Sensory Pathways To CNS

Question 1

The ventrobasal complex (nuclei) of the thalamus.

consists of…

Answer 1

• Ventral posterolateral nucleus receiving medial lemniscal fibers
• Ventral posteromedial nucleus receiving fibers fron trigeminal nuclei and
• Posterior thalamic nuclei receicing fibers from the anterolateral system

Question 2

Sensory signals from all modalities of sensation terminate in

Answer 2

the cerebral cortex posterior to the central fissure

Question 3

Projections from somatosensory area I are required for function of somatosensory area II. However, removal of parts of somatosensory area II has no apparent effect on the response of neurons in somatosensory area I. True or false?

Answer 3

True

Question 4

Functions of SSA 1 (Brodmann 3, 1, 2)

Answer 4

• Localize discretely the different sensations from the body parts
• Judge critical degrees of pressure against the body
• Judge the weight of objects
• Judge shapes of forms of object (inability: astereognosis)
• Judge texture of materials

Question 5

At what layer does the input sensory signals first enter the cortex? What happens here?

Answer 5

Layer IV. Here, the columns of neurons function almost entirely separately from one another.

Question 6

Brodmann’s area of SS association cortex

Answer 6

Brodmann’s areas 5 and 7 of the cerebral cortex, located in the parietal cortex behindsomatosensory area

Question 7

Importance of SS association

Answer 7

Deciphering deeper meanings of the sensory information in the somatosen­sory areas.

Question 8

How does the SS A decipher deeper sensory meanings?

Answer 8

It combines information arriving from multiple points in the primary somatosensory area to decipher its meaning.

Question 9

The SS A received signals from:

Answer 9

(1) somatosensory area I
[2) the ventrobasal nuclei of the thalamus
(3) other areas of the thalamus, (4) the visual cortex and the auditory cortex.

Question 10

Causes of visceral pain

Answer 10

• Ischemia of visceral tissue
• Spasm of the smooth muscle in a hollow viscus
• Distension of a hollow viscuss
• Stretching of the ligaments
• Transmitted in C-fibres

Question 11

Role of the thalamus in somatic sensation

Answer 11

• Helps to relay tactile information to the cortex
• Play a major role along with brainstem in discrimination of pain and temperature
• Receives regulatory corticofugal fibers (majorly inhibitory) from the cortex

Question 12

Role of the cortex in somatic sensation

Answer 12

Interpretation of the quality of pain

Question 13

Thalamic syndrome is caused by

Answer 13

Blockage of posterior cerebral that supplies posteroventral portion of the thalamus by thrombosis.

Question 14

Thalamus syndrome symptoms

Answer 14

• Loss of pain sensation from the opposite side of the body
• Ataxia: inability to control body mvmts precisely
• The threshold for sensory perception becomes higher after some weeks
• Perception of many affective sensations of extreme unpleasantness or pleasant

Question 15

Temperatures below the normal cold of the body and above the normal hot are detected by…

Answer 15

Nociceptors

Question 16

Thermal signals are transmitted in

Answer 16

the ALPW

Question 17

Transmission of thermal sensation

Answer 17

• ALPW
• The signals travel in the Tract of Lissauer and then terminate in laminae I, II & III
• The fibers also cross to the opposite side then ascend in the ALPW
  -The fibers terminate
  •The reticular areas of the brainstem
  •The VBC of the thalamus
  •Some to the SSA (Area 1)