Chapter 7, Part 1: Nervous System Overview

Overview

• Primary Control System: Nervous system is a primary control system providing mental function, emotional expression, and maintaining homeostasis.
• Regulation: Regulates muscle and gland activities.
• Function: Uses electrical and chemical signals for communication.

Key Functions

• Influences all body systems.
• Critical for immediate responses and survival.

Components of the Nervous System

• Sensory Input: Monitors changes called stimuli from inside/outside the body.
• Integration: Processes sensory input and decides on action.
• Motor Output: Activates muscles or glands as a response.

Divisions of the Nervous System

• Central Nervous System (CNS)
  • Composed of brain and spinal cord.
  • Acts as command center.
• Peripheral Nervous System (PNS)
  • Includes cranial and spinal nerves.
  • Links body parts by carrying impulses to and from CNS.

Functional Classification

• Sensory (Afferent): Carries information to CNS.
• Motor (Efferent): Carries information from CNS to muscles and glands.
  • Somatic: Controls skeletal muscles.
  • Autonomic: Controls cardiac/smooth muscles and glands.
    • Sympathetic: Prepares body for intense activities.
    • Parasympathetic: Conserves energy during rest.

Nervous Tissue and Supporting Cells

• Neuroglia: Support, insulate, protect neurons.
  • CNS Cells: Astrocytes, microglia, ependymal cells, oligodendrocytes.
  • PNS Cells: Schwann cells, satellite cells.

Neurons

• Structure: Cell body, dendrites, axons.
• Function: Transmit nerve impulses.
• Types:
  • Multipolar: Multiple extensions, common in CNS.
  • Bipolar: One axon and one dendrite, rare.
  • Unipolar: Single process, found in sensory neurons.

Action Potentials

• Resting Membrane Potential: Balance of sodium (outside) and potassium (inside) ions.
• Steps:
  1. Stimulus: Voltage-dependent channels open.
  2. Depolarization: Sodium enters, inside becomes more positive.
  3. Repolarization: Potassium exits, restores negative charge.
  4. Return to Resting Potential: Sodium-potassium pump re-establishes ionic balance.

Reflexes

• Definition: Rapid, predictable, involuntary responses.
• Types:
  • Somatic Reflexes: Affect skeletal muscles.
  • Autonomic Reflexes: Affect smooth muscles, heart, glands.
• Reflex Arc Components:
  1. Sensory receptor
  2. Sensory neuron
  3. Integration center
  4. Motor neuron
  5. Effector organ

Summary

• The nervous system is essential for controlling and coordinating various body functions.
• Structural and functional classifications help understand its complex operations.