Select your language

Suggested languages for you:
Log In Start studying!
StudySmarter - The all-in-one study app.
4.8 • +11k Ratings
More than 3 Million Downloads
Free
|
|

All-in-one learning app

  • Flashcards
  • NotesNotes
  • ExplanationsExplanations
  • Study Planner
  • Textbook solutions
Start studying

Hypothalamic-Pituitary-Adrenal System

Save Save
Print Print
Edit Edit
Sign up to use all features for free. Sign up now
Hypothalamic-Pituitary-Adrenal System

The hypothalamic-pituitary-adrenal system (HPA axis) is the body’s response system to chronic stress (long-term stress). The HPA axis does not react as fast as the sympathomedullary pathway, the body’s response, to acute stress. The HPA axis consists of the hypothalamus, pituitary gland (anterior pituitary) and adrenal gland. Here is an overview of the HPA axis, and we will describe the stages below:

Hypothalamic Pituitary Adrenal System Diagram StudySmarterDiagram of the hypothalamic-pituitary-adrenal system, Tyler Smith - StudySmarter Originals

The stages of the hypothalamic-pituitary-adrenal system

  1. The hypothalamic-pituitary-adrenal system kicks in after the initial fight or flight response. If a person experiences prolonged stress, the hypothalamus is activated. As a result, a chemical messenger corticotropin-releasing hormone (CRH) is released into the bloodstream.
  2. CRH causes the anterior pituitary gland (situated just above the brainstem) to produce and release adrenocorticotropic hormone (ACTH), transported to the adrenal glands.
  3. The adrenal cortex (the outer region of the adrenal glands) is stimulated to produce cortisol.
  4. Cortisol converts protein into glucose, releasing a steady supply of blood sugar, providing a constant stream of energy, allowing the person to deal with the stressor. Cortisol also results in:
    • Lowered pain sensitivity.

    • Lowered immune response.

    • Diminished cognitive functions such as concentration.

    • Slowing down of digestion.

  5. This whole process takes about 20 minutes.

The hypothalamic-pituitary-adrenal system is self-regulating via a ‘negative feedback loop’. The brain monitors the cortisol levels; if high levels are detected, the levels of CRH and ACTH decrease, leading to a reduction of cortisol levels.

Most cells in the body have cortisol receptors, so while cortisol is a stress hormone, it plays an important role in bodily function. Cortisol controls many things such as blood sugar levels, metabolism regulation, salt and water balance.

Research on the hypothalamic-pituitary-adrenal system

  • Heim et al. (2000) found that women who were sexually abused as children had higher levels of HPA responses to stress. This finding suggests that CRH hypersecretion, which leads to hyperactivity of the hypothalamic-pituitary-adrenal system, is a consequence of childhood abuse.

  • Newcomer et al. (1999) gave participants either high cortisol levels to produce blood sugar levels similar to those undergoing major surgery or lower cortisol levels similar to those undergoing minor surgery. The participants given high cortisol levels were worse at recalling prose passages, which shows the effects of stress on the hypothalamic-pituitary-adrenal system on memory.

  • Kiecolt-Glaser et al. (1984) took blood samples from 75 students one month before their examination (control condition) and on the first day of their exams (stress condition). They also completed questionnaires about levels of loneliness, number of life events and psychiatric state. They found the activity of natural killer (NK) and T cells, which help fight infection, were lowered in the stress condition. Loneliness and problems such as depression were also associated with a decreased immune system.

  • Kiecolt-Glaser et al. (1991) assessed depression, immune function and health in a group of people caring for a relative with Alzheimer’s disease (long-term stress group) and a control group. The stress group had significantly lower immune system functioning and higher infectious illness and depression instances.

Hypothalamic-pituitary-adrenal system abnormality and dysfunction

While a little bit of stress is normal, chronic stress is not good for your health, as the stress system is always activated and the body cannot relax, leading to prolonged effects of cortisol which affects health. HPA system dysfunction can also be a result of genetics (controls factors such as cortisol response), biological causes (e.g., glucocorticoid medications) and childhood trauma.

Effects of HPA system dysfunction include:

  • Anxiety and depression.

  • Digestive problems.

  • Headaches, muscle tension and pain (muscles in the body are in a constant state of guardedness against injury and pain).

  • Heart disease, heart attack, high blood pressure, and stroke.

  • Sleep problems (The hypothalamic-pituitary-adrenal system, which produces cortisol, also has a vital role in the sleep cycle. Cortisol has a 24-hour rhythm that controls sleep; this rhythm is disrupted due to chronic stress).

  • Weight gain (Your cells need energy, which causes your body to send signals to the brain that you are hungry and need to eat).

  • Memory and concentration impairment.

Glucocorticoids, including cortisol, play a role in regulating the immune system and reducing inflammation. Chronic stress (excess cortisol) can impair communication between the immune system and the hypothalamic-pituitary-adrenal system. As a result, several health conditions such as diabetes, obesity, depression and immune disorders may ensue.

Hypothalamic-Pituitary-Adrenal System Chronic stress StudySmarterChronic stress, Flaticon

Hypothalamic-pituitary-adrenal system and depression

If a person experiences chronic stress, the HPA system is always activated, leading to an excess of cortisol. The cortisol receptors become desensitised, leading to noradrenaline and serotonin transmission disturbances.

Noradrenaline and serotonin are important in the regulation of mood and emotional behaviour.

Hypothalamic-pituitary-adrenal system evaluation

  • Importance of the HPA system: Research has highlighted the importance of the HPA system in adaptive human behaviour. People who have their adrenal glands surgically removed need hormone supplements to combat stressors. This shows the vital role of the HPA system in dealing with stress.

  • Maladaptive stress response: Prolonged exposure to chronic stress has negative effects on health, suggesting the HPA system may be hindering survival and that this stress response is maladaptive. This is because our stress response is old; it reacts the same way as it would have done thousands of years ago. But it was not equipped to deal with the modern stressors we face today for months or years. Thus, it now wears our body down and is a hindrance.


Hypothalamic-Pituitary-Adrenal System - Key takeaways

  • The hypothalamic-pituitary-adrenal system is the body’s response to chronic stress.

  • If a person experiences prolonged stress, the hypothalamus is activated. Corticotropin-releasing hormone (CRH) is then released into the bloodstream. As a result, the anterior pituitary gland produces and releases adrenocorticotropic hormone (ACTH), which is then transported to the adrenal glands. The adrenal cortex is stimulated to produce cortisol. Cortisol converts protein into glucose, providing a constant stream of energy, allowing the person to deal with the stressor.

  • Cortisol also results in other changes, such as diminished memory and concentration.

  • Long-term chronic stress is not good as it can lead to physical and mental health problems.

  • While the hypothalamic-pituitary-adrenal system is vital in dealing with stress, it is also maladaptive due to the consequences of chronic stress.

Frequently Asked Questions about Hypothalamic-Pituitary-Adrenal System

Hypothalamic-pituitary-adrenal axis dysfunction occurs when the hypothalamic-pituitary-adrenal system stops working correctly, leading to an excess of cortisol in the body. Chronic stress mainly causes this dysfunction.

When we face chronic stress, the hypothalamus releases corticotropin-releasing hormone (CRH). This process initiates other responses in the HPA system ending with the adrenal cortex releasing cortisol.

The hypothalamus controls the pituitary gland and regulates many body functions. The pituitary controls the adrenal glands, ovaries, testes and thyroid gland. Hypothalamus dysfunction may lead to growth problems for children, either too little or too much growth. There may be problems with puberty onset, either too early or too late. If the dysfunction is due to a tumour it may lead to headaches or loss of vision. If the thyroid is affected, there may be symptoms of an underactive thyroid, such as feeling cold all the time. If the adrenal glands are affected, there may be symptoms of low adrenal function such as fatigue.

The hypothalamic-pituitary-adrenal system is the body’s response system to chronic stress.

Final Hypothalamic-Pituitary-Adrenal System Quiz

Question

The HPA axis consists of which three components?

Show answer

Answer

Hypothalamus, pituitary gland, and adrenal glands.

Show question

Question

What hormone does the pituitary gland produce? It is fine to use the shortened initials in answer.

Show answer

Answer

ACTH.

Show question

Question

What are the effects of cortisol? (5 effects)

Show answer

Answer

  • Releases a steady supply of blood sugar.
  • Lowered pain sensitivity.
  • Lowered immune response.
  • Diminished cognitive functions, such as concentration,
  • Slowing down of digestion.

Show question

Question

How long does the process of the HPA system take to complete?

Show answer

Answer

Around 20 minutes.

Show question

Question

The HPA system is self-regulating. What happens if high cortisol levels are detected?

Show answer

Answer

The levels of CRH and ACTH decrease, leading to a reduction of cortisol levels.  

Show question

Question

Which researchers demonstrated the effects of chronic stress on the immune system?

Show answer

Answer

Heim et al.

Show question

Question

What happens to the HPA system as a result of childhood trauma?

Show answer

Answer

Hypersecretion of CRH, leading to hyperactivity of the HPA system.

Show question

Question

Why is chronic stress not good for health?

Show answer

Answer

The body cannot relax, leading to excess cortisol in the body, leading to physical and mental health problems.

Show question

Question

What is the link between chronic stress and the immune system?

Show answer

Answer

Glucocorticoids, including cortisol, play a role in regulating the immune system and reducing inflammation. Chronic stress can impair communication between the immune system and the hypothalamic-pituitary-adrenal system.

Show question

Question

What is the link between the HPA system and depression?

Show answer

Answer

Due to an excess of cortisol, the cortisol receptors become desensitised, leading to noradrenaline and serotonin transmission disturbances.

Show question

Question

What do people who have had their adrenal glands removed need, showing the vital role of the HPA system in dealing with stress?

Show answer

Answer

Hormone supplements.

Show question

Question

Why is the HPA system not effective at dealing with long-term chronic stress?

Show answer

Answer

Our body system is old, still reacting the same way it would have done thousands of years ago when stress did not last as long. It was not equipped to deal with the modern stressors we face today for months or years.

Show question

More about Hypothalamic-Pituitary-Adrenal System
60%

of the users don't pass the Hypothalamic-Pituitary-Adrenal System quiz! Will you pass the quiz?

Start Quiz

Discover the right content for your subjects

No need to cheat if you have everything you need to succeed! Packed into one app!

Study Plan

Be perfectly prepared on time with an individual plan.

Quizzes

Test your knowledge with gamified quizzes.

Flashcards

Create and find flashcards in record time.

Notes

Create beautiful notes faster than ever before.

Study Sets

Have all your study materials in one place.

Documents

Upload unlimited documents and save them online.

Study Analytics

Identify your study strength and weaknesses.

Weekly Goals

Set individual study goals and earn points reaching them.

Smart Reminders

Stop procrastinating with our study reminders.

Rewards

Earn points, unlock badges and level up while studying.

Magic Marker

Create flashcards in notes completely automatically.

Smart Formatting

Create the most beautiful study materials using our templates.

Just Signed up?

Yes
No, I'll do it now

Sign up to highlight and take notes. It’s 100% free.