endocrine system

Question 1

Compare the nervous and endocrine systems in communication speed, specificity, and duration.

Answer 1

• Nervous: Fast, wired, uses electrical impulses & neurotransmitters, specific targets, short duration.
• Endocrine: Slow, wireless, uses hormones via blood, broad distribution but specific receptors, long-lasting.

Question 2

Define endocrinology.

Answer 2

The study of chemical adjustments/homeostasis and activities achieved by hormones secreted into the blood

Question 3

. List the major functions of the endocrine system

Answer 3

• Regulate metabolism & water/electrolyte balance
• Stress adaptation
• Growth and development
• Reproduction
• RBC production
• Control digestion/absorption with ANS

Question 4

. Classify hormones by solubility and give examples.

Answer 4

• Hydrophilic: Peptides/proteins (insulin), catecholamines (epinephrine, norepinephrine), indoleamines (melatonin).
• Lipophilic: Steroids (cortisol, estrogen, testosterone), thyroid hormone (T3, T4).

Question 5

Explain synthesis, storage, and secretion of peptide hormones

Answer 5

Preprohormones on RER → processed in Golgi → packed into secretory vesicles → stored → released by exocytosis when stimulated.

Question 6

Explain synthesis, storage, and secretion of steroid hormones

Answer 6

Derived from cholesterol via enzymes → not stored → diffuse out of cells immediately after synthesis.

Question 7

How are hydrophilic vs lipophilic hormones transported in blood?

Answer 7

Hydrophilic: dissolve freely. Lipophilic: bound to plasma proteins; only free form is active.

Question 8

Mechanism of action of hydrophilic hormones?

Answer 8

Bind surface receptor → activate G-protein → effector (adenylyl cyclase/ion channel) → 2nd messenger (cAMP/Ca²⁺) → activate kinases → modify proteins.

Question 9

Mechanism of action of lipophilic hormones?

Answer 9

Diffuse into cell → bind intracellular receptor → receptor-hormone complex binds DNA at HRE → gene transcription → mRNA → protein synthesis → cellular response

Question 10

What are tropic hormones? Example?

Answer 10

. Hormones that regulate secretion and growth of another endocrine gland. Example: TSH stimulates thyroid.

Question 11

. Factors influencing plasma hormone concentration?

Answer 11

Secretion rate, metabolic activation, transport/binding, inactivation, excretion

Question 12

. Mechanisms controlling secretion?

Answer 12

Negative feedback (thyroid), neuroendocrine reflexes (adrenaline release), circadian rhythms (cortisol).

Question 13

List types of endocrine disorders

Answer 13

Hyposecretion (too little), hypersecretion (too much), abnormal target-cell responsiveness (e.g., receptor/enzyme defects).

Question 14

Define down-regulation of receptors

Answer 14

Chronic high hormone → fewer receptors on target cells → decreased sensitivity (e.g., insulin).

Question 15

How can hormones influence each other’s effects?

Answer 15

• Permissiveness: One enhances another’s effect (thyroid hormone + epinephrine).
• Synergism: Combined > sum (FSH + testosterone on sperm).
• Antagonism: One reduces effect of another (progesterone vs estrogen in pregnancy).

Question 16

Location and structure of pituitary gland?

Answer 16

In bony cavity under hypothalamus, connected by stalk; two lobes: posterior (nervous tissue), anterior (glandular tissue).

Question 17

. Which hormones are secreted by posterior pituitary? Functions?

Answer 17

• Vasopressin: conserves water, vasoconstriction → ↑ BP.
• Oxytocin: uterine contractions, milk ejection.

Question 18

List anterior pituitary hormones and their functions

Answer 18

• TSH: thyroid hormone secretion & thyroid growth.
• ACTH: cortisol secretion & adrenal cortex growth.
• GH: growth, metabolism.
• FSH: gamete production (ova, sperm), estrogen secretion.
• LH: ovulation, luteinization, sex hormone secretion (testosterone, estrogen, progesterone).
• Prolactin: breast development, milk production (not tropic).

Question 19

What are hypophysiotropic hormones?

Answer 19

Hypothalamic hormones controlling anterior pituitary: releasing (TRH, CRH, GHRH, GnRH) and inhibiting (GHIH/somatostatin, PIH/dopamine).

Question 20

What is the hypothalamic–hypophyseal portal system?

Answer 20

. A direct capillary-to-capillary link carrying hypothalamic hormones straight to anterior pituitary → ensures high concentration, avoids dilution.

Question 21

Define endocrine axis with an example.

Answer 21

. Three-hormone chain: hypothalamic hormone → anterior pituitary hormone → target gland hormone. Example: CRH → ACTH → cortisol

Question 22

Explain negative feedback in CRH–ACTH–cortisol system.

Answer 22

Cortisol inhibits CRH (hypothalamus) and ACTH (pituitary), stabilizing cortisol levels

Question 23

Where is the pineal gland and what hormone does it secrete?

Answer 23

. Tiny gland in brain center; secretes melatonin (“hormone of darkness”).

Question 24

. Functions of melatonin?

Answer 24

Regulates circadian rhythms, promotes sleep, delays puberty, antioxidant, boosts immunity, may slow aging

Question 25

What is the SCN and its role?

Answer 25

Suprachiasmatic nucleus = body’s master biological clock; synchronizes circadian rhythms via light input from retina → regulates melatonin release.

Question 26

What factors besides GH influence growth?

Answer 26

Genetics, adequate nutrition, absence of disease/stress, normal thyroid hormone, insulin, and sex hormones.

Question 27

Metabolic effects of GH (not growth)?

Answer 27

* ↑ Fat breakdown (↑ blood fatty acids). * ↑ Blood glucose (↓ muscle uptake, ↑ liver release). * ↑ Protein synthesis, ↓ protein breakdown.

Question 28

How does GH promote growth?

Answer 28

. Indirectly via IGF-I from liver → stimulates protein synthesis, cell division, bone growth.

Question 29

How do bones grow in length and thickness?

Answer 29

* Thickness: osteoblasts deposit new bone; osteoclasts remodel inside. * Length: epiphyseal plates – cartilage divides → replaced by bone. Stops after puberty when plates ossify.

Question 30

How is GH secretion regulated?

Answer 30

* Stimulated by GHRH, inhibited by GHIH (somatostatin). * Negative feedback by IGF-I and GH. * Influenced by sleep, exercise, stress, low glucose, high amino acids, ghrelin.

Question 31

GH abnormalities?

Answer 31

* Childhood deficiency → dwarfism. * Childhood excess → gigantism. * Adult excess → acromegaly. * Receptor defects → Laron dwarfism. * IGF deficiency → pygmies

Question 32

Outline HPT axis

Answer 32

TRH (hypothalamus) → TSH (pituitary) → T3 & T4 (thyroid).

Question 33

Functions of thyroid hormones?

Answer 33

↑ Basal metabolic rate, heat production, growth & development (especially brain), permissive for catecholamines.

Question 34

Causes of hypothyroidism?

Answer 34

Failure of thyroid gland, lack of TSH/TRH, iodine deficiency

Question 35

Symptoms of hypothyroidism?

Answer 35

Reduced metabolism, weight gain, fatigue, cold intolerance, cretinism in infants.

Question 36

. Causes of hyperthyroidism?

Answer 36

Graves’ disease (autoimmune), tumors, excess TSH.

Question 37

Symptoms of hyperthyroidism?

Answer 37

. Increased metabolism, weight loss, heat intolerance, irritability, exophthalmos (Graves’).

Question 38

What hormones are secreted by adrenal cortex?

Answer 38

* Mineralocorticoids (aldosterone): Na⁺ reabsorption, K⁺ excretion. * Glucocorticoids (cortisol): metabolism, stress adaptation. * Sex hormones (androgens).

Question 39

What hormones are secreted by adrenal medulla?

Answer 39

Catecholamines (epinephrine, norepinephrine) → fight-or-flight

Question 40

Disorders of adrenal cortex?

Answer 40

* Conn’s syndrome (hyperaldosteronism). * Cushing’s syndrome (excess cortisol). * Adrenogenital syndrome (excess androgens). * Addison’s disease (all cortical hormones low).

Question 41

Outline stress response (HPA axis).

Answer 41

Stress → CRH → ACTH → cortisol ↑ → ↑ glucose, ↑ fat breakdown, ↑ amino acids, suppressed immunity. Catecholamines also ↑ HR, BP, respiration

Question 42

. Define anabolism vs catabolism

Answer 42

. Anabolism: synthesis/storage of molecules. Catabolism: breakdown of molecules for energy

Question 43

Differentiate absorptive vs postabsorptive states

Answer 43

* Absorptive (fed): nutrients absorbed, insulin ↑, anabolism dominates. * Postabsorptive (fasting): stored fuels used, glucagon ↑, catabolism dominates.

Question 44

Pancreatic hormones and functions?

Answer 44

* Insulin (β-cells): ↓ blood glucose, promotes storage (glycogen, fat, protein synthesis). * Glucagon (α-cells): ↑ blood glucose, fat breakdown, glycogenolysis, gluconeogenesis. * Somatostatin (δ-cells): inhibits insulin and glucagon secretion, regulates nutrient absorption.

Question 45

What regulates insulin secretion?

Answer 45

↑ Blood glucose (main), ↑ amino acids, parasympathetic stimulation; inhibited by sympathetic stimulation, low glucose

Question 46

Types of diabetes mellitus?

Answer 46

* Type I: autoimmune β-cell destruction → no insulin. * Type II: insulin resistance (target cells insensitive).

Question 47

Acute effects of diabetes?

Answer 47

Hyperglycemia, glucosuria, polyuria, dehydration, ketoacidosis (esp. type I).

Question 48

What is hypoglycemia and its effects?

Answer 48

Low blood glucose due to excess insulin → confusion, tremors, seizures, coma.