FIGHT OR FLIGHT
FIGHT OR FLIGHT RESPONSE
The fight or flight response including the role of adrenaline.
The sympathetic nervous system functions like a gas pedal in a car. It triggers the fight-or-flight response, providing the body with a burst of energy to respond to perceived dangers. The parasympathetic nervous system acts like a brake. It promotes the "rest and digest" response, which calms the body down after the danger has passed.
Key Words
1. The neocortex is the thinking part of the brain where logic and judgment reside. It is the outer portion of the brain and is divided into lobes. Think of the cortex as the strategy centre of the brain. When someone is experiencing and expressing anger, he or she is not using the thinking (cortex) part of the brain but primarily the limbic centre of the brain.
2. Limbic system: The brain's emotional centre is the limbic system. It is located lower in the brain and is considered to be more primitive than the cortex.
3. Hypothalamus: a region of the brain between the thalamus and the midbrain that functions as the main control centre for the autonomic nervous system by regulating sleep cycles, body temperature, appetite, etc., and that acts as an endocrine gland by producing hormones, including the releasing factors that control the hormonal secretions of the pituitary gland
4. Hippocampus: (named after it resembles the seahorse, is a major component of the brains of humans and other vertebrates. Humans and other mammals have two hippocampi on each side of the brain. It belongs to the limbic system and is important for consolidating information from short-term to long-term memory and spatial navigation. The hippocampus is located under the neocortex, and in primates, it is located in the medial temporal lobe, underneath the cortical surface
5. Thalamus: This is a midline symmetrical structure of two halves within the vertebrate brain, situated between the neocortex and the midbrain. Some of its functions are relaying sensory and motor signals to the neocortex and regulating consciousness, sleep, and alertness.
Quick facts:
The Amygdalae (singular: Amygdala; are two almond-shaped groups of nuclei located deep and within the brain's temporal lobes. The Amygdala is a primitive brain structure found in all vertebrates. The Amygdala has been shown in research to perform a primary role in the processing of:
Memory
Decision-making
Emotional responses
The role of the Amygdala
The Amygdalae, considered part of the limbic system—a collection of brain structures associated with emotions and urges—play a pivotal role in processing emotions and triggering survival instincts. Specifically, they orchestrate our "fight or flight" responses, which are natural survival mechanisms. It is believed that the Amygdalae evolved primarily as the fear response system. Fear, for vertebrates, is an adaptive reaction; without it, animals and humans would repeatedly walk into danger, often leading to severe injury or death.
The Amygdalae connect with several key brain regions, including the neocortex, hypothalamus, hippocampus, and thalamus. This intricate network regulates emotional responses and memory consolidation, as the amygdala works in conjunction with the hippocampus, which is vital for memory and learning. The Amygdalae-Hippocampus connection is particularly significant as it facilitates learning what to fear, thus sparing us from continually reassessing potentially dangerous situations. Since assessing threats consumes valuable time and delays reactions, this connection is indispensable for survival.
Moreover, the amygdala is closely connected to all our senses, receiving sensory input from the external environment and internal organs. This comprehensive sensory connectivity allows for the perception of danger across multiple sensory modalities. For instance, the Amygdalae enable us to visually detect threats, such as encountering a predator like a tiger, or olfactorily sense danger, such as detecting smoke. Furthermore, the Amygdalae receive input from the neocortex, enabling us to efficiently evaluate new behaviours or situations.
When the Amygdalae integrate sensory input associated with danger, they elicit fear or aggression responses, depending on an individual's assessment of their ability to handle the situation. In response to perceived threats, individuals may instinctively engage in fight, flight, freezing, or submission behaviours. However, the degree to which one resorts to these behaviours is influenced by self-efficacy—a belief in one's ability to succeed in specific situations.
During intense emotional states or when a sensory input matches a previously encountered threatening event, the amygdala can override rational brain processing. This phenomenon, known as Amygdala hijacking, results in instinctive reactions without cognitive assessment. Consequently, individuals may act impulsively, without much regard for the consequences, as the rational brain—the frontal/neocortex—is temporarily bypassed.
This emotional brain activity occurs milliseconds earlier than rational brain processing, enabling swift responses to perceived threats. If the Amygdalae perceive a memory match to a stimulus, they can trigger the hypothalamic-pituitary-adrenal (HPA) axis, inducing physiological stress responses. This can lead to increased heart rate, elevated blood pressure, and heightened arousal, preparing the body for action.
Additionally, individuals experiencing an Amygdala hijack may exhibit compromised reasoning and logical thinking, as the emotional brain overrides the rational brain. Once emotions are activated, a cascade of hormones is released, causing physical and emotional alarm, further preparing the individual for the fight or flight response.
Moreover, the Sympathetic-Adrenomedullary (SAM) system, which is part of the body's response to stress, works in concert with the HPA axis, particularly in immediate "fight-or-flight" situations. The sympathetic nervous system activates the SAM system, leading to the release of catecholamines, such as adrenaline and noradrenaline, from the adrenal medulla. These hormones induce rapid physiological changes, such as increased heart rate and expanded air passages, preparing the body to confront or flee the stressor.
In summary, in collaboration with other brain regions and physiological systems, the Amygdalae play a critical role in processing emotions, triggering survival instincts, and enabling rapid responses to perceived threats. Their ability to integrate sensory input and past experiences facilitates adaptive behaviours that enhance survival in challenging situations
THE SYMPATHETIC-ADRENOMEDULLARY (SAM) SYSTEM
Sympathetic Nervous System Activation: When encountering a stressor, the sympathetic nervous system (SNS) is quickly activated. This part of the autonomic nervous system prepares the body for rapid action.
Adrenal Medulla Response: The activation of the SNS stimulates the adrenal medulla, which is the inner part of the adrenal glands located on top of the kidneys.
Release of Catecholamines: The adrenal medulla then secretes catecholamines, mainly adrenaline (epinephrine) and noradrenaline (norepinephrine), into the bloodstream.
Physiological Changes: These hormones cause several changes in the body, such as increased heart rate, elevated blood pressure, expanded air passages in the lungs, and a release of glucose and fats to provide muscle energy. These changes prepare the body to either confront or flee from the stressor – the "fight-or-flight" response.
Rapid Response: Unlike the HPA axis, which is more gradual, the SAM system's response is almost immediate, allowing for a quick reaction to acute stress.
THE SYMPATHETIC-ADRENOMEDULLARY (SAM) SYSTEM APPLIED
For instance, if you were in a situation where you suddenly encountered a dangerous animal, like a polar bear, the SAM system would rapidly kick in, causing immediate physiological changes that would prepare you to either fight the bear or run away.
Applying the Sympathetic-Adrenomedullary (SAM) system to a scenario where you encounter a polar bear would look like this:
Immediate Recognition of Danger: As soon as you see the polar bear, your brain, particularly the amygdala, instantly recognises it as a significant threat.
Activation of the Sympathetic Nervous System: This recognition triggers the sympathetic nervous system, part of the autonomic nervous system responsible for the body's rapid involuntary response to dangerous or stressful situations.
Adrenal Medulla Response: Activating the sympathetic nervous system leads to the stimulation of the adrenal medulla, the inner part of your adrenal glands.
Release of Catecholamines: The adrenal medulla quickly releases catecholamines, especially adrenaline (epinephrine) and noradrenaline (norepinephrine), into your bloodstream.
Physiological Changes for Fight-or-Flight: These hormones cause your heart rate to spike, your blood pressure to rise, your pupils to dilate, and your airways to open up. Your liver releases glucose for extra energy, and blood flow is redirected to essential muscles, preparing you for rapid physical action.
Fight, Flight, or Freeze: In this heightened state, you are ready for the fight-or-flight response. You might find yourself either preparing to defend yourself against the polar bear (fight), looking for the quickest escape route (flight), or you might be momentarily paralyzed by fear (freeze), a common response when a threat seems overwhelming.
In this scenario, the SAM system enables you to react almost instantly to the sudden appearance of the polar bear, preparing your body to handle this acute stressor through a rapid physiological response.
HYPOTHALAMIC PITUITARY ADRENAL CORTEX (HPAC)
The hypothalamic-pituitary-adrenal (HPA) axis is a complex set of direct influences and feedback interactions among three components: the hypothalamus, the pituitary gland, and the adrenal (or suprarenal) glands. This axis plays a crucial role in the body's response to stress.
Hypothalamus: It initiates the stress response by releasing corticotropin-releasing hormone (CRH).
Pituitary Gland: In response to corticotropin-releasing hormone, the pituitary gland releases adrenocorticotropic hormone (ACTH).
Adrenal Glands: adrenocorticotropic hormone stimulates the adrenal glands to produce and release cortisol, a steroid hormone that helps the body manage stress.
Cortisol, in turn, has various functions including regulating metabolism, influencing immune response, and helping to regulate the body's response to stress. The HPA axis also involves feedback mechanisms, whereby increased cortisol levels eventually lead to a downregulation of CRH and ACTH production through negative feedback, thus regulating the system.
HYPOTHALAMIC PITUITARY ADRENAL CORTEX (HPAC) APPLIED
Imagine you are sitting in a room when suddenly a polar bear walks in. This unexpected and threatening situation would immediately activate your amygdala, a part of the brain responsible for processing emotions, especially fear and anxiety.
Amygdala Activation: The amygdala recognizes the polar bear as a threat, triggering an immediate fear response. This leads to the activation of the hypothalamic-pituitary-adrenal (HPA) axis.
HPA Axis Activation: In response to the signal from the amygdala, the hypothalamus releases corticotropin-releasing hormone (CRH).
Pituitary Gland Response: CRH stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH).
Adrenal Gland Response: ACTH prompts the adrenal glands to release cortisol, the stress hormone.
Physiological Changes: Cortisol and other stress-related neurotransmitters cause your body to undergo several changes. Your heart rate and blood pressure increase, breathing quickens, muscles tense, and your senses become sharper. These physiological changes prepare your body for a rapid response to the threat, commonly known as the "fight-or-flight" response.
Possible Actions: You might find yourself frozen in fear (a natural response to overwhelming threats), looking for an escape route, or even preparing to defend yourself.
This scenario illustrates how the HPA axis and the amygdala work together in response to a stressful and threatening situation, preparing the body to either face the danger or escape from it.
