Stress Psychophysiology

Stress Psychophysiology

(A)

The Brain

The brain is the main controller of the body and it instructs the rest of the body how to react and adjust to stressors. When the sense organs (eyes, nose, muscles, etc) detect stressors, the message of stressors will be passed along the nerves to the brain. These messages pass through the reticular activating system either from or to the limbic system and the thalamus. The limbic system is where emotion evolves while the thalamus is where decisions are made on how to deal with the incoming message. Then the hypothalamus comes to experience the stressors and activates two major stress reactivity pathways: the endocrine system and the autonomic nervous system.

 
(B)

The Endocrine System

The endocrine system consists of all the glands that secrete hormones. These hormones are carried through the circulatory system to the other parts of the body and change the function of their tissues.

When the anterior hypothalamus releases corticotropin releasing factor (CRF), and the pituitary gland releases adrenocorticotropic hormone (ACTH), the adrenal cortex will secrete glucocorticoids (primary cortisol) and mineralocorticoids (primary aldosterone). Cortisol increases blood sugar so as to provide energy for action. Aldosterone increases blood pressure so as to transport oxygen and food to organs and limbs.

The posterior hypothalamus activates the adrenal medullar through direct nerve pathway. The adrenal medullar secretes catecholamines epinephrine and norepinephrine which change the bodily functions as follow: (Greenberg , 1999 , p24)

  • acceleration of heart rate
  • increased force at which blood is pumped out of the heart
  • dilation of coronary arteries
  • dilation of bronchial tubes
  • increase in basal metabolic rate
  • constriction of blood vessels in the muscles and skin of the arms and legs
  • increase in oxygen consumption

Thyroid gland is activated by thyrotropic hormone (TTH) and secrets thyroxin. The thyroxin increases basal metabolic rate, and decreases feelings of tiredness.

 
(C)

The Autonomic Nervous System

The autonomic nervous system controls the involuntary functions of the body such as heart rate, respiratory rate, etc.. It consists of two components: the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is responsible for expending energy (e.g. increasing respiratory rate) while the parasympathetic nervous system is responsible for conserving energy (e.g. decreasing respiratory rate).

When a stressor is encountered, the hypothalamus will activate the sympathetic nervous system and lead to various changes within the body.(Greenberg , 1999 , p25)

  • acceleration of heart rate
  • increased force with which heart contracts
  • dilation of coronary arteries
  • constriction of abdominal arteries
  • dilation of pupils
  • dilation of bronchial tubes
  • increased strength of skeletal muscles
  • release glucose from liver
  • increase mental activity
  • dilation of skin and muscle arterioles
  • increase basal metabolic rate

 
(D)

The Cardiovascular System

When a stressor is encountered, the hypothalamus signals the pituitary to release oxytocin and vasopressin. These hormones cause contraction of the smooth muscles and hence leading to constriction in the walls of blood vessels and increment in blood pressure.

 
(E)

The Gastrointestinal System

The gastrointestinal system is responsible for accepting, breaking down and distributing food, and eliminating waste products. When a stressor is encountered, there are the following changes:(Greenberg , 1999 ,p29)

  • decreased amount of saliva, causing dry mouth
  • uncontrollable contractions of muscles of the esophagus, making swallowing difficult
  • increased amount of hydrochloric acid in the stomach, causing ulcers
  • alteration in the rhythmic movement of the intestines (peristalsis), leading to diarrhea or constipation
  • blockage of bile and pancreatic ducts, as well as pancreatitis (inflammation of the pancreas)

 
(F)

The Muscles

Stress leads to muscles contraction, i.e. tensing / bracing. This may lead to tension headaches and backaches.

 
(G)

The Skin

When a stressor is encountered, perspiration increases and the surface temperature of the skin decreases. The skin is cold and pale. Moreover, there may be connections between acne, dandruff and stress.

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Stress & Illness

(i) Stress-related diseases include hypertension, stroke, coronary heart disease, ulcers, migraine headaches, tension headaches, cancer, allergies, asthma, hay fever, rheumatoid arthritis, backache, and TMJ syndrome.
(ii) Since stress increases blood pressure and serum cholesterol, it is no surprise that studies have found it associated with hypertension, stroke, and coronary heart disease.
(iii) Stress decreases the effectiveness of immunological system by decreasing the number of T-lymphocytes. A less effective immunological system is suspected of resulting in allergic reactions, asthma, and even cancer.
(iv) Stress results in increased muscle tension and bracing. It is this phenomenon that is thought to be the cause of headaches, backaches, and neck and shoulder pain.

The Effects of Excessive Stress Level on Physiological, Cognitive, Emotional & Behavioral Changes

Stress Responses

Unbalanced

Balanced

Physiological

Headaches

Heart rate increases

Fitness improves

Mental health improves

Protective ability strengthens

Stress endurance increases

Painful neck

Breathing difficult

Stomachaches

Muscles tension

Dizzy

Blood pressure raises

Cramp

Vomit

Backaches

Feeling cold & hot

Back pain

Cognitive

Difficult to concentrate

Attention diffuses

Concentrate

More observant

Setting goals

Do things systematically

Positive life philosophy

Making objective judgement

Always make mistakes

Memory declines

Illusion

Judgement decreases

Confuse

Responses slow down

Ability of organization and long-term planning slows down

Emotional

Depressed

Anxious

Hopeful

Aggressive

Frightened

Accept challenge

Helpless

Disturbed

Self-control

Hopeless

Angry

Accept self-value

Upset

Bored

Recognize one's ability

Cannot stand or sit still

Diffused

Behavior

Tired

Always daydreaming

Think deeply

Exercise

Odd-behavior

Ignore new things

Relax oneself

Self-evaluation

Absence from work

Have suicidal intention

Take more rest

Care for others

Avoid solving problem

Poor interpersonal relationship

Accept new things

Forgive others

Irresponsible

Language problem increases

Glad of self-development

Drug abuse

Insomnia or sleep too much

Keep good interpersonal relationship

Play all the time

Eat too much or too less

Excessive eating

Interest and enthusiasm lose

Results

Extreme anxious

Lack of security

Low productivity

Poor interpersonal relationship

Less anxious

Feel secure

High productivity

Intimate interpersonal relationship

The Short-term and Long-term Responses towards Stress

Short-term Responses

Long-term Reponses

Endocrine System

Release epinephrine and norepinephrine into the blood, then release a large amount of blood to the muscles and lungs in order to increase energy supply, response rate, heart rate, blood pressure, blood glucose and metabolic rate. It allows people to response to stressors immediately.

Release thyroxin into the blood, so as to speed up metabolic rate, increase energy consumption and change to body activity rate.

Release cholesterol into the blood, in order to increase energy supply and improve muscular sports.

If they have not been changed into immediate responses, after a long period of time, they will lead to heart disease, stroke, etc. Also, higher blood pressure will damage the function of kidneys. In addition, the abnormal high level of blood glucose will increase the incidence of diabetes and anemia.

However, the condition prolongs for a long period, physical health will be affected, e.g feel tired, lose weight, etc.

If the level of cholesterol remains high, it will increase the danger of arterio-sclerosis, even lead to heart disease.

Energy Support

Blood is diverted from the digestive system to the muscles and lungs, and hence increases their functions. Also, the mouth will become dry and reduce the saliva in the stomach.

The circulation of blood to the skin increases. Sweating also increases so as to cool the muscles.

The lungs are enlarged. The frequency of breathing increases so as to capture more oxygen for the blood.

If the digestive system is deprived of blood for too long, it will become dysfunctional and cause stomachache.

Too much sweating will cause uncomfortable feeling and drain away body fluid and body heat. It will affect the natural moderator of the body temperature.

Hyperventilation (excessive breathing) will make people feeling dizzy and to have abnormal heart beat.

Concentration

Release hormones from the hypothalamus to reduce pain during injuries.

Release glucocorticoids from the adrenal cortex, so as to reduce tension in breathing.

Increase the alertness to the surroundings, and improve our psychological health.

Reduce sex hormones, so as to reduce sexual inclination and hence reduce the poor concentration caused by pregnancy.

If the hormones are not available, people will be over sensitive to the environmental stimuli.

However, this can reduce our ability to resist infection, and increase the danger of digestive ulcers. Also, tense responses will appear in a more serious way.

After a prolonged period, it will damage our sensory and psychological responses.

If the sexual inclination has been suppressed excessively, it will lead to male hypogonadism and so on.

Protective Responses

Blood vessels contract and blood content concentrates, so as to reduce the flowing of blood and increase the clotting ability of blood in case of injuries.

However, it increases the workload of the heart. It also increases the chances of coronary heart diseases and stroke.

 

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