BROWN SEQUARD SYNDROME

Q. A 23-year-old man is stabbed in the neck. Once stabilized, his MRI shows a right hemisection of the cord at C6. What is the expected result of this injury?
A. Paralysed diaphragm
B. Absent sensation to temperature in the left hand
C. Paralysis of the left hand
D. Absent sensation to light touch in the left hand
E. Brisk right biceps reflex

Ans: B

Hemisection of the cord is also known as Brown–Séquard syndome. This results in ipsilateral paralysis and loss of light touch and vibration sensation and contralateral loss in pain and temperature below the point of the lesion. The spinothalamic tracts cross at the level of the cord, so sensation to pain and temperature is lost in the contralateral limbs . C3, 4, 5 keep the diaphragm alive (A), so breathing should be preserved. As the right corticospinal tract has been severed, the right, ipsilateral hand would be paralysed as well as the right leg. The left dorsal columns carry light touch fibres from the left limb . They have been unaffected by the injury. C6 is responsible for the biceps reflex and would be lost . Reflexes distal to the lesion would be brisk.







source: Greys anatomy.

CELL MEMBRANE

Q. Several segments of the polypeptide chain of integral membrane proteins usually span the lipid bilayer. These segments frequently
A) Adopt an α-helical configurati on
B) Contain many hydrophilic amino acids
C) Form covalent bonds with cholesterol
D) Contain unusually strong pepti de bonds

ans: A

Membrane-spanning segments of integral proteins frequently adopt an α -helical
conforma on because this structure maximizes the opportuni es for the polar pep de
bonds to form hydrogen bonds with one another in the hydrophobic interior of the lipid
bilayer. These segments are composed largely of amino acids with nonpolar hydrophobic side
chains that interact with the surrounding lipids. There are no covalent bonds with cholesterol or phospholipids, and the pepti de bonds are not unusually strong.



Exp. Adopt an α-helical configura on Ref: Ganong - Review of Medical Physiology 23rd
Ed Page 8,9