Somatosensory Part 1 Flashcards
What are the three levels of integration associated with the primary and secondary somatosensory cortices?
Somatis sensation (somesthesis, consciousness of stimuli), somatic perception (interpretation of somatic stimuli into a meaningful picture of the world), somatic representation (abstract knowledge, beliefs about ones body)
What are four attributes of sensory systems?
intensity, sensory adaptation, modality, localization
How is intensity signalled?
increased stimulus intensity enhances the amplitude of the receptor potential and the frequency of the AP
What are the two types of sensory adaptation and what do they tell the CNS?
rapid adaptation (rapid offset of stimulus, telling the CNS that something occurs) and slow adaptation (slow decrease in activity, telling the CNS what is occurring)
What are the different types of tactile and proprioceptive modalities that nerves can detect?
touch (pressure, vibration, texture), pain, temperature, joint position, muslce sense, movement
What type of ion channels are sensory receptor proteins?
transient receptor type ion channels (TRPs)
What is “adequate stimulus”? How does this differ to the way in which taste is sensed?
adequate stimulus is the energy that elicits the greatest response, determining which type of neuron will be responsible for the sensory perception
What type of nerve conduct APs faster?
large diameter, myelinated neurons
What is a compound action potential?
a group of summed APs measured at a particular site on a nerve
What nerve types are the fastest? Type 1/A? or Type 4/C?
Type 1/A
What type of nerve conducts proprioception information?
Type Aalpha
What kind of information do nerve type Abeta send?
light touch
What type of nerve conducts information on fast pain?
Adelta
What kind of information do C nerve send?
slow pain
What is meant by localization?
cutaneous receptive fields of mechanoreceptors
Which receptor field is larger? Which is more innervated?One in the periphery or a proximal one?
proximal RFs are larger and less innervated. Peripheral RFs are smaller and densely innervated
How does ones body reconize specificity?
By responding to differences among secondary RFs that are comprised of smaller, overlapping primary RFs
What are the four submodalities of tactile sensation?
discriminitive touch, non-discriminitve touch, temperature, pain
What type of neurons are mechanoreceptors for discriminative touch?
Abeta
What kind of neuron are Merkel cells (fast/slow adapting?) and what do Merkel cells sense? Where are they located?
type SA1,
detect form, texture, fingers scanning a surface,
in basal layer.
What kind of neurons are Ruffini corpuscles (slow/fast adapting?) and what do Ruffini corpuscles sense? Where are they located?
type SA2,
detect skin stretch, perception of hand shape and position.
deep in the dermis
What kind of neurons are Meissner corpuscles (slow/fast adapting?) and what do Meisner corpuscles sense?
FA, detect skin movement and slip for grip control
What kind of neurons are Pacinian corpuscles (slow/fast adapting?) and what do Pacinian corpuscles sense?
FA, vibratory stimuli detected through hand held objects
What kind of neurons are hair follicles (slow/fast adapting?) and what do hair follicles detect?
FA, motion/direction of tactile stimuli
What two types of discriminative tactile receptors are slow adapting?
Merkel cells and Ruffini corpuscles
What and where are meissner corpuscles?
lamellar cells (Schwann and CT) embedded in the dermis
What compound triggers and AP in pacinian corpuscles? How does the pacinian corpuscle adapt to stimulation?
glutamate is released from the axon and lamellar cells in response to physical pressure –> AP. stimulus releases GABA from lamellar cells which inhibits the AP
What kind of receptors have small RFs, generally concentrated at the fingertips?
Meissner (FA) and Merkel (SA1)
What kind of receptors have larger RFs and are generally located in the palms or over large regions of the fingers?
Pacinian and Ruffini
What receptor type is FA and has small RFs, generally along the fingers
Meissner
What receptor type is SA and has large RFs?
Ruffni
What receptor type is FA and has large RFs?
Pacinian
What receptor type is SA and has small RFs?
Merkel cells
What kind of receptors mediate remaining somesthetis modalities such as pain and temperature?
free nerve endings, = non-discriminative touch. these have poor localization
What is proprioception?
somatic sensitivity to join position, location, orientation and movement of the joints, muscles and fascia
Spindles detect _____ of muscles
length
Golgi tendon organs detect ____ of muscles
tension
What pathways are low threshold, Rapid AP conduction in the dorsal-column-lemniscal setting, providing quantitative sense of stimulus localization?
discriminative touch and proprioception
What pathways are high treshold free nerve endings with slower AP conduction in the antero-lateral system, providing qualitative experience of the stimulus
non-discriminative touch, pain , temperature
What pathways involve the doral column-lateral system of communication to the spinal cord, brain stem, thalamus and cerebral cortex?
discriminative touch and proprioception
Where are first order neurons? what do they synapse with?
sensory Abeta neurons that form dorsal columns (cuneate and gracile fasciculi). they synapse onto the dorasal column nuclei in the medulla
What are the second order neurons? what do they synapse with?
cuneate and gracile nuclei that decussate in the medulla, form a medial lemniscus and synapse with neurons in the thalamus
What are the first order neurons? what do they synapse with?
form the internal capsule in the thalamus, project to the primary somatosensory cortex in the postcentral gyrus
The anterolateral system provides what type of sensory feedback?
non-discriminative touch (free nerve endings), pain, temperature
What kinds of neurotransmitters do sensory first-order neurons use to communicate with second order neurons in the anterolateral system?
Substance P, glutamate, NO
What groups of Rexeds lamina are for pain?
Lamina I, II
What groups of Rexeds lamina are for touch?
Lamina IV
What are the two tracts of the anterolateal system?
neospinothalamic tract, paleospinothalamic tract
Where does the neospinothalamic tract project to and what does it sense?
projects to the lateral thalamus and somatosensory cortex. localization of sensation
Where does the paleospinothalamic tract project to and what does it sense?
projects to the reticular formation, medial thalamus and cortex. detects qualitative aspects of pain, temperature and non-discriminative touch
Where do third oder lateral thalamic nuclei project to and what do they do?
project to the primary somatosensory cortex (arranged somatotopically). stimulus location (homunculus
Where do third order medial thalamic nuclei project to and what do they do?
project to cingulate gyrus, insula and detect qualitative aspects of the pain, temp. may generate alerting responses or the dulling of pain
What is syringomyelia and what are the symptoms?
cysts in the cervical grey matter preventing decussation of anterolateral tracts. –> bilateral loss of pain and temperature sensation, but not discriminative or proprioception from the dermatome of that level
What is brown-sequard syndrom, what are the symptoms?
hemisection of the spinal cord that cuts through the anterolateral and dorsal column tracts. —> loss of ipsilateral discriminative touch; loss of contralateral pain and temperature sensation; loss of ipsilateral motor control
What are dermatomes and why are they so hard to map? What technique is the best for mapping dermatomes?
areas of the skin that are innervated by one spinal segment. difficult to map because there is considerable overlap. best way is to map using pain and temperature.
touch, pain and temperature of the face are mediated by what nerve?
the trigeminal nerve, CN V
What are the three branches of the trigeminal nerve?
Ophthalmic, maxillary and mandibular
What branch of the trigeminal nerve innervates the acoustic meatus, tympanic membrane and the ear?
the mandibular division
Where does the trigeminal nerve originate?
the pons
What foramina does the ophthamic division of CN V go through?
superior orbital fissure
What foramina does the maxillary divison of CN V go through?
foramen rotundum
What foramina does the mandibular division of CN V go though?
foramen ovale
The principle sensory nucleus detects:
discriminative touch of the face
The spinal trigeminal nucleus detects:
pain and temperature of the face
The mesencephalic nucleus detects:
proprioception from masticators the mediate muscle reflexes
The motor nucleus detects/does:
motor innervation to masticating muscles
sensory nucleo from the trigeminal nerve go to:
VPM of the thalamus, and then to the cerebral cortex
