If you are not passionate about biology, knowing the difference between a neurotransmitter and a hormone may seem really overwhelming. The nervous system and endocrine system are 2 completely different systems in the body, although they are both responsible for communication throughout the body. This why looking at the 2 components side by side can be helpful in distinguishing the difference between nervous system and endocrine system functions
In order to pass the EPPP you do not need to know the nervous system and endocrine system in great detail, but you do need to understand the basics (and there is a lot of information to just understand the basics). The topic of Biological Bases of Behavior is weighted at 12%, and there is a wide variety of information to know in this topic, so know enough to have a good grasp of how our biology is related to human behavior and disorders, and some of the methods to biologically treat these disorders. The study tips page can give you some advice on how to go about learning this information. This information is meant to be supplemented with the information you have already been taught in your degrees, your previous notes or textbooks, and additional study tools as needed. In order top have the best possible chance of being successful on the EPPP, please take a look at the product reviews page for a variety of additional study tools available.
Breakdown of a Neuron
The entire nervous system is covered in the post The Nervous System which may be helpful to read first. The nervous system communicates will all components of our body with both electrical and chemical messengers known as neurotransmitters. But in order to first understand neurotransmitters, it is helpful to review and breakdown the components of a neuron or nerve cell. Each neuron is comprised of three parts:
- Dendrites: A single neuron may have hundred of dendrites. Their purpose is to receive information from other neurons by picking up or capturing neurotransmitters that are released into the small space between neurons (known as the synaptic cleft).
- Soma: Also known as the “cell body,” and the purpose of the soma is to process the information that the dendrites have received. This is the part of the neuron cell that contains the nucleus (or the “brain” of the neuron), which contains the cells DNA.
- Axon: a long tube like structure that has the purpose of transmitting information.
Action Potential: This is how cells communicate with each other. First it is important to understand that all neurons have an electrical charge, and when a neuron is not firing (or at rest) the inside has a negative charge in relation to the outside of the cell which has a more positive charge. This is because (again at rest) the outside of the cell has an excess of sodium ions (Na+) while the inside has an excess of potassium ions (K+), and the imbalance creates a negative charge inside the axon of approximately -65mV. When neurotransmitters bind to receptor sites in the dendrites they increase the charge on the inside of the axon, and when this reaches a specific threshold Na+ ions from outside of the cell rush inside and K+ move outside changing the charge of the axon to approximately +40mV.
This electrical change is typically referred to as the neuron “firing” and travels to the axon terminal at about 100m/s, which then signals the release of neurotransmitters into the synaptic cleft. Some of the neurotransmitters bind the the dendrites of adjacent neurons which then continues the process of action potential into the next neuron. Neurotransmitters that are not picked up by adjacent dendrites are taken up by the axon terminal that released them through a process known as re-uptake (a concept that is important to know when discussing how different medications affect neurotransmitters).
All or Nothing Principle: This describes how neurons either fire or do not fire, there is no partial action potential and it doesn’t vary in strength. Think of it as an light switch that is either on or off. After firing there is a short period that the neuron can not fire because the Na+ and K+ ions need to return to normal before another action potential can occur.
Neurotransmitters are typically either excitatory because they increase the chance of an action potential, or inhibitory because they decrease the chance of an action potential. Substances added to the body can either be agonist because they enhance the effect of a neurotransmitter or antagonist because they inhibit the effect of a neurotransmitter.
Acetylcholine (Ach): This is involved in voluntary movement and memory. Alzheimer’s disease is associated with significantly low levels of Ach.
Catecholamines: These are typically synthesized from dietary components (tyrosine and phenylalanine), and there are 2 primary catecholamines:
- Dopamine (DA): Involved in thought, movement, and emotion. The dopamine hypothesis of schizophrenia believes that the psychotic symptoms of schizophrenia are related to excessdopamine. Traditional anti-psychotics are typically dopamine antagonists and block post-synaptic dopamine receptors on the dendrites. Second generation antipsychotics work in conjunction with blocking serotonin and therefore block fewer dopamine receptors. On the other hand Parkinson’s disease involves the degeneration of neurons in the substantia nigra (which controls movement) and results in less dopamine in the basal ganglia (where the substantia nigra is located also involved in coordination and movement). L-Dopa is an amino acid that can be manufactured and administered to treat Parkinson’s disease, as it it a precursor to dopamine production.
- Norepinephrine (NE): Involved in mood, pain, and sleep, and also referred to as noradrenalin. Depression is associated with deficits while mania associated with excess norepinephrine. This one can confuse people because it can also released as a hormone into the blood stream and so it is a part of both the nervous system and endocrine system. As a hormone it causes increased heart rate and contracts blood vessels.
Serotonin: Also known as 5-HT and is involved in mood, sleep, appetite, aggression, sexual activity, and pain perception, and is produced through the dietary modification of tryptophan. Imbalances of serotonin are linked with impulsivity and suicidality, and deficits play a role in mood disorders when combined with imbalances in norepinephrine. So low serotonin and low norepinephrine are linked to depression, where as low serotonin and high norepinephrine are linked with mania.
Amino Acids: There are 2 main amino acids we are concerned about in psychology:
- GABA: Has a calming effect due to being an inhibitory neurotransmitters in the CNS. Anxiety and epileptic seizures are associated with low GABA. For the treatment of anxiety often benzodiazepines are used which are a GABA agonist.
- Glutamate: A very common neurotransmiter and is involved in fast excitatory synaptic transmission. Imbalances in glutamate can be related to schizophrenia, depression, Autism Spectrum Disorder, and OCD.
Peptide Neurotransmitters: There are many different types of peptide neurotransmitters, and they are all made up of long chains of amino acids. Included under this classification are endorphin’s, which help to regulate stress and pain.
The endocrine system is not a part of the nervous system and does not utilize neurons. Instead it releases chemical hormones into the blood stream from glands, and these hormones target specific areas of the body. So if a chemical is released from a neurotransmitter it is a part of the nervous system, but if it is released into the blood stream it is a part of the endocrine system, but both are controlled by the hypothalamus (for the majority). In regards to the endocrine system the hypothalamus controls the pituitary gland which controls hormone release from other glands in the body.
Hyperthyroidism: Is when the thyroid gland overproduces the hormone thyroxin and can result in heat sensitivity, sweating, weight loss despite increased appetite, fatigue, diarrhea, tremors, depression, poor memory, insomnia, and in some cases hallucinations and delusions.
Hypothyroidism: Is when the thyroid gland underproduces the hormone thyroxin and can result in fatigue, sluggishness, weight gain, sensitivity to cold, and poor memory.
Diabetes: This is as a result of an imbalance of insulin which is produced by the pancreas, and is responsible for regulating blood sugar levels. Diabetes often results is hyperglycemia (high blood sugar levels) and the symptoms include increased urination, thirst, and appetite. Medications can manage this but needs to be careful not to lower blood sugar too much and result is hypoglycemia, which symptoms include irritability, headaches, comfusion, fatigue, nervousness, trembling, cold sweats, hunger, and rapid heart rate. There are 3 types of diabetes:
- Type 1 Diabetes: This type of diabetes involves life long insulin injections and typically develops before the age of 30 (which is why it is sometimes referred to as juvenile diabetes).
- Type 2 Diabetes: This type of diabetes can occasionally be controlled with diet and exercise, but often requires oral medication and sometime insulin injections. Obesity and a sedentary lifestyle are risk factors for developing type 2 diabetes.
- Gestational Diabetes: This type of diabetes is only diagnosed in pregnant women without a previous history of diabetes, and can be a precursor to type 2 diabetes. It occurs in approximately 3% of pregnancies.
Hypopituitarism: A low amount of growth hormone produced by the pituitary gland, and can cause a delay in puberty and dwarfism.
Hyperpituitarism: A high amount of growth hormone produced by the pituitary gland causes overgrowth in the skeleton resulting in acromegaly and gigantism.
Cushing’s Disease: An over-secretion of corticosteriods from the adrenal cortex, and can include symptoms of irritability, poor memory, depression, emotional liability, suicidal ideation, and swelling of the face and neck.
Addison’s Disease: An under-secretion of corticosteriods from the adrenal cortex, and can include symptoms of irritability, depression, weakness, apathy, and gastrointestinal issues.
***There are many more neurotransmitters and hormones, as well as conditions that result from them being imbalanced. The ones listed are the ones most likely to be related to a psychological condition and therefore important to know for the EPPP. How do you think it could be useful for a psychologist to know this information? Can you think of any way that this may be useful in your work with your clients? Anything you think is important to add to this list? Please comment below as this will help improve the study experience.
The information on this site may not be enough to help you feel confident about your ability to pass the exam, and because of that there are a variety of study aids and varying prices that can help you have the best chance possible of passing. Also if this information seems overwhelming to you it does NOT mean you will fail the exam, but you may require a little more in depth material than is offered here. That is why there is a Product Reviews page which will give you a variety of additional options, as well as practice exam questions which I highly recommend as explained on the Study Tips page.