Neurophysiology II Flashcards
Which sensory pathway is considered as the most rapid conduction in any pathway in the CNS?
Spinocerebellar pathway
Which of the 2 spinocerebellar tracts is excited mainly by motor signals arriving in the anterior horns of the spinal cord instead of peripheral receptors?
Ventral spinocerebellar (G683)
In the descending control of ascending pain pathways, presynaptic action might prevent release of ______ from nociceptors.
substance P
Which Central Somatosensory Pathway conveys information about fine-touch and vibratory sensations?
Dorsal Column-Medial Lemnisci Pathway
Thalamic nucleus responsible for proprioception
VPS
Thalamic nucleus responsible for Pain and Temperature
VPI
Thalamic nucleus responsible for fine touch sensation from the face
VPM
Thalamic nucleus responsible for fine touch and vibration from the body
VPL
Which ionic channel is upregulated with neuropathic pain?
Na+ channels
Type of pain caused by activity in the neural pathways in response to potentially tissue damaging stimuli
Nociceptive pain
Which of the following is considered Neuropathic pain? A. Post-operative pain B. Post-herpetic pain C. Mechanical low back pain D. Sports / exercise injuries E. Sickle cell crisis
B. Post-herpetic pain Other examples: ● Neuropathic low back pain ● Distal polyneuropathy ● Central post-stroke pain ● Complex regional pain syndrome ● Trigeminal neuralgia
Tract that excites motor neurons that supply extensor muscles of the proximal part of the limb that are important for postural control
Lateral vestibulospinal tract
Tract that receives sensory input from the labyrinth (chiefly from the semicircular canals) to function in mediating adjustments in head position in response to angular acceleration of the head
Medial vestibulospinal tract
Rexed lamina targets of Aδ fibers
Lamina I (marginal nucleus; the most dorsal) Lamina V (neck of the dorsal horn) Lamin X (around central canal)
Rexed lamina targets for C fibers
Lamina I and II
In the gate control theory of pain, which neurotransmitter is released with the activation of the large fibers?
GABA
Approximate limits of temperature prior to being perceived as pain
43°C and 15°C
Pain axonal fiber class that is sensitive to heat and mechanical stimuli
C mechanoheat-sensitive fibers (also called polymodal fibers).
Reflex responsible for a compensatory response of the neck muscles when head motion is sensed by the vestibular organs in the inner ear.
Vestibulocollic reflex
Tract responsible for the compensatory response of the neck muscles when head motion is sensed by the vestibular organs in the inner ear.
Medial vestibulospinal tract = vestibulocollic reflex
Term for the conversion of any sensory input to electrical signal that is eventually transmitted to nervous system
Transduction
4 physiologic processes undergone by sensory stimuli:
Transduction
Transmission
Modulation
Perception
Cells that have been found to express Piezo 2 channel protein
Low-threshold and nociceptive-type of cells
Mechanotransducer protein found in main proprioceptors
Piezo 2
The channel protein underlying the transduction for cutaneous mechanical rapidly adapting responses because it forms a non-selective cation pore that opens in response to mechanical stimuli
Piezo 2
The mechanotransducer protein that belongs to DEG/ENaC family (sodium family)
Acid-sensing Ion Channel Proteins (ASIC)
Receptor protein activated by capsaicin
TRPV1
Receptor protein activated by camphor
TRPV3
Receptor protein activated by menthol
TRPM8
Receptor protein activated by mustard oil
TRPA1
What are the excitatory voltage-gated channels
Na+ and Ca++
What is the inhibitory voltage-gated channel?
K+ channels
Where are the locomotor regions of the brainstem located?
from subthalamus to the medulla
At which level of the midbrain is the locomotor region located?
inferior colliculus
Sequence of activation of locomotion via the midbrain locomotor region
▪ Motor cortex → corticobulbar fibers → midbrain locomotor region → reticular formation → reticulospinal tracts → SC
2 classifications of the somatosensory nervous system, wherein the classification is the type of information they carry
Fine Discriminatory Touch Sensations
Pain and Temperature Sensations
Identify the functional subdivision of the S-I Cortex or Primary Somatosensory Cortex for:
cutaneous input
3b & 1
Identify the functional subdivision of the S-I Cortex or Primary Somatosensory Cortex for:
muscle and joint input
3a & 2
Higher percentage of cells in this cortical area involve in planning of movement with external cues (from the environment)
Premotor cortex
Higher percentage of cells in this cortical area involve in planning of movement with internal cues
Supplementary motor cortex
Postural reflex with the rotation of the head activating sensory receptors of the semicircular canals
Vestibular reflex
Postural reflex that generate eye movements and postural adjustments
Vestibular reflex
Vestibular reflexes are mediated by which descending tracts?
lateral and medial vestibulospinal tracts and the reticulospinal tracts
A disease that irritates the left labyrinth will cause the person to tend to fall to which side?
Right
Any disease that eliminates labyrinthine function in the right ear will cause the person to tend to fall to which side?
right
Descending tract that activates extensor muscles that support posture
Lateral vestibulospinal tract
Descending tract that causes contractions of neck muscles that oppose the induced movement
Medial vestibulospinal tract
These reflexes are activated by the muscle spindles found in neck muscles
Tonic Neck reflexes
If the neck is bent to the left, the extensor muscles in which limbs contract more?
Left
These reflexes tend to restore an altered position of the head and body toward normal
Righting reflex
Neural circuits in the spinal cord for locomotion
Central pattern generators
Transduction of thermal or mechanical to electrical signal by generator or receptor potentials occurs in the distal end of axons of which order of somatosensory neurons?
1st
The 3rd order neurons project to which part of the cortex
Primary somatosensory cortex (S-1)
3 SUBDIVISIONS OF THE SOMATOSENSORY NS Based on distribution of Receptors:
Enteroceptive
Exteroceptive
Proprioceptive
SUBDIVISIONS OF THE SOMATOSENSORY NS Based on distribution of Receptors: contact of skin with external world
Exteroceptive
SUBDIVISIONS OF THE SOMATOSENSORY NS Based on distribution of Receptors: provides info about body and limb position and movement
Proprioceptive
SUBDIVISIONS OF THE SOMATOSENSORY NS Based on distribution of Receptors: monitors internal state of the body
Enteroceptive
SUBDIVISIONS OF THE SOMATOSENSORY NS Based on the type of information they carry:
Fine Discriminatory Touch sensations
Pain and Temperature sensations
Which of the following is not under the classification of Fine Discriminatory Touch Sensation? A. Tension B. Pressure C. Vibration D. Flutter E. NOTA
E. NOTA (also includes light or crude touch and stretch)
Which of the following is not under the classification of Pain and Temperature Sensation? A. Stretch B. Innocuous C. Itch D. Noxious E. NOTA
A. Stretch is under fine discriminatory
Pain and Temp class include: noxious, innocuous cold and warmth, mechanical and chemical pain and itch
Nerve Fiber class for fine discriminatory sensation NS subdivision (specify diameter and myelination)
Large-diameter, myelinated fibers in A-beta class
Nerve Fiber class for pain and temperature sensation NS subdivision (specify diameter and myelination)
Small-diameter, lightly myelinated A-delta fibers and unmyelinated C fibers
Ascending somatosensory tract for pain, thermal and tactile information to the superior colliculus for spinovisual reflexes
Spinotectal tract
Ascending tract for indirect afferent info to reach cerebellum
Spino-olivary tract
Known as low-frequency vibration
Flutter
Type of response to low-threshold mechanoreceptors that involve continuous AP for the duration of the stimulus
Slow-adapting response
Type of response to low-threshold mechanoreceptors that involve burst of AP at onset or removal of tactile stimulus
Fast-adapting response
region of skin from which stimuli can evoke a response
Receptive field
Type of receptive field that is particular in glabrous skin
Type 1 unit
Type of receptive field that is that is ideal for 2-point discrimination due to its sharp-decreasing sensitivity at border
Type 1 unit
Type of receptive field that underlies special acuity with small receptive field
Type 1
Type of receptive field that contains wide fields with poorly defined borders
Type 2
Type of receptive field that covers most or all of a finger
Type 2 unit
Four main classes of low-threshold mechanosensitive afferents
FA1 - fine touch and low-frequency vibration
FA2 - gross pressure and high-frequency vibrations
SA1 - sustained light touch
SA2 - sustained pressure of skin stretch
Specific class of low-threshold mechanosensitive afferent for skin stretch
SA2
Specific class of low-threshold mechanosensitive afferent found below epidermis
FA1 - Meissner corpuscles
Specific class of low-threshold mechanosensitive afferent for high-frequency vibrations
FA2 - Pacinian corpuscles
Specific class of low-threshold mechanosensitive afferent found in basal epidermis for sustained light touch
SA1 - Merkel discs
receptor for the class of low-threshold mechanosensitive afferent responsible for sustained pressure and stretch
Ruffini endings
Which class of low-threshold mechanosensitive afferent are different in hairy skin?
FA
FA2 - not found in hairy
FA1 - hair and field units
Specific class of low-threshold mechanosensitive afferent for hairy units
FA1
Location of FA2 in hairy skin
muscles and blood vessels (deep tissues)
Threshold distance is most closely related to _____ of type 1 units
density
Area of the skin innervated by sensory fibers of a spinal
nerve
Dermatome
T/F:
transection of a single dorsal root causes little sensory
loss in the corresponding dermatome
T:
Dermatome receives its densest innervation from the corresponding spinal cord segment but also receives from adjacent spinal segments
Dermatome of inguinal or groin
T12
Dermatome spinal level of lateral margin of foot and little toe
S1
The large myelinated primary afferent fibers assume a (medial/lateral?) position in the dorsal root
medial
Group of muscles innervated by the motor fibers of a spinal nerve
Myotomes
The deep somatic tract innervated by the same signal spinal nerve
Sclerotome
Dermatome-like regions in the face are innervated by peripheral processes of neurons in which ganglion?
trigeminal ganglion (also called the Gasserian or semilunar ganglion)
Trigeminal nuclear complex division that is analogous to dorsal root ganglion
mesencephalic division
The mesencephalic nucleus actually contains first-order neurons & thus is analogous to a dorsal root ganglion
Pain & temp sensation from the face runs to which nucleus?
Spinal nucleus (trigeminal)
Trigeminal nucleus that controls jaw-jerk reflexes, proprioception
Mesencephalic nucleus
Course through which trigeminal nucleus resembles the medial lemniscus pathway?
Main sensory
(Fine touch, pressure, 2-point discrimination)
→ Fibers of CN V (1st order) enters brainstem → synapse with main sensory nucleus (2nd order) in pons → cross to opposite side → ascend to thalamus (VPM)
Course through the spinal nucleus of CN V resembles the which ascending pathway?
spinothalamic pathway
→ Fibers of CN V (1st order) enters brainstem → synapse with spinal nucleus (2nd order) in medulla and releases glutamate or sub. P → cross to opposite side → ascend to thalamus
Neurotransmitters released with the synapsing of CN V fibers in the spinal nucleus
Glutamate and Substance P
How is the central somatosensory pathways categorized?
By main pathways for:
- cutaneous information
- proprioception and tactile information
Main pathways for cutaneous information:
Dorsal column-medial lemniscus pathway Spinothalamic pathway (anterolateral system)
Central somatosensory pathway that conveys crude touch information from the body
Spinothalamic (anterolateral system) pathway
Pathway that partially overlaps with dorsal column-medial lemniscal pathway
Spinocerebellar and cuneocerebellar pathways
These refer to axons of dorsal column nuclear projection neurons that exit the nuclei as they sweep ventrally and then medially to cross the midline at the same medullary level as the nuclei
Internal arcuate fibers
The internal arcuate fibers, after crossing the midline, form the _________ which project rostrally to the thalamus
medial lemniscus
The main sensory nucleus relays tactile information to the contralateral ventral posterior medial (VPM) thalamic nucleus by way of the _________ tract
trigeminothalamic tract
The most important sensory pathway for nocireceptors and thermoreceptors from the body transmits input to the which thalamic nucleus?
VPI = anterolateral spinothalamic pathway
SC (Rexed) laminae for anterolateral system in the dorsal horn
Primarily I and IV to VI
Corresponding NT in the substantia gelatinosa for acute and chronic pain
Acute = glutamate Chronic = substance P
Fibers of the anterolateral system from 1st order neurons travel via the dorsal spinal nerve roots and ascend or descend 1-2 segments in ___________ tract
Lissauer’s Tract
Cortex that are involved in affective responses for nociceptive signals
cingulate and insular cortices
- have limbic system functions
Among the 2 main central targets of proprioceptive information, which uses the information for motor coordination?
Cerebellum
Among the 2 main central targets of proprioceptive information, which uses the information for the basis of conscious awareness of the body part (kinesthesia)?
Cerebral cortex
For the trunk and lower limb, the spinocerebellar pathway starts with dorsal root ganglion cells whose axons synapse in:
Clarke’s column (nucleus dorsalis)
To provide proprioceptive information from the lower limb to the cerebral cortex
→ The main axons of the dorsal spinocerebellar tract give off a branch in the medulla that terminates in ________ , which is just rostral to the nucleus gracilis
nucleus z
The nucleus with axons of cells, which carry proprioceptive input, form part of the internal arcuate fibers and medial lemniscus and ascend to the VPL (ventral posterolateral) nucleus of the thalamus
Nucleus Z
The 2 major nuclei of the Ventroposterior Nuclear Complex of the thalamus
→ Ventral Posterolateral (VPL) – Major nuclei
▪ Input: Medial Lemniscus
→ Ventral Posteromedial (VPM) – Major nuclei
▪ Input: Trigeminothalamic Tract
Minor nucleus of the Ventroposterior Nuclear Complex of the thalamus
Ventral Posterior Inferior (VPI) – Minor Nuclei
▪ Input: Spinothalamic Tract
VPL and VPM nuclei contain what type of interneurons?
GABAergic inhibitory
One of the MAIN SOMATOSENSORY RECEIVING AREAS OF THE CORTEX that is located at the postcentral gyrus, above the lateral fissure
S-I cortex (primary)
One of the MAIN SOMATOSENSORY RECEIVING AREAS OF THE CORTEX in the superior bank of the lateral fissure
S-II (secondary)
Compound that enhance the sensitivity of pain endings but not directly excite them
Prostaglandin
Type of nociceptors for bradykinin, serotonin, histamine, K+, H+, PG, ACh, proteolytic enzymes
Chemical pain receptors
pain from non-painful stimuli
allodynia
STT originates from second-order neurons located in the spinal cord primarily Rexed laminae
I, IV to VI
Pharmacology:
Ca2+ channel blocker for neuropathic pain
Gabapentin
Pharmacology:
Na+ channel blocker for pain
Lidocaine
The descending pathway that modulates (gates) starts in the:
periaqueductal gray (PAG)
These are neuropeptides that activate one of several types of opiate receptors.
Endogenous opioids
Because motor neurons represent the ONLY route for CNS activity to control muscle activity, motor neurons have been termed the _________ pathway
final common
The recruitment pattern in w/c the motor units are recruited in order of motor neuron axon size (smaller → larger axons)
Size principle
The descending motor system that influences reflex arcs that control fine movement of the distal ends of limbs, as well as of those that activate supporting musculatures in the proximal ends of limbs
Lateral system
Motor tract that supplies muscles of the lower part of the face and in the hypoglossal nucleus
Corticobulbar tract
______ neurons receive input from the cerebellum and from the motor cortex; thus, making this an area of integration of activity from these two motor systems
Redu nucleus
Descending system with interneurons that connect bilaterally with motor neurons that control the axial musculature and thereby contribute to balance and posture
Medial system
The cells that give rise to the pontine reticulospinal tract are in the:
medial pontine reticular formation
Tract that functions to excite motor neurons to the proximal extensor muscles to support posture
Pontine reticulospinal tract
Tract that arises from neurons of the medial medulla, particularly those of the gigantocellularis reticular nucleus
Medullary reticulospinal tract
Which of the pontine and medullary reticulospinal tract is mainly inhibitory?
Medullary reticulospinal tract
This tract assists in postural adjustments after angular and linear accelerations of the head
Lateral vestibulospinal tract
● Excitatory input
→ From semicircular canals and otolith organs
● Inhibitory input; Excites motor neurons that supply extensor muscles of the proximal part of the limb that are important for postural control
→ Purkinje cells of the anterior vermis region of the cerebellar cortex; Inhibits flexor motor neurons
Tract that mediates adjustments in head position in response to ANGULAR ACCELERATION of the head
Medial vestibulospinal tract
Tract that regulates head movement in response to visual, auditory, and somatic stimuli
tectospinal tract
These pathways may alter the responsiveness of spinal cord circuits, including the reflex arcs and induce widespread changes in excitability rather than discrete movements or specific changes in behavior
Monoaminergic pathways
This nucleus reduces nociceptive transmission (via dorsal horn) and enhance motor activity (via ventral horn) with the NT serotonin
Raphe nucleus
These are inhibitory nuclei that contain NE in neurons and projects to the spinal cord in the lateral funiculus
Locus coeruleus and Nucleus subcoeruleus
If only the corticospinal tract is interrupted, as can occur with a lesion of the medullary pyramid, most of the UMNL signs are much (reduced or enhanced?)
reduced/absent
Initial reduction in the tone of postural muscles & loss of righting reflexes occurs with lesion in which descending system?
Medial system
Long term deficits that may result in medial system interruption
locomotor impairment and frequent falling
