Summary: Chemical Coordination And Integration

Multiple Choice Questions - Key Points

• Anterior pituitary produces six hormones: Growth Hormone (GH), Prolactin (PRL), Thyroid Stimulating Hormone (TSH), Adrenocorticotropic Hormone (ACTH), Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH).
• Oxytocin and Vasopressin are made in the hypothalamus and stored in the posterior pituitary (not secreted by anterior pituitary).
• Adrenaline and noradrenaline cause the "fight or flight" response: increased heart rate, rapid breathing and sweating.
• Aldosterone regulates water and electrolyte balance by acting on kidneys to reabsorb sodium and water and excrete potassium and phosphate.
• Thymosin promotes differentiation of T-lymphocytes and supports cell-mediated immunity.
• Cyclic AMP is a common second messenger in the mechanism of action of protein hormones.
• Leydig cells produce androgens (mainly testosterone).
• Corpus luteum secretes progesterone for endometrium maintenance after ovulation.
• Cortisol is secreted from the adrenal cortex (zona fasciculata) and affects carbohydrate, protein and fat metabolism; it is anti-inflammatory.
• Melatonin (from the pineal gland) regulates the sleep-wake cycle (circadian rhythm).
• Protein hormones bind receptors on the plasma membrane of target cells and use second messengers to alter cell metabolism.
• Cardiac atrial cells secrete atrial natriuretic factor (ANF) to regulate blood volume by increasing excretion of ions and water.
• Calcium balance involves vitamin D, parathyroid hormone (raises blood Ca2+) and thyrocalcitonin (lowers blood Ca2%); thymosin is not involved.
• The liver does not have a cortical and medullary region; ovary, adrenal and kidney do.
• Exophthalmia is linked to hyperthyroidism; cretinism, myxedema and goitre are linked to thyroid deficiency.

Very Short Answer - Core Facts

• Ovary is absent in males; testis is absent in females.
• Zona glomerulosa is the outermost and zona reticularis the innermost layer of adrenal cortex.
• Erythropoiesis is RBC formation stimulated by erythropoietin.
• Pars intermedia secretes Melanocyte Stimulating Hormone (MSH).
• Calcitonin (thyrocalcitonin) from thyroid lowers blood calcium.
• Second messengers relay signals from membrane-bound hormone receptors to regulate cell metabolism.
• True statements given: gastrointestinal tract, kidney and heart produce hormones; pars distalis makes six trophic hormones; B-lymphocytes do not provide cell-mediated immunity; insulin resistance causes diabetes mellitus.
• Vasopressin (ADH) is measured when diabetes insipidus (excessive urination, thirst, low BP) is suspected.
• Corrections: insulin is a peptide (not steroid); TSH from anterior pituitary (not corpus luteum); tetraiodothyronine is a maintenance hormone; adrenal gland lies on kidney (not pineal).

Short Answer - Mechanisms & Disorders

• LH in males stimulates Leydig cells to produce testosterone; in females it triggers ovulation.
• Second messengers are released when first messengers (extracellular hormones) bind membrane receptors; they trigger intracellular physiological changes.
• Goitre results from dietary iodine deficiency and during pregnancy can cause defective fetal development (cretinism), mental retardation and sensory defects.
• Jet lag arises from disruption of the body's circadian rhythm, causing sleep disturbance, appetite and bowel changes.
• Cortisol (from adrenal cortex) controls inflammation, stimulates RBC production and helps the body respond to stress.
• Age-related thymus degeneration reduces thymosin production, weakening immune responses in older people.
• Hypothyroidism in pregnancy risks stunted fetal growth and lasting neurological defects.
• Differences between hypothyroidism and hyperthyroidism: low vs high thyroid hormone, decreased vs increased metabolic rate, causes and symptoms differ (e.g., fatigue and dry skin vs heat intolerance and increased heart rate).
• Feedback example: high LH with low E2 indicates ovarian failure/menopause (loss of feedback); high LH with high E2 suggests another imbalance.

Long Answer - Pathways and Comparisons

• Oxytocin positive feedback (milk let-down): Suckling → nerve impulses to hypothalamus → release of oxytocin → contraction of myoepithelial cells around alveoli → milk ejection.
• High glucose and ketone bodies in urine: related gland is pancreas; hormone is insulin; insulin acts on hepatocytes and adipocytes; condition is diabetes and is managed by diet, drugs and sometimes insulin.
• Calcium homeostasis: Thyrocalcitonin (from thyroid) lowers blood Ca2+ to aid bone uptake; Parathyroid Hormone raises blood Ca2+; their actions are antagonistic to maintain balance.
• Mechanism comparison:
  • Protein hormones: bind membrane receptors, generate second messengers, alter cellular metabolism (examples: insulin, glucagon).
  • Steroid hormones: diffuse into cells, bind intracellular receptors, regulate gene expression/chromosome function (examples: cortisol, testosterone).
• Hypothalamus as "Super Master Gland": contains neurosecretory nuclei that produce releasing and inhibiting hormones to control pituitary secretion; pituitary hormones then regulate other endocrine glands (e.g., TSH→thyroid, ACTH→adrenal, LH→gonads).