Bio32 - Introduction to the Nervous System

Overview of the Nervous System

• Role: Regulates physiological and psychological actions.
• Fast-acting control system: Controls both nervous and endocrine systems (slow-acting).
• Functions:
  • Sensory Input: Reception of stimuli (visual, taste, hearing, touch)
  • Integration: Processing of sensory input by brain and spinal cord.
  • Motor Output: Activation of effectors (muscles or glands) to respond.

Structural and Functional Classifications

• Central Nervous System (CNS): Brain and spinal cord
• Peripheral Nervous System (PNS): Everything outside the CNS
• Functional Divisions:
  • Sensory (Afferent) Division: Sends information to CNS.
  • Motor (Efferent) Division: Sends information from CNS to effectors.
  • Somatic Nervous System: Controls voluntary actions (skeletal muscles).
  • Autonomic Nervous System (ANS): Controls involuntary actions (smooth muscle, cardiac muscle, glands).
    • Sympathetic Division: Fight-or-flight-or-freeze response.
    • Parasympathetic Division: Rest-and-digest response.

Nervous Tissue

• Cell Types:
  • Neurons: Carry electrical signals (action potentials), amitotic (do not divide).
  • Neuroglial Cells: Support neurons, capable of mitosis.
    • CNS Glial Cells: Astrocytes, Microglial Cells, Ependymal Cells, Oligodendrocytes.
    • PNS Glial Cells: Satellite Cells, Schwann Cells.

Neuron Anatomy

• Cell Body (Soma): Contains nucleus and organelles, metabolic center.
• Dendrites: Receive signals, conduct impulses to cell body.
• Axon: Transmits impulses away from cell body, covered in myelin sheath for faster signal transmission.
• Myelin Sheath: Insulates axons, increases speed of signal transmission.
• Nodes of Ranvier: Gaps in myelin sheath, facilitate quick signal transmission.

Neuron Classification

• Structural: Multipolar, Bipolar, Unipolar.
• Functional: Sensory (afferent), Motor (efferent), Interneurons.

Synapses

• Types: Neuron-neuron, neuromuscular.
• Chemical Synapses: Involve neurotransmitters (e.g., norepinephrine).
• Neurotransmitter Regulation: Reuptake, degradation, diffusion.
• Excitatory/Inhibitory Postsynaptic Potentials (EPSP/IPSP).

Clinical Insights

• Multiple Sclerosis (MS): Demyelination leads to slow impulse travel, progressive.
• Role of Neurotransmitters: Influence mood, energy levels, regulated by reuptake inhibitors like MAOIs.

Key Terms and Concepts

• Cell Body Location: Nuclei (CNS), Ganglia (PNS).
• Nerve Fibers: Tracts (CNS), Nerves (PNS).
• White Matter: Myelinated, Gray Matter: Unmyelinated.

This lecture provides a foundational understanding of the nervous system, critical for further exploration of its structure and function in future classes.