The neurological processes of the human brain provide insight into the complexities of the biological basis of human behavior (Wickens, 2005). Biological psychology seeks to understand these chemical and electrical processes as a means to address their implication in human behavior and its dysfunction (Wickens, 2005). The extent of neural processes pervades all of human existence as it dictates health, sense of well-being, the ability to move and recognize, and enables human individual perception (Wickens, 2005). The ability to perceive engages the individual in the experience of both the internal world of thought and the external world and is the source for understanding "reality." The entirety of human experience and behavior functions according to the biological neurological processes of the brain and its nervous system (Wickens, 2005). Without understanding this system, psychology cannot fully serve the needs of humanity.
Roles in the Production and Regulation of Behavior
Excitatory and Inhibitory Postsynaptic Potentials
According to Wickens (2005), "The neuron is like a tiny biological battery with the negative pole inside the cell and the positive one outside" (p. 19). The neuron maintains this somewhat unstable polarity with the sodium-potassium pump (Wickens, 2005). During the constant bombardment of neurotransmitters on the neurons, ion channels open briefly causing fluctuations in the resting potential (Wickens, 2005). In a complex series of events, the bombardment results in the neuron becoming either more negative or more positive (Wickens, 2005). If the charge inside the cell becomes more positive, it is called an excitatory postsynaptic potential, and if the cell becomes more negative, it is called an inhibitory postsynaptic potential (Wickens, 2005). The function of the postsynaptic potential is to initiate or inhibit another action potential (Wickens, 2005).
When the action potential reaches the synaptic cleft, it causes stimulation prompting the process of exocytosis, when the synaptic vesicles fuse with presynaptic membranes and release neurotransmitters into the gap (Wickens, 2005). This is an ongoing process resulting in the continual secretion of neurotransmitters (Wickens, 2005). The synaptic gap is a very small fluid-filled space between the presynaptic neuron and the postsynaptic neuron in which the neurotransmitters travel between the neurons (Wickens, 2005). Once the neurotransmitters travel across the synaptic gap, they bond with their own specific type of receptors and are later broken down to prevent it from producing any further effects on the neuron (Wickens, 2005). When the neurotransmitter is taken back into the pre-synaptic neuron, the process it called re-uptake (Wickens, 2005).
Receptors are a specialized protein molecule in the membrane of the neuron and each receptor is affected only by a specific neurotransmitter (Wickens, 2005). Each neurotransmitter can only bind with a specific receptor type (Wickens, 2005). When the neurotransmitter binds to its receptor in the postsynaptic neuron, it increases or decreases the resting electrical charge of the neuron (Wickens, 2005). If the charge surpasses an excitation level at its axon hillock, a signal is generated along its axon and it starts the process of an action potential again (Wickens, 2005). This is the basic parameter of the neural network that enables neurons to transfer information from one neuron to the next (Wickens, 2005). The postsynaptic receptor is a decision maker, as it determines whether the charge of the signal is strong enough to pass it along (Wickens, 2005).
The Role of Primary Neurotransmitters in Brain Function and Behavior
The primary neurotransmitter types are amino acids, peptides, and monoamines (Wickens, 2005). Neurotransmitters facilitate neural communication across the synapse and inhibit or promote specific communication in the brain, and play a distinct role in producing certain behaviors (Wickens, 2005) The quality and efficiency of the chemical transmission determines the amount of neurotransmitters that convey messages across the brain, and determine the brain's reaction in the form of behavior (Wickens, 2005). Dysfunction in the neurological process can cause problems that range from mild depression to diseases such as Parkinson's disease, and other disruptive behaviors and symptoms (Spoont, 1992).
In addressing the roles of individual neurotransmitters, common examples include dopamine, which is responsible for feeling vital, maintaining the immune system, sexual arousal, and the ability to remain calm amidst life's calamity (Wickens, 2005). Without dopamine there is a tendency to feel sluggish and become inattentive (Wickens, 2005). Serotonin enables normal sleep patterns, regulates blood pressure, promotes calmness, and plays a significant role in daily learning, and memory (Spoont, 1992). Without serotonin, people may become aggressive, suffer from disruptive sleep, and may develop obsessive-compulsive eating disorders (Spoont, 1992). Extreme deviations in serotonin activity result in neural information processing that appears to have a direct effect on behavior, inducing conditions such as violent and aggressive behavior (Spoont, 1992).
Norepinephrine, also referred to as noradrenalin, is synthesized from tyrosine, helps us feel alert, and contributes to well-functioning memory, and a sense of well being (Wickens, 2005). Similar to serotonin, norepinephrine plays a significant role in depression ("Neurotransmitters," 2005). Acetylcholine, which is made from choline rather than amino acids, is essential for memory, brain plasticity and plays a role in initiating and maintaining concentration ("Neurotransmitters", 2005, Wickens, 2005).
Neurological Processes and Disease
The dysfunction of neurological processes is implicated in many diseases and dysfunctions (Wickens, 2005). According to Haber (1997), the dopamine system in the midbrain plays a significant role in emotional and motivational behaviors. When the function of this single neurotransmitter compromises the neural system, individuals experience a variety of symptoms, suggesting that dopamine has a role in several functions (Haber, 1997). Dopamine neurons have an enormous affect on many regions of the brain as they receive and transmit information to and from the limbic system, the cortex, amygdala, and motor areas, and influence the emotional and motivational aspect of behaviors (Haber, 1997). Dopamine neurons have been implicated in schizophrenia with disturbances of perception and psychomotor function as well as wide-ranging thought disorders (Haber, 1997) and in Parkinson's and Huntington's disease (Wickens, 2005).
It is a currently accepted theory that depression may be the result of a decreased amount of serotonin and other neurotransmitters in the synapse (Wickens, 2005). Treatments such as selective serotonin re-uptake inhibitors decrease the amount of re-uptake of serotonin, and in the case of the tri-cyclic anti-depressants, norepinephrine and serotonin, in the synapses (Marks, Pae, & Patkar, 2008). Reuptake is the process by which the presynaptic terminal of a neuron reabsorbs and recycles the molecules of neurotransmitters it has previously secreted while sending an impulse to another neuron (Wickens, 2005). In many cases, re-uptake inhibitors lessen depressive symptoms (Marks et al., 2008). By lessening the re-uptake and providing more neurotransmitters in the system, normal neural function is restored which seems to elevate mood and alleviate depressive symptoms (Marks et al., 2008).
Implications in Biological Psychology
Understanding neurological processes, neurotransmitters and their relationship to behavior gives biological psychology a starting place for diagnosing and treating mental imbalance and dysfunction (Wickens, 2005). Biological psychology, in collaboration with brain science, applies the information obtained through studies of neural behavior to illness, injury, and dysfunction of individuals in daily life (Wickens, 2005). Neurotransmitters are key to understanding the chemical and electrical nature of the central nervous system and its influence in human behavior (Wickens, 2005). This understanding provides the opportunity to modify brain function and human behavior by creating drugs and other treatments to counterbalance deficiencies and excesses of the chemical system (Wickens, 2005). According to Wickens (2005) the discovery of chemical transmission was "one of the pivotal points in the history of biological science" (p. 14).
The implications of many diseases and dysfunctions rest in the neural processes of the brain and without understanding these processes, there are no means by which to treat and relieve the dysfunctions (Wickens, 2005). The ability to understand and discover the mechanisms of neurological processes enables psychology to understand the fundamental biological basis of behavior and the ability to change and modify that which is maladaptive and malfunctioning (Wickens, 2005). Biological psychology bridges the gap between the science of neurological discovery and its human application in the diseases, dysfunctions, and maintenance of the delicate neural balance (Wickens, 20050. The implications for this branch of psychology are as tremendous as the need for relief from the incapacitating symptoms of the imbalance of the tiny, yet significantly life altering, chemical components of the neurological system.
Haber, S. N. (1997). The interface between dopamine neurons and the amygdala: Implications for schizophrenia. Schizophrenia Bulletin, 23(3), 471-482. Retrieved October 20, 2010, from PsychARTICLES.
Marks, D. M., Pae, C., & Patkar, A. A. (2008). Triple Reuptake Inhibitors: The Next Generation of Antidepressants. Current Neuropharmacology, 6(4), 338-343. doi: 10.2174/157015908787386078
Neurotransmitters. (2005). In Encyclopedia of Cognitive Science. Retrieved from http://www.credoreference.com/entry/wileycs/neurotransmitters
Spoont, M. R. (1992). Modulatory role of serotonin in neural information processing: Implications for human psychopathology. Psychological Bulletin, 112(2), 330-350. doi: 10.1037/0033-2909.112.2.330
Wickens, A.P. (2005). Foundations of Biopsychology (2nd ed.). New York: Pearson/Prentice Hall.