Nervous System and Reflex Actions

Overview

• Objective: Understand the structure and functions of the nervous system, including the reflex arc.
• Key Concepts:
  • Relationship between structure and function of the nervous system.
  • Structure of the reflex arc.
  • Importance of reflex actions.

Homeostasis

• Definition: The body's ability to maintain internal conditions as constant as possible.
• Control Systems:
  • Stimulus
  • Receptor
  • Coordination Center
  • Effector
  • Response

Nervous System

• Components:
  • Central Nervous System (CNS): Includes the brain and spinal cord.
  • Peripheral System: Nerves that run to and from the CNS.
• Function:
  • Enables reaction to surroundings.
  • Coordinates behavior.

Neurons (Nerve Cells)

• Role in Nervous System:
  • Receptors detect stimulus and send electrical impulses via neurons to the CNS.
  • CNS coordinates sending of impulses to effectors.
• Types of Neurons:
  • Sensory Neurons: Connected to receptors; send signals to CNS.
  • Relay Neurons: Transmit impulses within CNS.
  • Motor Neurons: Send signals from CNS to effectors.

Reflex Arc

• Process:
  • Stimulus Detection: Detected by receptors (e.g., skin receptors detecting heat).
  • Impulse Transmission:
    • From receptor via sensory neuron to CNS.
    • Across synapses through chemical diffusion triggering relay neuron.
    • From relay neuron to motor neuron via synapses.
  • Response Activation:
    • Motor neuron triggers effector (muscle/gland) to respond.
    • Example: Muscle contraction to pull hand away from heat.
• Characteristics:
  • Reflexes are automatic and rapid.
  • No decision-making by the conscious brain.
  • Protects from danger by being quick.

Importance of Reflex Actions

• Provide rapid responses to potentially harmful stimuli.
• Protect the body by enabling quick reactions without conscious thought.

Study Resources

• Additional questions and exercises can be found in the vision workbook for further practice on the nervous system and reflex arc.

Note: This lecture emphasizes understanding the connection between the structure and function of the nervous system and the reflex arc's role in rapid, protective responses.