Neurophysiology Lab Outline
Introduction
The Nervous System and Neurons
Everything that we sense in the world, and all of the movements that we perform, are due to activity in the nervous system. The afferent branch of your (human) peripheral nervous system (PNS) – the sensory nervous system – sends information about touch, sound, sight, smell, and taste towards your central nervous system (CNS, brain and spinal cord). The efferent branch of your PNS – the motor system – sends motor commands to your muscles, in response to sensory input. If you would like to review the nervous system in more detail (i.e. structure, function, action potentials and communication between neurons) check out this resource.
Neurons are the basic unit of the nervous system. Most neurons have a small anatomical gap between them called a synapse, and neurons typically release chemicals that diffuse across the synapse to affect other neurons. (Note the qualifiers “most” and “typical.” Neurons are very diverse in their anatomy and physiology, and this description can only discuss common features of neurons.)
How a nervous system functions depends in large part on the physiological connections between the neurons. The connections are often described as a “circuit” by analogy with electrical circuits, although neural circuits differ in important ways. For example, connections between neurons are much more dynamic and flexible than in electrical circuits. Be suspicious if you hear someone saying brains are “hard-wired” for things!
Models of the Nervous System
We are limited to some lower resolution imaging techniques if we want to look at living human brains – such as magnetic resonance imaging (MRI), or computerized tomography (CT) scans. If we want to look deeper, at the actual neurons, this requires tissue that has been removed from an organism. While a muscle biopsy or tumour biopsy might be something you see in human medicine for histological purposes, you definitely would not be taking an entire coronal section of a human brain unless this came from an individual who had passed away and donated their body to science, or if an autopsy was being performed.
We can, however, work with model organisms. Just like in the histology lab, tissues can be collected from a model organism for research studies. The use of model organisms requires extensive ethical consideration, and in order to use and euthanize mice for a research study, your proposal must be examined and approved by the Canadian Council for Animal Care (CCAC) and your institutional animal ethics board (at McMaster, this is called the McMaster Animal Research Ethics Board (AREB)).
Brain models are important for researchers to learn more about neurodegenerative diseases, such as Alzheimers, Parkinson’s, Huntington’s, or Amyotrophic Lateral Sclerosis (ALS). It is difficult to see just how the neurons are being affected by a neurodegenerative disease in a clinical setting, and the use of a model organism allows us to loo