L8&9 NEW Flashcards
What does ANS consist of and how its parts are connected to other organs?
Preganglionic neurons: Located in the spinal cord and brainstem, project to postganglionic neurons.
Postganglionic neurons: Located in autonomic ganglia, project to visceral organs, blood vessels, and glands.
What does SNS consist of?
The sympathetic branch of the ANS can be further subdivided into the sympathetic nervous system (SNS), which includes the sympathetic ganglia, and the sympathetic adre- nomedullary (SAM) system, which includes the adrenal medulla.
Catecholamines include
Norepinephrine, epinephrine, and dopamine
Where do noradrenaline and adrenaline bind & what processes cause?
Both NE and EPI bind to adrenergic receptors throughout the body and mediate rapid metabolic effects that are part of the “fight-or-flight” response, including energy mobilization; enhanced cardiovascular function; decreased blood flow to the skin and abdominal and pelvic organs; increased blood flow to skeletal muscles, the heart, and the brain; and enhanced arousal and vigilance
HPA consists of
Hypothalamus (PVN of Hypothalamus)
Pituitary gland (anterior pituitary)
Adrenal gland (adrenal cortex)
Process of cortisol release through HPA
- CRH + AVP released by neuroendocrine cells of PVN into hypophyseal portal system
- In the anterior pituitary CRH + AVP trigger ACTH release
- ACTH is then transported to the adrenal glands where it stimulates release of glucocorticoids (GCs) - cortisol in humans (main GC in humans)
What is the additional job of HPA aside from stress response?
The HPA axis also displays basal circadian and ultradian rhythmic activity, which includes fluctuations in HPA axis hormones with a period of about 24 h and 60 min, respectively
Where do GCs (cortisol) binds and what processes happen?
mineralocorticoid receptors (MRs) - have high affinity for GCs and are 90% occupied at basal GC concentrations -> promotes the start of stress response
glucocorticoid receptors (GRs) - ten times lower affinity for GCs and become occupied only at elevated GC levels -> termination of cortisol release
Difference between genomic and non-genomic effects of GCs
Non-genomic effects of GCs manifest themselves within seconds to a few minutes, genomic effects of GCs take at least 60 min to develop and can last for hours to days
What is it needed for: GCs can easily bind to intracellular receptors, which regulate the transcription of a large number of genes (1–2% of total genes)
GCs can exert both rapid effects on cell function and long-term changes in gene transcription depending on the receptors they activate
What are afferent systems and efferent circuits for?
Afferent systems - stressor detection and affective appraisal of sensory information
Efferent circuits generate the physiological and behavioral stress responses via activation of peripheral effector systems
Which sensory systems detect physical stressors, and what do they monitor?
How are psychological stressors detected?
Interoceptive sensory systems, which monitor the internal milieu and body integrity.
Through exteroceptive sensory systems that process sensory information from the external environment.
What is the role of the innate alarm system in stress detection?
It performs a rapid and crude analysis of the biological significance of incoming sensory information to detect external threats.
What is stressor specificity?
It is the involvement of distinct neural circuits in the detection of physical versus psychological stressors.
What are the sensors responsible for detecting deviations in blood volume, oxygenation, and electrolyte balance?
Arterial baroreceptors: Detect blood volume and pressure deviations.
Chemoreceptors (brainstem): Detect blood oxygenation and pH levels.
Osmoreceptors (forebrain): Detect electrolyte imbalances.
What is the primary role of the nucleus of the solitary tract (NTS) in stress response?
The NTS, located in the medulla oblongata, is the main integration center for viscerosensory stress signals, integrates viscerosensory stress signals from baroreceptors, chemoreceptors, and other sensory systems. It generates compensatory reflexes and relays information to brainstem and forebrain centers for autonomic, endocrine, and behavioral responses.
What types of sensory information does the NTS receive?
The NTS receives information from:
Arterial baroreceptors and chemoreceptors: Blood pressure and oxygenation.
Cardiorespiratory receptors: Heart activity.
Gastrointestinal receptors: Nutrient levels.
Visceral and somatic pain receptors:
Via cranial nerves and spinal cord projections.
How does the NTS respond to homeostatic threats?
The NTS generates compensatory physiological responses, such as visceral reflexes and patterned responses (e.g., cardiovascular and respiratory reflexes), by projecting to effector nuclei that control the ANS and HPA axis.
What is the role of the parabrachial nuclei (PBN) in stress response?
The PBN receives viscerosensory inputs from the NTS and relays them to higher brainstem and forebrain structures for further processing and integration of homeostatic information.
What are circumventricular organs, and what do they detect?
Circumventricular organs are specialized brain structures that detect humoral homeostatic signals (e.g., nutrient levels, hormones, toxins) in the bloodstream and relay this information to the hypothalamus.
What role does the hypothalamus play in response to humoral stress signals?
The hypothalamus initiates physiological and behavioral responses to humoral stress signals by projecting to effector nuclei that control the ANS and HPA axis.
What is the innate alarm system?
The innate alarm system is a neural network that rapidly and unconsciously assesses the biological and emotional significance of sensory stimuli (e.g., “threat,” “reward,” or “neutral”) and monitors the environment for external threats, initiating appropriate physiological and behavioral responses.
Key structure - amygdala
What are the roles of the basolateral amygdala (BLA) and central nucleus of the amygdala (CeA)?
Basolateral amygdala (BLA): Acts as a gateway for multimodal sensory inputs, receiving signals from the thalamus, sensory cortices, association cortices, and hippocampus.
Central nucleus of the amygdala (CeA): Serves as the primary output region, controlling autonomic, endocrine, and behavioral responses to threats via projections to the brainstem (behaviour responses), hypothalamus (activates ANS and HPA), and forebrain.
What are the “low road” and “high road” pathways to the amygdala in threat detection?
Low Road: A rapid pathway sending crude sensory information from the thalamus to the amygdala for quick, reflexive threat responses.
High Road: A slower pathway sending highly processed sensory information from sensory cortices to the amygdala, incorporating memory and context for accurate threat evaluation.
How does the body generate physiological stress responses when a stressor is detected?
Afferent systems detect the stressor and send signals to the brain.
The Autonomic Nervous System (ANS) and HPA axis are activated to adjust body functions and release stress hormones.
The central efferent system directs peripheral systems (e.g., adrenal glands, autonomic ganglia) to produce stress mediators (hormones and neurotransmitters) that act on target organs.
What are the roles of central effectors in the stress response?
For the ANS: Preganglionic neurons (sympathetic and parasympathetic) control autonomic ganglia and adrenal medulla, directed by preautonomic neurons acting as “pattern generators” for reflexive responses.
For the HPA Axis: Neuroendocrine neurons in the PVN release CRH and AVP to stimulate the pituitary, leading to cortisol release via the adrenal cortex.
Higher Regulation: The hypothalamus, influenced by the limbic system and cortex, coordinates these responses.
How do physical and psychological stressors differ in their activation of the stress response?
Physical Stressors: Trigger reactive physiological responses through direct projections from interoceptive systems to central effectors or through autonomic pattern generators and higher brain areas.
Psychological Stressors: Elicit anticipatory responses via relay centers in the limbic forebrain, hypothalamus, and brainstem, involving cognitive, affective, and motivational networks for higher-order processing and behavior regulation.
Visceral reflex is
The simplest and most stereotypical response to a homeostatic challenge is a visceral reflex.
Visceral reflexes are mediated by neuronal circuits in the brainstem and spinal cord and can be directly initiated by viscerosensory nuclei that detect physical stress signals, such as the NTS
The baroreflex is
The baroreflex (baroreceptor reflex) is a critical physiological mechanism that helps maintain stable blood pressure in the body by providing rapid, reflexive responses to changes in blood pressure. It involves sensory receptors called baroreceptors located in the walls of arteries, particularly in the carotid sinus and aortic arch.
Rostral ventrolateral medulla (RVLM) is
Rostral ventrolateral medulla (RVLM) is a brainstem nucleus involved in the
regulation of cardiovascular activity and maintenance of adequate blood pressure and organ perfusion
