Week 3.2: The neurobiological aspects of the stress response Flashcards
This is the body’s automatic reaction to perceived threats, preparing us to either confront (fight) or escape (flight) the danger.
Fight or Flight Response
Some experts add this as a third reaction, where an individual becomes immobile in the face of a threat
Freeze
The body’s attempt to maintain a stable internal environment.
When homeostasis is threatened, the body initiates responses to restore balance. This includes changes in heart rate, hormone levels, and behavior.
Homeostasis
What are causes of stress?
Threats to Well-being: Stress can arise from situations that threaten an individual’s physical or psychological well-being.
Perceived Threats: Even if a situation isn’t objectively dangerous, if it’s perceived as threatening, it can cause stress.
An Austrian-Canadian endocrinologist known for his pioneering work on stress. He was nominated for the Nobel Prize multiple times for his contributions to endocrinology and the study of stress.
Hans Selye
Selye’s term for the body’s general response to stress
General Adaptation Syndrome (GAS)
The body’s response to demands placed upon it, involving the production of stress hormones.
General Adaptation Syndrome / Stress Response
What are the Stages of GAS (General Adaptation Syndrome)?
Alarm Stage
Resistance Stage
Exhaustion Stage
The initial reaction to a stressor, activating the fight or flight response.
Alarm Stage
The body attempts to adapt to the stressor.
Resistance Change
Prolonged exposure to the stressor depletes the body’s resources, leading to potential health problems.
Exhaustion Stage
The main stress hormone in humans, produced in the adrenal cortex and released into the bloodstream.
Cortisol
As these hormones regulate glucose metabolism, so ‘gluco’, they are synthesised in the adrenal cortex, so ‘cort’, and chemically the structure is classified as steroid, so ‘oid’, which is the last part of the word.
Glucocorticoids
Has a low affinity for cortisol and is primarily activated by high cortisol levels during stress.
Glucocorticoid Receptor (GR)
Has a high affinity for cortisol and is activated by low or basal cortisol levels.
Mineralocorticoid Receptor (MR
The fluid inside the cell
Cytoplasm
The cell’s control center
Nucleus
Once GR is in the nucleus, it attaches to these specific parts of the DNA
Glucocorticoid Response Elements (GREs
Are special proteins found on the surface of or inside cells.
They act like locks that can be opened by specific keys, which are usually molecules like hormones, neurotransmitters, or drugs.
Receptors
What are the physiological roles of cortisol?
1) Controls energy metabolism
2) Maintains electrolyte balance and blood pressure
3) Modulates immune responses
Suppresses the immune system to prioritize immediate survival needs.
Cortisol
The endocrine system includes hormones, glands, and receptors.
Hormones like cortisol are part of this system, which uses chemical signals to regulate various body functions.
Endocrine System
How is cortisol produced and regulated?
1) Stress Trigger:
Hypothalamus releases two hormones: CRH and AVP
2) Hormone Cascade:
CRH and AVP tell the pituitary gland to release ACTH.
ACTH travels to the adrenal glands (on top of the kidneys).
The adrenal glands produce and release cortisol.
3) Cortisol’s Role:
Energy Release: Cortisol helps release stored glucose from the liver for energy to face the stressor.
Immune Suppression: Cortisol temporarily suppresses the immune system to focus on immediate survival.
4) Negative Feedback Regulation: When cortisol levels are high, it signals the brain to reduce its production.
This reduces the release of ACTH and CRH, lowering cortisol levels and maintaining balance.
Neurotransmitters are part of this system, which uses electrical and chemical signals to communicate between nerve cells.
Nervous System
Organs that produce and secrete hormones.
Glands
Releases ACTH
Pituitary Gland
A hormone released by the pituitary gland that stimulates the adrenal glands.
Adrenocorticotropic Hormone (ACTH):
Small glands located on top of the kidneys that produce cortisol and other hormones.
Adrenal Glands
A primary stress hormone that increases blood sugar and helps the body respond to stress.
Cortisol
Measures stress levels by assessing life events in the recent past.
Categories: The RLCQ includes five categories of stressors:
Work
Home and Family
Health
Personal and Social
Financial
Recent Life Changes Questionnaire
An immediate reaction to a perceived threat, preparing the body to either fight or flee.
Acute Stress Response
The ability of the stress response to help us survive by mobilizing energy quickly.
Adaptive Role of Stress
What are the effects of acute stress?
Increased Blood Flow to the Brain: Helps with better thinking and alertness.
Faster Breathing and Increased Blood Pressure: Prepares the body for action.
Slowed Digestion: The body prioritizes energy for immediate survival over digestion.
Increased Perspiration: Helps cool the body down.
Increased Cortisol Levels: Cortisol is a hormone that increases energy availability.
Increased Muscle Tension: Prepares muscles for quick action.
Refers to the process of making energy resources available for immediate use.
Mobilizing
Prolonged exposure to stress, which can alter brain circuits and increase the risk of depression and anxiety.
Chronic Stress
What are the effects of chronic stress?
Digestive Problems: Increased stomach acids can lead to issues like ulcers.
Increased Cholesterol and Fatty Acids: Can contribute to heart disease.
Increased Blood Pressure and Blood Sugar: Can lead to hypertension and diabetes.
Reproductive Issues:
Women: Menstrual cycle irregularities.
Men: Reduced sperm count and testosterone levels.
Increased Infection Risk: Weakened immune system.
Mental Health: Severe stress can lead to depression.
What is the connection between stress and depression?
High stress can increase the risk of depression, especially in individuals with high neuroticism.
A personality trait characterized by emotional instability and anxiety.
Neuroticism
The process of forming new neurons in the brain.
Neurogenesis
Imbalance in neurotransmitters like serotonin, dopamine, and norepinephrine.
Monoamine Dysfunction
The ability of synapses (connections between neurons) to strengthen or weaken over time.
Synaptic Plasticity
A region of the brain involved in memory and emotional regulation.
Hippocampus
Is a primary glucocorticoid
Cortisol
What are the effects of high glucocorticoid levels?
Depression-like Behaviour
Decreased Neurogenesis
Monoamine Dysfunction
Impaired Synaptic Plasticity
Reduced Hippocampal Volume
What happens when humans have a high dose of glucocorticoids?
Initial Effects: Manic symptoms (elevated mood, hyperactivity).
Long-term Effects: Depressive symptoms (low mood, fatigue).
A disorder caused by overproduction of cortisol.
Cushing’s Syndrome
Treatment of inflammatory conditions like asthma and autoimmune diseases.
Glucocorticoids
A central stress response system.
Hypothalamic-Pituitary-Adrenal (HPA) Axis
A region of the brain that controls the release of hormones.
Hypothalamus
What are hormones released by the hypothalamus?
Corticotropin Releasing Hormone (CRH): Stimulates the pituitary gland.
Arginine Vasopressin (AVP): Works with CRH.
What happens when glucocorticoid receptors (GR) are impaired?
Cortisol cannot effectively signal back to the hypothalamus and pituitary to stop the release of CRH and ACTH which means cortisol levels remain high and risks contributing to conditions like depression
When this feedback loop fails due to impaired GR function, cortisol levels remain high, which can contribute to conditions like depression.
Glucocorticoid Resistance
Elevated levels of cortisol in the body.
Hypercortisolism
Lower than normal levels of cortisol.
Hypocortisolism
A subtype of depression characterized by an unreactive mood and lack of pleasure in most activities.
Melancholic Depression
A subtype of depression characterized by a reactive mood, increased appetite, and sensitivity to environmental circumstances.
Atypical Depression
Common in classic and melancholic depression, where the mood does not improve in response to positive events
Unreactive Mood
Mood is strongly reactive to environmental circumstances, and there is often increased appetite
Reactive Mood
What is the connection between cortisol and inflammation?
Paradoxically Linked:
Although cortisol is a powerful anti-inflammatory hormone, in depressed patients, it is linked to increased inflammation, which seems contradictory
Refers to the body’s extremities and organs outside the brain and spinal cord.
Periphery
These are undifferentiated cells that can develop into different cell types.
Stem Cells
The main glucocorticoid hormone in rodents, similar to cortisol in humans.
Corticosterone
Hormones produced by the adrenal glands, such as corticosterone.
Adrenal Steroids
The rapid increase in the number of cells.
Cell Proliferation
The process by which cells become specialized in structure and function.
Cell Differentiation
A substance produced naturally within the body.
Endogenous Compound
What are the effects of adrenalectomy?
No Corticosterone Present: Absence of corticosterone due to the removal of adrenal glands.
Increased Neurogenesis: Enhanced formation of new neurons in the hippocampus.
Surgical removal of the adrenal glands.
Adrenalectomy
Is a compound used to label new cells, allowing researchers to track cell proliferation.
BrdU (Bromodeoxyuridine)
What are the roles of exercise and antidepressants on neurogenesis?
Physical exercise and antidepressant medications increase neurogenesis.
Refers to difficult or challenging situations that cause stress or hardship.
Adversity
The brain’s resident immune cells, responsible for defending against infections and helping to remodel neural circuits.
Microglia
A protein that plays a role in the survival, proliferation, and differentiation of microglia.
CSF1 (Colony Stimulating Factor 1)
Is a type of RNA that carries genetic information from DNA to the ribosomes, where proteins are made.
Think of it as a messenger that delivers instructions from the DNA in the nucleus to the ribosomes in the cell, which then use these instructions to build proteins
Messenger RNA
These are stem cells derived from the hippocampus, a brain region involved in memory and mood regulation.
Human Hippocampal Progenitor Cells
These cells have been altered to proliferate (multiply) indefinitely when exposed to certain growth factors and chemicals.
Genetically Modified Cell Line
Nerve cells that transmit information.
Neurons
Supportive glial cells in the brain.
Astrocytes
Glial cells that produce myelin, which insulates nerve fibers.
Oligodendrocytes
Are non-neuronal cells in the central nervous system (CNS) that provide support and protection for neurons.
They play several crucial roles in maintaining the health and functionality of the nervous system.
Glial Cells
What are the three main types of glial cells?
Astrocytes
Oligodendrocytes
Microglia
A synthetic Glucocorticoid that specifically activates glucocorticoid receptors (GR) but not mineralocorticoid receptors (MR), unlike cortisol which activates both
Dexamethasone
A man-made steroid that mimics the effects of cortisol.
Synthetic Glucocorticoid
The natural, internal process that regulates the sleep-wake cycle and repeats roughly every 24 hours.
Circadian Rythm
A sharp increase in cortisol levels that occurs 30 to 45 minutes after waking up
Cortisol Awakening Response (CAR)
This term describes the baseline level of hormone secretion throughout the day, reflecting the body’s natural rhythm
Basal Secretion
How can and why is hair used to measure cortisol levels?
Hair Growth: As hair grows, it incorporates cortisol from the bloodstream into the hair shaft. This process captures a record of cortisol levels over time.
Segment Analysis: By analyzing different segments of hair, researchers can determine cortisol levels for specific periods. For example, a 1 cm segment of hair typically represents about one month of cortisol exposure.
Cumulative Record: Unlike blood or saliva, which provide a snapshot of cortisol levels at a single point in time, hair offers a cumulative record of cortisol exposure over several months.
Non-Invasive: Collecting hair samples is easy and non-invasive, making it practical for long-term studies
Are a class of steroid hormones that are either produced naturally by the adrenal glands or made synthetically.
They have powerful anti-inflammatory and immunosuppressive properties, making them useful for treating a variety of conditions.
Corticosteroids
Changes in gene expression caused by environmental factors, without altering the DNA sequence.
Ex. Prolonged stress might turn on or off certain genes related to stress response, making you more prone to anxiety or depression.
Epigenetic Factors
Inherited traits that influence how the body responds to stress.
Ex. A family history of anxiety disorders can increase your risk of developing anxiety.
Genetic Factors
Observable characteristics or traits resulting from the interaction of genetics and environment.
Ex. In anxiety, behaviors like avoidance and physiological responses like increased heart rate.
Phenotype
The non-specific response of the body to any demand for change. (Hans Selye)
Stress
