Nervous System Lecture Notes

Introduction

• Nervous system is complex, often challenging for students.
• Importance of understanding the system for exams as it carries significant weight.

Key Terms

• Sensory: Conveying impulses to the central nervous system.
• Integration: Interpretation of messages received at the central nervous system.
• Motor Output: Sending interpreted messages to muscles and glands.

Nerve Cells

• Types of Cells:
  • Neurons: Functional nerve cells responsible for producing and sending impulses.
  • Neuroglial Cells: Supportive cells, six types (e.g., Schwann cells, astrocytes).
• Neuron Structure:
  • Cell body (Soma/Pericarion): Contains organelles.
  • Dendrites: Slender processes that receive messages.
  • Axon: Single process that transmits messages away.
  • Myelin Sheath: Insulates axons, speeds up impulse transmission.

Nervous System Functions

• Sensory: Stimulate receptors, send messages to CNS.
• Integration: Interpretation of sensory information by interneurons.
• Motor: Messages sent to effectors (muscles, glands).

Central and Peripheral Nervous Systems

• Central Nervous System (CNS): Brain and spinal cord.
• Peripheral Nervous System (PNS): Nerves extending from CNS.

Neuron Classification

• By Structure:
  • Multipolar: Majority of neurons, found in CNS.
  • Bipolar: Special sense organs.
  • Unipolar: Sensory neurons.
• By Function:
  • Sensory (Afferent): Carry impulses to CNS.
  • Interneurons: Connect sensory and motor neurons.
  • Motor (Efferent): Carry impulses away to effectors.

Neuroglial Cells

• CNS:
  • Astrocytes: Most abundant, form blood-brain barrier.
  • Oligodendrocytes: Form myelin in CNS axons.
  • Microglial Cells: Act like immune cells.
  • Ependymal Cells: Line brain ventricles, aid CSF movement.
• PNS:
  • Schwann Cells: Form myelin in PNS axons.
  • Satellite Cells: Protect neuron cell bodies.

Action Potential

• Polarized State: Resting potential (-70 mV).
• Threshold: Minimum change needed (-55 mV) to trigger action potential.
• Depolarization: Sodium ions enter, creating action potential.
• Repolarization: Potassium ions exit, returning to resting state.
• Sodium-Potassium Pump: Restores original ion distribution.

All or None Response

• A stimulus must reach threshold to generate a response.

Refractory Period

• Absolute: No response regardless of stimulus strength.
• Relative: Possible response with strong enough stimulus.

Saltatory Conduction

• Impulse jumps between nodes of Ranvier, increasing speed.

Synapse

• Definition: Connection between two neurons.
• Components:
  • Presynaptic Membrane: Releases neurotransmitters.
  • Postsynaptic Membrane: Contains receptors for neurotransmitters.
• Importance: Proper function critical for impulse transmission.

Diseases Related to Synapse Malfunction

• ALS: Affects motor neuron communication.
• Myasthenia Gravis: Autoimmune disorder affecting receptor sites.

These notes provide a comprehensive overview of the nervous system as discussed in the lecture, focusing on main functions, structure, processes, and associated disorders.