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Endocrine System Physiology
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Endocrine System Physiology
Endocrine System Physiology
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1
Question
Answer
2
Question
Answer
3
Question
What is juxtacrine secretion
Answer
signal requires direct cell-to-cell contact > No secretion into space > Membrane-bound signal
4
Question
Neurocrine and examples
Answer
A neuron releases a signal locally to another cell across a synapse. ❗ Key points > Local / Fast / Neurotransmitters Example: acetylcholine, dopamine (synaptic)
5
Question
Where is DHEA produced, and into what hormones is it converted in peripheral tissues?
Answer
DHEA is produced by the adrenal cortex. In peripheral tissues such as fat, skin, and liver, it is converted into androgens and estrogens.
6
Question
What are examples of endocrine secretions?
Answer
Insulin and thyroid hormones.
7
Question
What is the biological definition of a hormone?
Page 1
Answer
A hormone is a chemical messenger produced by specific cells and released to control functions such as metabolism, growth, reproduction, stress response, and fluid balance.
8
Question
How are endocrine glands distinguished from exocrine glands?
Page 1
Answer
Endocrine glands have no ducts and release hormones directly into the blood. Exocrine glands possess ducts and release secretions onto body surfaces or into cavities.
9
Question
What are the primary chemical precursors for amino acid-derived hormones?
Page 1
Answer
Amino acid-derived hormones are mainly derived from tyrosine or tryptophan.
10
Question
Describe the synthesis pathway for epinephrine starting from phenylalanine.
Page 1
Answer
Phenylalanine → tyrosine → DOPA → dopamine → norepinephrine → epinephrine.
11
Question
Where are thyroid hormones synthesized and stored within the gland?
Page 2
Answer
Thyroglobulin is synthesized in follicular cells and stored in the colloid.
12
Question
Where does cortisol synthesis occur, and which organelle is involved in its first and last steps?
Page 2
Answer
Cortisol is synthesized from cholesterol in the adrenal cortex. The first and last steps of its synthesis occur in the mitochondria.
13
Question
Explain the peripheral conversion of Thyroid Hormone T4 into its active form.
Page 2
Answer
T4 is a weakly active form that is converted into T3 (the active form) in the liver and pituitary.
14
Question
How is testosterone activated in secondary sex organs, and what enzyme is responsible?
Page 2
Answer
In secondary sex organs (prostate, skin, genitalia), the enzyme 5-α reductase converts testosterone into dihydrotestosterone (DHT), which is more potent.
15
Question
Outline the two-step activation process of Vitamin D3 in the body.
Page 2
Answer
Vitamin D3 is first converted to 25-hydroxyvitamin D in the Liver, and then to 1,25-dihydroxyvitamin D (the active form) in the Kidney.
16
Question
What is the difference between negative feedback and positive feedback in hormone regulation?
Page 2
Answer
Negative feedback occurs when high hormone levels suppress further release to maintain stability. Positive feedback occurs when a hormone increases its own release, leading to a surge.
17
Question
Define Paracrine vs. Autocrine signaling.
Page 3
Answer
Paracrine signaling involves a hormone acting on nearby cells. Autocrine signaling involves a hormone acting on the same cell that released it.
18
Question
What is the primary difference between Autocrine and Intracrine signaling?
Page 3
Answer
In autocrine signaling, the hormone is secreted and then acts on the same cell. In intracrine signaling, the hormone acts inside the cell without ever being secreted.
19
Question
Explain Neuroendocrine signaling and provide an example.
Page 3
Answer
Neuroendocrine signaling occurs when a neuron releases a hormone into the blood to act on distant cells. Examples include ADH and oxytocin.
20
Question
What are the key characteristics of hormone receptors?
Page 3
Answer
Hormone receptors exhibit high specificity (acting only on cells with the right receptor) and high affinity (responding to very low hormone concentrations).
21
Question
Distinguish between the transport and half-life of Lipophilic vs. Hydrophilic hormones.
Page 4
Answer
Lipophilic hormones require transport proteins and have a long half-life. Hydrophilic hormones do not require transport proteins and have a short half-life.
22
Question
What occurs during receptor Down-regulation?
Page 4
Answer
When hormone levels are high, receptors are internalized (pulled inside the cell) and degraded (broken down) to reduce cell sensitivity.
23
Question
Define 'Desensitization' and how it relates to drug tolerance.
Page 4
Answer
Desensitization is when a cell's response is reduced even if the hormone/drug is present. This explains drug tolerance, where higher doses are needed as target cells become less responsive.
24
Question
What is the solubility exception for Amino acid-derived hormones?
Page 5
Answer
While most are water-soluble, Thyroid hormones (T3, T4) are lipid-soluble and require transport proteins.
25
Question
Compare Group 1 and Group 2 hormones regarding solubility and receptors.
Page 5
Answer
Group 1: Lipophilic (fat-soluble), intracellular receptors. Group 2: Hydrophilic (water-soluble), membrane (cell surface) receptors.
26
Question
Contrast the mechanism and effect type of Group 1 vs. Group 2 hormones.
Page 6
Answer
Group 1: Directly binds DNA to change gene transcription; effects are slow and long-lasting. Group 2: Uses secondary messengers to change cell activity; effects are fast and short-term.
27
Question
Describe the step-by-step mechanism for Group 1 hormones.
Page 6
Answer
1. Diffuses into cell. 2. Binds cytoplasmic/nuclear receptor. 3. Hormone-receptor complex enters nucleus. 4. Binds hormone response elements on DNA. 5. Initiates transcription of mRNA. 6. Signal ends via receptor recycling/degradation.
28
Question
Explain the cAMP/cGMP pathway used by Group 2 hormones.
Page 6
Answer
Hormone binds membrane receptor → G protein activated (α subunit exchanges GDP for GTP) → α activates adenylyl/guanylyl cyclase → ATP/GTP converted to cAMP/cGMP → Protein kinases activated → Target proteins phosphorylated.
29
Question
How does the Calcium-IP3-DAG system trigger cellular responses?
Page 6
Answer
Hormone activates receptor → generates IP3 → IP3 releases \(Ca^{2+}\) from the ER → \(Ca^{2+}\) binds calmodulin → protein kinases activated → fast cellular responses (secretion/contraction).
30
Question
Explain the Tyrosine Kinase pathway mechanism, using insulin as an example.
Page 7
Answer
Hormone binding causes receptor dimerization and autophosphorylation of tyrosine residues. This activates signaling cascades, which for insulin increases glucose uptake via GLUT transporters.