We continued with an examination of the anatomy and some physiology of the human brain. The cerebrum and the cerebral lobes were the main concentration, with a brief discussion of the major functions of each section. Assign: A series of questions was presented to Vlad to take home and complete the analysis of each. These questions dealt with material covered in the first few weeks.

The major structures and functions of the parts of the brain were outlined. The evolution of the brain, and the differences in size of the main divisions, the cerebrum, cerebellum, and medulla were discussed and read. The structure and function of other brain divisions will be studied next, with a lead into how chemicals, both endogenous and exogenous (drugs) affect the activity.

The transmission of an impulse from neuron to neuron or neuron to muscle or gland was reviewed. The fact that neurotransmitters can cause stimulation of inhibition of a response was explained by the type of receptor which binds to it. Dilation or constriction of pupils, dilation or relaxation of bronchioles, increase or decrease in heart rate, dilation or constriction of blood vessels, and contraction or relaxation of muscles were all shown to be dependent on the receptor. That many drugs mimic the action of the endogenous neurotransmitter was defined as an example of agonist activity. We also discussed the botanical history of most of the original medications.

The charge on the cell membrane of the neuron was discussed in terms of positive ions and negative ions which are found in different concentrations outside and inside the axon membrane.
The change in permeability of the membrane due to a stimulus was shown to cause an influx of positive sodium ions into the cell with a corresponding change in charge. This was a change from a polarized nerve cell to a depolarized nerve cell. The wave of depolarization along the axon was defined as the nerve impulse. The secretion of neurotransmitter into the synapse by the axon terminal of one nerve cell and binding to a second nerve cell was introduced as the method by which the nerve transmission moves from one cell to another. A short video was looked at which showed this transmission.

Continuing with the anatomical and physiological outline of the neuron and nerve fiber, the synapse was introduced. The nerve impulse was shown to be a depolarization of the neuron by the movement of positive ions through the cell membrane. The polarized nerve cell was drawn, and then how depolarization occurs due to a stimulus applied to the neuron. The nerve transmission was described as an electric current, flowing along the membrane. We viewed the process on a short video, which helped explain the movement of the ions into and out of the nerve cell.

Nerve tissue and nerve fibers are composed of neurons or nerve cells. Using an unlabeled diagram of a neuron,the main structures are labeled and described as to function. These include the cyton, nucleus, dendrites, axon, myelin sheath, nodes, and terminal branches. The myelin sheath's importance in protection of the neuron and prevention of "short circuit" of impulse was stressed by describing some auto immune disorders, like multiple sclerosis which occurs. We researched a few others, like ALS to show the effect on muscles and paralysis of muscles.

The functions of the nervous system were introduced, with examples of each given, and their application to homeostasis. The anatomical makeup was shown to be divided into central nervous system and peripheral nervous system. The central being the brain and spinal cord and the peripheral being cranial nerves and the nerves from the spinal cord. The internal and external environment was explained, and that the nervous system is involved with changes which occur to those environments.

The third factor to influence activity, after absorption and distribution, is metabolism. Metabolism was defined as conversion into metabolites. The different classification of metabolites was outlined and that specific enzymes are required for the conversion of specific metabolic compounds(drugs). The chemical definition of an enzyme was shown, using the decomposition of hydrogen peroxide into water and oxygen. The importance of the metabolites, is that many are the active chemical which brings about the response. That the action of a drug could be enhanced by the inhibition of a chemical which would degrade was explained by the presence of enzymes which destroy that drug. Some enzyme systems cause more drug be metabolized, resulting in less drug action.

A quick review of absorption was listed before the lesson on distribution was given. The definition of distribution as it relates to exogenous chemicals was stated. Factors which affect the distribution, include protein binding, solubility, extracellular fluids, and intracellular fluids were discussed. The brain-spinal cord relationship was shown and cerebral spinal fluid explained. The action of the blood-brain barrier in preventing certain drugs from reaching the central nervous system was discussed. The reason that an antihistamine like Benadryl was useful as a sleeping agent but not an antihistamine like Claritin was explained in terms of passing through the blood brain barrier and entering the central nervous system.

The class started with a review and expansion on the antigen-antibody reaction, allergens, and anaphylactic reaction. The factors which would affect exogenous chemical responses in the body were outlined and discussed. They included the process of absorption, the routes of administration (oral iv, transdermal, etc), the physical form of the chemical (liquid, tablet, powder, etc). The organ of absorption,the small intestine along with the villi were examined. Distribution and metabolism will be next.