1. Regarding a spinal nerve, all ventral rami (except T2 - T12) ________ and the

Question

1. Regarding a spinal nerve, all ventral rami (except T2 - T12) ________ and the dorsal rami _________.

a. form plexuses; innervate the back muscles + skin form the intercostal nerves;

b. form plexuses form plexuses;

c. form the intercostal nerves innervate the organs;

d. form plexuses

2. Which spinal tract carries sensory information from receptors for pain, temperature, itch, and tickle, to the thalamus?

a. direct motor pathways

b. spinothalamic tract

c. indirect motor pathways

d. posterior column

3. Which type of reflex enables you to balance on the left leg if the right leg is flexing in response to a stimulus?

a. flexor reflex

b. crossed extensor reflex

c. stretch reflex

d.tendon reflex

4. Which major nerves arise from the lumbar and sacral plexuses, respectively?

a. axillary nerve; gluteal nerve

b. femoral nerve; sciatic nerve

c.phrenic nerve; radial nerve

d. obturator nerve; femoral nerve

Explanation / Answer

1. Answer: Option a. form plexuses; innervate the back muscles + skin form the intercostal nerves;

Explanation: All ventral rami except T2-T12 form interwoven nerve networks called nerve plexus viz., cerebral, brachial, lumbar, and sacral. Ventral rami of T2-T12 supply muscles of ribs, anterolateral thorax and abdominal wall as intercostal nerves.

Hence the first blank is filled with form plexus. Dorsal rami innervate the muscles and blood vessels of the back (dorsal surface of the trunk). So, the second blank is filled with innervate the back muscles + skin form the intercostal nerves

2. Answer: Option b. spinothalamic tract.

Explanation: Spinothalamic tract is one of the smaller tracts which is present on the anterolateral system. It carries signals for pain, pressure, temperature, light touch, tickle, itch.

3. Answer: Option b. crossed extensor reflex

Explanation: Crossed extensor reflex is a withdrawl reflex on one side accompanied by inhibitory pathways to maintain balance and coordination. For example, balancing on left leg if right leg is withdrawn.

Hence, the answer is option b

4. Answer: Option b. Femoral and Sciatic Nerve

Explanation: Lumbar plexus consists of anterior or ventral rami from L1-L4 and supplies to the skin and muscles of the abdominal wall, external genitalia, part of the lower limbs. The major nerves of lumbar plexus are femoral and obtuator nerves.

Sacral plexus consists of anterior or ventral rami from L4-S4. It supplies the butt_ocks , perineum and most of the lower limbs. The major nerves of the sacral plexus are Pudendal and Sciatic nerve.

Hence the correct answer is option b. Option d is wrong as it is written in reverse order. While remaining options are not correct as the nerves are not the major nerves arising from lumbar and sacral plexus.

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