Neur2201 module 3

Stress

Stress

A feeling triggered by threat, with acute responses being adaptive for active threat response, while chronic responses are detrimental to health.

Autonomic Nervous System (ANS)

Controls smooth muscles, glands, and cardiac muscle involuntarily, contributing to homeostasis with sympathetic and parasympathetic branches.

Sympathetic Nervous System

Branch of ANS with preganglionic neurons in thoracic cord T1-L2, using norepinephrine as neurotransmitter and acting via alpha and beta adrenergic receptors.

Parasympathetic Nervous System

ANS branch with preganglionic neurons in brainstem and sacral cord, using acetylcholine as neurotransmitter and acting via muscarinic receptors.

Cortisol

Stress hormone released in the endocrine response, controlled by the pituitary gland or hypothalamus, impacting metabolism, immune function, and gluconeogenesis.

Limbic System

Brain structure including the amygdala, involved in emotional responses and stress modulation, connecting sensory stimuli with emotional valence.

Prefrontal Cortex

Brain region linked to limbic system and amygdala, responsible for conscious modulation of emotional responses, judgment, and planning.

Hippocampus

Receives information from the cortex and can inhibit the release of CRH to stop the stress response

Prefrontal Cortex (PFC)

Regulates cognition; includes dmPFC for reality checks and error monitoring, DIPFC for attention regulation, thought, and action, rIPFC for inhibiting inappropriate motor responses

vmPFC

Connects with subcortical structures generating emotional responses, regulates emotions, and determines stress handling ability

Top-down regulation

PFC's control over lower brain regions; sensitive to detrimental effects of stress exposure

Chronic stress effects

Impaired PFC regulation, strengthened amygdala function, and shift to rapid emotional responses

Neuroplasticity of vmPFC

Key to resilience-coping during stress, signals increased emotional and behavioral control

5-HTP

Precursor to serotonin, effective in mood swings, depression, anxiety, and conditions associated with low serotonin

SSRIs

Selective serotonin reuptake inhibitors, commonly used antidepressants, enhance serotonin levels in the brain

Beta-Blockers

Antagonize beta-adrenergic receptors, reduce physiological symptoms of stress like rapid heartbeat, shaking, and sweating

HPA Axis

The hypothalamic-pituitary-adrenal axis, a complex set of interactions among the hypothalamus, pituitary gland, and adrenal glands that regulates stress response.

CRF

Corticotropin-releasing factor, a hormone involved in the body's response to stress.

Heartbreak

Emotional distress or pain caused by the ending of a romantic relationship or separation from a loved one.

BNST

Bed nucleus of the stria terminalis, a region in the brain involved in stress response and emotional behaviors.

Function of Hypothalamic neurons

Project to brainstem centres and during a stress response override their homeostatic activity to prepare the organism for a fight/flight response

Noreadrenaline

Released from the sympathetic nerves into the organs (e.g. heart, blood vessels, gut)

Adrenaline

Released from the adrenal medulla into teh blood stream to further magnify the sympathetic response

Posterior pituitary

An extension of the hypothalamus, has hormones oxytocin and vasopressin

Where are the hormones synthesised to get to the posterior pituitary?

In the neuronal cell body in the hypothalamus

Where does the hormone travel to get to posterior pituitary?

Down the axon to be stored in the neuronal terminals with the posterior pituitary

What happens when the neuron in the posterior pituitary is excited?

The stored hormone is released from these terminals into the systemic blood for distribution throughout the body

CRH = ?

Corticotropin releasing hormone ; is the hypophysiotropic hormone for the release of ACTH

ACTH = ?

Adrenocorticotropic hormone = corticotropin

What are the endocrine components of a stress response

1. Hypothalamus releases CRH into the portal veins of the anterior pituitary gland

2. Anterior lobe of the pituitary gland releases ACTH into blood stream

3. ACTH acts on the cortex of the adrenal gland to release cortisol

What are the main actions of cortisol?

Gluconeogenesis, increased metabolism and decreased immune function

Amygdala (emotional stress)

Receives sensory information from hypothalamus and cortex
Is also responsible for fear response, stimulating release of CRH

Hippocampus (emotional stress)

Receives information from the cortex and can inhibit the release of CRH to stop the stress response

dmPFC

reality checks and error monitoring

DIPFC

Regulates attention, thought and action

rIPFC

Inhibits inappropriate motor responses

vmPFC

connects with subcortical strctures that generate emotional responses, such as fear responses.
Also regalates emotion

Orbitofrontal PFC

orchestrates regulation of behaviour, thought and emotion
top down regulation

PFC during chronic stress

Bottom up regulation
Impaired PFC regulation and strengthened amygdala function

Hyperactivity of the vmPFC suggests..

you are likely to have maladaptive coping behaviours to stress

5-HTP (5-hydroxy-L-tryptophan)

a derivative of the amino acid L-tryptophan, which is found in high-protein foods such as dairy products, fish, lean meats and the seed of Griffonia simplicifolia tree

5-HTP is a precusor for ?

5-HTP is the precursor of serotonin (5-HT). It may be helped to promote neurotransmitter balance following daily use for 2-6 weeks

Mechanisms of action: Benzodiazepines

Bind to regulatory site on GABA-A receptor, increases frequency of opening of GABA activated Cl- channels which hyperpolarises post-synaptic neuron, which then increases affinity of GABA of the receptor

End result of mechanisms of action: Benzodiazepines

Potentiate inhibitory effects of GABA throughout CNS

Anxiolytic actions

Are immediate (sedation and induction of sleep)

Tricyclics

Inhibit reuptake of noradrenaline and serotonin from the synaptic cleft

Monoamine Oxidase inhibitors are used when…

Indicated for patients who have failed to respond to more commonly used drugs for depression and anxiety

Monoamine oxidase inhibitors side effects

Orthostatic hypotension with dizziness, weight gain

Tricyclic Antidepressants side effects

Weight gain, off-target effects (Alpha adrenoceptors, muscarinic receptors, histamine receptors). Highly dangerous if overdosed

SSRIs

Inhibit serotonin reuptake

SSRIs

Antidepressant and anxiolytic effect involves adaptation to chronically elevate brain serotonin

SSRIs side effects

Nausea, sexual difficulties and nervousness

Beta-Blockers

Reduce symptoms associated with sympathetic activation: e.g., palpitation (rapid heartbeat), tremor (shaking), blushing and nervous sweating)

Glucocorticoids does what…

Energy for fight or flight ; Increase vigilance to environmental stimuli