Different Systems
Which system of the body is faster and why?
nervous system because it is directly connected whereas endocrine goes through bloodstream
Name the neurosecretory cell types that control the anterior and posterior pituitary, respectively.
Parvocellular → anterior pituitary; Magnocellular → posterior pituitary
Classify peptide, amine, and steroid hormones by solubility and receptor location.
Peptide/amine → hydrophilic, bind extracellular; Steroid → hydrophobic, bind intracellular.
Define receptor upregulation and explain its purpose under low-hormone conditions.
Cells increase receptor density to enhance sensitivity when ligand levels are chronically low.
Name a homeostatic processes regulated by hypothalamic neurohormones via pituitary signaling.
Water balance (ADH production)
Explain why endocrine signaling can influence distant targets even at very low hormone concentrations.
Amplification from proteins can yield high response even with low concentration
ADH and oxytocin differ in physiological role, but share this unique structural and transport feature.
They are both neurohormones synthesized in the hypothalamus, transported along axons, and released directly into the bloodstream by the posterior pituitary
Explain why peptide and amine hormones often trigger faster responses than steroid hormones.
They act through membrane receptor cascades that alter enzyme activity within seconds, whereas steroid hormones require transcriptional changes.
Explain how receptor downregulation can contribute to drug tolerance.
Chronic exposure reduces receptor availability, requiring higher doses for the same effect.
Name the two neurohormones synthesized by magnocellular neurosecretory cells.
oxytocin and antidiuretic hormone (ADH)
Neuroendocrine cells release this type of signaling molecule that bridges the nervous and endocrine systems.
Neurohormones
Explain why thyroid function tests typically measure both TSH and T3/T4 levels, not just one.
Because feedback between the hypothalamus, pituitary, and thyroid means abnormal T3/T4 can result from pituitary or thyroid dysfunction, measuring both locates the disruption.
Explain why steroid hormones require carrier proteins for circulation, but their receptors are intracellular rather than membrane-bound.
They are hydrophobic, so carriers maintain solubility in plasma, but their lipid solubility allows direct diffusion through membranes to intracellular receptors
Why would long-term melatonin supplement use decrease its sleep-inducing efficacy?
Persistent melatonin exposure leads to downregulation of hormone receptors, decreasing sensitivity.
Predict the cellular consequence if a mutation prevented steroid hormone binding to its intracellular receptor.
Target genes would fail to activate, preventing appropriate protein synthesis and physiological response
Neuroendocrine cells act as hybrids between which two cell types, and how does this specialization optimize systemic control?
They combine neuronal signal detection with endocrine hormone secretion, allowing rapid neural control of widespread hormonal effects
Describe how the pituitary integrates multi-gland feedback loops and why this “hub” design is evolutionarily advantageous.
It allows hierarchical control where one brain region regulates multiple systems via secondary messengers
Lipid-soluble hormones require these molecules to move through the bloodstream.
Carrier proteins
After several days of cold exposure, brown adipose tissue becomes more responsive to thyroid hormone (T₃). What receptor-level change accounts for this increased capacity?
Upregulation of T₃ receptors
Explain how a single hypothalamic dysfunction could produce widespread physiological disturbances across multiple systems
Because the hypothalamus coordinates endocrine release through the pituitary, dysfunction disrupts downstream glands controlling metabolism, stress, reproduction, and water balance.
Describe a physiological situation where both systems coordinate and identifying which system initiates and which sustains the response.
The nervous system initiates the “fight-or-flight” response via sympathetic activation; the endocrine system sustains it through adrenal cortisol release
During chronic psychological stress, trace the hormone cascade from hypothalamus to target organ and identify the final hormone’s physiological effect.
CRH → ACTH → cortisol; cortisol mobilizes energy, elevates blood glucose, and suppresses nonessential functions
Compare the storage and release differences between peptide/amine hormones and steroid hormones.
Peptide/amine hormones are stored in vesicles and released on demand; steroid hormones diffuse out immediately after synthesis.
From an evolutionary standpoint, why would it be energetically costly and potentially dangerous for hormone receptors to remain static rather than adaptive?
Maintaining constant high receptor density consumes metabolic energy and risks overactivation from transient hormone surges (stress hormones). Adaptability allows cells to scale receptor production to physiological need, conserving resources
Explain why the effects of cortisol persist long after stress has subsided.
Cortisol regulates gene transcription and protein synthesis (steroid hormone), processes that take hours to reverse