Nervous System Overview

Introduction

• Multicellular organisms like humans require communication between body parts to coordinate behavior and respond to the environment.
• Two main organ systems for communication:
  • Nervous System
  • Endocrine System (covered separately)

Structure of a Neuron

• Neurons (nerve cells) carry electrical impulses.
• Characteristics:
  • Long and thin
  • Branch connections at each end
• Function like biological wires carrying a small current.
• Communication between neurons occurs at synapses:
  • Electrical impulse triggers release of chemicals.
  • Chemicals diffuse across synapse to trigger new impulse in next neuron.

Nervous System Composition

• 100 billion neurons make up the nervous system.
• Central Nervous System (CNS):
  • Composed of the brain and spinal cord.
  • Processes sensory information and sends responses.
• Sensory Neurons:
  • Carry information from receptors throughout the body to CNS.
  • Information includes temperature changes, carbon dioxide levels, etc.
• Motor Neurons:
  • Transmit impulses from CNS to effectors (muscles or glands).
  • Effectors act by contracting or releasing hormones.

Reflex Arc

• Reflex arc underlies unconscious reflexes (e.g., pulling hand away from hot object).
• Benefits: Rapid and automatic response to prevent injury.
• Example process:
  • Stimulus: Sharp object detected by receptor cells in skin.
  • Sensory Neuron: Carries impulse to spinal cord.
  • Relay Neuron: Transfers impulse within spinal cord.
  • Motor Neuron: Sends impulse to effector (e.g., muscle contraction to move hand away).
• Synapses present between neurons convert electrical signals to chemical signals.

Additional Resources

• Cognito.org offers videos, questions, flashcards, exam-style questions, and tracking of study progress.
• Accessible on Cognito's website and YouTube channel.