PHYS II - Exam I, Part I (Somatic Sensation)

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