Acute Stress is short-term stress, and it causes a reaction in the body to cope with it, fight or flight. This is when the sympthamedullary pathway causes the body to fight the danger, or run from it, through the release of Noradrenaline and Adrenaline. This response happens as shown below:
1) Body detects a threat
2) Message sent to the Amygdala at the back of the brain, this then sends a message to the Hypothalamus.
3) The Hypothalamus instructs the Adrenal Medulla to produce Adrenaline through messages down the Spinal Chord
This Adrenaline then creates changes to many vital organs, helping the body to fight the danger, or run from it. For example the body dilates the Pupils to improve vision, it also accelerates the Heart rate and increases blood sugar levels so the muscles can work faster. These changes are categorized as the Sympathetic Nervous System.
Once the danger has passed the body needs to relax again, this is done by the Parasympathetic Nervous System. The Adrenal Medulla restricts the release of Adrenaline, resulting in changes such as a normal Heart Rate and normal Pupil dilation.
Chronic stress is stress over a long period of time, beyond the threat of an immediate danger. It is caused by the pituitary-adrenal system, as shown below.
1) Body perceives stress
2) Hypothalamus responds producing corticotrophic-releasing factor (CRF)
3) At the pituitary gland CRF causes the release of ACTH. This is carried in the bloodstream to the Adrenal Cortex.
4) The Adrenal Cortex releases Cortisol
5) Cortisol can lead to feeling more stressed, which leads to the process restarting. This is known as negative feedback.
Cortisol has some positive effects, for example a lower sensitivity to pain is useful in fight or flight, but some negative too.
Cortisol increases heart rate, blood sugar levels etc, which are useful in fight or flight, but by their nature are dangerous over long time periods. This is why Chronic stress can lead to cardiovascular problems.
Cortisol also leads to a weakened immune system. This is because a lower sensitivity of pain is needed in or for Fight or Flight, however over time this can lead to Immunosuppression.