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The sodium/potassium pump maintains the RMP by pumping _______ out of the cell
3 Na+
The sodium/potassium pump maintains the RMP by pumping _______ into the cell
2 K+
The resting membrane potential of neurons is held at?
-70 mV
Threshold for depolarization that leads to an action potential occurs once the neuron reaches?
-55 mV
What does the Nerst potential describe?
opposes movement of ions across cell membrane
Is depolarization excitatory or inhibitory?
excitatory (more +)
Depolarization increases permeability to __________
cations (Na+)
An increase in membrane permeability to Na+ would trigger a sensory receptor to be...
stimulated/activated
An inhibitory postsynaptic potential would bring a neuron....
away from depolarization by increasing permeability to Cl-
Is hyperpolarization excitatory or inhibitory?
inhibitory (more -)
Hyperpolarization increases permeability to _________
anions (Cl-)
In a graded potential, what happens to the signal?
Is there machinery involved?
signals degrades
no channels/machinery
Graded potentials must be ___________ to reach initial segment
strong or summated
In an action potential, what happens to the signal?
Is there machinery involved?
signal does NOT degrade
yes - voltage gated Na+ channels needed for AP
WHY do action potentials not degrade?
voltage gated sodium channels in the initial segment
What would happen if all voltage gated channels have been blocked?
brain never gets the signal
What kind of synapse are most common in adult human nervous system? What do they rely on?
chemical synapses
rely on chemical messengers
An increased permeability for something negative does what to action potential?
shuts it down
An increased permeability for something positive does what to action potential?
helps action potential
Ionotropic refers to _________
Are they fast or slow?
ion channels
FAST
Metabotropic refers to ________
Are they fast or slow?
g-protein coupled receptors
SLOW
What is summation?
multiple converging signals to increase strength
(increased presynaptic input onto post)
What is spatial summation?
threshold reached due to NUMBER of presynaptic neurons
Spatial summation results in increased pathway signal strength due to....
increased NUMBER of neurons converging
What is temporal summation?
threshold reached due to FREQUENCY of firing from 1 presynaptic neuron
Long-term potentiation strengthens or weakens?
Long-term depression?
strengthens
weakens
Long-term potentiation AND long-term depression are regulated by ________ receptors, _______ and ________
glutamate
NMDA
AMPA
In long-term potentiation, NMDA lets what in?
Na+ and Ca+
In long-term potentiation, AMPA lets what in?
Na+
An influx of _______ leads to an increased number of AMPA receptors therefore a _______ in responsiveness to stimuli
calcium
increase
Long-term depression only opens ________ receptors
This leads to _______ intracellular levels of _________
AMPA
low, calcium
Removing AMPA receptors does what to neuron's reponsiveness to stimuli?
weakens
In lateral inhibition, where is the signal strong? Where is weak?
decreased strength in periphery, strong in center
T/F? lateral inhibition is used by most sensory pathways in order to INCREASE contrast of signal
True
Measuring withdrawl reflex following a painful stimulus pertains to....
synaptic fatigue
Decreased activity and neuronal excitement would be an example of....
acidosis
Increased activity and neuronal excitement would be an example of....
alkalosis
T/F? Seizures and hyperventilation are examples of acidosis
False - alkalosis
Oxygen deprivation is known as....
hypoxia
What does caffeine do to threshold?
increases excitability so decreases threshold
What do anesthetics do to threshold?
decrease excitability so increases threshold
Myelination does what to the speed of the signal?
speeds it up via saltatory conduction (jump from node to node)
ALL somatic sensory receptors are __________ neurons within the cell body of _________ and _________
pseudounipolar neurons
DRG and CNS nuclei
What is sensory transduction?
conversion of environmental stimulus to electrical impulse (AP)
Activation occurs IF the change in membrane permeability results in ______ influx to meet ________?
Na+ influx
depolarization (threshold)
NO activation occurs IF the change in membrane results in ______ (in) or ______ (out) therefore the threshold is not reached
Cl- influx
K+ out
Which receptors are sensitive to external stimuli?
externoreceptors
How are mechanoreceptors classified?
by how quickly they adapt
Rapidly adapting mechanoreceptors AKA ________ include what 3 types?
phasic
1. pacinian
2. meissner
3. hair follicles
Slowly adapting mechanoreceptors AKA ______ include what 3 types?
tonic
1. ruffini
2. merkel
3. tactile disc
Which is the FASTEST adapting mechanoreceptor?
Pacinian
What modality does Pacinian mechanoreceptor detect?
What is the size of receptive field?
vibration
large receptive field
Where is Pacinian mechanoreceptor found?
deep in dermis and intramuscular
What modality does Meissner mechanoreceptor detect?
What is the size of receptive field?
precise/fine touch
small receptive field
Where is Meissner mechanoreceptor found?
superficial dermis, especially fingertips and lips
T/F? Meissner mechanoreceptor works with overlapping fields
False - small receptive field
What modality does Ruffini mechanoreceptor detect?
What is the size of receptive field?
stretch
large receptive field
Where is Ruffini mechanoreceptor found?
deep in dermis and joint capsules
What modality does Merkel (discs) mechanoreceptor detect?
What is the size of receptive field?
light touch and deep pressure
small receptive field
Where is Merkel (disc) mechanoreceptor found?
superficial epidermis-dermis junction
There is a _______ in receptor action potentials over time with a constant stimulus
decrease (ie: deactivates as it gets used to the signal)
A strong stimulus does what to the frequency of action potentials?
Weak?
increase AP
decrease AP
What are the 3 types of free nerve endings?
nociceptors
thermoreceptors
tickle and itch
Free nerve endings are most common in ______ and _______ tissue
epithelial and connective
Free nerve endings are connected to ______ and ______ fibers which are myelinated or not?
A-Delta and C-fibers
NOT myelinated
Nociceptors detect what?
Do they have a high or low threshold?
stimuli capable of causing tissue damage
HIGH threshold
Multimodal nociceptors can detect...
chemical, thermal, AND mechanical
T/F? Mechanical , thermal, and chemical respond only to extreme conditions
True
Thermal nociceptors respond to temperatures greater than ______ (F) and less than ________ (F)
120-42 F
T/F? There are high concentrations of nociceptors within deep tissues such as brain and GI tract
False- less likely to be pain generating
Fast pain (pricking/first) travels in ________ fibers
A-delta
Slow pain (aching) travels in ______ fibers of what tract?
C-fibers of paleo-spinothalamic tract
T/F? Fast pain has a large receptive field
False - small, sharp and well localized
Which of the following would be the LEAST well localized, slow pain or fast pain?
slow pain
T/F? A-delta fibers are FASTER than C-fibers
True
A: 5-40 m/sec
C: 0.5-2.0 m/sec
T/F? Slow pain has a large receptive field
True - diffuse and poorly localized
Warm thermoreceptors utilize what channels?
vanilloid transient receptor potential channels (TRP)
Cool thermoreceptors utilize what channels?
melastatin transient receptor potential channels (TRPM)
Which thermoreceptors also transduce capsaicin (found in spicy foods like wasabi)
warm
Warm thermoreceptors utilize which fiber type?
C-fibers, SLOW
Cool thermoreceptors utilize which fiber type?
A-delta, FAST
Which thermoreceptors also transduce methnol found in topical pain relievers?
cool
T/F? If temperature is 125 F, warm thermoreceptors will activate
False - nociceptors because is is extreme temperature, greater than 120 F
Tickle and itch receptors are almost exclusively found....
superficial skin (very thin)
Tickle receptors have a high or low threshold?
Very LOW - sensitive to light touch
Itch receptors respond to what kind of stimuli?
chemical
Histamine and the allergic response would pertain to which mechanoreceptor?
itch
A mosquito landing and swatting it away would pertain to which mechanoreceptor?
tickle
There are 2 classification systems of nerve fibers, which fiber classification type is BOTH motor and sensory?
Erlanger's
There are 2 classification systems of nerve fibers, which fiber classification, which type is sensory ONLY?
LLoyd's
The fastest fibers classified in Erlanger's system are type?
A-alpha
Erlanger's type _______ fibers carry vibratory sensation
A-beta
The thinnest fibers classified by Lloyd's, are the unmyelinated type ______ fibers
IV
Erlanger's type ________ fibers carry fast pain, crude touch, deep pressure, and cold temp
A-delta
Erlanger's type ______ fibers carry slow pain, heat, tickle, postgagnlionic autonomic, and olfaction
C-fibers
The fastest fibers classified in Lloyd's system are?
Type IA
________ is primarily used to describe proprioceptive sensory signals from muscle spindles
Lloyd's Type IA
LLoyd's type ______ fibers are associated with crude touch, pressure, fast pain, temp
Type III
Ascending tracts relay sensory information FROM ______ TO ________
sensory fibers
thalamus
Dorsal column-medial lemniscal tracts have a high or low degree of speed?
HIGH degree of speed
