PSYC 222 1st Edition Lecture 5Outline of Last Lecture • Extent of Drug Use• II. National Surverys• III. Correlates of drug use •• IV. Antecedents of drug use • V. Gateway substancesOutline of Current Lecture The Nervous Systemi. Homeostasisii. Excitability and Chemical signaling in nerve cellsiii. Neuronsiv. Glia- Astrocytes- Oligodendrocytes- Microgliav. Neurotransmission- Action Potential - Brief chain of eventsCurrent Lecturei. Homeostasis: Humans maintain their internal enviornment within certain limits. Ex. Body temp, water content, glucose concetrations. Psychoactive drugs influence homeostasis . Alcohol inhibits vasopressin release (antidiuretic hormones). Thus after a drink more urine is produced. Compared to light drinkers, heavy drinkers produce less urine after a drink. During alcohol withdrawl, heavy drinkers exhibit increaed vasopressin release.ii. Thoughts emotions and behaviors come about because of biochemical and electrochemical processes in neurons.iii. Major function of neurons are to analyze and transmit information. They have four defined regions: Cell body which contains the nucleus and other sustaining substances, Dendrites which contains receptors which respond to chemical signs (Psychoactive drugs activate or inhibit neuron based on type of receptor), Axons conduct the action potential, and Axon terminals contain synaptic vesicles which store neurotransmittersiv. Major functions of Glia (glial cell) are to provide firmness and structure to the brain, get nutrients into the system, eliminate waste, form myelin, and communicate with other glia and neurons. Glia also creates the blood-brain barrier which protects the brain from toxic chemicals.Psychoactive drug molecules must be able to pass the barrier. • Astrocytes: ensheathe synaptic connections between neurons and are required for synapse information and maintenence • Oligidendrocytes: wrap layers of myelin membrane around axons to insulate them for impulse conduction, which serve important metabolic and supportive functions• Microglia: residential immune cellsv. Neurons transmit information by generating electrical changes in one part of the cell, conducting these electrical changes to distant parts of the cell, and releasing chemical signals onto neighboring neurons.• Action Potential: a brief electrical signal transmitted along the axon• Brief Chain of events:1. Resting potential: caused by uneven distribution of ions. The neuron is hyperpolarized2. Ion channels open allowing electrically charged particles to move inside the cell. As the result the neuron may become depolarized. All or none action action potential occurs. NOTE: Blocking ion channels prevents the action potential and disrupts neuronal communications.3. Neurotransmitters are released. Neurons are electrically active. They generate electrical impulses in response to changes in their enviornment. They propagate those eletrical signals. Under baseline conditions each neuron is polarized. The neuron has a voltage differene between the inside and outside of the cell known as the resting membrane potential. The neuron is analogous to a tiny biological battery with positive poles outsidethe cell and negative poles inside the