Sensory Cortex & Dorsal Column Sensations Flashcards
S-II recieves fibers from …..
Both sides of the body
Mention areas where SII axons are sent
Association cortex, motor cortex, insula, amygdala, hippocampus
Describe SII lesion
Deficits in learning by object manipulation & recognizing texture & size of hand-held objects
Functions of posterior parietal area
Recieves signals from:
1. SI & II
2. Visual & auditory cortices
3. Sensory nuclei & other areas in thalamus
Name sensory association areas lesion
Astereognosis
Thalamus is formed of …groups of nuclei, which are …..
5
A, P, L, M, V
Non specific nuclei of thalamus recieve input from ….& project to whole cortex
Reticular formation
Mention functions of thalamus
- Highest center for crude sensations
- Relay for fine, auditory, visual sensations & motor fibers from basal ganglia & cerebellum
- Connected to RAS has role in consciousness
- Connected to prefrontal cortex, thus personality
- Connected to limbic system thus emotions
- Responsible for alpha waves of EEG
Mention origin of pyramidal tract
Mainly motor area 4 & premotor area 6 but also fibers from area 3,1,2 and parietal cortex A5
GR; Fibers from the sensory cortex descend to terminate on the contralateral dorsal horn of spinal cord
For modulation of sensations
Describe course of pyramidal tract in brain
Converge in corona radiata then pass in ant 2/3 of post limb of internal capsule
Describe course of pyramidal tract in brain stem
Pass in middle 3/5 of crus cerebri (basis pedunculi of midbrain) then
As scattered bundles in the basis pontis separated by transverse pontine fibers
Fibers collect to form pyramid of medulla oblongata
80% of fibers cross at the lowermost part of medulla
Describe course of pyramidal tract in spinal cord
Crossed fibers continue in spinal cord as lateral corticospinal tract while uncrossed fibers continue as ant corticospinal tract
Describe lamination in internal capsule & spinal cord(midbrain) of pyramidal tract
C, genu-face, UL most ant & LL most post in post limb of internal capsule
SC, cervical is med, sacral is lat
Crossed fibers of PT end on …. While uncrossed fiber end on …..
Lateral group of AHC (limbs)
Medial group (trunk)
Mention importance of ipsilateral corticospinal tract
Help recovery in case of upper motor neuron lesion
The part of pyramidal tract concerned with facial muscles is …..
Corticonuclear/corticobulbar tract
Uncrossed fibers & ipsilateral corticospinal tract supply …….
Abdominal & respiratory muscles
All parts of the corticobulbar tract pass both ipsilaterally & contralaterally except the following:
- The part of motor nucleus of facial nerve supplying lower part of face
- Part of nucleus of hypoglossal nerve supplying genioglossus
There recieve ONLY contralateral fibers
Compare roles of pyramidal & extrapyramidal tracts
P, skilled voluntary movements in distal parts of limbs
EP, adjusting muscle tone, posture & semiautomatic movements such as swinging arms during walking
Compare tecto-spinal & rubrospinal tracts with respect, origin, crossing & end
TS, originate in superior colliculus at upper level of midbrain, cross at dorsal tegmental decussation and end at medial group of cervical AHCs to neck muscles
RS, originate in red nucleus in upper level of midbrain & cross at ventral tegmental decussation end at lat group of cervical AHCs (UL)
Compare med & lat vestibulo sp. tracts with respect, site & end
Med ,Ant column down to T3
Lat , Ant column in whole cord
Alpha & gamma neurons of extensor muscles
Compare med & lat reticulospinal tracts with respect, origin, end
M, Pontine RF
L, medullary RF
End at gamma motor neurons of Lamina XI
In somatosensory area, most ant columnar resposnsible for ….., posterior parts for…., more post for …., while most post …..
Muscle, tendon, joint stretch receptors
Slowly adapting cutaneous receptors
Deep pressure
Respond if stimulus moves across the skin
The sizes of the body parts representations in somatosensory cortex is proportional to …..
Number of specialized receptors
Compare adaptation of vibration & deep pressure
Vib: rapid
D.P.:slow
Mention receptors of vibration & their ranges of frequency
Pacinain corpuscle: 30-800 cycle/sec
Meissner’s corpuscle: 2-80 cycle/sec
The type of receptor which functions in sense of movement but not position is ….
Pacinian corpuscle
Adaptation of tactile receptors is …..while of proproceptive ones is …..
Rapid
Slow (tonic)
Define sense of position & movement
P: ability of body to detect the position of different body parts relative to each other & space
M, ability of body to detect direction & rate of movement of different body oarts relative to each other & space.
Compared to areas with high threshold distance, areas with low threshold distance are characterized by:
- Large number of receptors
- Large number of afferents
- Less convergence
- Higher sensory acuity
- Large representative area in S. Cortex
- Small receptive field
Define threshold distance
The minimal distance between two points felt as 2 separate points
Mention the test for tactile discrimination & localization
D, Two marker test
L, Weber compass test
Mention the name of receptors & afferent fibers of tactile discrimination & localization
Meissner’s, Merckel’s,Ruffini end organ & Pacinian corpuscle
Abeta fibera
Describe lesion of S-I
- Inability to localize the different sensations in the different parts of the body but it can be crudely localized by thalamus
- Inability to judge critical degrees of pressure
- Inability to judge the weight of objects
- Pain & temp are poorly affected by their localization is affected
