L15 Stimulated Excitable Cells Flashcards
excitable cells respond to ____ stimuli
specific
which neurons have integral membrane proteins?
efferent neurons
interneurons
what is the function of the integral binding proteins?
chemoreceptors with binding sites for NTs - ACh, glutamine, GABA etc.
what do afferent neurons have?
membrane receptor responding to specific type of stimulus
what are sensory stimuli converted into?
local graded changes of membrane potential
local grade potential spread ___ with ____
passively
decrement
a stimulus to the sensory end of the afferent neuron produces a _______
local depolarization
*adjacent areas are also depolarized but spread is less effective
where is a change in conductance seen?
only in the stimulated region!
what has a length constant?
every cable-like structure
when a charge is spreading, it is continually ____ in quantity
diminishing
define length constant
indicates how far a current will spread along the inside of a neurite and thereby influence the voltage along that distance
the length constant (lambda) increases with increasing values of ?
radius of cylinder
resistance across cell surface - is membrane leaky or not…
what monitors the length of muscles fibers?
afferent neurons
what are muscle spindles made of?
intrafusal fibers
what is stimulated by stretching of muscle?
intrafusal fibers in muscle spindles
golgi tendon organ
what does the golgi tension organ monitor when it receives a stimulus? ?
tension
what does muscle spinal measure when it receives a stimulus?
length
most muscle afferent neurons are what?
mechanoreceptors
what do muscle spindle afferents have?
stretch gated ion channels
what mainly pass through the stretch gated ion channels in the non-contractile central region of the intrafusal fiber?
cations - mainly Na
pass through channels = depolarization
what does stretch produce in the afferent neuron?
graded receptor potential
what happens in the dark to cGMP and Na+ Channels
we have plenty of cGMP
open Na+ channels
what happens in the light to cGMP and Na+ channels?
less cGMP because its broken down
closed Na+ channels =
HYPERPOLARIZATION
= reduce the amount of GLUTAMATE into retinal bipolar cells
*the more light, the more hyper polarization!
what is the rods receptor potential?
graded hyperpolarization
what happens when odorant molecules bind to receptors?
increase cAMP
*bind odorant molecules –> activate G protein —> ride in Adenylate cyclase —> increase cAMP
what happens with an increase in cAMP?
cation channels open -
entry of Na+ and Ca2+ into cell = depolarization
what does the rise in Ca2+ in the olfactory neuron cause?
causes Cl- channels to open - cl- leave the cell = more depolarization!
change in membrane potential is linearly related to the ?
magnitude of the current pulse
what is the purpose of a graded potential?
to drive the axon hillock or initiation zone to threshold membrane potential - to gen. AP!
where is the impulse initiation zone in multipolar neurons?
axon hillock
where is the impulse initiation zone in pseudounipolar and bipolar neurons?
near the sensory endings of afferent neurons
where is the impulse initiation zone in skeletal muscle fibers?
close to the central region that receives ACh released by the motor neuron
impulse initiation zones have a high density of what?
voltage-gated Na+ channels
what is idiopathic focal dystonia?
abnormalities of posture, involuntary movements and muscular spasm likely to be caused by a physical property of specialized stretch receptors present in skeletal muscle spindles. these are responsible for signaling about body position and muscular effort
what is anosmia?
head injury that severs/compresses the axons of the olfactory neurons
in the elderly due to degen. loss of fraction of the population of olfactory neurons
occasionally congenital and sometimes hereditary
what is night blindness?
rods are responsible for our vision in low light levels
cones are excellent for day vision and color detection
vitamin A deficiency = lack of rhodopsin
where are graded potentials found (hyperpolarization and depolarization?)
- afferent fibers in muscle spindles
- rods of retina
- olfactory neurons in nasal cavity
