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HS3-WK 1-Stress Response Learning Package
Health Sciences 3 (Mohawk College)
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HEALTH SCIENCES 3
Stress Response
Stress as a Response
OVERVIEW
You have already studied how the nervous system and endocrine system work closely
together to integrate the body’s response to changes in the internal and external
environment. We will now increase the breadth and depth of this understanding. In this
learning package you will be studying the concept of stress. Stress is an unavoidable
part of daily life and plays an important role as it helps us to survive. A prolonged stress
response can become an issue as it can lead to a decrease in health status and an
increased propensity to illness.
LEARNING OBJECTIVES
Throughout this learning package you will develop knowledge and understanding of:
¨
stress response
¨
the roles of the hypothalamus, pituitary gland and adrenal glands during stress
response
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specific hormones involved in stress response
¨
the harmful effects that can be caused by a prolonged stress response
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PRE-CLASS ACTIVITIES
1. Define the following terms:
Stressor: Is any factor that can stimulate a response. It can be external or internal, and
there are several types. Physical, psychological, biological, emotional, and
environmental. Stressors cause the release of hormones in the body and stressors
activate the sympathetic nervous system. Stressors affect each person differently and
are a normal part of life. They can be positive when dealt with appropriately.
Stress: A state of mental or emotional strain or tension resulting from adverse or very
demanding circumstances.
Eustress: This is stress associated with positive events. Like winning a competition,
birth of a baby, exercising, falling in love, or attending an event you’ve been anticipating.
This is good stress.
Allostasis: This is the process that the body uses to establish homeostasis when facing
stressors. If the internal and external environments and resources are both adequate
and okay for the body and cells to maintain homeostasis, then the body returns to its
normal healthy state.
2. Identify various examples of stressors considering:
Physiological: Exposure to things that are harmful or potentially harmful to cells,
tissues, organs, or body systems. Ex, extreme temperatures, decreased oxygen
concentration, infections, injury, prolonged heavy exercise, loud sounds, or noises.
Others include burns, chronic pain, birth of a baby and malnutrition.
Emotional/psychological: These are thoughts of real or imagined or perceived
dangers such as personal lose, unpleasant social interactions, or no social interaction.
Feelings of anger, fear, anxiety, depression, guilt, or grief are considered psychological
stressors. Psychological stress can also be highly variable from one person to another.
Environmental: Toxins, chemicals, pollutants, lighting, workplace, disaster, pesticides,
noise, privacy, electromagnetic waves temperature, traffic and waiting.
Work-related: Physical work environment, job content or demands, bad management
practices, lack of support and role conflict can all be contributing factors.
Situational: Can involve some type of conflict and usually involve situations that you
have no control over that are short term. Ex. Death of a pet.
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Hans Selye explored how the body responds and adapts to stress, calling the
response the General Adaptation Syndrome (GAS). Though types of stressors
vary widely, the response they evoke is remarkably consistent.
3. Describe the three stages in the general adaptation syndrome (GAS).
Alarm: Is when the body perceives a
stressor, and the sympathetic nervous
system is stimulated. The stressor initiates
the stress response in the body. The
sympathetic nervous system stimulates the
endocrine system, both systems release
hormones (such as catecholamines, cortisol,
corticosteroids)that target other organs and
tissues in the body to become active or not
active depending on the tissue or organ that
is affected. This stage cannot be sustained
indefinitely.
Resistance: This is when the body is in full
stress mode and is at its peak performance.
Exhaustion: This occurs when the stressors
is over or has been removed and the body
attempts to return to homeostasis. If the body is not able to return to homeostasis illness
and disease can develop.
The body responds to both actual and perceived stressors. The three primary
body systems directly involved in the physiological response to stress are the
nervous, endocrine, and immune systems.
Nervous System
4. Which division of the
nervous system is stimulated
during stress response?
• The autonomic nervous
system and the sympathetic
division of the nervous
system.
• Sympathetic nervous system
stimulates the endocrine
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system, which will then release epinephrin and norepinephrine. This is the body’s fight
or flight response hormones.
5. Describe the role of the following nervous system structures in the
physiological response to stress:
Cerebral cortex: Evaluates the emotional
psychological aspect of the stressor. It refers to
past experiences and memory to evaluate the
emotional impact of the stressor. It also tries to plan
future consequences and then plans a course of
actions for the stressor. These functions are all
involved in the perception of the stressor or how the
brain perceives the stressor. How severe the
stressor is, is it a physical or emotional stressor, the
intensity, the duration and what is causing it.
Limbic system: Is located in the inner mid portion
of the brain located near the base of the brain is
involved with motivation, learning, emotion, and
memory. It plays a role in influencing the endocrine
system and the autonomic nervous system as well.
Limbic system is extremely important in emotions
and behaviors related to emotions. When the limbic
system is activated during stress response
emotions, feelings and behaviors that guarantee
survival and self-preservation will occur. Once it’s
been activated it also stimulates the hypothalamus.
Reticular formation: Located near the lower end
of the brain stem and the thalamus. It contains the
reticular activating system which is the most
important part of the brain for the state of
wakefulness. When the reticular activating system
is stimulated it produced arousal and emotional
response to the stressor. An example would be, if
someone was sleeping and their awoken
suddenly, it is the reticular activating system that
sends impulses to the limbic system and the
cerebral cortex and that causes the wakefulness.
Hypothalamus: One of the most important organs that maintains homeostasis during
stress mode. As soon as the limbic system stimulates the hypothalamus it stimulates
the sympathetic nervous system. During stress the hypothalamus receives information
from all over the body and then responds to that information by increasing blood
glucose levels, heart rate, blood pressure, respiratory rate. The hypothalamus also
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causes a dilation of the bronchioles, shunting of blood from the skin and digestive
organs into skeletal muscles during stress mode and its responsible for the increase of
epinephrin from the adrenal medulla in adrenal glands. The hypothalamus releases a
substance called corticotrophin releasing factor which stimulates the anterior pituitary
gland to release adrenal corticotropic hormone. This hormone stimulates the cortex of
the adrenal gland to release cortisol. Hypothalamus also makes antidiuretic hormone,
which is sent to the posterior pituitary where it is stored. During stress mode antidiuretic
hormone is release from the posterior pituitary, which then targets the kidneys and
stimulates them the nephrons to increase water absorption. ADH also causes
vasoconstriction of blood vessels to non-essential organs during stress mode. ADH also
stimulate the anterior pituitary gland to release ore adrenal corticotropic hormones.
Pituitary gland: Also
called the hypophysis and
is located proximal to the
hypothalamus and is
connected to the
hypothalamus by a stock.
Has two part the anterior
and the posterior. The
anterior pituitary is the
largest part of the pituitary
gland and is regulated by
the hypothalamus and
relates tropic hormones
such as corticotropic hormones and follicle
stimulating hormone. The anterior pituitary also synthesizes and secretes luteinizing
hormone and growth hormone. It has several biological functions and actions including
the metabolism of macronutrients (proteins, nutrients, and carbohydrates). The
posterior pituitary is an extension of the hypothalamus and secretes two hormones,
ADH and oxytocin. These two hormones are made in the hypothalamus and stored in
the posterior pituitary.
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Endocrine System
6. Describe the role of the adrenal glands in the physiological response to stress.
•
•
•
•
• There are two adrenal glands which sit
on top of both kidneys and there are
two parts to each adrenal glands, the
medulla or the middle part and the
cortex or the outer part. The medulla
secretes catecholamines and the
cortex secretes corticosteroids
(glucocorticoids, mineralocorticoids,
and androgens).
• The adrenal medulla secretes
catecholamines which are epinephrin,
norepinephrine, and dopamine.
Catecholamines are normally neurotransmitters but when they are secreted by the
adrenal gland, they are considered hormones due to the fact that they go into the
bloodstream and target specific organs.
The adrenal cortex like mentioned before secretes corticosteroids. Glucocorticoids
such as cortisol has an effect
on glucose metabolism.
Mineralocorticoids such as
aldosterone, help maintain
fluid and electrolyte balance.
Cortisol is the most abundant
glucocorticoid and is
necessary to maintain life.
Another effect is their antiinflammatory response to
stress. They reduce
inflammation due to the
ability to stabilize cell
membranes in cells that release inflammatory chemicals, and they stabilize
lysosomes. This in turn reduces capillary permeability. Cortisol also helps to maintain
blood vessel integrity and fluid volume in blood vessels. Major control of cortisol is
through a negative feedback mechanism.
Cortisol also increases in blood stream with surgical stress, burns, infection, fever,
acute anxiety and with hypoglycemia.
Aldosterone is a mineral corticoid, and it helps to maintain extracellular fluid volume, it
acts on the kidneys and helps them to absorb sodium and excrete potassium. This in
turn retains water in the body.
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7. Glucocorticoid hormones and mineralocorticoid hormones are the main
hormones produced by the adrenal cortex. What are the physiological effects of
these hormones
during stress
response?
• Glucocorticoids
help to break
down proteins
and fats and
convert that to
glucose, which
then causes
glucose to be
released into the
bloodstream.
They also
suppress the
immune system
to help reduce
inflammation.
8. Catecholamines are the primary hormones produced by the adrenal medulla.
What are the physiological effects of these hormones during stress response?
• Catecholamines cause glycogen in
the liver to be converted to be
glucose and then release glucose
into the bloodstream. We need an
increase in glucose in the blood
stream for cells to respond to the
fight or flight mode. Epinephrin and
norepinephrine also increase blood
pressure, respiratory rate, and
cellular metabolic rate.
• Catecholamines stimulate the
pancreas to release more glucagon
and less insulin. Glucagon then
stimulates the liver to convert stored
glycogen into glucose and release it
into the bloodstream.
Catecholamines also stimulate
lipolysis which is the breakdown of
fats into fatty acids. They also
increase the heart rate and the
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conduction or contractility, so that the heart rate increase and the contractions of the
heart become stronger.
• Corticosteroids also cause the smooth muscles in the respiratory tract to relax, which
causes bronchodilation.
• Epinephrin also causes vasodilation in skeletal muscles and in cardiac muscles.
Effects of epinephrin are short lived but the effects of norepinephrine are prolonged.
9. Describe the effect of adrenal
gland hormones on:
Heart rate: Increases
Blood vessel diameter in skin
and viscera: Vasoconstriction
Blood vessel diameter in skeletal
muscle: Vasodilation
Mental alertness: Heightened
mental alertness
Smooth muscle of bronchi:
Bronchodilation of the airways
Plasma glucose level: Increase
blood glucose levels
Inflammatory response: Decrease in inflammatory response
Antibody production: Decreases antibody production
Gastric mucosa: Decrease in secretion of acids from mucosa.
Usually, the body is able to deal with the stressor, and the stress response
diminishes. If a stress response is severe or prolonged, harmful physical effects
can occur from the sustained action of the above hormones.
Immune System
10. Why would an individual experiencing prolonged or severe stress be prone to
infections?
• There is an increased depression of the inflammatory response and immune system.
Corticoid steroids reduce the inflammatory response and reduce the activity of white
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Stress Response
blood cells related to immunity. Due to defense mechanism being reduced, then
opportunistic infection may develop.
• We become susceptible to infection particularly with organisms that normally aren’t
pathogenic. Over time with prolonged stress lymph tissues atrophy and circulating
WBC decrease in number and function.
• Over time increased stress also impedes or differs wound healing due to glucose
corticoids reduce protein synthesis and tissues regeneration. Catecholamines cause
vasoconstriction and therefore decreases oxygenated blood flow and nutrients to
wounds that need to heal.
Stress and Disease
11. Discuss how stress can be an exacerbating factor for many diseases and
disorders.
• Preexisting health conditions can worsen or they can return if they are in remission.
• Stress causes vasoconstriction in many organs and tissues. This can occur in organs
or tissues that may already be damaged or diseased.
• Stress mode further cause ischemia and hypoxia to tissues and organs, which can
worsen the disorder.
12. What is the complication of prolonged or severe stress on the kidneys? Why
does this occur?
• Acute renal failure is the result of severe or prolonged stress on the kidneys due to
severe vasoconstriction and reduced oxygenated/nutrient rich blood supply going to
the kidneys.
13. How does prolonged vasoconstriction affect the gastrointestinal system?
• During stress mode blood is shunted out of the blood vessels in the GI system and are
taken to essential organs and tissues related to stress. The oxygenated/nutrient rich
blood supply of the GI tract is reduced during stress mode, which then causes
ischemia and hypoxia. This can result in tissue breakdown, peptic ulcers, duodenal
ulcers, and infection.
14. What happens to intellectual function and memory because of prolonged or
severe stress? Why does this occur?
• Reduced during prolonged or severe stress due to the prolonged release of
corticosteroids causes structural changes in the brain in the hypo campus and the
prefrontal cortex, which is involved in learning, memory, critical thinking, and problem
solving.
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15. Describe the physiological mechanisms which cause stress-induced
hyperglycemia.
• In stress mode, stress hormones cause increased levels of glucose in the blood
stream. Prolonged hyperglycemia can result in the micro and microvascular
complications of diabetes. This includes peripheral neuropathy, stroke, retinopathy,
neuropathy and many more.
16. Describe the effects of stress on the cardiovascular system.
• Myocardial ischemia
• Left ventricular dysfunction
• Changes in conduction system due to prolonged increased levels of catecholamines.
Cardiac conduction system can then malfunction, and this can lead to dysrhythmias.
• Eventually with prolonged stress CAD and hypertension will occur.
17. Discuss how stress is related to cancer.
• T cells are the only cell in the immune system that fight cancer and the immune
system in depressed during stress mode. This then becomes the prime environment
for cancer cells to evolve.
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