MD137 Introduction to Electrophysiology

Introduction to Electrophysiology

• The lecture covers the structure and function of cells in the nervous system.
• The course is MD137, Introduction to Physiology, at the University of Galway.
• The lecturer is Leo Quinlan.

Learning Outcomes

• Understand the basic organization of the nervous system.
• Identify the cells of the nervous system and their function(s).
• Describe the structure-function relationships within a neuron.
• Detail the functions of the three main parts of a neuron.

Functional Organisation of the Nervous System

• Sensory: Gathers information about changes inside and outside the body (e.g., light, oxygen levels, body temperature). Signals are sent to the Central Nervous System (CNS).
• Integrative: Processes the sensory information; interprets, creates sensations, thoughts, memories, and makes decisions.
• Motor: Sends signals to muscles or glands to elicit a response.

Central Nervous System (CNS)

• The CNS is comprised of the brain and spinal cord.
• Regenerative capacity is limited if damaged.

Peripheral Nervous System (PNS)

• Made up of nerves connecting the CNS to the rest of the body
• The PNS has some capacity for regeneration.
• Components of the PNS are divided into 2 parts:
  • Autonomic nervous system
  • Somatic nervous system

Autonomic Nervous System

• Divided into two branches:
  • Parasympathetic: "rest and digest"
    • Decreases heart rate, bronchiole dilation, blood glucose, blood to skeletal muscle
    • Increases digestion, pupillary size, urinary output.
  • Sympathetic: "fight or flight"
    • Decreases digestion, pupillary size, urinary output
    • Increases heart rate, bronchiole dilation, blood glucose, blood to skeletal muscle

Somatic Nerves

• All nerves outside the autonomic nervous system, outside the CNS
• Two-way communication
• Connect the CNS to the peripheral end organs (skin and muscles)
• Connect the peripheral end organs (skin and muscles) to the CNS

Cells of the Nervous System

• Wide array of cell types
• Billions of interconnections
• Neurons are cable-like bundles of axons.
• Neuroglial cells provide support, insulation (myelin), and nutrients for neurons

Neurons

• Base unit of the nervous system
• Simple function to decide whether to transmit a signal.
• Billions of neurons (estimated 100 billion)
• Complex interconnections
• Create systems/circuits able to function independently (parallel processing)
• "Simple decisions" passed to "higher" levels for additional processing
• Very expensive, using approximately 20% of the body's energy in spite of representing only 2% of body mass.

Types of Neurons - Function

• Sensory neurons: Carry messages to the brain.
• Motor neurons: Carry messages to muscles.
• Interneurons (e.g., pyramidal): Connect other neurons.
• Can be excitatory or inhibitory depending on the neurotransmitter they release.

Types of Neurons - Anatomy

• Classified based on axonal outgrowths.
  • Unipolar: One stalk that splits into two branches
  • Bipolar: One axon, one dendritic tree
  • Multipolar: One axon, many dendritic branches

Networks of Neurons - Neural Circuit

• Networks of neurons are interconnected.

Networks of Neurons - Reflex

• Reflexes are rapid, automatic responses to stimuli.
• A sequence of neural events.

Typical Neuron

• Made up of cell body, dendrites, and axons.
• Dendrites receive information.
• Axons send information.
• Larger axons are enclosed by myelin sheaths produced by Schwann cells.
• Narrow gaps in the myelin sheath between Schwann cells are called nodes of Ranvier.

Cells of Glial Nervous System

• Glial cells support neurons.
  • Satellite cells (PNS)
  • Schwann cells (PNS)
  • Oligodendrocytes (CNS)
  • Astrocytes (CNS)
  • Microglia (CNS)
  • Ependymal cells (CNS)

This quiz focuses on the basics of electrophysiology, covering the structure and function of the nervous system's cells. It includes essential concepts regarding the organization and roles of sensory, integrative, and motor functions. Test your understanding of neurons and the central nervous system with this quiz.