1. The Pineal Gland The pineal gland is a small endocrine gland
attached to the roof of the
third ventricle – it is part of
the epithalamus
The pineal gland secretes the hormone melatonin, which contributes to maintaining the biological clock (seasonal and daily cycles)
more melatonin is secreted in darkness; the pineal gland is very developed in nocturnal animals

2. The Thymus gland
The thymus gland secretes thymosin, which promotes the proliferation and maturation of T cells
T cells are a type of white blood cell (lymphocyte) that destroys microorganisms
and foreign substances
through direct
cellular contact

3. General Adaptation Syndrome
The general adaptation syndrome (GAS) or stress response refers to the consequences of failure to respond appropriately to emotional or physical threats, whether actual or imagined
Interestingly, stressful situations can be events normally considered to be “good”, as well as bad
for instance, a marriage can be as stressful as a divorce, a birth as stressful as a death, etc.
Psychologist Hans Selye described the General Adaptation Syndrome (GAS) where initial observations about infectious reactions led to the discovery that stress can lead to infection, illness, disease and death. There are three stages that he discovered: Alarm, Resistance and Exhaustion.
Alarm
When we are surprised or threatened, we have an immediate physical reaction, often called the Fight-or-Flight reaction. This prepares the body for life-threatening situations, channeling away resources from such as the digestive and immune system to more immediate muscular and emotional needs. This leads to the immune system being depressed, making us susceptible to disease.
Resistance
As we become used to the stress levels, we initially become more resistance to disease, which leads us to believe we can easily adapt to these more stressful situations. However, this is only the immune system fighting to keep up with demands and expectations, but requires it to work at abnormally high levels.
Exhaustion
Eventually reality kicks in and our bodies give up on trying to maintain a high level of stress. Parts of the body literally start to break down and we become very unwell. If we continue to fight this situation, we may even die.

4. General Adaptation Syndrome
It is impossible to remove all of the stress from our everyday lives, and some levels of stress actually help us perform well and be productive. Regardless, the body’s homeostatic mechanisms attempt to counteract stress, and maintain a constant internal environment whenever possible
If stress is extreme, unusual, or long lasting, the normal mechanisms may not be enough, and they may elicit a series of changes called the stress response or GAS

5. General Adaptation Syndrome
There are three stages to a prolonged stress response: alarm reaction, resistance reaction, and exhaustion
The alarm reaction is the short-lived fight-or-flight response initiated by the hypothalamus and mediated by the sympathetic division of the ANS
it brings huge amounts of glucose and oxygen to the brain, the lungs, and skeletal muscles
the RAAS is also activated to maintain blood volume and BP

6. THE ALARM REACTION (Interactions Animation)
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7. General Adaptation Syndrome
The three stages to the GAS continued…
The resistance reaction is initiated in large part by hypothalamic releasing hormones and is a longer-lasting response. The release of high levels of cortisol and thyroid hormones assures that the tissues of the body can sustain necessary metabolic needs

8. General Adaptation Syndrome
The alarm reaction leads to a resistance response.

9. General Adaptation Syndrome
The three stages to the GAS continued…
Exhaustion occurs when the body’s reserves become so depleted that they cannot sustain the resistance stage
Prolonged exposure to high levels of cortisol and other hormones causes wasting of muscle, suppression of the immune system, ulceration of the GI tract, and failure of pancreatic beta cells… disease often ensues

10. THE GAS (Interactions Animation)
General Adaptation Syndrome
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11. End of Chapter 18
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