Spinal Nerve videos

Question 1

What are the neural structure outside of brain?

Answer 1

• Sensory receptors
• Peripheral nerves and associated ganglia
• Motor endings

Question 2

What are dermatomes?

Answer 2

• Specific segment of skin supplied by single spinal nerve
• All spinal nerves except Cl
• Skin divided into segments into a dermatome map
• E.g., horizontal skin around umbilicus
• supplied by anterior ramus of T10

Question 3

What are the components of a typical spinal nerve?

Answer 3

Anterior root containing motor axons only; posterior root containing sensory axons only; smaller posterior ramus, larger anterior ramus

Question 4

Components of spinal roots

Answer 4

• Each spinal nerve connects to the spinal cord via two roots
  **Ventral roots **
• Contain motor (efferent) fibers from the ventral horn motor neurons
• Fibers innervate skeletal muscles)

Question 5

What is functon of dorsal root?

Answer 5

• Contain sensory (afferent) fibers from sensory neurons in the dorsal root ganglia
• Conduct impulses from peripheral receptors

Question 6

How do dorsal root and ventral root work together?

Answer 6

• Dorsal and ventral roots unite to form spinal nerves, which then emerge from the vertebral column via the intervertebral foramina

Question 7

What does each spinal nerve branch into?

Answer 7

• Dorsal ramus
• Larger ventral ramus
• Meningeal branch
  Rami communicantes (autonomic pathways) join to the ventral rami in the thoracic region

Question 8

What is purpose of ramus/rami?

Answer 8

• All ventral rami except T2-T12
  form interlacing nerve networks called plexuses (cervical, brachial, lumbar, and sacral)
• The back is innervated by dorsal rami via several branches
• Ventral rami of T2-T12 as intercostal nerves supply muscles of the ribs, anterolateral thorax, and abdominal wall

Question 9

What is cervial plexus?

Answer 9

• Formed by ventral rami of G-C
• Innervates skin and muscles of the neck, ear, back of head, and shoulders
  Phrenic nerve
• Major motor and sensory nerve of the diaphragm (receives fibers from C3-(5)

Question 10

Generally, what do the cervical plexuses innervate?

Answer 10

Anterior neck muscles; skin of the neck, portions of head and shoulders

Question 11

What is brachial plexus?

Answer 11

• Formed by ventral rami of C5-
  Cg and T1 (and often Cy and Tz)
• It gives rise to the nerves that innervate the upper limb
  Major branches of this plexus:
• Roots—five ventral rami
  (C5-T1)
• Trunks-upper, middle, and lower
• Divisions-anterior and posterior
• Cords-lateral, medial, and posterior

Question 12

Which nerve might you have damaged if you have difficulty extending your forearm, and have anesthesia along the posterior arm, forearm, and lateral 3 digits?

Answer 12

Radial nerve

Question 13

What is lumbar plexus ?

Answer 13

• Arises from L1-44
• Innervates the thigh,
  abdominal wall, and psoas
  quadriceps and skin of
  muscle
• Femoral nerve —innervates
  anterior thigh and medial
  surface of leg
• Obturator nerve —passes
  through obturator foramen
  to innervate adductor
  muscles

Question 14

Which nerve might you have damaged if you have difficulty extending your knee?

Answer 14

Femoral nerve

Question 15

What is sacral plexus?

Answer 15

• Arises from L4-54
• Serves the buttock, lower limb, pelvic structures, and perineum
• Sciatic nerve
• Longest and thickest nerve of the body
• Innervates the hamstring muscles, adductor magnus, and most muscles in the leg and foot
• Composed of two nerves: tibial and common fibular

Question 16

What anterior rami form the sacral nerve plexus, and what general areas of the body does it innervate?

Answer 16

L4-S4. It innervates the gluteal region, pelvis, perineum, posterior thigh, and almost all of leg and foot.