BEH225/Introduction to Behavioral Science
June 23, 2013
Professor Pamela Applewhite
Part I The communication process of neurons in the brain is an amazingly delicate and specific process that requires many different steps to find completion. To begin, it is important to understand the specialized structure of a neuron. In addition to a nucleus, cytoplasm, and cell wall, each neuron has many dendrites, which receive information, and one axon, that sends out information to other neurons, muscles, or glands. The dendrites and axon of a neuron stretch in all directions, allowing one neuron to have thousands of neighbors, yet not touch any of them. A synapse contains the ends of one neuron’s dendrites and axon, the ends of its neighbor’s dendrites and axon, and the space in between, called the synaptic space. The first step in communication is a neural impulse. This happens when a resting neuron is polarized, having more negative ions inside it than out. When stimulated by an incoming message or impulse from a dendrite, the neuron becomes depolarized and a chain reaction begins. The neuron “fires” and an outgoing message is generated and sent down the axon to be distributed to other destinations. Not just any stimulus will compel a neuron to fire, though. A single message from another neuron would not be enough. The neuron has to reach the threshold of excitation – many messages received from many other neurons – to activate or fire. Once the neuron has fired, the electrical signal travels down the axon and to the synaptic knob, from which point neurotransmitters are released to bridge the synaptic space and reach neighboring neurons. Each neurotransmitter triggers specific actions as it fits into a unique receptor on the other side of the synaptic space. Neurotransmitters are the instructions to the neuron as to what action should take place. The brain contains hundreds of neurotransmitters, but there are five that have been studied extensively: acetylcholine (ACh), dopamine, serotonin, norepinephrine, and endorphins. Acetylcholine works in both the central and peripheral nervous systems and is involved in many functions. Acetylcholine helps regulate memory, attention, and motivation (Morris & Maisto, 2010). Dopamine plays a part in behavior motived by reward, regulation of certain hormones, memory, and emotions. It is also important to note that where dopamine is produced in the brain impacts the effects it has. Serotonin effects mood, appetite, and sleep. Norepinephrine also impacts mood, as well as alertness, memory, and the ability to learn. Finally, endorphins can mute pain, induce a feeling of being relaxed, and generally leave a person feeling good. All of the neurotransmitters outlined impact a person’s behavior. The levels of neurotransmitters in the human body are delicately balanced. This slightest imbalance can have serious consequences. Too little serotonin in the body can cause a person to have severe insomnia, while too much dopamine may trigger addictive behaviors. The “natural high” produced by endorphins also can be addicting, sometimes leaving a person to seek out other drug-induced sources to provide that same feeling. Many mental illnesses, such as Bipolar Disorder are thought to be impacted by unbalanced neurotransmitters (Newburg et al., 2008).
Part II The human brain is nature’s supercomputer. Over the millennia human beings have been on the planet, their brains have been learning, growing, and changing to form the mysterious and complicated central processor recognized today. Much is known about the brain, but not nearly as much as there is still to learn. To begin to understand how the brain works and impacts human behavior, the three major regions and their functions must be understood. The central core of the brain is common to humans and other vertebrates, as it…