Unit 1 Somatic Senses Flashcards
All sensory systems mediate what 4 attributes of a stimulus no matter what type of sensation?
- Modality
- Location
- Intensity
- Timing
Describe transduction
When a stimulus is changed into an electrical signal.
What are the two systems of classifying nerve fibers?
Erlanger’s and Lloyds
How does myelination effect conduction velocity?
Myelination increases conduction velocity by 6 fold
An unmyelinated fiber 5 microns in diameter conducts a signal how fast?
5m/second
How fast does a myelinated fiber 5 microns in diameter conduct a signal?
30m/second
Using Erlanger’s system, what is the diameter of a type A alpha fiber?
8 to 20 microns
Using Erlanger’s system, what is the diameter of type A beta fibers?
5 to 12 microns
Using Erlanger’s system, what is the diameter of a type A gamma fiber?
2 to 8 microns
Using Erlanger’s system, what is the diameter of a type A delta fiber?
1 to 5 microns
Using Erlanger’s system, what is the diameter of a type B fiber?
1 to 3 microns
Using Erlanger’s system, what is the diameter of type C fibers?
<1 microns
Using Lloyd’s system, what is the diameter of type I fibers?
12 to 20 microns
Using Lloyd’s system, what is the diameter of type II fibers?
4 to 12 microns
Using Lloyd’s system, what is the diameter of type III fibers?
1 to 4 microns
Using Lloyd’s system, what is the diameter of type IV fibers?
<1 micron
Describe the labeled line principle.
The specificity of nerve fibers transmitting only one modality of sensation.
Describe adaptation
When a neuron experiences a sustained stimulus it will show a decreased firing rate over time. This is known as adaptation.
Describe slow adapting receptors
Continuous information relatively non adapting in response to a sustained stimulus
Describe what fast adapting receptors do.
Fast adapting receptors react strongly when a change is taking place.
Name two slow adapting receptors.
- Merkel’s discs
- Ruffini corpuscles
Name two fast adapting receptors.
- Pacinian corpuscles
- Meissner’s corpuscles
Describe the receptive field of Merkel’s Discs.
Merkel’s Discs have a punctate receptive field. Meaning its studded or marked with tiny dots or holes.
How are Ruffini corpuscles activated?
Ruffini corpuscles are activated by stretching the skin.
What type of receptors are in the outer layer of the joint capsule?
Type I mechanoreceptors
Describe type I mechanoreceptors.
Type I mechanoreceptors are slow and low.
Describe type III mechanoreceptors.
Type III mechanoreceptors are slow and high.
Describe type II mechanoreceptors.
Type II mechanoreceptors are rapid and low
Describe type IV mechanoreceptors.
Type IV mechanoreceptors are nociceptors with a high threshold
What is an example of a type III mechanoreceptor?
Joint version of a golgi tendon organ.
This type of receptor fires dynamically with movement.
Type I mechanoreceptors
This type of receptor is completely immobile in inactive joints.
Type II mechanoreceptors
This type of receptor functions in joint movement monitoring
Type II mechanoreceptors
This type of receptor has a phasic effect on lower motor neuron pools.
type II mechanoreceptors
This type of receptor has a tonic effect of lower motor neuron pools
Type I mechanoreceptors
This type of receptor is completely inactive in physiologic normal joint. Instead they fire under increased capsule pressure and chemical irritation.
Type IV mechanoreceptors
What is stereognosis?
The ability to perceive form through touch.
What are our sensory modalities?
- pressure receptors
- cold receptors
- warmth receptors
- nociceptors
What type of receptor signals when hairless skin is ran over the edge on a object?
Meissner’s Corpuscles
What type of receptor signals when subcutaneous tissue is run over the edge of an object?
Pacinian corpuscles
What type of receptor senses curvature of an object’s surface?
Merkel’s discs
What type of receptors are activated by stretching the skin?
Ruffini corpuscles
What are superficial receptors of the skin?
- Meissner’s corpuscles
- Merkel’s discs
What are deep receptors of the skin?
- Pacinian corpuscles
- Ruffini corpuscles
What are rapidly adapting receptors of the skin?
- Meissner’s
- Pacinian corpuscles
What are slowly adapting receptors of the skin?
- Ruffini corpuscles
- Merkel’s discs
Name the types of receptors of the skin that are activated by sustained pressure.
- Merkel’s discs
- Ruffini corpuscles
What types of receptors of the skin have a small receptive field?
- Meissner’s corpuscles
- Merkel’s discs
What types of skin receptors have a large receptive field?
- Pacinian corpuscles
- Ruffini corpusles
This type of skin receptor has a small receptive field and are activated by vibration.
Meissner’s corpuscles
This type of skin receptor has a large receptive field and is activated by vibration.
Pacinian corpuscles
This type of receptor has a small receptive field and is activated by sustained pressure.
Merkel’s discs
This type of receptor has a large receptive field and is activated by sustained pressure
Ruffini corpuscles
This type of receptor is superficial and rapidly adapting
Meissner’s corpuscles
This type of receptor is superficial and slowly adapting
Merkel’s discs
This type of receptor is deep and rapidly adapting.
Pacinian corpuscles
This type of receptor is deep and slow adapting.
Ruffini corpuscles
Most aspects of touch and proprioception come from what pathway?
Medial lemniscal system (dorsal column)
Sensations of crude touch, nociception, temperature, tickle, itch, and sexual sensation come from which pathway?
Anterolateral system
Where do 2nd order neurons in the medial lemniscal system (dorsal column) cross over?
Brain Stem
Where do 2nd order neurons in the anterolateral system cross over?
Spinal cord
Which side of the cord has a lesion of there is a loss of vibration and proprioception?
Ipsilateral
Which side of the cord has a lesion if there is a loss of sense of temperature (analgesia)
Contralateral
What brodman area forms muscles stretch receptors?
3a
What brodman area forms cutaneous receptors?
3b
What brodman area forms deep pressure receptors?
2
What brodman area forms rapidly adapting cutaneous receptors?
1
What type of neurons respond well to movement in all directions but not selectively to movement in any one direction?
Motion sensitive neurons
What type of neurons respond much better to movement in one direction than in another direction?
Direction sensitive neurons
What neurons respond best to movement along a specific axis?
Orientation sensitive neurons
Motion, direction, and orientation sensitive neurons are all neurons in which brodman areas?
1 and 2
What brodman area integrates tactile information from mechanoreceptors in skin with proprioceptive inputs from underlying muscles and joints?
Brodman area 5
What brodman area receives visual, tactile, and proprioceptive inputs?
Brodman area 7
Are thermoreceptors slow or rapidly adapting?
slow adapting
What is the range for extreme thermoreceptors?
50 degrees C
What are the three ways that nociceptors can be activated?
- mechanical
- thermal
- chemical
What are sensations of pain?
- pricking
- burning
- aching
- stinging
- soreness
What are the cardinal signs of inflammation?
Rubor - redness
Calor - heat
Tumor - swelling
Dalor - pain
What does potassium from damaged cells do to nociceptors?
Activates nociceptors
What does serotonin from platelets do to nociceptors?
Activates nociceptors
What does bradykinin from plasma kininogen do to nociceptors?
Activates nociceptors
What does histamine from mast cells do to nociceptors?
activates nociceptors
What do prostaglandins and leukotriends from ARA damaged cells do to nociceptors?
Sensitizes nociceptors
What does substance P from the primary afferent do to nociceptors?
Sensitives nociceptors
What type of fibers secrete both substance P and glutamate?
C fibers
This is responsible for slow pain
Substance P
Epicritic describes what pathway?
dorsal column - medial lemniscal system
Protopathic describes what pathway?
anterolateral system
This pathway is old phylogenetically and initiates actions.
Protopathic
This pathway is new phylogenetically and modifies actions.
Epicritic
Describe endogenous opioids from the pariaquedutal gray
enkephaline projections to Raphe
Describe endogenous opioids from the Raphe N.
Serotonin projections to the cord
What do inhibitory interneurons in the cord do?
Release enkephalin, inhibits C, A delta fibers and 2nd order projection neurons.
This nerve supplies most sensory innervation of head and face.
Trigeminal (C.N. V)
What type of muscle receptors respond to stretch?
Muscle spindles
What type of muscle receptors respond to tension?
Golgi tendon organs
These receptors are located withing the belly of the muscle parallel with extrafusal fibers
muscle spindles
This type of receptor is located at the junction of the muscle and tendon.
Golgi tendon organs
What type of receptor in innervated by two types of myelinated afferent fibers?
muscle spindles
What are two types of myelinated afferent fibers that innervate muscle spindles?
- Group Ia (large diameter)
- Group II (small diameter)
What is the innervation of golgi tendon organs?
GTOs are innervated by group Ib afferent fibers
What happens when a spindle is activated by stretch of a muscle?
A muscle contraction
What happens when a GTO is stimulated by either a stretch or a contraction of a muscle?
Inhibition of muscle contraction
What type of muscle spindle is most responsive to muscle shortening?
group II
What type of muscle spindle is most responsive to muscle lengthening?
group Ia
What is the afferent innervation of a GTO
Group Ib
What is the afferent innervation of a muscle spindle?
Group Ia
Group II
What is the efferent innervation of a GTO?
There is none.
What is the efferent innervation of a spindle?
y fibers
What are endogenous cannabinoids produced by the brain?
- anandamide
- 2 arachidonoylglycerol (2-AG)
The production of this is increased during exercise and contributes to “runner’s high”
Endogenous Cannabinoids
Relationship to extrafusal fiber of GTO
Series
Relationship to extrafusal fibers of spindle
parallel
What is the primary GTO stimulus?
Contraction (tension)
What is the primary spindle stimulus?
Stretch
What is the reflex response of a GTO
Inhibition of extrafusal fibers
What is the reflex response of a spindle
Contraction of extrafusal fibers
What innervates intrafusal fibers?
Gamma (y) motor system
Mesencephalic area appears to regulate rhythmic gate in what structure?
Reticular formation
What system facilitates gamma motor neuron antigravity control?
Vestibular system
Where do you find cutaneous sensory receptors?
Over skeletal muscle, sensory afferent activating gamma motor neurons
Describe spatial summation.
Increased signal strength transmitted by progressively greater number of fibers
Describe temporal summation
Increased signal strength by increased frequency of firing with the same number of fibers.
