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Biology LibreTexts

16: The Nervous System Lab

  • Page ID
    20764
  • Nervous Systems Lab

    Introduction: In this lab we will explore the anatomy & physiology of the nervous system.  Nervous systems are unique to animals, and are critical for detecting and interpreting information, making decisions, and regulating body functions and movements. Nervous systems are constructed from neurons and glia. Neurons are the main functional cells, while glia play a variety of support roles.

    Nervous systems develop as interconnected networks of cells. The largest nervous organs are the brains of vertebrates, while animals as simple as jellyfish have a ‘nerve net’. A critical concept related to nervous systems is consciousness, or ‘self-awareness’. That idea will be discussed from one perspective in the next lab, distinguishing sensation from perception.

    The exercises here will review cellular function and structure, and explore several basic neural networks within the larger body. We will use a combination of models and microscopic analysis, gross anatomical dissection, and physiological exercises to study nervous systems.

    An overview of the components of Nervous Systems:

    Cellular Components
    Cell Structures Cell Functions
    Neurons

    Cells with membrane extensions, or neurites (axons {1 per neuron} & dendrites), interconnected at synapses. Identified by the extent of neurite branching:

    Multipolar = 2 or more dendrites

    Bipolar = 1 axon + 1 dendrite

    Unipolar = 1 neurite (functions as dendrite and axon, seen in specialized sensory neurons)

    • Excitable cells based on maintenance of ion - concentration gradients (for Na+ and K+) and membrane ion channel proteins.
    • Membrane polarity (or membrane potential, or voltage) for a cell at rest is negative inside relative to out, based on an excess flow of K+ out of the cell.
    • An Action potential is the activation of a neuron, and the membrane polarity reverses, due to an inward flow of Na+.

    Synapses – physical junctions between neurons, as well as between neurons and other cells, that allow for communication. 

    Chemical synapses (most common type) use an action potential to signal the exocytosis of neurotransmitter chemicals (over 100 different neurotransmitters known in humans).  Each neurotransmitter requires a receptor protein (multiple subtypes known for each different neurotransmitter). 

    Electrical synapses are direct membrane junctions between cells that allow continuations of action potentials.

    Glia (or glial cells, or neuroglia)
    Oligodendrocytes & Schwann cells Cells that wrap axons in myelin sheaths (glial membrane extensions) that increase action potential velocity
    Astrocytes, Satellite cells & Ependymal cells Cells that form borders between nervous tissues and other body tissues
    Microglia Immune cells that clear cellular debris from nervous tissues

     Figure \(\PageIndex{1}\) A drawing detailing some of the basic anatomical neural structures.

    Nervous System Lab 1.PNG

    Tissue and Organ Components of the Nervous System

    Central Nervous System (CNS) – the brain & spinal cord in vertebrates.

    Peripheral Nervous System (PNS) – All other nervous tissue (nerves & ganglia).

    Structures & Systems Functions

    White matter – myelinated axons in the CNS. Sometimes referred to as tracts, or fasciculi (or may have older, unique names).

    Connections between CNS regions to coordinate functions. Allows integration of information.

    Gray matter – neuron cell bodies in the CNS, includes cortical tissue (e.g. cerebral cortex) and nuclei (e.g. caudate nucleus assists with motor coordination).

    Sites of information integration and decision-making, e.g. temporal cortex in the brain processes auditory signals and interprets speech.

    Nerve – bundle of axons in the PNS

    Can be classified as sensory (or afferent) for signals coming into the CNS from PNS, or motor (or efferent) for signals from CNS to PNS.

    Most nerves are mixed, and carry both sensory and motor information.

    Ganglia – clusters of neuron cell bodies in the PNS

    Various functions controlling and monitoring body functions, e.g. dorsal root ganglia are sensory neurons clustered lateral to the spinal cord

    Somatic Nervous System (or voluntary)

    Nervous tissues related to conscious perception and voluntary body control.

    Autonomic Nervous System (or visceral) – subdivided into the Sympathetic and Parasympathetic subdivisions. Nervous tissues related to unconscious perception and involuntary body control.

    Sympathetic – regulates ‘fight-or-flight’, short term stress responses (e.g., increase heart rate, pupil  dilation); 

    Parasympathetic – regulates ‘rest and digest’ functions (e.g., decrease in skeletal muscle activity, increase in digestive function – liver, pancreas function)

    Figure \(\PageIndex{2}\) An overview of the anatomical structures in the body.

    Nervous System Lab 2.PNG

    Figure \(\PageIndex{3}\) An external view of brain anatomy, with major structures.

    Nervous System Lab 3.PNG

    This lab has been adapted from material from Rice University and Exercise 4 is adapted from https://backyardbrains.com/experiments/skin. This lab is licensed under a Creative Commons Attribution License License (3.0).