The Body

Contents —

Nervous system
Endocrine system
Enteric system
Immune system
Limbic system
Brain Imaging

This is a selection of generally readable sites about the Body — the works of established, reliable people.


Psychology has moved steadily from speculation about behaviour toward a more objective and scientific approach as the technology available to study human behaviour has improved — ref1040 — Evolution of psychology

By the 1920’s Psychologists were advised to focus exclusively on measurable, observable behaviour.

By the late 20th Century psychologists were once again grappling with the issue of Consciousness.  New tools, notably brain scanning techniques and theories of Cognition, offered new approaches to studying Conscious and Unconscious mental activity.

From ref999  — Brain imaging techniques can be used to show brain structures or functions. An old technique, Electroencephalography (the EEG) yields more information now with computer enhancements. PET scans show fluctuations of brain activity in real time as a person thinks or acts.

Another technique, — MRI —  was originally used to visualize tumours and soft tissue structures of the brain. A variation called functional MRI (fMRI) became the most commonly used brain scanning technique in Cognitive Neuroscience —  It can spot small, brief areas of activity.

To Start

The human body has evolved to give us what we are. It has many similar features to other mammals on our planet. The structure and its interconnections are complex and, so far, we are unable to understand and adequately explain much of how it functions.

By the 1920’s Psychologists were advised to focus exclusively on measurable, observable behaviour.

By the late 20th Century psychologists were once again grappling with the issue of Consciousness. New tools, notably brain scanning techniques and theories of Cognition, offered new approaches to studying Conscious and Unconscious mental activity.

From ref999 — Brain imaging techniques can be used to show brain structures or functions. An old technique, Electroencephalography (the EEG) yields more information now with computer enhancements. PET scans show fluctuations of brain activity in real time as a person thinks or acts.

Another technique, — MRI was originally used to visualize tumours and soft tissue structures of the brain. A variation called functional MRI (fMRI) became the most commonly used brain scanning technique in Cognitive Neuroscience — It can spot small, brief areas of activity.

However, .according to Thomas Scheff, the Emeritus professor of sociology at UC Santa Barbara, intuition could be the catalyst that enables psychology to progress in areas in which it has stagnated — ref374 — The Shame of Psychology.

Humans have adapted to living in different climates, regimes, etc – and also to travel — and become adept at making and using tools and weapons, developing a system of communication through symbols and sounds, and developing social, political and economic systems of interaction.

We each compete and commune as we experience life. Our Human Body/Mind is the result of how humans evolved to deal with these opposite demands.

Each generation has to grow from a zygote — the single cell resulting from the fertilization of the female egg cell by the male sperm cell. The basic program for our development is in our individual DNA. — ref861

Evolution has provided us with the means by which a human grows, learns and develops. Our “Apps” include a wide range of the good habits/skills needed to relieve us of having to consciously work through routine daily activities.

But our ability to learn these and further life enhancing Apps also means that we can acquire bad Apps – damage-prone habits and antagonizing attitudes. These may emerge in response to unfortunate experiences such as Toxic Stresses.

From  Ref2005 “Soft-wired” by Dr Michael Merzenich  — However, the Non-conscious is not a static store of memories, comptences, habits, etc — it has to be maintained as a dynamic “business” — continually revewing its ideas, stock, capabilities, etc.  Humans are vulnerable — our environment tends to be full of threats — Stress, infection, etc — leading to dis-eases such as Depression, which injures the essential activities of the Nonconscious.


Each generation has to grow from a zygote — the single cell resulting from the fertilization

Fig 209
It is now known that Genomes are not identical —  ref 044 06Nov2001.
( From ref 505 — Epigenetics is providing explanations of how our diets, our exposure to toxins, our stress levels at work – even one-off traumatic events – might be subtly altering the genetic legacy we pass on to our children)

The approach used in the following is to select references that —
1. Illustrate the functioning of the Body
2. Focus on what can go wrong
3. Focus on examples of particular concern , such as Appetite/Nutrition and Alcohol/Addiction, depression, etc

To Start


A genotype refers to all of the genes that a person has inherited.

A phenotype is how these genes are actually expressed.

The phenotype can include physical traits, such as height and color or the eyes, as well as non  physical traits such as shyness and extroversion

From  ref 505     Epigenetics Controls Genes

Epigenetics is providing explanations of how our diets, our exposure to toxins, our stress levels at work – even one off traumatic events

  • Affect how we develop as we pass through our life cycle, and
  • Are subtly altering the genetic legacy we pass on to our children

This is achieved through   

  • Nature epigenetics is what determines a cell’s specialization (e.g., skin cell, blood cell, hair cell, liver cells, etc.) as a fetus develops into a baby through gene expression (active) or silencing (dormant); and
  • Nurture  environmental stimuli can also cause genes to be turned off or turned on.

Epigenetics affects every aspect of life    What you eat, where you live, who you interact with, when you sleep, how you exerciseaging – all of these can eventually cause chemical modifications around the genes that will turn those genes on or off over time.

Additionally, in certain diseases such as cancer or Alzheimer’s, various genes will be switched into the opposite state, away from the normal/healthy state.

 Epigenetics Makes Us Unique. Even though we are all human, why do some of us have blonde hair or darker skin? Why do some of us hate the taste of mushrooms or eggplants? Why are some of us more sociable than others? The different combinations of genes that are turned on or off is what makes each one of us unique. Furthermore, there have been indications that some epigenetic changes can even be inherited.

 Epigenetics Is Reversible     With more than 20,000 genes, what will be the result of the different combinations of genes being turned on or off?

The possible arrangements are enormous!

And if we could map every single cause and effect of the different combinations, and if we could reverse the gene’s state to keep the good while eliminating the bad    then we could hypothetically cure cancer, slow aging, stop obesity, and so much more.

From  ref1136      When life begins

An individual human life begins at conception when a sperm cell from the father fuses with an egg cell from the mother, to form a new cell, the zygote, the first embryonic stage.

The zygote grows and divides into two daughter cells, each of which grows and divides into two grand  daughter cells, and this cell growth/division process continues on, over and over again. 

The zygote is the start of a biological continuum that automatically grows and develops, passing gradually and sequentially through the stages we call foetus, baby, child, adult, old person and ending eventually in death.

The full genetic instructions to guide the development of the continuum, in interaction with its environment, are present in the zygote. Every stage along the continuum is biologically human and each point along the continuum has the full human properties appropriate to that point.

From  ref1122


Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells also contain the body’s hereditary material and can make copies of themselves.

Cells have many parts, each with a different function. Some of these parts, called organelles, are specialized structures that perform certain tasks within the cell. Human cells contain the following major parts   —   see ref1122 for details    

Endoplasmic reticulum (ER)
Golgi apparatus
Lysosomes and peroxisomes
Plasma membrane

Fig122    Human Cell

Fron  ref1131       Understanding genomics and what is a genome

Your genome is the instructions for making and maintaining you.

It is written in a chemical code called DNA. All living things have a genome     animals, plants, bacteria, and viruses.

Your genome is all 3.2 billion letters of your DNA. It contains around 20,000 genes. Genes are the instructions for making the proteins our bodies are built of – from the keratin in hair and fingernails to the antibody proteins that fight infection.

The process of turning on a gene to produce RNA and protein is called gene expression.

Gene regulation is how a cell controls which genes, out of the many genes in its genome, are “turned on” (expressed).

Thanks to gene regulation, each cell type in your body has a different set of active genes —despite the fact that almost all the cells of your body contain the exact same DNA.

These different patterns of gene expression cause your various cell types to have different sets of proteins, making each cell type uniquely specialized to do its job.

Whether in a simple unicellular organism or a complex multi cellular organism, each cell controls when and how its genes are expressed.  xxx

Genes make up about 1 5% of your genome    The rest of the DNA, between the genes is important for regulating the genes and the genome     For example, it can switch genes on and off at the right time.

There is still much more to learn about what it all does.

From ref1130      central  dogma  DNA to functional product

The ‘Central Dogma’ is the process by which the instructions in DNA are converted into a functional product. It was first proposed in 1958 by Francis Crick, discoverer of the structure of DNA.

The central dogma of molecular biology explains the flow of genetic information, from DNA to RNA?, to make a functional product, a protein?.

The central dogma suggests that DNA contains the information needed to make all of our proteins, and that RNA is a messenger that carries this information to the ribosomes?.

The ribosomes serve as factories in the cell where the information is ‘translated’ from a code into the functional product.

The process by which the DNA instructions are converted into the functional product is called gene expression?.

Gene expression has two key stages    transcription? and translation?.

In transcription, the information in the DNA of every cell is converted into small, portable RNA messages.

During translation, these messages travel from where the DNA is in the cell nucleus to the ribosomes where they are ‘read’ to make specific proteins.

The central dogma states that the pattern of information that occurs most frequently in our cells is      

  • From existing DNA to make new DNA (DNA replication?)
  • From DNA to make new RNA (transcription)
  • From RNA to make new proteins (translation).

Fig 290  ref1130    DNA to functional product

From  ref1137      Chromosomes

Each chromosome contains information about specific traits of an organism. These chromosomes can be sorted into two categories — autosomes and sex chromosomes.

For humans most of their chromosomes come in matched sets known as homologous pairs. 

The 46 chromosomes of a human cell are organized into 23 pairs, and the two members of each pair are said to be homologues of one another (with the slight exception of the X and Y chromosomes; see below).

In humans, the X and Y chromosomes determine a person’s biological sex, with XX for female and XY for male.

While the two X chromosomes in a woman’s cells are genuinely homologous, the X and Y chromosomes of a man’s cells are not.

They differ in size and shape, with the X being much larger than the Y, and contain mostly different genes (although they do have small regions of similarity).

The X and Y chromosomes are known as sex chromosomes, while the other 44 human chromosomes are called autosomes.

Fig 291  Chromosomes ref1137

To Start

An Overview

Our control systems —
Central Nervous system (including the Limbic system)
Peripheral Nervous system — Autonomic and Somatic Elements
Endocrine (Hormonal) System
Enteric system
Immune system

From  ref1087 — Overview of the body

Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living.

The job of the circulatory system is to move blood, nutrients, oxygen, carbon dioxide, and hormones, around the body. It consists of the heart, blood, blood vessels,arteries and veins.

The digestive system consists of a series of connected organs that together, allow the body to break down and absorb food, and remove waste. It includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The liver and pancreas also play a role in the digestive system because they produce digestive juices.

The endocrine system consists of eight major glands that secrete hormones into the blood. These hormones, in turn, travel to different tissues and regulate various bodily functions, such as metabolism, growth and sexual function.

The immune system is the body’s defense against bacteria, viruses and other pathogens that may be harmful. It includes lymph nodes, the spleen, bone marrow, lymphocytes (including B-cells and T-cells), the thymus and leukocytes, which are white blood cells.


The lymphatic system includes lymph nodes, lymph ducts and lymph vessels, and also plays a role in the body’s defenses. Its main job is to make is to make and move lymph, a clear fluid that contains white blood cells, which help the body fight infection. The lymphatic system also removes excess lymph fluid from bodily tissues, and returns it to the blood.


To Start

The Nervous system and Communications

Fig 280 ref1085 — Nervous system

Functions of the nervous system —

· Sensation and perception
· Motor function
· Cognition (thinking) and problem-solving
· Executive function and planning
· Language comprehension and creation
· Memory
· Emotion and emotional expression
· Balance and coordination
· Regulation of endocrine organs
· Regulation of heart rate, breathing rate, vascular resistance, temperature, and exocrine glands

From  ref1092 — Neural Communication

Glia and neurons are the two cell types that make up the nervous system. While glia generally play supporting roles, the communication between neurons is fundamental to all of the functions associated with the nervous system.

Glial cells, which outnumber neurons ten to one, are traditionally thought to play a supportive role to neurons, both physically and metabolically. Glial cells provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses. 

Neurons, on the other hand, serve as interconnected information processors that are essential for all of the tasks of the nervous system

Neuronal communication is made possible by the neuron’s specialized structures, like the soma, dendrites, axons, terminal buttons, and synaptic vesicles.

Neuronal communication is an electrochemical event. The dendrites contain receptors for neurotransmitters released by nearby neurons. If the signals received from other neurons are sufficiently strong, an action potential will travel down the length of the axon to the terminal buttons, resulting in the release of neurotransmitters into the synapse.

Different neurotransmitters are associated with different functions. Often, psychological disorders involve imbalances in a given neurotransmitter system. Therefore, psychotropic drugs are prescribed in an attempt to bring the neurotransmitters back into balance. Drugs can act either as agonists or as antagonists for a given neurotransmitter system.

Fig 138 Synapse

From ref1046 Neurotransmitters

Neurotransmitters are chemical messengers in the Nervous system.. Their job is to transmit signals from nerve cells to target cells. These target cells may be in muscles, glands, or other nerves.
The brain needs neurotransmitters to regulate many necessary functions, including:
• heart rate
• breathing
• sleep cycles
• digestion
• mood
• concentration
• appetite
• muscle movement

The nervous system controls the body’s organs, psychological functions, and physical functions. Nerve cells, also known as neurons, and their neurotransmitters play important roles in this system.

Nerve cells fire nerve impulses. They do this by releasing neurotransmitters, which are chemicals that carry signals to other cells.

Neurotransmitters relay their messages by traveling between cells and attaching to specific receptors on target cells.

Each neurotransmitter attaches to a different receptor — for example, dopamine molecules attach to dopamine receptors. When they attach, this triggers action in the target cells.

After neurotransmitters deliver their messages, the body breaks down or recycles them.

Key types of neurotransmitter

Many bodily functions need neurotransmitters to help communicate with the brain.

Experts have identified more than 100 neurotransmitters to date.

Neurotransmitters have different types of action:
• Excitatory neurotransmitters encourage a target cell to take action.
• Inhibitory neurotransmitters decrease the chances of the target cell taking action. In some cases, these neurotransmitters have a relaxation-like effect.
• Modulatory neurotransmitters can send messages to many neurons at the same time. They also communicate with other neurotransmitters.

Some neurotransmitters can carry out various functions, depending on the type of receptor that they are connecting to.

From ref1091 Communications —  The Nervous and Endocrine Systems

The nervous system has three overlapping functions — Sensory input, integration, and motor output.

Input is the conduction of signals from sensory receptors to integration centers of the nervous system.

Integrating the information requires that the sensations triggered by environmental stimulation of receptors be interpreted and associated with appropriate responses of the body.

Motor output is the conduction of signals from the brain or other processing center of the nervous system to effector cells. Effector cells are the muscle cells or gland cells that actually perform the body’s responses to stimuli.

The nervous and endocrine systems are related in three main areas, structure, chemical, and function.

The endocrine and nervous system work parallel with each other and in conjunction function in maintaining homeostasis, development and reproduction.

Both systems are the communication links of the body and aid the body’s life systems to function correctly and in relation to each other.

Cranial nerves and spinal nerves

Nerves that connect the brain with the eyes, ears, nose, and throat and with various parts of the head, neck, and trunk are called cranial nerves. There are 12 pairs of them.

Nerves that connect the spinal cord with other parts of the body are called spinal nerves. The brain communicates with most of the body through the spinal nerves. There are 31 pairs of them, located at intervals along the length of the spinal cord.

Several cranial nerves and most spinal nerves are involved in both the somatic and autonomic parts of the peripheral nervous system.

Spinal nerves emerge from the spinal cord through spaces between the vertebrae. Each nerve emerges as two short branches (called spinal nerve roots): one at the front of the spinal cord and one at the back.

Motor nerve root — The motor root emerges from the front of the spinal cord. Motor nerve fibers carry commands from the brain and spinal cord to other parts of the body, particularly to skeletal muscles.

Sensory nerve root — The sensory root enters the back of the spinal cord. Sensory nerve fibers carry sensory information (about body position, light, touch, temperature, and pain) to the brain from other parts of the body. The sensory nerve fibers in each sensory nerve root carry information from a specific area of the body, called a dermatome (see Figure: Dermatomes).

After leaving the spinal cord, the corresponding motor and sensory nerve roots join to form a single spinal nerve.

From  ref1090

The brain and spinal cord contain support cells called glial cells. There are several types, including the following:

  • Astrocytes:These cells provide nutrients to nerve cells and control the chemical composition of fluids around nerve cells, enabling them to thrive. They also influence how often nerve cells send impulses and thus regulate how active groups of nerve cells may be.
  • Oligodendrocytes:These cells make myelin, a fatty substance that insulates nerve axons and speeds the conduction of impulses along nerve fibers.
  • Glial progenitor cells:These cells can produce new astrocytes and oligodendrocytes to replace those destroyed by injuries or disorders. Glial progenitor cells are present throughout the brain in adults.
  • Microglia:These cells help protect the brain against infection and help remove debris from dead cells.

From Nerves. — Typical Structure of a Nerve Cell

A nerve cell (neuron) consists of a large cell body and nerve fibers—one elongated extension (axon) for sending impulses and usually many branches (dendrites) for receiving impulses.

Each large axon is surrounded by oligodendrocytes in the brain and spinal cord and by Schwann cells in the peripheral nervous system. The membranes of these cells consist of a fat (lipoprotein) called myelin. The membranes are wrapped tightly around the axon, forming a multilayered sheath. This myelin sheath resembles insulation, such as that around an electrical wire. Nerve impulses travel much faster in nerves with a myelin sheath than in those without one.

If the myelin sheath of a nerve is damaged, nerve transmission slows or stops. The myelin sheath may be damaged by various conditions that damage the brain or peripheral nerves including —

  • Multiple sclerosis
  • Certain types of strokes
  • Certain autoimmune disorders (such as Guillain-Barré syndrome)
  • Certain infections
  • Drugs and toxins
  • Certain hereditary disorders

The Central Nervous system

The brain and spinal cord consist of gray and white matter.

Gray matter consists of nerve cell bodies, dendrites and axons, glial cells, and capillaries (the smallest of the body’s blood vessels).

 White matter contains relatively very few neurons and consists mainly of axons that are wrapped with many layers of myelin and of the oligodendrocytes that make the myelin. Myelin is what makes the white matter white.

A useful model of the brain is — 

Fig 128   ref1010

From  ref1010 – Brainwaves, and what the brain does

Amygdala —  Lying deep in the center of the limbic emotional brain, this powerful structure, the size and shape of an almond, is constantly alert to the needs of basic survival including sex, emotional reactions such as anger and fear.

Consequently it inspires aversive cues, such as sweaty palms, and has recently been associated with a range of mental conditions including depression to even autism.

It is larger in male brains, often enlarged in the brains of sociopaths and it shrinks in the elderly.

Brain Stem —  The part of the brain that connects to the spinal cord. The brain stem controls functions basic to the survival of all animals, such as heart rate, breathing, digesting foods, and sleeping. It is the lowest, most primitive area of the human brain.

Cerebellum —  Two peach-size mounds of folded tissue located at the top of the brain stem, the cerebellum is the guru of skilled, coordinated movement (e.g., returning a tennis serve or throwing a slider down and in) and is involved in some learning pathways.

Cerebrum —  This is the largest brain structure in humans and accounts for about two-thirds of the brain’s mass.

It is divided into two sides — the left and right hemispheres—that are separated by a deep groove down the center from the back of the brain to the forehead.

These two halves are connected by long neuron branches called the corpus callosum which is relatively larger in women’s brains than in men’s.

The cerebrum is positioned over and around most other brain structures, and its four lobes are specialized by function but are richly connected.

The outer 3 millimeters of “gray matter” is the cerebral cortex which consists of closely packed neurons that control most of our body functions, including the mysterious state of consciousness, the senses, the body’s motor skills, reasoning and language.

The Frontal Lobe is the most recently-evolved part of the brain and the last to develop in young adulthood. It’s dorso-lateral prefrontal circuit is the brain’s top executive.

It organizes responses to complex problems, plans steps to an objective, searches memory for relevant experience, adapts strategies to accommodate new data, guides behavior with verbal skills and houses working memory.

Its orbitofrontal circuit manages emotional impulses in socially appropriate ways for productive behaviors including empathy, altruism, interpretation of facial expressions.

Stroke in this area typically releases foul language and fatuous behavior patterns. xxx

The Temporal Lobe controls memory storage area, emotion, hearing, and, on the left side, language.

The Parietal Lobe receives and processes sensory information from the body including calculating location and speed of objects.

The Occipital Lobe processes visual data and routes it to other parts of the brain for identification and storage.

Hippocampus —  located deep within the brain, it processes new memories for long-term storage.

If you didn’t have it, you couldn’t live in the present, you’d be stuck in the past of old memories. It is among the first functions to falter in Alzheimer’s. xxx

Hypothalamus —  Located at the base of the brain where signals from the brain and the body’s hormonal system interact, the hypothalamus maintains the body’s status quo.

It monitors numerous bodily functions such as blood pressure and body temperature, as well as controlling body weight and appetite.

Thalamus —  Located at the top of the brain stem, the thalamus acts as a two-way relay station, sorting, processing, and directing signals from the spinal cord and mid-brain structures up to the cerebrum, and, conversely, from the cerebrum down the spinal cord to the nervous system.                    


From  ref1086 — Left brain and Right brain

Later research has shown that the brain is not nearly as separate as once thought. For example, research has shown that abilities in subjects such as math are strongest when both halves of the brain work together.

Today, neuroscientists know that the two sides of the brain collaborate to perform a broad variety of tasks and that the two hemispheres communicate through the corpus callosum.

The notion of a left brain and a right brain doesn’t capture their intimate working relationship.

The left hemisphere specializes in picking out the sounds that form words and working out the syntax of the phrase, for example, but it does not have a monopoly on language processing.

The right hemisphere is more sensitive to the emotional features of language, tuning in to the slow rhythms of speech that carry intonation and stress.”

It’s absolutely true that some brain functions occur in one or the other side of the brain.

Language tends to be on the left, attention more on the right.

But people don’t tend to have a stronger left- or right-sided brain network.

The Limbic System

From ref 448Limbic_system — Wikipedia
The limbic system itself is best thought of as a component of a larger emotional processing plant, that is essentially responsible for sifting through, organizing, lower order processing, and relaying sensory information to other brain areas for higher order emotional processing.

From ref1065 — Limbic system an overview

The structures and nuclei of the limbic system are exceedingly ancient, some of which began to evolve over 450 million years ago. Over the course of evolution, these emotional structures have expanded in size, some becoming increasingly cortical in response to increased environmental opportunities and demands. In fact, as the neocortical forebrain expanded and until as recently as 50 million years ago, the cerebrum of the ancestral line that would eventually give rise to humans, was dominated by the limbic system.

However, over the course of evolution a mantle of neocortex began to develop and enshroud the limbic system; evolving at first to serve limbic needs in a way that would maximize the survival of the organism, and to more efficiently, effectively, and safely satisfy limbic needs and impulses.

In consequence, the frontal, temporal, parietal, and occipital lobes evolved covered with a neocortical mantle, that in humans would come to be associated with the conscious, rational mind.   Sometimes, however, even in the most rational of humans, emotions can hijack the logical mind, and the neocortex, and even peaceful people might be impelled to murder even those they love.

From ref 579 Functions of the Limbic System
The limbic system serves a variety of fundamental cognitive and emotional functions.

The hippocampi, which lay on the inside edge of the temporal lobes, is essential to memory formation.

From ref 05, book entitled  “Soft-wired” by Dr Merzenich — The Hippocampus receives information about “what’s happening” from most of the rest of our forebrain. It converts it from the world of vision, sound, feeling, smell and movement to generate multidimensional episodic memeries that play out like a movie on a framework of “real” place, and “real” time.

We lose this crucial ability if we injure this highest level memory facility, or it degenerates on a path towards Alzheimer’s

The amygdalae sit on top of the front portion of each hippocampus. Each amygdala is thought to be important in processing emotion. The amygdala communicates closely with the hippocampus, which helps explain why we remember things that are more emotionally important. The amygdala also communicates closely with the hypothalamus, the area of the brain that is responsible for regulating temperature, appetite, and several other basic processes required for life.

Through the hypothalamus, as well as some key areas in the brainstem, the limbic system communicates with our autonomic nervous system (which regulates things like heartbeat and blood pressure), endocrine system, and the viscera (gut).

Nerve cells in the brain are organized in different fashions depending on location.

The cerebral cortex is predominantly neocortical, meaning that cells exist in 6 layers.

This is different from the limbic system, where cells are either arranged in fewer layers (e.g. paleocorticoid), or more jumbled (corticoid) — This less complex organization of the limbic system, as well as the limbic system’s control of fundamental processes of life, has led doctors to believe that the limbic structure is evolutionarily older than the cerebral cortex.


The Peripheral nervous system — autonomic 

The autonomic system (ANS) is controlled by the hypothalamus and medula oblongata of the brain, which regulate the smooth muscle, cardiac muscle, and specific glands.


Fig 212 Autonomic system

One of its most important effects is causing the adrenal glands (which sit on top of the kidneys) to release epinephrine (aka adrenalin) into the blood stream. Epinephrine is a powerful hormone that causes various parts of the body to respond in much the same way as the sympathetic nervous system. Being in the blood stream, it takes a bit longer to stop its effects.

This is why, when you get upset, it sometimes takes a while before you can calm yourself down again!

The sympathetic nervous system also takes in information concerning pain from internal organs. Because the nerves that carry information about organ pain often travel along the same paths that carry information about pain from more surface areas of the body, the information sometimes get confused.

This is called referred pain, and the best known example is the pain some people feel in the left shoulder and arm when they are having a heart attack.

The other part of the autonomic nervous system is called the parasympathetic nervous system. It has its roots in the brainstem and in the spinal cord of the lower back. Its function is to bring the body back from the emergency status that the sympathetic nervous system puts it into.

Some of the details of parasympathetic arousal include —
• pupil constriction
• activation of the salivary glands
• stimulating the secretions of the stomach
• stimulating the activity of the intestines
• stimulating secretions in the lungs
• constricting the bronchial tubes
• decreasing heart rate

The parasympathetic nervous system also has some sensory abilities: It receives information about blood pressure, levels of carbon dioxide in the blood, and so on.

There is actually one more part of the autonomic nervous system that we don’t mention too often: The enteric nervous system. This is a complex of nerves that regulate the activity of the stomach. When you get sick to your stomach or feel butterflies when you get nervous, you can blame the enteric nervous system.


If we look at the Needs and Motivations of human beings, let’s say as conceived by Maslow — 

Fig 210 — ref 58a

The Limbic system concerns itself with motivations mainly up to around the  lower levels of ego — 


To Start
The Endocrine system

The endocrine system is a series of glands that produce and secrete hormones that the body uses for a wide range of functions. These control many different bodily functions, including:

Respiration, Metabolism, Reproduction, Sensory perception, Movement, Sexual development, Growth

Hormones are produced by glands and sent into the bloodstream to the various tissues in the body. They send signals to those tissues to tell them what they are supposed to do. When the glands do not produce the right amount of hormones, diseases develop that can affect many aspects of life.

The main hormone glands are — 
• Hypothalamus  (limbic system) — The hypothalamus is responsible for body temperature, hunger, moods and the release of hormones from other glands; and also controls thirst, sleep and sex drive.
• Pituitary —  Considered the “master control gland,” the pituitary gland controls other glands and makes the hormones that trigger growth.
• Parathyroid —  This gland controls the amount of calcium in the body.
• Pancreas —  This gland produces the insulin that helps control blood sugar levels.
• Thyroid — The thyroid produces hormones associated with calorie burning and heart rate.
• Adrenal —  Adrenal glands produce the hormones that control sex drive and cortisol, the stress hormone.
• Pineal —  This gland produces melatonin which affect sleep.
• Ovaries —  The ovaries secrete estrogen, testosterone and progesterone, the female sex hormones.
• Testes —  The testes produce the male sex hormone, testosterone, and produce sperm

From ref 674
Negative emotions, such as grief, anxiety, frustration, and fear, activate the amygdala, which in turn activate the hypothalamic-pituitary-adrenal axis and increase the production and secretion of stress hormones.

These hormones further activate the amygdala and inhibit the hippocampus and prefrontal cortex, resulting in severe depression.

Regular exercise helped clear stress-based Cortisol out of the body, but our sedentary lifestyle allows Cortisol to keep circulating, which increases it as fast as you can and avoid it if possible.

Fig277 Endocrine system

To Start

Enteric System

From ref 156The second brain in the gut
The Enteric nervous system or intrinsic nervous system consists of a mesh like system of neurons that governs the function of the gastrointestinal tract. It is called the second brain because while it communicates with the brain, it also has the ability to act independently and influence behaviour.

It’s estimated that there are between 400 and 600 million neurons in your gut – You’re not conscious of your gut thinking, but the system produces about 95% of the Serotonin and 50% of the Dopamine found in your body.
Researchers at Monash University have looked at the appetite hormone ghrelin, which is produced in the second brain in your gut and plays a role regulating eating behaviour, weight gain and metabolism. It also helps with building muscle mass, reduces anxiety and enhances memory. Receptors for the hormone are found throughout the body, including in the brain in your head. Ghrelin can produce an anxiety response that goes away when you eat.

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Immune System: Diseases, Disorders & Function

From  ref865 and ref864— How the immune system works

Our immune system is essential for our survival. Without an immune system, our bodies would be open to attack from bacteria, viruses, parasites, and more. It is our immune system that keeps us healthy as we drift through a sea of pathogens.

The immune system is spread throughout the body and involves many types of cells, organs, proteins, and tissues. Crucially, it can distinguish our tissue from foreign tissue — self from non-self. Dead and faulty cells are also recognized and cleared away by the immune system.

If the immune system encounters a pathogen, for instance, a bacterium, virus, or parasite, it mounts a so-called immune response.

Everyone’s immune system is different but, as a general rule, it becomes stronger during adulthood as, by this time, we have been exposed to more pathogens and developed more immunity.

That is why teens and adults tend to get sick less often than children.
Once an antibody has been produced, a copy remains in the body so that if the same antigen appears again, it can be dealt with more quickly.

The immune system can be broadly sorted into categories: innate immunity and adaptive immunity.

Innate immunity is the immune system you’re born with, and mainly consists of barriers on and in the body that keep foreign threats out.
Components of innate immunity include skin, stomach acid, enzymes found in tears and skin oils, mucus and the cough reflex. There are also chemical components of innate immunity, including a substances called interferon .
Innate immunity is non-specific, meaning it doesn’t protect against any specific threats.

The immune system needs to be able to tell self from non-self. It does this by detecting proteins that are found on the surface of all cells. It learns to ignore its own or self proteins at an early stage.

An antigen is any substance that can spark an immune response.
In many cases, an antigen is a bacterium, fungus, virus, toxin, or foreign body. But it can also be one of our own cells that is faulty or dead. Initially, a range of cell types works together to recognize the antigen as an invader.
This response is more general and non-specific. If the pathogen manages to dodge the innate immune system, adaptive or acquired immunity kicks in.

Adaptive (acquired) immunity

This protect from pathogens develops as we go through life. As we are exposed to diseases or get vaccinated, we build up a library of antibodies to different pathogens. This is sometimes referred to as immunological memory because our immune system remembers previous enemies.

Passive immunity
This type of immunity is “borrowed” from another source, but it does not last indefinitely. For instance, a baby receives antibodies from the mother through the placenta before birth and in breast milk following birth. This passive immunity protects the baby from some infections during the early years of their life.

Immunization introduces antigens or weakened pathogens to a person in such a way that the individual does not become sick but still produces antibodies. Because the body saves copies of the antibodies, it is protected if the threat should reappear later in life.

From ref865 — Immune System: Diseases, Disorders & Function

Major components —

Lymph nodes — Produce and store cells that fight infection. Lymph nodes also contain lymph, the clear fluid that carries those cells to different parts of the body. When the body is fighting infection, lymph nodes can become enlarged and feel sore.
Spleen — Contains white blood cells that fight infection or disease — also helps control the amount of blood in the body and disposes of old or damaged blood cells.
Bone marrow — The yellow tissue in the center of the bones produces white blood cells. Contains immature cells, called stem cells — prized for their flexibility in being able to morph into any human cell.
Lymphocytes —  These small white blood cells play a large role in defending the body against disease.
Thymus — Trigger or maintain the production of antibodies that can result in muscle weakness.
Leukocytes — These disease-fighting white blood cells identify and eliminate pathogens and are the second arm of the innate immune system.

Diseases of the immune system

If immune system-related diseases are defined very broadly, then allergic diseases such as allergic rhinitis, asthma and eczema are very common.
Auto-immune diseases such Lupus and rheumatoid Arthritis

Disorders of the immune system can result in autoimmune diseases, inflammatory diseases and cancer — Lupus and rheumatoid Arthritis
Immunodeficiency occurs when the immune system is not as strong as normal, resulting in recurring and life-threatening infections.

On the opposite end of the spectrum, autoimmunity results from a hyperactive immune system attacking normal tissues as if they were foreign bodies.

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Brain Imaging

Psychology has moved steadily from speculation about behaviour toward a more objective and scientific approach as the technology available to study human behaviour has improved — ref1040 — Evolution of psychology

By the 1920’s Psychologists were advised to focus exclusively on measurable, observable behaviour.

By the late 20th Century psychologists were once again grappling with the issue of Consciousness.  New tools, notably brain scanning techniques and theories of Cognition, offered new approaches to studying Conscious and Unconscious mental activity.

From ref999  — Brain imaging techniques can be used to show brain structures or functions. An old technique, Electroencephalography (the EEG) yields more information now with computer enhancements. PET scans show fluctuations of brain activity in real time as a person thinks or acts.

Another technique, — MRI —  was originally used to visualize tumours and soft tissue structures of the brain. A variation called functional MRI (fMRI) became the most commonly used brain scanning technique in Cognitive Neuroscience —  It can spot small, brief areas of activity.

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