It is impossible to discuss the source of any psychological disorder, or why we function the way we do without examining our biological roots. This highly imperative unit will describe and explain the three biological systems essential to our behavior (with multiple subsections!): The Nervous System, The Endocrine System, and The Brain.
The Nervous System
The nervous system is a fast communications system that consists of the central nervous system and the peripheral nervous system. The central nervous system includes the brain and the spinal cord, while the peripheral nervous system has two divisions: the somatic and autonomic nervous system (ANS).
While the somatic nervous system is involved in voluntary movement, the autonomic nervous system is involved in involuntary movement. The autonomic nervous system has two important divisions otherwise known as the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system is a division of the ANS that activates and prepares the body in a fight-or-flight situation. In the case of a sympathetic response, the body is affected in the following ways:
Dilated pupils
Digestion is inhibited
Heartbeat accelerates
Stimulates Norepinephrine and Epinephrine release
Relaxes the bladder
Stimulates glucose release by liver
Stimulates ejaculation in male
Meanwhile, in a parasympathetic response, the body is affected in the following ways:
Contracted pupils
Digestion is stimulated
Heartbeat slows
Stimulates gallbladder
Contracts the bladder
Allows blood to flow to sex organs Simply put, the parasympathetic response occurs when the body is in a state of homeostasis (Homeostasis article).
Snapshot of Myers' AP Psychology Textbook Diagram | 3.1 Sympathetic vs. Parasympathetic Nervous System
The nervous system is also responsible for neural communication, which is typically carried out by neurons. To learn more about their anatomy and specific functions, refer to the article: Neurons: cells of the Nervous System.
a) Neurotransmission
The space between the axon tip and the presynaptic (sending) neuron is called the synapse, in which neurotransmitters carry chemical messages to the postsynaptic (receiving) neuron. They cross a gap called the synaptic gap (less than 40 mm wide) and bind to their corresponding receptor sites located on the postsynaptic neuron.
First, electric impulses or action potentials travel throughout the neuron until it reaches the synapse. Once the action potentials reach the synapse, they are automatically converted to a chemical signal. The moment neurotransmitters are stored in vesicles, they are ready for their release. These vesicles carry neurotransmitters for the purpose of fusing with the presynaptic membrane, allowing them to cross the gap. They bind to their corresponding receptor sites of the postsynaptic neuron in a lock-and-key mechanism, much like how a particular key is used to unlock a particular door. For instance, the dopamine neurotransmitter would bind to a dopamine receptor site - it would never bind to an acetylcholine receptor site. Normally, there will be an excess of neurons left in the synapse, so to avoid the signal from being repeated, regulate the number of neurotransmitters to remain in the synapse, and to control how long a signal should be released, the reuptake process recycles and reabsorbs the remaining neurotransmitters. They are sent back to the presynaptic neuron afterward.
It is also important to note which specific neurotransmitters are present. Below are the major ones to familiarize yourself with:
Acetylcholine [ACh]
Function: Muscle action, learning, memory
Impairment: ACh neurotransmitters will deteriorate with the development of Alzheimer's
Disease and Dementia.
Additional Information For Understanding: This is the chief neurotransmitter in the body's
parasympathetic response because it contracts our smooth muscles, increases bodily secretions,
and slows the heart rate. It tells our neurons to activate muscle action.
Dopamine
Function: Influences movement, learning, attention, and emotion
Impairment: An undersupply of dopamine is linked to depression and Parkinson's Disease, while
an oversupply of it may lead to the development of schizophrenia.
Additional Information For Understanding: This is directly linked to the brain's reward and
pleasure systems. Unlike serotonin, it deals with pleasure and addiction, which affects
our mood. This is why when people experience an undersupply of dopamine, they no longer have
the motivation to pursue their previous interests - it is associated with how you deal with pleasure (addiction disorders, for example. Here are articles that detail dopamine's involvement within our body's messaging system: How Your Phone Can Be An Addictive Stimulant and Why Does Coffee Help Us Stay Awake).
Serotonin
Function: Affects mood, sleep, arousal, and hunger
Impairment: An undersupply may lead to depression and other mental health disorders
Additional Information For Understanding: This is directly linked to how we process our
emotions, thus it affects our overall mood. It regulates basic maintenance activities that
we consider pleasurable, such as eating and sleeping. Here is an example detailed in our article,
Endorphins
Function: Inhibits transmission of pain signals, promoting signals of relief. It also stimulates
euphoria with the release of dopamine, norepinephrine, and serotonin. The brain produces them
naturally.
Norepinephrine
Function: Helps control alertness and arousal
Impairment: An undersupply may lead to a depressive mood.
Additional Information For Understanding: While the ACh is the chief neurotransmitter in the
body's parasympathetic response, Norepinephrine (on the other hand) is the chief
neurotransmitter in the body's sympathetic response (along with epinephrine - or adrenaline).
The reason why that is is that it's involved in also increasing our heart rate and contracting our
blood vessels. It stimulates energy in our bodies by increasing our sugar levels.
b) Types of Neurotransmitters and Examples
The three types of neurotransmitters that our bodies receive are agonists, antagonists, and reuptake inhibitors. It is frequently divided into two types, agonists and antagonists, since reuptake inhibitors have the same function as antagonists but conducted in a different part of the neuron.
Agonist neurotransmitters are molecular structures that mimic the body's naturally released neurotransmitter so close that it fits into the receptor, leading the receiving neuron to mistake it for the actual message. An example of this includes the drug heroin, which could be mistaken for the neurotransmitter dopamine in the neuron. In effect, it can produce similar effects and signals like dopamine, though supplying the body more with a "high" or a "happier" mood amplifying dopamine's natural effects.
Meanwhile, antagonist neurotransmitters block the natural neurotransmitter from their corresponding receptor site so that no other molecules can use it. Examples of this include injected drugs used to balance the release of neurotransmission signals within the neurons, a well-known known one being NSAIDs (Non-Steroidal Anti-Inflammatory Drugs). They work as the antagonist to prostaglandins (a group of lipids released in the sites of tissue damage to regulate processes of inflammation and blood flow) by inhibiting the function of prostaglandins to reduce pain in order to increase relief.
The Endocrine System
The endocrine system is the body's slow chemical communications system, where chemical messages are carried out by hormones rather than neurons. Hormones in the endocrine system are similar to neurons in the Nervous System, but they are chemicals created by endocrine glands secreted into the bloodstream. They affect the brain and other various tissues in the body.
i.e. adrenaline or epinephrine increases heart rate, blood rate, and sugar levels during a fight-or-flight
situation.
a) Types of Glands
Pituitary glands are called the "the master glands". They consist of the anterior lobe and the posterior lobe.
Functions Include: releasing hormones that regulate many other glands
the posterior lobe regulates H20 and salt balance
and is responsible for producing the HGH (Human Growth Hormone), a hormone that causes
tissues to grow from birth to early 20s with increases during puberty
Thyroid glands regulate the body's metabolic rate
Parathyroid glands regulate calcium levels
Adrenal glands are responsible for releasing adrenaline and noradrenaline (or, epinephrine and norepinephrine) during the body's fight-or-flight response.
The pancreas is responsible for making and secreting insulin, which regulates blood sugar levels and thus controls energy.
An undersupply of insulin may lead to Hypoglycemia (constantly reduces insulin in the body)
Meanwhile, an oversupply of it may lead to Diabetes (constantly increases insulin in the body)
Lastly, the gonads are referred to as our sexual reproductive organs, regulating our bodily development, responsible for reproduction and secondary characteristics, and controls libido. Testosterone exists in both biological genders to control libido (or sex drive).
Note that ovaries evolved first (therefore, female is the default sex)
Primary sex characteristics are directly related to reproduction
Secondary sex characteristics refer to biological differences unrelated to reproduction
i.e. size of breasts, facial hair, body hair, Adam's Apple, broad shoulders, wide hips, etc..
Snapshot of Myers' AP Psychology Textbook Diagram | 3.2 The Endocrine System
The Brain Anatomy
Below is a pdf about the various mnemonics regarding the brain!
REFERENCES:
Anthony, Peter. “Psychology Blog: Agonists and Antagonists.” Pamoja, 6 Aug. 2020, pamojaeducation.com/blog/psychology-blog-agonists-and-antagonists.
"Exploring the World of Disorders Part I" STEM To Go, 26 June 2020, https://onlinestemtogo.wixsite.com/website/post/exploring-the-world-of-disorders-part-i
Jaggi, Elina. "How Your Phone Chime Can Be An Addictive Stimulant." STEM To Go, 12 August 2020, https://onlinestemtogo.wixsite.com/website/post/how-your-phone-chime-can-be-an-addictive-stimulant
Lin Lectures. “The Influence of Drugs on Neurotransmitters - AP Psychology.” YouTube, uploaded by Lin Lectures, 30 June 2016, www.youtube.com/watch?v=mVJjWYXS4JM.
Liu, Ashlee. "Science Behind Dementia." STEM To Go, 13 August 2020, https://onlinestemtogo.wixsite.com/website/post/science-behind-dementia
Neuroscientifically Challenged. “2-Minute Neuroscience: Synaptic Transmission.” YouTube, uploaded by Neuroscientifically Challenged, 22 July 2014, www.youtube.com/watch?v=WhowH0kb7n0&t=14s.
Wang, Benetta. "Homeostasis." STEM To Go, 12 September 2020, https://onlinestemtogo.wixsite.com/website/post/homeostasis
Wang, Benetta. "Neurons: cells of the Nervous System." STEM To Go, 11 July 2020, https://onlinestemtogo.wixsite.com/website/post/neurons-cells-of-the-nervous-system
"Why Does Coffee Help Us Stay Awake?" STEM To Go, 3 July 2020, https://onlinestemtogo.wixsite.com/website/post/why-does-coffee-help-us-stay-awake
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