Integration of Nervous and Endocrine Signaling (3A) - Bio & Biochem
- Identify the feedback type: rising reduces TRH and TSH secretion.
- Negative feedback. This regulatory loop suppresses TRH and TSH to prevent excessive thyroid hormone levels and maintain metabolic equilibrium.
- What type of signaling is used when a neuron releases a hormone into the bloodstream?
- Neuroendocrine signaling. This mechanism allows neurons to influence distant targets by secreting hormones into the blood, bridging neural and endocrine systems.
- What is the term for a hormone acting on the same cell that secreted it?
- Autocrine signaling. This self-regulatory mechanism enables cells to modulate their own activity through receptors binding their secreted signaling molecules.
- What is the immediate second messenger produced by adenylyl cyclase in GPCR signaling?
- cAMP. Adenylyl cyclase catalyzes ATP conversion to cAMP, which activates protein kinase A to propagate GPCR-mediated signals.
- What type of feedback does cortisol exert on CRH and ACTH secretion under normal physiology?
- Negative feedback on hypothalamus and anterior pituitary. This mechanism inhibits CRH and ACTH production to maintain glucocorticoid homeostasis and prevent overactivation of the stress response.
- What is the main anatomical link that integrates the nervous and endocrine systems?
- Hypothalamus (via control of the pituitary gland). The hypothalamus receives neural inputs and modulates endocrine activity by regulating pituitary hormone secretion through releasing and inhibiting factors.
- What is the key difference in how the anterior versus posterior pituitary releases hormones?
- Anterior: secretes; posterior: releases hypothalamic-made hormones. The anterior pituitary synthesizes its own hormones in response to hypothalamic signals, while the posterior stores and secretes pre-made hypothalamic hormones.
- What is the hypothalamic-pituitary-thyroid (HPT) axis hormone sequence for thyroid hormone release?
- TRH $ $ TSH $ $ . TRH prompts pituitary TSH secretion, which stimulates thyroid production of and for metabolic regulation.
- Which adrenal region secretes steroid hormones such as cortisol and aldosterone?
- Adrenal cortex. Derived from mesoderm, it produces glucocorticoids, mineralocorticoids, and androgens to regulate metabolism, electrolytes, and reproduction.
- What is the term for a hormone acting on nearby cells without entering systemic circulation?
- Paracrine signaling. Local diffusion of signaling molecules affects neighboring cells, facilitating tissue-specific communication without broad systemic effects.
- Which class of hormones typically binds intracellular receptors and alters gene transcription?
- Steroid hormones (and thyroid hormone). These lipophilic molecules cross membranes to bind nuclear receptors, directly influencing DNA transcription for prolonged effects.
- Which adrenal region secretes catecholamines and is functionally analogous to a sympathetic ganglion?
- Adrenal medulla. As a modified sympathetic ganglion, it releases catecholamines in response to neural input, amplifying fight-or-flight effects.
- What is the hypothalamic-pituitary-adrenal (HPA) axis hormone sequence for cortisol release?
- CRH $ $ ACTH $ $ cortisol. CRH from the hypothalamus stimulates pituitary ACTH release, which induces adrenal cortisol production for stress adaptation.
- What is the term for a hormone traveling through blood to act on distant target tissues?
- Endocrine signaling. Hormones secreted into the bloodstream reach distant organs, enabling coordinated physiological responses across the body.
- Which class of hormones typically binds cell-surface receptors and uses second messengers?
- Peptide/protein hormones and catecholamines. Hydrophilic nature prevents membrane crossing, so they activate surface receptors, triggering intracellular cascades via molecules like cAMP.
- What is the physiologic role of the sympathetic-adrenal medullary axis in acute stress?
- Rapid release of epinephrine and norepinephrine for fight-or-flight. Sympathetic stimulation of the adrenal medulla triggers catecholamine release, preparing the body for immediate stress response via metabolic and cardiovascular changes.
- What is the portal blood system that carries hypothalamic hormones to the anterior pituitary?
- Hypothalamic-hypophyseal portal system. This vascular connection enables direct delivery of hypothalamic regulatory hormones to anterior pituitary cells, bypassing systemic circulation for efficient control.
- What is the hypothalamic-pituitary-gonadal (HPG) axis pituitary hormone released in response to GnRH?
- LH and FSH. GnRH stimulates release of these gonadotropins, which regulate gametogenesis and sex hormone production in the gonads.
- What is the defining feature of a target cell for a given hormone?
- It expresses the specific receptor for that hormone. Hormone specificity arises from receptor expression, allowing only responsive cells to transduce the signal into cellular changes.
- Which anterior pituitary hormone is primarily inhibited (not stimulated) by hypothalamic dopamine?
- Prolactin. Dopamine from the hypothalamus tonically inhibits prolactin to control lactation, reproduction, and immune functions.
- Which option best describes epinephrine action: intracellular receptor or cell-surface receptor?
- Cell-surface receptor (adrenergic GPCR). As a hydrophilic catecholamine, it activates membrane-bound GPCRs to initiate rapid intracellular signaling via second messengers.
- Which hormone mediates uterine contractions and milk ejection and is classically regulated by positive feedback?
- Oxytocin. Positive feedback amplifies its release during labor and nursing, enhancing contractions and milk let-down for parturition and breastfeeding.
- Identify the endocrine hormone released in response to increased plasma osmolarity to conserve water.
- ADH (vasopressin). Detected by hypothalamic osmoreceptors, it triggers ADH release to enhance renal water reabsorption and maintain osmotic balance.