Anatomy and Physiology Lecture Notes

Introduction

• Presenter: Professor Long
• Course: Human Anatomy and Physiology 1
• Institution: Del Mar College
• Mode: Online due to coronavirus shutdown
• Content: Nerve plexuses, reflexes
• Intended Audience: Students in nursing, OTA, PTA

Nerve Plexuses

Definition

• Plexus: A network of nerves that innervate a specific region of the body.

Types of Plexuses

1. Cervical Plexus:

   • Innervates neck muscles
   • Contains the phrenic nerve, which innervates the diaphragm (C3, C4, C5 nerves)
   • Mnemonic: "C3, 4, 5 keep the diaphragm alive"

2. Brachial Plexus:

   • Innervates the shoulder girdle and upper arm
   • Radial Nerve: Innervates extensor muscles of the wrist (thumb side)
   • Ulnar Nerve: Innervates flexor muscles (pinky side)
   • Mnemonic: "ERFU" (Extensor Radial, Flexor Ulnar)

3. Lumbar Plexus:

   • Innervates the thigh region
   • Major nerve: Femoral nerve

4. Sacral Plexus:

   • Innervates the lower leg (calf, shin)
   • Sciatic Nerve: Related to issues like sciatica
   • Pudendal Nerve: Controls anal and urethral sphincters

Reflexes

Definition

• Reflex: An automatic motor response designed to preserve homeostasis.

Reflex Arc Steps

1. Detection of stimulus at sensory receptor
2. Activation of sensory neuron
3. Information processing at the CNS
4. Activation of motor neuron
5. Response at effector

Types of Reflexes

• Innate Reflexes: Inborn, e.g., blinking, suckling
• Acquired Reflexes: Learned through experience, e.g., walking
• Cranial Reflexes: Involve cranial nerves
• Spinal Reflexes: Involve spinal nerves
• Somatic Reflexes: Involve skeletal muscle
• Visceral Reflexes: Involve smooth and cardiac muscle

Synapses and Lateral Reflexes

1. Monosynaptic Reflexes:

   • Single synapse (e.g., stretch reflex)
   • Ipsilateral: Response on the same side as stimulus

2. Polysynaptic Reflexes:

   • Multiple synapses
   • Contralateral: Response on the opposite side

Specific Reflexes

1. Withdrawal Reflex (Flexor Reflex):

   • Polysynaptic and ipsilateral
   • Excites flexor muscles, inhibits extensor muscles

2. Crossed Extensor Reflex:

   • Polysynaptic and contralateral
   • Excites extensors on opposite side to maintain balance when withdrawing

Summary

• Reviewed nerve plexuses and their functions
• Detailed explanations of reflexes and their pathways
• Important for students in healthcare fields to understand these concepts

Next Steps:

• Review notes and worksheets
• Prepare for quizzes scheduled around the end of the month

Note: Lecture conducted under constraints due to pandemic, video quality may vary.