-there is more surface area

Term
propagation speed and temperature
Definition
nerve fibers conduct signals faster in warm temperatures
Supporting users have an ad free experience!