Nerve Plexuses & Reflex Actions

Nerve Plexuses

• In the context of Nerve Plexuses & Reflex Actions, a nerve plexus is a complex network of intersecting nerves that redistributes fibers from multiple spinal nerves, enabling shared sensory and motor functions.
• The four major nerve plexuses are:

1.Cervical Plexus (C1-C4):

• Located in the neck, supplies muscles and skin of the neck and head.
• Includes the phrenic nerve, crucial for diaphragm function and breathing.

2. Brachial Plexus (C5-T1):

• Located in the shoulder; innervates the upper limbs (shoulder, arm, forearm, hand).
• Major nerves: median, ulnar, radial, axillary, and musculocutaneous

3. Lumbar Plexus (L1-L4):

• Located in the lower back; supplies the lower abdomen, groin, and anterior thigh.
• Major nerves: femoral and obturator

4. Sacral Plexus (L4-S4):

• Located in the pelvis; innervates the buttocks, posterior thigh, leg, and foot.
• Major nerve: sciatic nerve, the largest in the body.

Reflex Actions

• A reflex action is a fast, involuntary response to stimuli that bypasses the brain and follows a reflex arc. It involves:
  1. Receptor: Detects stimulus (pain, pressure, etc.).
  2. Sensory Neuron: Carries the signal to the spinal cord.
  3. Integration Center: Processes information in the spinal cord.
  4. Motor Neuron: Sends the response to the effector.
  5. Effector: Carries out the response (muscle contraction or gland secretion).

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