Lecture Notes: The Nervous System

Overview

• The nervous system is key in maintaining a feedback cycle involving:
  • Sensory receptors
  • Input
  • Control center
  • Output
  • Effectors

Functions of the Nervous System

1. Sensory Function

   • Involves taking information from peripheral parts of the body to the central parts.
   • Conducted by sensory neurons, also known as afferent neurons.

2. Integrative Function

   • Occurs in the control center, which includes the brain or spinal cord.
   • Facilitated by interneurons (association neurons) found in gray matter, which lack a myelin sheath.

3. Motor Function

   • Sends information from the brain and spinal cord to peripheral areas.
   • Conducted by motor neurons, also known as efferent neurons.

Central vs. Peripheral Nervous System

• Central Nervous System (CNS)

  • Comprises the brain and spinal cord.

• Peripheral Nervous System (PNS)

  • Includes everything outside the CNS: cranial nerves, spinal nerves, ganglia, receptors.
  • Subdivided into cranial nerves (12 pairs), spinal nerves, and ganglia.

Subdivisions of the Peripheral Nervous System

1. Somatic Nervous System

   • Serves mainly skeletal muscles.
   • Somatic sensory neurons convey information from skeletal muscles to the CNS.
   • Somatic motor neurons convey information from CNS to skeletal muscles.
   • Associated with voluntary control.

2. Autonomic Nervous System

   • Innervates smooth muscle, cardiac muscle, and glands.
   • Associated with involuntary control.
   • Further divided into:
     • Sympathetic Division: "Fight or Flight" for high-energy situations.
     • Parasympathetic Division: "Rest and Digest" for conserving energy.

Key Terms & Concepts

• Afferent neurons: Carry information to the CNS.
• Efferent neurons: Carry information from the CNS.
• Gray Matter: Contains neurons without myelin sheath.
• Enteric Plexus: Network of nerves in the digestive tract.

Summary

• The nervous system is divided into the central and peripheral systems, each with distinct roles and subdivisions.
• Understanding the functions and pathways of the nervous system is crucial for comprehending how the body responds to internal and external stimuli.