The Physiology of Stress Flashcards
What is stress?
An emotional response to situations of threat. Such threats may be physical such as a spider about to attack you, and some threats may be psychological, for example worrying about exams.
How does your body respond to stress?
Your body produces a short-term (immediate) response and, should the stressor continue, a long term (ongoing) response.
What is the short term response to stress?
The Sympathomedullary Pathway
How does the Sympathomedullary pathway respond to stress?
A signal is sent down the sympathetic branch (SNS) of the Autonomic Nervous System (ANS) which then stimulates the Adrenal Medulla.
The signal is sent via the Central Nervous System to the two endocrine glands located just above the kidneys. The middle part of the adrenal gland (Adrenal Medulla) responds by releasing Adrenaline and smaller amounts of Noradrenaline into our bloodstreams.
Adrenaline and noradrenaline circulates through our bodies and affect the key target organs such as the heart and muscles.
After a few minutes the Parasympathetic branch of the ANS will start. This will reduce the “fight or flight” response and bring the body back to normal.
What is the long term response to stress?
The Hypothalamic Pituitary-Adrenal System
How does the Hypothalamic Pituitary-Adrenal System respond to stress?
The Hypothalamus is stimulated when the brain notices a stressor.
A signal is sent to the pituitary gland in the brain which releases a hormone called ACTH.
ACTH travels through the bloodstream down to the Adrenal Cortex (the outside of the adrenal gland) which stimulates it to release cortisol into the bloodstream.
The cortisol releases glucose from the liver to be used by the muscles as energy and suppresses the immune system to redirect energies to other areas of the body, for example brain and muscles. This process is called immunosuppression.
What is the General Adaptation Syndrome (GAS)?
When animals are exposed to unpleasant stimuli, they display the universal response to all stressors.
What did Seyle research and what did he do?
GAS - observed that in lab animals and human patients the fight or flight response was only the first of a series of reactions
He reported that the rats that he was experimenting on showed physiological changes that were directly linked to the injections that they received during the experiments, but that what was actually being injectors was less important than the fact they were getting an injection.
The rats were then exposed to various types of harmful stimuli, including extreme cold, surgical injury, excessive exercise, severing the spinal cord and nearly lethal doses of drugs.
The rats developed the same physiological symptoms each time, including (over time) the development of stomach ulcers
What did Seyle conclude from his research?
Stress is “the non-specific response of the body to any demand”
What are the three stages of GAS?
Alarm reaction
Resistance
Exhaustion
What is the alarm reaction stage of GAS?
When we come across a stressor the fight/flight reaction is triggered. This is part of the sympathetic branch of the autonomic nervous system(ANS). This stage deals with acute stressors. It is at this stage that the sympathetic adrenal-medullary system (SAM) becomes activated. This is controlled by electric impulses through nerves, making the response fast.
What is the resistance stage of the GAS?
If the stressor is not dealt with then the endocrine system helps us to maintain our response, through the Hypothalamic pituitary adrenocortical axis (HPA). This is a hormonal response and travels through the blood, making this a slower response.
The hypothalamus sends a message to the pituitary gland which releases ACTH. This is what causes the adrenal Cortex to release cortisol. This stimulates the liver to release glucose and also suppresses the immune system
What is the exhaustion stage of the GAS?
This stage occurs when the body can no longer keep up with the stressor, and the body’s resources have become depleted. It is caused by severe long term or repeated stress, and it is in this stage that illness is most likely.
Once ACTH and cortisol are in the blood stream, the production of more is inhibited. The adrenal glands no longer function properly and they actually increase in size. Blood glucose levels tend to drop, which can result in death. Psychophysiological disorders may develop, e.g hypertension, asthma and peptic ulcers.
Behaviours/Emotions in the Alarm Reaction stage?
Heartbeats faster
Pupils dilate
Behaviours/emotions in the exhaustion stage?
Exhausted
Lack of sex drive
Lack of interest