Lecture Notes on Nervous System and Body Cell Diversity

Introduction

• Cells in the body are diverse and specialized.
• Examples:
  • Parietal cells (digestive system): Produce stomach acid.
  • Mast cells (immune system): Contain histamine, critical for inflammatory response.
  • Skeletal muscle cells (muscular system): Cylindrical, multi-nucleated, essential for muscle contraction.
• Favorite cell: Neuron (nervous system).

Nervous System Overview

Central Nervous System (CNS)

• Consists of the brain and spinal cord.
• Processes information and acts as a command center.

Brain Regions

• Hindbrain: Includes medulla, pons, and cerebellum.
  • Medulla: Regulates breathing, blood pressure, heart rate.
  • Pons: Coordinates signals with the rest of the brain.
  • Cerebellum: Balance and movement coordination.
• Midbrain: Involved in alertness, sleep/wake cycle, motor activity.
• Forebrain: Includes cerebrum (divided into right and left hemispheres), thalamus, and hypothalamus.
  • Cerebrum: Responsible for speech, thinking, reasoning, sensing, emotions.
  • Thalamus: Involved in sensory and motor information.
  • Hypothalamus: Major control of the endocrine system.

Peripheral Nervous System (PNS)

• Consists of all other nervous system components (nerves throughout the body).
• Divided into:
  • Somatic Nervous System (SNS): Motor functions of skeletal muscle, voluntary actions, and somatic reflexes.
  • Autonomic Nervous System (ANS): Internal environment regulation (gastrointestinal, excretory, endocrine, smooth, and cardiac muscle), autonomic reflexes.
    • Further divided into:
      • Sympathetic system: Fight or flight response.
      • Parasympathetic system: Rest and digest.

Cells of the Nervous System

Neurons

• Main cell type in nervous tissue.
• General structure:
  • Cell body: Contains nucleus and most organelles.
  • Dendrites: Receive signals.
  • Axon: Carries signal away to another cell; communication junction is called a synapse.

Glial Cells (Glia)

• Supporting cells, essential roles beyond structural support.
• Functions:
  • Balance chemicals in the space between cells.
  • Maintain the blood-brain barrier.
  • Produce myelin (insulates axon, aids signal transfer).
  • Produce cerebrospinal fluid (protective, essential for homeostasis).
  • Important immune functions.

Action Potential

• Neurons communicate via action potentials.
• Resting potential: More negative charge inside neuron (~-70 mV).
• Action Potential Process:
  • Dendrite receives signal, generates action potential along axon.
  • Depolarization: Na+ ions flood inside the axon, charge becomes more positive.
  • Signal moves from one axon region to the next.
  • Axon regions restore back after signal passes.
  • Myelinated neurons: Action potential jumps from node to node.
  • Action potential is all-or-none: either occurs or doesn’t.
• Neurotransmitters: Released from synaptic vesicles, cross synaptic cleft, bind to specific receptors on the next neuron.

Summary

• Overview of CNS and PNS.
• Major brain regions and functions.
• PNS divisions: SNS and ANS (with sympathetic and parasympathetic systems).
• Major nervous system cell types: Neurons and glial cells.
• Action potential and neurotransmitter signaling.
• Importance of ongoing research in neurology.

Stay Curious!