Nervous System Notes

Introduction

• Nervous system: the body's ultimate control center.
• Oversees communication among all other systems.
• Works with the endocrine system (covered in Concept 3).

Basic Functionality

• Takes sensory input via sensory receptors.
• Integrates stimuli (processes input and decides responses).
• Triggers motor output to effector organs.
• Example: Seeing a red light -> visual stimulus -> process -> motor output (hit brake).

Structure

• Composed of nervous tissue: neurons and neuroglia.

• Neurons (Nerve Cells):

  • Excitable cells that conduct impulses to transmit signals.
  • Only 10% of nervous tissue.
  • Parts:
    • Soma (cell body): Contains nucleus and organelles.
    • Dendrites: Receptors for signals (input region).
    • Axon: Generates and transmits nerve impulses (conducting region).
    • Axon Terminal: Releases neurotransmitters in synapses (secretory region).
    • Myelin Sheath: Insulates axons, increases impulse speed.
  • Types: Multipolar, Bipolar, Unipolar.

• Neuroglia (Glial Cells):

  • Supportive cells, 90% of nervous tissue.
  • Provide nutrition, insulation, and assist signal transmission.

Neuron Classifications

• Structural:
  • Multipolar: >3 processes, majority of neurons.
  • Bipolar: 2 processes, rare.
  • Unipolar: 1 process, sensory neurons.
• Functional:
  • Sensory (afferent): Transmit info to CNS.
  • Motor (efferent): Transmit info from CNS to body.
  • Interneurons: Transmit info between sensory and motor neurons.

Central Nervous System (CNS)

• Components: Brain and Spinal Cord.
• Protection: Skull, meninges, cerebrospinal fluid.
• Brain Divisions:
  • Cerebrum: Largest part, divided into hemispheres and lobes.
  • Cerebellum: Under cerebrum, posture and balance.
  • Brain Stem: Base of cerebrum, controls automatic functions.

Peripheral Nervous System (PNS)

• Divisions:
  • Sensory (afferent): Carries info to CNS.
  • Motor (efferent): Carries info from CNS.
    • Somatic: Voluntary control, skeletal muscles.
    • Autonomic: Involuntary control, cardiac/smooth muscles and glands.
      • Sympathetic: Fight-or-flight.
      • Parasympathetic: Rest and digest.

Reflexes

• Automatic response to stimuli.
• Reflex Arc Components:
  • Receptor
  • Sensory Neuron
  • Integration Center
  • Motor Neuron
  • Effector

Sensory Receptors

• Types:
  • Mechanoreceptors: Mechanical force.
  • Thermoreceptors: Change in temperature.
  • Photoreceptors: Light stimuli.
  • Chemoreceptors: Chemicals (taste, smell).
  • Nociceptors: Pain.

Honors Class Extension

• Cranial Nerves:
  • 12 pairs, classified as sensory, motor, or both.
  • Examples: Olfactory (sensory), Optic (sensory), Facial (both).

This concludes the key points for Concept 1 of the nervous system. The next concepts will cover more on the senses and the endocrine system.