neural tissue (wilcox) Flashcards
t/f. theres higher [potassium] inside the cell and higher [sodium] outside the cell.
true.
transmembrane potential of sodium
+66 mV
transmembrane potential of potassium
-90 mV
Na/K ATPase
powered by ATP and carries 3 NA out and 2K in, balanaces passive forces of diffusion to maintain the resting potential
passive channels
aka leak channels, always open, permeability changes with conditions
active channels
aka gated channels, open and close in response to stimuli; at rest, most gated channels are closed
3 classes of gated channels
chemical, voltage, mechanical
how do chemical gated channels open and where are they found?
open by binding chemical (like ACh), and found on neuron cell bodies and dendrites
how do voltade gated channels open and where are they found?
open in response to change in transmembrane potental, and found on axons, skeletal muscle sarcolemma, cardiac muscle
what is a characteristic of an excitable membrane?
voltage gated channel
how do mechanical gated channels open and where are the found?
open in response to membrane distortion, found on sensory receptors (touch, pressure, vibration)
what happens in depolarization?
transmemb potential moves toward 0 because NA is rushing through channel to produce a local current
what happens in repolarization
stimulus is removed and transmemb potential returns to normal by potassium leaving the cell
what happens in hyperpolarization
the negativity of the resting potential increases
4 characteristics of graded potentials
- effect decreases with distance 2. effect spreads passively due to local currents 3. depolarization or hyperpolarization 4. the stronger the stimulus, the greater the change in TM potential and the larger the area affected
how do you initiate an AP?
a graded depolarization of an axon hillock must be large enough to change the resting potential to the threshold level of the voltage gated sodium channels
t/f. if a stimulus excess the threshold amount, the AP is the same, no matter how large the stimulus.
true.
how do you stop an AP?
inactivate the Na channels and activate the voltage gated K channels (repolarization) and return to normal permeability (resting potential)
t/f. during the refractory period, the membrane can respond normally to additional stimuli
false. it cannot respond to any additional stimuli
absolute refractory period
no AP possible
relative refractory period
membrane potential almost normal, a very large stimulus can initiate AP
continuous propagation
unmyelinated axons
saltatory propagation
myelinated axons
type A axon fibers
myelinated, large diameter; for position, balance, touch, and motor impulses
type B axon fibers
myelinated, medium diameter; for sensory info, peripheral effectors
type C axon fibers
unmyelinated, small diameter; for invountary muscle, gland controls
electrical synapses
direct physical contact between cells
chemical synapses
signal transmitted across a gap by a chemical NT
excitatory NT
cause depolarization of postsynaptic membranes and promote AP
inhibitory NT
cause hyperpolarization of postsynaptic membranes and suppress AP
after the AP reaches the synaptic end, the extracellular influx of what ion causes NT to be exocytosed?
calcium
what removed ACh from the post synaptic receptors?
AChE
t/f. fewer synapses mean fewer synaptic delay
true.
when NT cannot recycle fast enough to meet demands of intense stimmuli
synaptic fatigue
what are the 4 important NT we need to know
NE, dopamine, serotinin, GABA
t/f. GABA is both excitatory and inhibitory.
false. ALWAYS INHIBITORY
3 ways nt and neuromodulators work
- direct effects on membrane channels 2. indirect effects via G proteins 3. indirect effects via intracellular enzymes
t/f. G proteins activate adenylate cyclase, producing the second messenger cAMP
true.
excitatory postsynaptic potential (EPSP)
graded depolarization of postsynaptic memb
inhibitory postsynaptic potential (IPSP)
graded hyperpolarization of post synaptic memb
t/f. inhibition of a postsynaptic neuron happens when it receives many IPSPs
true.
temporal summation
keep using the same stimuli until you trigger an AP, one synapse
spatial summation
use more than one stimuli until you trigger an AP, multiple synapses
t/f. neruomodulators and hormones can change membrane sensitivity to NT.
true.
