True or False? 1. Merkel cells discern skin movement and slip for grip control 2. Ruffini Corpuscles discern skin stretch and hand shape/ position 3. Meissner corpuscles discern the motion/ direction of tactile stimuli 4. Pacinian corpuscles discern vibratory stimuli via hand-held objects 5. Hair follicles discern form and texture when fingers scan a surface

1. F (Merkel = form & texture) 2. T 3. F (Meissner = movement, slip/ grip control) 4. T 5. F (Hair = motion/ direction)

Somatosensation and ascending spinal pathways Flashcards by Robin Erickson

Name the three levels of somatosensory integration

Somatic sensation, somatic perception, somatic representation

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definition: consciousness of stimuli on somatic receptors

Somatic Sensation

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definition: selection, organization & interpretation of somatic objects& events, + one’s own body, into coherent picture…

somatic perception

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definition: abstract knowledge, beliefs and attitude about one’s own body

somatic representation

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Which is not an attribute of sensory systems?

a. intensity
b. temporality
c. adaptation
d. modality
e. localization

b. (temporality)

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increased stimulus intensity leads to an increase in the frequency of _____

AP’s

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definition: decrease in neural activity with sustained stimulation

sensory adaptation

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describe the components of tactile sensation (a sensory modality)

touch – pressure, vibration, texture
pain
temperature

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describe the components or proprioception (a sensory modality)

joint position
muscle sense
movement

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Axon membrane receptors respond to:

a. CT capsules
b. modified epithelial cells
c. hairs
d. membrane of free nerve endings
e. c & d only
f. a, b & c only
g. a, b, c & d

g. (all four are mediators)

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Sensory receptor proteins are _____. Each responds maximally to _____, and less to ______

Transient Receptor (TRP) type ion channels; one stimulus (“adequate stimulus”); others

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definition: the energy that elicits the greatest response; determines which neurons will generate perception of the sensory modality

Adequate Stimulus

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use for measuring conduction velocity?

gross distinction of modalities (compound AP’s)

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Compound action potentials (graphs): what do the peaks correspond to?

the population size of axons with a particular diameter of myelination

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Match:

A. A-alpha
B. A-beta
C. A-delta
D. C

with:

fast pain
slow pain
proprioception, motor neuron
light touch

A. 3
B. 4
C. 1
D. 2

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definition: the area of skin that is innervated by the branches of a single neuron

Cutaneous receptive field

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Peripheral receptive fields are ______ and ______; proximal receptive fields are _____ and _______.

densely innervated, small in area; less innervated, large

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What attribute of sensory systems is associated with the cutaneous receptive fields?

Localization

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The relative size and density of receptive fields enable the CNS to determine three categories of information. Name them

identify the location of stimulus on the body
distinguish size and shape of the stimulus
resolve spatial resolution

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Several primary receptive fields comprise a ______

secondary RF

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Secondary RF’s overlap; spinal neurons can discern_____

subtle differences among them (think: green barrel of monkeys)

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Which is not a submodality of tactile sensation?

a. discriminitive touch
b. non-discriminitive touch
c. temperature
d. pressure
e. pain
f. none of the above

d. (pressure)

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AMong the discriminative touch mechanoreceptors, which are fast acting and which are slow acting: Merkel cells, Ruffini corpuscles, Meissner corpuscles, Pacinian corpuscles, Hair follicles?

Slow: Merkel (SA1) and Ruffini (SA2)
Fast: Meissner, Pacinian, Hair follicle
(note: all five are A-beta)

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True or False?

Merkel cells discern skin movement and slip for grip control
Ruffini Corpuscles discern skin stretch and hand shape/ position
Meissner corpuscles discern the motion/ direction of tactile stimuli
Pacinian corpuscles discern vibratory stimuli via hand-held objects
Hair follicles discern form and texture when fingers scan a surface

F (Merkel = form & texture)
T
F (Meissner = movement, slip/ grip control)
T
F (Hair = motion/ direction)

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Describe the Merkel cell-neurite complex

clusters of Merkel cells in basal epidermis, "synapse" with sensory axon terminals

Describe Ruffini Endings

layers of perineural tissue form large, thin, spindle-shaped cylinders; deep in dermis

What are the make up and location of Meissner corpuscles?

lamellar Schwann (tortorus) and CT cells; in dermis just below epidermis

Describe Pacinican corpuscles?

lamellar, onion shaped (inner layers = Schwann, outer layers = fibroblasts), encapsulate a single axon; axon ends in dermis of Glabrous (hair-free/ smooth) skin.

Is this the correct mechanism / sequence? -- physical pressure stimulates Pacinian corpuscle -> creates receptor potential -> Glutamate released from axon or lamellar cells -> Glutamate triggers AP

Yes, according to Dr. B

What neurotransmitter is involved in Pacinian adaptation, and what is it's action?

GABA inhibits AP's

True or False? -- Merkel and Meissner sensor receptor fields are small and concentrated on the sides of the fingers

False -- concentrated on fingertips

True or False? - - Ruffini only detect stretch in specific diretions - - Pacinian are located along median and ulnar nerves - -Ruffini have large receptor fields, but Pacinian have small RF's

False -- all true, but both have large RF's

Which types of sensation are associated with free nerve endings, and where are they located?

Temperature (within dermis) and pain (epidermis via C and A-delta axons)

Which type of pain receptors receive tap, squeeze, rub, skin stretch & non-discriminative touch signals?

Mechanoreceptors (SA; A-delta & C)

Which type of pain receptors receive hot & cold signals?

Thermoreceptors (SA; A-delta & C)

Which type of pain receptors receive mechanical or thermal tissue damage signals?

mechano-thermal nociceptors (SA; A-delta)

Which type of pain receptors receive heat, tissue damage, chemical stimulation (bradykinin, histamine, insect venom) signals?

polymodal nociceptors (SA; C)

Proprioception involves somatic sensitivity to multiple categories of input: what are they?

position, location, orientation, movement -- of joints, muscles, fascia

Match the receptor(s) with the sensitivity/ -ies: A. Ruffini B. Pacinian Corpuscle C. Muscle spindles D. Golgi Tendon Organs (GTO's) 1. Joint & fascia; CT stretch 2. Muscle tension 3. Muscle length 4. Skin stretch

A. 1 & 4 B. 1 C. 3 D. 2

Match the receptor with its general sensation: A. Ruffini B. Pacinian Corpuscle C. Free Nerve Endings 1. Joint position and velocity 2. Pain sensation/ nociceptor 3. Pressure

A. 1 B. 3 C. 2

True or False: GTO's and Ruffini endings are associated with a slow adaptive response to stretch, while Pacinian corpuscles are associated with rapid adaptation to movement

True

Match the following to either (A) discriminative touch and proprioception, or (B) non-discriminitive touch, pain, and temperature: 1. High threshold free nerve endings 2. Provides qualitative experience of stimulus 3. Dorsal column/ lemniscal system 4. Low threshold mechanoreceptors 5. Rapid AP conduction 6. Slower AP conduction 7. Anterolateral system/ spinothalamic 8. Provides quantitative sense/ localization of the stimulus

A. 3, 4, 5, 8 | B. 1, 2, 6, 7

What is the afferent route of 1st, 2nd and 3rd order neurons in the lemniscal system pathway?

spinal cord -> brain stem -> thalamus -> cerebral cortex

What type(s) of axons are used by the proprioceptive receptors?

Large; A-alpha and Beta

Describe 3rd order Thalamic neurons

part of internal capsule; project to primary somatosensory cortex (post central gyrus)

Describe 2nd order Thalamic neurons

decussate in the medulla; axons form medial lemniscus & synapse onto interthalamic neurons

Describe 1st order Thalamic neurons

sensory axons form cuneate and gracile fasciculi of dorsal columns; axons synapse with neurons in the medulla

True or False: Mechanoreceptor axons innervate several segments of the spinal cord before entering the brain stem

True

True or False: When axons leave a dorsal root, they bifurcate, sprouting multiple collaterals

True

True or False: one long neuron travels from the Great Toe to the Medulla

True!

The anterolateral system is less _________, making it slower than the dorsolateral system

myelinated

The _______ governs responses to stressful situations: A. VPL nucleus of Thalamus B. Superior Colliculus C. Periaqueductal grey matter (PAG) D. Pontine Reticular Formation

C. Periaqueductal grey matter

Which of the following is relayed via the anterolateral system? A. non-discriminitive touch B. pain C. Temperature D. All of the above

D. All of the above

In the anterolateral system, 2nd order dorsal horn neurons receive messages from 1st order sensory neurons via which neurotransmitters?

Substance P, glutamate, NO

Sense associated with Rexed's Lamina I & II?

pain

Sense associated with Rexed's Lamina IV?

touch

2nd order neurons in dorsal horn ________ to the anterolateral system

decussate

Name the two spinothalamic tracts

Neo- and Paleo-

Match the neo- and paleo- spinothalamic tracts with their respective regions: 1. Lateral Thalamus 2. Medial Thalamus 3. Cortex 4. Somatosensory cortex 5. Reticular formation

Neo: 1, 4 Paleo: 2, 3, 5 (I'm not clear on specifics -- if any -- of 3, this is verbatim from the good Dr.)

The anterolateral system has ____ type(s) of 3rd order neurons, which are ________

2; lateral thalamic and medial thalamic

True or false: Lateral thalamic neurons project to the prefrontal cortex and are somatotopically arranged, with a homunculus for stimulus localization

False; the neurons project to the somatosensory cortex. All the rest is true

Medial thalamic neurons project to ________ and ______, signalling _______________ of pain, temperature, etc.

cingulate gyrus & insula; affective qualities

True or false: all medial thalamic neurons generate the experience of dull, persistent pain

False: some generate alerting responses to get your attention

Where do cysts form in Syringomyelia, and what do they interrupt?

in center of cervical grey matter; decussation of 2nd order anterolateral (spinothalamic) neurons

True or false: the lesion(s) attendant with Syringomyelia cause bilateral loss of cervicothoracic senses of pain, temperature, discriminitive touch, and proprioception

False: discriminitive touch, and proprioception are not affected. (The loss IS bilateral, and IS localized to the cervical and thoracic regions of the body)

The heimsection of Brown-Sequard syndrome refers to a __________cut through dorsal and anterolateral colunms

unilateral

True or false: Symptoms of Brown-Sequard syndrome include ipsilateral loss of discriminative touch, pain, temperature and motor control

False: the loss of pain and temperature sensitivity is CONTRAlateral

Why is ipsilateral discriminative touch lost in Brown-Sequard syndrome?

Because the sensory neurons cannot decussate at the level of the lesion

Why is contralateral pain and temperature sensation lost in Brown-Sequard syndrome?

Because the 2nd order neurons decussate below the lesion

A dermatome is an area of the skin said to be innervated by one spinal segment. However, dermatomes overlap. Which types of sensation overlap more and which overlap less?

More: touch, pressure, vibration Less: pain, temperature (Thus we can protect ourselves from the most immediate injuries more immediately, hooray!)

Dermatome maps, in spite of their imperfections, are clinically useful to reveal sites of damage to______

spinal nerves or the spinal cord

Which senses are mediated by the Trigeminal Nerve (choose as many as apply)? A. Proprioception B. Discriminitive touch C. Temperature D. Pain

A, B, C, D

Match the Cavity, foramen and dermatome(s) to the correct branch of CN V: Opthalmic Maxillary Mandibular Nasal cavity Orbital cavity Oral cavity Foramen ovale Superior orbital fissure Foramen rotundum ``` Chin Side of face cheek area dorsum of nose tympanic membrane external auditory meatus forehead ear ```

Opthalmic: Orbital cavity; Superior orbital fissure; forehead and dorsum of nose Maxillary: Nasal cavity; Foramen rotundum; cheek area Mandibular: Oral cavity; Foramen ovale; tympanic membrane, external auditory meatus, Chin, Side of face, ear

Name at least three foramina that allow egress of cutaneous branches of the Trigeminal nerve...

supraorbital, infraorbital, mental | followed in our notes by "etc."...

How many nuclei does CN V have, and what are their names?

Four: Principal (Chief, Main) Sensory nucleus, Spinal Trigeminal nucleus, Mesencephalic nucleus, Motor nucleus

which division of CN V innervates the masticators and the soft palate?

Mandibular

describe the projection of the sensory nuclei of CN V

to VPM of thalamus and thence to cerebral cortex

Match the nuclei with their sense(s): Principal (Chief, Main) Sensory nucleus Spinal Trigeminal nucleus Mesencephalic nucleus Motor nucleus ``` Temperature from face Motor to Masticating muscles Muscle reflexes Discriminative touch from face Proprioception from masticators Pain from face ```

Principal (Chief, Main) Sensory nucleus: Discriminative touch from face Spinal Trigeminal nucleus: Temperature from face, Pain from face Mesencephalic nucleus: Proprioception from masticators, Muscle reflexes Motor nucleus: Motor to Masticating muscles