Stress Physiology: Linking Brain, Endocrine Regulation, and Metabolism

Comprehensive vocabulary flashcards covering the neuroanatomy, autonomic pathways, endocrine cascades, and metabolic outcomes of stress physiology from ANSC 415.

Metabolism

The complete range of biological and biochemical processes occurring within the body, categorized broadly into anabolism and catabolism.

Anabolism

The metabolic process that utilizes $ATP$ to assemble larger, complex molecules (such as cell walls, cytoplasmic membranes, and ribosomes) from smaller building blocks.

Catabolism

The metabolic process that breaks down complex nutrient molecules into smaller components (such as amino acids and nucleotides), generating $ATP$, heat, and waste products.

Glucocorticoids (Metabolic Function)

Steroid hormones that adjust metabolic processes to promote the increase and maintenance of blood glucose concentrations during periods of stress.

Gluconeogenesis

A hepatic metabolic pathway stimulated by glucocorticoids that synthesizes new glucose from non-carbohydrate carbon substrates (such as amino acids) to increase blood glucose levels.

Lipolysis

The metabolic breakdown of lipids in skeletal muscle and adipose tissue, which is increased by glucocorticoids to elevate blood lipid levels.

Lactate

A metabolite produced when tissue oxygen availability is reduced enough to inhibit oxidative phosphorylation (the Electron Transport Chain) and upstream $TCA$ cycle reactions, heavily upregulated by epinephrine.

Ketone Bodies

Metabolic products of lipid metabolism comprising acetone (excreted by the kidneys as waste), acetoacetate, and $\beta$-hydroxybutyrate (both used as alternate fuel for the brain and heart when glucose is low).

Blood Urea Nitrogen (BUN)

A metabolic waste product excreted by the kidneys that results from protein catabolism after dietary or stored muscle proteins are broken into amino acids and processed by the liver for gluconeogenesis.

Stressor

Any event that produces an arousing effect on the body, classified either as positive (eustress) or negative (distress).

Eustress

A positive classification of a stressor that exerts an arousing effect on the body.

Distress

A negative classification of a stressor that exerts an arousing effect on the body.

Stress Response

The collective suite of behavioral and physiological processes utilized by an animal to cope with stressful events.

Afferent Neurons

Neurons that carry incoming sensory signals from peripheral receptors and head sensory organs toward the brain.

Efferent Neurons

Neurons that convey motor instructions away from the brain to excitatory tissues and effector organs.

Cranial Nerves

Twelve pairs of nerves that transmit afferent and efferent signals between the sensory organs of the head, the brain stem, and excitatory tissues.

Tectum

A midbrain (mesencephalon) structure that controls rapid orientation reflexes toward auditory or visual stimuli.

Superior Colliculi

Paired dorsal structures of the midbrain tectum that receive afferent visual projections from the optic nerve.

Inferior Colliculi

Paired dorsal structures of the midbrain tectum that receive afferent auditory signals via the auditory vestibular nerve.

Thalamus

A diencephalic relay station that processes incoming sensory input and communicates with both the frontal lobe of the cerebral cortex and the hypothalamus.

Lateral Geniculate Nucleus

A specific sensory relay nucleus in the thalamus that processes afferent signals from the optic nerve.

Medial Geniculate Nucleus

A specific sensory relay nucleus within the thalamus that processes afferent acoustic signals from the auditory vestibular nerve.

Rapid Stress Response

The fast neural stress pathway driven by direct sympathetic preganglionic innervation from the intermediolateral column ($\text{T}_1\text{--L}_2$) to the adrenal medulla.

Slow Stress Response

The neuroendocrine stress pathway mediated by humoral signaling cascade through the hypothalamic-pituitary-adrenal (HPA) axis to the adrenal cortex.

Chromaffin Cells

Neuroendocrine cells situated in the adrenal medulla that constitute the only site of epinephrine synthesis in the body.

Tyrosine Hydroxylase (TH)

The rate-limiting enzyme in catecholamine synthesis that converts diet-derived L-tyrosine to L-DOPA in the presence of tetrahydrobiopterin, $\text{Fe}^{2+}$, and $\text{O}_2$.

Phenylethanolamine-N-methyltransferase (PNMT)

The terminal enzyme in chromaffin cells that converts L-noradrenaline to L-adrenaline, which is upregulated by cortisol delivered via adrenal portal circulation.

Paraventricular Nucleus (PVN)

A hypothalamic nucleus containing hypophysiotropic neurons within its medial parvocellular subdivision that secrete CRF and AVP.

Corticotropin Releasing Factor (CRF)

A hypothalamic releasing peptide produced by PVN neurons that is released at the median eminence to trigger pituitary ACTH release.

Arginine Vasopressin (AVP)

A hypothalamic neurohormone whose production increases during acute stressors occurring against a backdrop of chronic stress, maintaining ACTH responsiveness to novel stressors.

Hypophyseal Portal System

A specialized vascular network consisting of primary and secondary capillary plexuses that carries hypothalamic hypophysiotropic neurohormones directly to the anterior pituitary.

Adrenocorticotropin Hormone (ACTH)

A peptide hormone synthesized by corticotropic cells of the anterior pituitary that promotes the conversion of cholesterol to $\delta\text{-5}$ pregnenolone in the adrenal cortex.

Pro-opiomelanocortin (POMC)

A prohormone polypeptide precursor produced in corticotropic cells that is cleaved to yield ACTH, $\beta$-endorphin, $\beta$-lipotropic hormone ($\beta\text{-LPH}$), and melanocortins.

Zona Fasciculata

The middle layer of the adrenal cortex whose parenchymal cells synthesize glucocorticoids (cortisol in most mammals; corticosterone in rodents and birds).

CRFR1 (CRF Receptor 1)

The primary G-protein coupled receptor for CRF, highly abundant in the anterior pituitary, olfactory bulb, cerebral cortex, hippocampus, and cerebellum.

MC2-R (Melanocortin Type 2 Receptor)

The cell-surface ACTH receptor found predominantly on the parenchymal cells of the adrenal cortical zona fasciculata.

Glucocorticoid Receptor (GR)

A nuclear receptor widely distributed throughout the brain and periphery that binds cortisol/corticosterone and regulates gene expression via interactions with transcription factors.

Adrenal Portal Circulation

The vascular architecture that channels glucocorticoid-rich capillary blood from the cortical sinusoids directly into the medullary capillary plexus, bathing chromaffin cells.

Hippocampal Negative Feedback

The inhibitory mechanism whereby elevated circulating cortisol acts on dense populations of hippocampal glucocorticoid receptors, which send axonal projections to attenuate hypothalamic HPA output.

Glucocorticoid Neurotoxicity Hypothesis

The principle suggested by Robert Sapolsky in vervet monkeys showing that prolonged cortisol exposure damages hippocampal neurons, decreasing negative feedback and creating a feedforward loop of hypercortisolemia.

Sympathetic Nervous System

The autonomic division that activates the fight-or-flight response, causing pupil dilation, bronchial dilation, increased heart rate and contractility, peripheral vasoconstriction, and hepatic glucose release.

Vagus Nerve (CN X)

The tenth cranial nerve, responsible for regulating autonomic functions of the heart, blood vessels, and viscera, as well as the motor control of the larynx and pharynx.

Trigeminal Nerve (CN V)

The fifth cranial nerve, responsible for masticatory (chewing) movements and sensory innervation of the face.