Anatomy · MU Sofia

PNS · 182. Spinal nerves - formation. Spinal ganglia. Reflex arch.

Covers how the 31 pairs of spinal nerves are grouped by region, from cervical to coccygeal, and how anterior and posterior roots join to form each nerve before dividing into rami. Describes the spinal ganglia, their structure and neuron types, and sorts them into sensory and autonomic groups. Explains the reflex arc through its five components, then contrasts monosynaptic stretch reflexes with polysynaptic flexion reflexes.

Inside: 5 sections · 5 labelled pictures · 10 flashcards · 5 min

Topic 166 of 264 in the MU Sofia syllabus for Anatomy (Dental Medicine, Year 2). The free AceMed note covers it in 5 sections, about 730 words (5 min of reading), with 10 flashcards.

In this note

  1. SPINAL NERVES
  2. Spinal Ganglia :
  3. Formation of spinal Nerves:
  4. 182 cont.
  5. Reflex Arch :

SPINAL NERVES

  • Spinal nerves emerge intermittently from the spinal cord, exiting the vertebral canal.
  • There are a total of 31 pairs of spinal nerves.
  • These pairs are categorized based on their locations:
  • Cervical nerves (C1–C8): These exit the neck region.
  • Thoracic nerves (T1–T12): They exit the torso region.
  • Lumbar nerves (L1–L5): These exit the lower back.
  • Sacral nerves (S1–S5): They exit from the base of the spine.
  • Coccygeal nerve pair: This exits from the tailbone (coccyx).

Spinal Ganglia :

  • Structure: Ganglia are oval in shape and contain neuronal cell bodies (somata), satellite cells (a type of glial cell), and a protective connective tissue layer.
  • Neuron Types:
  • Sensory ganglia usually contain unipolar or pseudo-unipolar neurons.
  • Autonomic ganglia contain multipolar neurons.

– Can be broadly categorized into 2 groups :

  1. 1. Sensory Ganglia:
  • Dorsal Root Ganglia: These are associated with spinal nerves. Each dorsal root ganglion is located at the proximal end of each posterior root. They contain the cell bodies of sensory nerve fibers 1 .
  • Sensory Ganglia of Cranial Nerves: These are found in selected cranial nerves.
  1. 2. Autonomic ganglia :
  • Sympathetic
  • Parasympathetic

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