Biological and Biochemical Foundations of Living Systems: Content Category 3A

Structure and functions of the nervous and endocrine systems and ways in which these systems coordinate the organ systems
The nervous and endocrine systems work together to detect external and internal signals, transmit and integrate information, and maintain homeostasis. They do all of this by producing appropriate responses to internal and external cues and stressors. The integration of these systems both with one another, and with the other organ systems, ultimately results in the successful and adaptive behaviors that allow for the propagation of the species.

Animals have evolved a nervous system that senses and processes internal and external information that is used to facilitate and enhance survival, growth, and reproduction. The nervous system interfaces with sensory and internal body systems to coordinate physiological and behavioral responses ranging from simple movements and small metabolic changes to long-distance migrations and social interactions. The physiological processes for nerve signal generation and propagation involve specialized membranes with associated proteins that respond to ligands and/or electrical field changes, signaling molecules and, by extension, the establishment and replenishment of ionic electrochemical gradients requiring ATP.

The endocrine system of animals has evolved to produce chemical signals that function internally to regulate stress responses, reproduction, development, energy metabolism, growth, and various individual and interactive behaviors. The integrated contributions of the nervous and endocrine systems to bodily functions are exemplified by the process whereby the signaling of neurons regulates hormone release, and by the targeting of membrane or nuclear receptors on neurons by circulating hormones.

The content in this category covers the structure, function, and basic aspects of nervous and endocrine systems, and their integration. The structure and function of nerve cells is also included in this category.

Topic Level Key:

The abbreviations found in parentheses indicate the course(s) in which undergraduate students at many colleges and universities learn about the topics and associated subtopics. The course abbreviations are:

BC = first-semester biochemistry
BIO = two-semester sequence of introductory biology
GC = two-semester sequence of general chemistry
OC = two-semester sequence of organic chemistry

Please note topics that appear on multiple content lists will be treated differently. Questions will focus on the topics as they are described in the narrative for the content category.

Nervous System: Structure and Function (BIO)
  • Major Functions
    • High level control and integration of body systems
    • Adaptive capability to external influences
  • Organization of vertebrate nervous system
  • Sensor and effector neurons
  • Sympathetic and parasympathetic nervous systems: antagonistic control
  • Reflexes
    • Feedback loop, reflex arc
    • Role of spinal cord and supraspinal circuits
  • Integration with endocrine system: feedback control
Nerve Cell (BIO)
  • Cell body: site of nucleus, organelles
  • Dendrites: branched extensions of cell body
  • Axon: structure and function
  • Myelin sheath, Schwann cells, insulation of axon
  • Nodes of Ranvier: propagation of nerve impulse along axon
  • Synapse: site of impulse propagation between cells
  • Synaptic activity: transmitter molecules
  • Resting potential: electrochemical gradient
  • Action potential
    • Threshold, all-or-none
    • Sodium/potassium pump
  • Excitatory and inhibitory nerve fibers: summation, frequency of firing
  • Glial cells, neuroglia
Electrochemistry (GC)
  • Concentration cell: direction of electron flow, Nernst equation
Biosignalling (BC)
  • Gated ion channels
    • Voltage gated
    • Ligand gated
  • Receptor enzymes
  • G protein-coupled receptors
Lipids (BC, OC)
  • Description; structure
    • Steroids
    • Terpenes and terpenoids
Endocrine System: Hormones and Their Sources (BIO)
  • Function of endocrine system: specific chemical control at cell, tissue, and organ level
  • Definitions of endocrine gland, hormone
  • Major endocrine glands: names, locations, products
  • Major types of hormones
  • Neuroendrocrinology ― relation between neurons and hormonal systems
Endocrine System: Mechanisms of Hormone Action (BIO)
  • Cellular mechanisms of hormone action
  • Transport of hormones: blood supply
  • Specificity of hormones: target tissue
  • Integration with nervous system: feedback control
  • Regulation by second messengers

To support your studies, see the following video tutorials below from the Khan Academy MCAT Collection. The videos and associated questions were created by the Khan Academy in collaboration with the AAMC and the Robert Wood Johnson Foundation.