Somatosensory Tracts 1: Proprioception and Tactile Flashcards
The somatosensory system transmits and analyzes what types of information from external and internal locations on the body and head?
Discrimintive Touch
Vibration
Proprioception (body postion in space)
Crude Touch
Temperature
Nociception (pain)
Discriminitive touch, vibration (flutter), and proprioception sensations from the body are transmitted through what pathway/
What pathway relays these same sensations, including pain, from the face?
Medial Leminiscal Pathway (posterior column, dorsal column)
Trigeminothalamic PAthway
Two-point discrimination varies widley over different parts of the body, and the more sensitive areas have a higher density of peripheral nerve endings, called a receptive field. Which of the following best describes the receptive field of the hand?
A. Small receptive field with low receptor desnity
B. Small receptive field with high receptor density
C. Large receptive field with high receptor density
D. Large receptive field with low receptor density
Small receptive field with high receptor density
NOTE: the smaller receptive fields will ALWAYS have higher receptor density
Primary afferent fibers (sensory expns with cell bodies in the dorsal root ganglia) will enter the spinal cord, branch, and terminate in what general structure of the spinal cord?
Spinal Gray Matter
T/F: Peripheral distribution of afferent nerves delineats segmental pattern of dermatomes
True
The largest set of branches ascend cranially and form the posterior columns. What structure is found more medially in the posterior column and recieves afferent from the lower extremities?
What spinal cord levels is the structure/region found in?
Fasculus Gracilis
Everything below T6
The largest set of branches ascend cranially and form the posterior columns. What structure is found more laterally in the posterior column and receives afferents from the upper extremities?
What spinal cord levels is the structure/region found in?
Fasciculus Cuneatus
T6 to C1
Fibers within the posterior columns are organized topographically. Going from most medial to lateral, what spinal cord regions would be found.
Coccygeal > Sacral > Lumbar > Thoracic > Cervical
A lesion of the spinal cord in the Fasciulus Gracilis region would generally result in which of the following issues?
A. Ipsilateral loss of discriminitive, positional, and vibratory sensations of the upper extremity
B. Contralateral loss of discriminitive, postional, and vibratory sensation of the upper extremity
C. Ipsilateral loss of discriminitive, positional, and vibratory sensations of the lower extremity
D. Contralateral loss of discriminitive, positional, and vibratory sensation of the lower extremity
Ipsilateral loss of discriminitive, positional, and vibratory sensations of the lower extremity
NOTE: lesions of the primary, 2nd, or 3rd order neurons will not affect strength
Loss of muscle stretch (tendon) reflex is called sensory ataxia. How does this symptom result?
A. Spinal Cord Lesion
B. Damage to second order neurons
C. Damage to 3rd order neurons
D. All of the above
Spinal Cord Lesion
- damage to primary afferent neurons
T/F: A patient who is seen walking with a wide-based stance that places the feet to the floor with excessive force may be acting in an effort to compensate for missing proprioceptive input
True
1st order neurons synapse on second order neurons in what anatomical structure?
Primary neurons from the Fasciculus Gracilis synapse on 2nd order neurons in what nuclei?
Posterior Medulla
Nucleus Gracilis
NOTE: Likewise, Nucelus Cuneatus recieves input from the corresponding fasciculus cuneatus
Within their nuclei, 2nd order neurons send there axons to which of the following places in the medial leminiscal pathway after using what fiber to loop anteromedially in the medulla? What does the 2nd order neuon ascend as?
A. Ipsilateral medulla; internal arcuate fibers
B. Ipsilateral Thalmus; external arcuate fibers
C. Contralateral Thalamus; internal arcuate fibers
D. Contralateral Thalamus; external arcuate fibers
Contralateral Thalamus;internal arcuate fibers
Medial Lemnicus
As the medial lemincus rotates laterally in the pons on its way up to the thalamus, the upper extremity fibers now lie ______, while the lower extremity fibers now lie _______.
As the medial lemincus rotates laterally in the pons on its way up to the thalamus, the upper extremity fibers now lie medially, while the lower extremity fibers now lie laterally.
Where does the medial lemnicus terminate in the thalamus when carrying sensory information for the body?
Ventral Posterolateral Nucleus (VPL)
The thalmus is the “gate-keeper” of all sensory information EXCEPT for what sense?
Olfaction
What wedge-shaped cell group is located in the caudal thalamus and receives sensory input from the face via Trigeminal Pathway?
Ventral Posteromedial Nuclei (VPM)
The Ventral Posterior Nuclei (both medial and lateral) in the caudal thalamus are supplied by Thalamogeniculate branch that comes off what artery?
Posterior Cerebral A.
Third order neurons in the medial lemniscal pathway traverse the posterior limb of the internal capsule and travel to what two potential locations?
Primary Somatosensory Cortex (S1)
Secondary Somatosensory Cortex (S2)
The Primary Somatosensory Cortex (S1) comprises what two gyri?
Postcentral Gyrus
Posterior Paracentral Gyrus
Bordered anteriorly by the central sulcus, and posteriorly by the postcentral sulcus?
The Postcentral gyrus portion of the Primary Somatosensory Cortex (S1) is subdivided anterior to posteriorly into regions named 3a, 3b, 1, and 2. What is the name of this subdivided area?
Brodmanns Areas
Blood supply to the S1 cortical areas is provided by what two arteries?
Lesions to either of these two arteries produce what specific affects?
Middle Cerebral A. : tactile loss over the contralateral upper body and face
Anterior Cerebral A. : loss of tactile sensation over contralateral lower limg
The Secondary Somatosensory Cortex (S2) has a more integrative function for sensation. It relates to the inner face of the upper bank of the lateral sulcus, and gets inputs from the ipsilateral S1 cortex and VEntral Posterior Inferior Nucleus of the Thalamsu. This region is supplied by which of the following portions of Middle Cerebral A.?
A. M1
B. M2
C. M3
D. M4
M2
The Parietal Cortical regions also receives tactile input and a lesion in this association can produce adnosia in the contralateral region. What is agnosia?
The limb is not recognized as the patients own body, so while we get physical sensation, we don’t know what our limb is doing
The primary afferents of the Trigeminal Pathway largely come off the trigeminal divisions V1, V2, V3. These function to transmit not ony touch and proprioception of the face, but also pain, temperature and nondiscriminative touch. Additionally, primary afferents arise from what cranial nerves?
Include the ganglia they’re arising from
CN VII via Geniculate Ganglion
CN IX and CN X from the Superior Ganglion
What nucleus do primary affernts conveying proprioceptive information for masticatory muscles, extraocular muscles, and periodontal ligaments arise from?
Mesencephalic Nucleus
The Trigeminal Nuclei forms an elongated, continuous column that extends from the rostral midbrain to the spinomedullary junction. It’s comprised of 4 components that relate to different sensations. Which of the following relates to proprioceptive afferents from the TMJ, masticatory muscles and extraocular muscles?
A. Mesencephalic Nucleus
B. Chief Sensory Nucelus
C. Trigeminal Motor Nucleus
D. Spinal Nucleus
Mesencephalic Nucleus
The Trigeminal Nuclei forms an elongated, continuous column that extends from the rostral midbrain to the spinomedullary junction. It’s comprised of 4 components that relate to different sensations. Which of the following relates to discriminitive touch and pressure?
A. Mesencephalic Nucleus
B. Chief Sensory Nucelus
C. Trigeminal Motor Nucleus
D. Spinal Nucleus
Chief Sensory Nucelus
The Trigeminal Nuclei forms an elongated, continuous column that extends from the rostral midbrain to the spinomedullary junction. It’s comprised of 4 components that relate to different sensations. Which of the following relates to pain, temperature, and nondiscriminitive touch?
A. Mesencephalic Nucleus
B. Chief Sensory Nucelus
C. Trigeminal Motor Nucleus
D. Spinal Nucleus
Spinal Nucleus
What structures will each of the following nuclei related to the Trigeminal Nuclei be found in?
Mesencephalic nucleus:
Trigeminal Motor Nucleus:
Chief Sensory Nucleus:
Spinal Nucleus:
Mesencephalic nucleus: midbrain
Trigeminal Motor Nucleus: midpons
Chief Sensory Nucleus: midpons
Spinal Nucleus: obex (C2,C3)
In the Trigeminal Pathway there are two divisions of 2nd order neurons that relay discriminitive tactile and proprioceptive information to the VPM. The Dorsomedial divsion, and the Ventrolateral division.
Which on relates to the oral cavity?
Which one relates to V1. V2. V3?
Dorsomedial Division: Oral cavity
Ventrolateral Division: V1, V2, V3
Which of the following correctly explains the projection of the 2nd order neurons travelling the ventrolateral division of the trigeminal pathway?
A. Contralateral via posterior trigeminothalmic tract
B. Ipsilaterally via posterior trigeminothalmic tract
C. Contralaterally via anterior trigeminothalmic tract
D. Ipsilaterally via anterior trigeminothalmic tract
Contralaterally via anterior trigeminothalmic tract
Which of the following correctly explains the projection of the 2nd order neurons travelling the dorsomedial division of the trigeminal pathway?
A. Contralateral via posterior trigeminothalmic tract
B. Ipsilaterally via posterior trigeminothalmic tract
C. Contralaterally via anterior trigeminothalmic tract
D. Ipsilaterally via anterior trigeminothalmic tract
Ipsilaterally via posterior trigeminothalmic tract
In the trigeminal pathway, 3rd order neurons from the VPM from what structure to the primary somatosensory cortex?
Posterior Limb of Internal Capsule
What is the name of the nucleus comprised of pseudounipolar neurons that is the ONLY nucleus within the CNS?
Mesencephalic Nucleus
The Jaw-Jerk reflex is the stretching of the masseter when you tap on the chin that causes a bilateral contraction. Describe the neuronal arc of the jaw jerk reflex.
The afferent limb comes from the mesencaphalic trigeminal neuron that innervates the muscle spindles of the masseter.
The central process of the mesencephalic nucleus synpases on the efferent limb called the a trigeminal motor neuron
What deficits would you expect with a lesion on the longcircumferential branches of the basilar A. and branches of the Anterior Inferior Cerebellar A.?
A. Damage to Mesencephalic Nucleus and Tract
B. Damage to Mesencephalic Nucleus
C. Damage to Trigeminal Motor Nucleus
D. Damage to principal sensory nucleus
E. All but A .
All but A.
NOTE: Damage to the Superior Cerebellar A. would result in deficits related to the mesencephalic nucleus and tract
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