Stress response system Flashcards
What is Homeostasis?
Examples:
- self regulating biological systems that allows organisms to survive and adapt to environments
- Body temp ( sweating)
- Blood Pressure ( When BP rises, blood vessels open more which slows heart rate and returns blood pressure to normal.
- Food - When you’re hungry, you eat. If you have less food, your body adjusts to a slower metabolism rate.
Why is Homeostasis essential for bodily functions?
is essential for optimal functioning of the body.
It allows the body to maintain conditions that are ideal for enzyme action and cell functions.
what would happen if homeostasis wasn’t a thing?
Without homeostasis, cells would quickly die when there aren’t enough nutrients
what did Hans Selye (1936) do?
General adaptation syndrome
- Injected rats with sex hormone
- Peptic ulcers, enlarged adrenal glands, involution of immune tissues
-Is this a result of the sex hormone? NO= same physiological responses rats injected with other chemicals and physical restrain
Same changes happened in the follow up study with other chemicals
why does heart beat (homeostasis) change during exercise?
- to get oxygen around body specifically muscles
what does repeated or chronic stress lead to?
to common diseases of modern life
what can stress be defined as?
Stress can be defined as events that are threatening to an individual and which elicit physiological and behavioral responses
What is Allostasis?
active process that leads to adaptation to a stressor
Exposed to a new situation - change average stress point to a new one to adapt to new condition and once new condition goes away system is back to average point
what is the autonomic nervous system
‘fight or flight’
what are the divisions of the autonomic nervous system?
sympathetic and parasympathetic
what is the first system triggered with stress?
Autonomic nervous system
What role do adrenaline and noradrenaline play in the body’s response to stress?
They act as neurotransmitters that make the heart work faster, preparing the body for action.
play a crucial role in fight or flight system
adrenaline plays a crucial role in action potential
what are the two major systems orchestrating the stress response?
Hypothalamic-pituitary-adrenal axis and autonomic nervous system
which limbic structures regulate HPA axis?
Prefrontal cortex, hippocampus and amygdala
Where are adrenaline and noradrenaline primarily released from?
Adrenal medulla
effects of acute stress
Acute stress has effects in the immune system by mobilizing the lymphocytes
(natural killer cells)
anti inflammatory effects
what does the hypothalamus release in response to stress?
corticotropin-releasing hormone
what does the anterior pituitary release?
adrenocorticotropin hormone
where is cortisol released?
Adrenal Cortex
where is adrenal gland located?
Above kidneys
How does the autonomic nervous system contribute to the release of adrenaline?
Autonomic nervous system send messages to adrenal medulla which then releases adrenaline to prepare the body for a fast response
What is the autonomic nervous system mediated by?
neurons
why is autonomic nervous system considered a very fast system?
it is mediated by neurons, allowing an immediate response, such as increased heart rate and sweating when feeling anxious. or movement
Which hormones are involved in the HPA axis?
CRH (Corticotropin-Releasing Hormone), ACTH (Adrenocorticotropic Hormone), and Cortisol.
what is the HPA axis mediated by?
Hormones
what is the secondary stress response system?
HPA axis, occurs a few minutes after 1st response
Steps of the HPA axis stress response
- hypothalamus releases CRH- travels to anterior pituitary gland
- CRH works on anterior pituitary and stimulates gland which releases a second hormone called adrenocorticotropic hormone (ACTH)
- ACTH travels from pituitary to adrenal gland via bloodstream- This then stimulates adrenal cortex
-Adrenal cortex releases cortisol finally
-When cortisol levels are high, cortisol informs the pituitary gland to stop producing ACTH. - The pituitary then signals the hypothalamus to stop releasing CRH.
-This shuts down the stress response to maintain balance (homeostasis).
how does cortisol act in the body
cortisol acts in body to release sugar and make energy available for fight or flight
how does hypothalamus initiate stress response
It releases CRH, which travels to the anterior pituitary gland.
What is the role of adrenocorticotropic hormone (ACTH) in the stress response?
It travels via the bloodstream to the adrenal gland, stimulating the adrenal cortex to release cortisol.
How does cortisol regulate the HPA axis through negative feedback?
Cortisol signals the pituitary gland to stop releasing ACTH, which then informs the hypothalamus to stop releasing CRH, shutting down the stress response.
what is the HPA axis modulated by
Modulated by limbic system
How do limbic structures influence the HPA axis? (inhibit, trigger)
Amygdala triggering the release of CRH
Hippocampus and prefrontal cortex inhibits release of CRH
What role does the amygdala play in triggering the stress response?
It processes fear and anxiety and decides whether to activate the stress response based on previous experiences.
detecting threats and initiating the “fight-or-flight” response through signals to the hypothalamus,
How does the body respond to physical stressors differently from psychological stressors?
Physical stressors trigger an autonomic response via the brainstem, while psychological stressors involve limbic structures and cognitive processing.
How do the hippocampus and prefrontal cortex regulate stress
They inhibit the release of CRH to prevent excessive cortisol production and protect the brain.
Why does the prefrontal cortex inhibit the release of CRH?
To prevent excessive cortisol levels, which can be neurotoxic and disrupt neurons in the prefrontal cortex, affecting memory and decision-making.
Why do physical stressors not require cortical activation?
Because they are processed by the brainstem and trigger an automatic stress response without conscious thought (e.g., reacting to a cut).
What is an example of a top-down stress response?
Feeling stressed about a presentation the next day—limbic structures trigger the hypothalamus in anticipation.
feeling stressed about an exam
what factors are involved in top down stress responses ?
cognitive and emotional factors
What are the different temporal responses to stress?
- Immediate responses is mediated by neurotransmitters - monoamines
- short term stress response (occurs few mins after), hormones like CRH ACTH, Cortisol
- Long term exposure to stress- genomic and structural effects
How do neurotransmitters mediate the immediate stress response?
Monoamines such as adrenaline and noradrenaline trigger a rapid physiological response.
What physiological markers can be used to measure stress?
Blood pressure, heart rate, skin conductance, and cortisol levels.
what is the purpose of the stroop test in measuring stress?
It induces cognitive stress, and EEG can be used to measure neural responses.
How does skin conductance relate to stress?
It increases due to heightened sympathetic nervous system activity.
how does cold pressor test measure stress?
A test where a person immerses their arm in cold water (4°C) for 1-3 minutes to induce physical stress, measuring heart rate and adrenaline levels.
heart rate increases during exposure and returns to baseline when the stressor is removed.
how does the socially evaluated cold pressor test measure stress?
leads to the activation of both physiological stress pathways: the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis, which is evidenced by increased blood pressure and cortisol.
most used test in literature
Keep arm in water for 3 mins, give them negative feedback saying they can do better
how does the trier social test measure stress?
Participants perform a mock job interview while being judged, followed by a math task, inducing psychological stress.
when measuring cortisol levels in saliva, how long do you have to wait?
20 mins
when measuring cortisol levels in blood, how long do you have to wait?
after 3 mins
why is cortisol measured when measuring stress
cortisol levels indicate physiological stress response.
What are some common animal models used to study stress?
Forced swim test (depression), intruder paradigm (aggression), and social isolation.
features of Acute stress
mobilisation of lymphocytes (lymphocytes continuously circulate between the blood and lymphatic system, enabling them to encounter antigens and initiate an immune response)
anti inflammatory effects
how can stress impact cardiovascular health?
Stress increases inflammation, leading to plaque buildup in arteries, which can cause heart disease and other cardiovascular conditions.
chronic stress features
hyper activation of immune response
increase in pro inflammatory substances
