Stress hormones modulate many aspects of body functioning (plants and animals) in a genomic fashion. To understand the mechanisms that underlie stress hormone-mediated effects, profiling stress-responsive gene patterns may be useful to generate new hypotheses.

Stress hormones definition: As the human body perceives stress, certain glands produce and release specific hormones into the bloodstream for a response. These hormones are often called stress hormones and they cause various physical effects that increase your heart rate and blood pressure. They can also be found in the plant body.

In general, stress hormones can be categorised into:

Human stress hormones
Plant stress hormones

The following is a summary of both stress hormones.

Human Stress Hormones

These are hormones that secrete in response to stress or an emergency and are responsible for a reaction known as fight or flight:

There are Three Types of Human Stress Hormones:

Epinephrine or adrenaline
Nor-adrenaline or nor-epinephrine
Glucocorticoids

Epinephrines and Norepinephrines (Called Together as Catecholamine)

Epinephrine (adrenalin) and Nor-epinephrine (noradrenaline) create an immediate reaction under stress. They increase the rate of respiration, increased alertness, heartbeat, pupillary, sweating, dilation and piloerection (raising of hairs.

Catecholamines stimulate the breakdown of glycogen thus increasing blood glucose levels. The surge of energy that might be required to run away from a dangerous or harmful situation.
Catecholamine also stimulates the breakdown of proteins and lipids.
These hormones shift the blood flow away from areas that are less crucial under stress conditions to areas such as muscles which need it more during stress.
Depending on the situation, it may take half an hour to two days to return to the normal resting state.
Epinephrine acts on adipose tissue and releases free fatty acids into the circulation.
Epinephrine is an effective stimulant of heart action. It increases the irritability and the rate and strength of contraction of cardiac muscle and increases cardiac output. It causes vasodilatation of the arterioles of the skin and mucous membranes. Norepinephrine has less effect on cardiac output.
Epinephrine causes relaxation of the smooth muscles of the stomach, intestine, bronchioles and urinary bladder. This hormone is valuable in the treatment of asthmatic attacks.

Glucocorticoids or Cortisol

Cortisol increases glucose, amino acids and fatty acid levels in the blood.
In the muscle and adipose tissues, they cause protein depletion.
In the adipose tissue, cortisol increases lipolysis and in muscle, they cause depletion of stored protein.
Glucocorticoids increase the levels of alanine-α-ketoglutarate and tyrosine transaminases as well as tryptophan pyrrolase.
They increase the key enzymes in the regulation of gluconeogenesis (Phosphoenolpyruvate carboxykinase, Pyruvate carboxylase, glucose-6- phosphatase and Fructose-1 6-di-phosphatase).
In the liver, cortisol acts on the fixation of carbon dioxide at the level of pyruvate carboxylase which is the key enzyme in gluconeogenesis.
This group of hormones is inactive on red cells, heart and the brain.
They have immune-suppressive and anti-inflammatory effects.
They have effects on bone, exocrine secretion, cyclic AMP and stress.

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Plant Stress Hormones:

When plants are exposed to different types of stress such as salinity, heat, cold and drought etc. Phytohormones play an integral role during stressful conditions and assist the plant body in adapting to adverse environmental conditions.

Several phytohormones like Salicylates, Jasmonates and ABA interact together and act in hormone signal transduction cascade or “crosstalk” between hormones to form a defence network against environmental stresses. An important plan for stress hormone is Abscisic acid.

Abscisic Acid (ABA)

(ABA) acts as a plant growth inhibitor and regulates dormancy and abscission. It is called a stress hormone because the synthesis of ABA is stimulated by stressful environmental conditions such as waterlogging, drought etc. It plays a critical role in tolerating abiotic stress. The functions of ABA are mentioned below:

This hormone stimulates the closure of stomata during high salinity and reduces the loss of water by transpiration. ABA interacts with other phytohormones such as nitric oxide, Jasmonates and signalling molecules to induce stomatal closure.
Abscisic acid induces seed dormancy and thereby helps seeds to withstand unfavourable conditions such as desiccation for the growth.
ABA also plays a role in the growth and modification of the root system during nitrogen deficiency and drought. It regulates gene expression that’s required for water uptake and root growth maintenance.
The hormone regulates protein-encoding genes and biosynthesis of fats (lipids) and storage proteins.
ABA plays a critical role during signal transduction pathway during a stress response.
This hormone is involved in the synthesis of osmoprotectants, dehydrins and protective proteins.

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FAQs on Stress Hormones: Functions and Importance

1. What are stress hormones and why are they important for the body?

Stress hormones are chemical messengers released by the endocrine system in response to physical or psychological stress. They are crucial for survival as they trigger a series of physiological changes, collectively known as the 'fight-or-flight' response. This response prepares the body to either confront or flee from a perceived threat by mobilising energy reserves and increasing alertness.

2. What are the main types of stress hormones in humans?

The main stress hormones in the human body can be grouped into two primary categories based on where they are produced in the adrenal glands:

Catecholamines: Produced in the adrenal medulla, these include adrenaline (epinephrine) and noradrenaline (norepinephrine). They are responsible for the immediate, short-term stress response.
Glucocorticoids: The most important of these is cortisol, which is produced in the adrenal cortex. It manages the body's response to long-term or chronic stress.

3. How does adrenaline prepare the body for a 'fight or flight' response?

Adrenaline rapidly prepares the body for intense physical activity by initiating several key changes:

It increases heart rate and blood pressure, ensuring oxygen and nutrients are quickly delivered to muscles.
It stimulates the breakdown of glycogen into glucose in the liver, providing an immediate source of energy.
It causes dilation of the pupils to enhance vision and increases the rate of breathing.
It redirects blood flow away from non-essential functions like digestion towards the skeletal muscles, brain, and heart.

4. What is the role of cortisol as the primary stress hormone?

Cortisol is often called the primary stress hormone because it manages the body's response to prolonged stress. Unlike adrenaline's rapid effects, cortisol's actions are slower and more sustained. Its primary roles include increasing blood sugar (glucose) levels through gluconeogenesis, suppressing the immune system to reduce inflammation, and aiding in the metabolism of fat, protein, and carbohydrates to ensure a steady supply of energy.

5. What are the symptoms of chronically high stress hormone levels?

When stress hormone levels, particularly cortisol, remain elevated for extended periods, it can lead to various health issues. Common symptoms include persistent anxiety, sleep disturbances, digestive problems, weight gain (especially around the abdomen), impaired memory and concentration, and a weakened immune system, leading to frequent illnesses. A medical condition caused by extremely high cortisol levels is known as Cushing's syndrome.

6. What is the difference between the short-term and long-term stress response?

The key difference lies in the hormones involved and the speed of the response. The short-term response is an immediate, nerve-driven reaction involving the release of adrenaline and noradrenaline from the adrenal medulla, triggering the 'fight-or-flight' state. The long-term response is a slower, more prolonged process controlled by hormones like cortisol from the adrenal cortex, which helps the body cope with sustained stress by managing energy resources over time.

7. Do plants also have stress hormones?

Yes, plants also produce hormones to cope with environmental stress. A key phyto-stress hormone is Abscisic acid (ABA). It is often called the 'stress hormone' in plants because its levels increase significantly in response to stresses like drought, high salinity, or cold temperatures. ABA helps the plant conserve water by triggering the closure of stomata (pores on leaves) and promoting dormancy.

8. Are there any 'anti-stress' hormones that counteract the effects of stress?

While not direct antagonists in a simple sense, some hormones can produce effects that counteract stress. For example, oxytocin is known for promoting feelings of bonding and calm, which can lower blood pressure and cortisol levels. Similarly, endorphins, the body's natural painkillers, can induce feelings of pleasure and well-being, helping to mitigate the perception of stress.

9. How are the adrenal glands involved in the stress response?

The adrenal glands, located on top of the kidneys, are central to the stress response. They are composed of two distinct parts: the inner adrenal medulla, which releases adrenaline and noradrenaline for the rapid, short-term response, and the outer adrenal cortex, which secretes cortisol to manage the slower, long-term stress adaptation. This dual-functionality allows the body to react to both immediate dangers and chronic pressures.