Endocrine System Study Guide PDF

1. Nervous vs. Endocrine System Regulation Compare and Contrast: Nervous System: o Regulates via electrical signals (action potentials). o Responses are fast and short-lived. o Controls muscles and glands directly. o Uses neurotransmitters. Endocrine...

1. Nervous vs. Endocrine System Regulation Compare and Contrast: Nervous System: o Regulates via electrical signals (action potentials). o Responses are fast and short-lived. o Controls muscles and glands directly. o Uses neurotransmitters. Endocrine System: o Regulates via hormones (chemical signals). o Responses are slower but longer-lasting. o Controls metabolic activity and homeostasis. o Releases hormones into the bloodstream. 2. General Functions of the Endocrine System Regulates growth and development. Maintains homeostasis of electrolytes, water, and nutrients. Controls metabolism and energy balance. Coordinates reproduction. Helps the body respond to stress. 3. Locations of Endocrine Glands Hypothalamus (brain). Pituitary gland (below hypothalamus). Thyroid gland (neck, below larynx). Parathyroid glands (posterior thyroid). Adrenal glands (on top of kidneys). Pancreas (behind stomach). Pineal gland (brain). Thymus (upper chest, behind sternum).  Gonads (testes in males, ovaries in females). 4. Gland Tissues and Histology Pituitary gland: Anterior (glandular) and posterior (neural) lobes. Thyroid gland: Follicles with colloid (T3, T4 production). Adrenal gland: Cortex (three layers) and medulla. Pancreas: Islets of Langerhans (endocrine function). Pineal gland: Pinealocytes. 5. Stimulation of Hormone Synthesis and Release Humoral Stimuli: Response to changes in blood levels (e.g., calcium). Neural Stimuli: Nerve fibers stimulate release (e.g., adrenal medulla). Hormonal Stimuli: One hormone stimulates another gland (e.g., hypothalamic- pituitary axis). 6. Local vs. Circulating Hormones Local Hormones: o Paracrine: Affect nearby cells. o Autocrine: Affect the same cell that secretes them. Circulating Hormones: o Travel through the bloodstream to distant targets. 7. Hormone Transport in Blood Water-Soluble Hormones: o Travel freely in plasma. o Bind to surface receptors. Lipid-Soluble Hormones:  o Bind to transport proteins. o Diffuse through cell membranes. 8. Water-Soluble vs. Lipid-Soluble Hormones Water-Soluble Hormones: Structure: Amino-acid based. Function: Bind to surface receptors; activate second messengers. Examples: Insulin, epinephrine. Lipid-Soluble Hormones: Structure: Steroids and thyroid hormones. Function: Diffuse into cells; bind to intracellular receptors to affect gene transcription. Examples: Cortisol, T3, T4. 9. Up and Down Regulation Up-Regulation: Increase in receptor numbers to enhance sensitivity. Down-Regulation: Decrease in receptor numbers to reduce sensitivity. 10. Hypothalamus and Pituitary Gland Relationship Hypothalamus controls pituitary via: o Releasing/inhibiting hormones. o Hypophyseal portal system (anterior pituitary). o Neural connections (posterior pituitary). Pituitary secretes hormones that regulate other endocrine glands. 11. Growth Hormones Regulation: Stimulated by GHRH; inhibited by somatostatin. Effects: Stimulates growth of tissues, protein synthesis, and fat breakdown. 12. Thyroid Structure and Histology Composed of follicles filled with colloid. Follicular cells produce T3 and T4. Parafollicular cells produce calcitonin. 13. Thyroid Hormone Regulation and Effects Regulation: TSH from anterior pituitary. Effects: Increases metabolic rate, protein synthesis, and energy usage. 14. Calcitonin Regulation and Effects Regulation: Stimulated by high blood calcium levels. Effects: Lowers calcium levels by inhibiting osteoclasts. 15. Adrenal Gland Structure and Histology Cortex: Three zones: o Zona glomerulosa: Produces mineralocorticoids (aldosterone). o Zona fasciculata: Produces glucocorticoids (cortisol). o Zona reticularis: Produces androgens. Medulla: Produces catecholamines (epinephrine, norepinephrine). 16. Pancreas Structure and Histology Structure: Exocrine (acinar cells) and endocrine (islets of Langerhans). Histology: Islets contain alpha (glucagon), beta (insulin), delta (somatostatin) cells. 17. Pancreas Hormones Regulation and Effects Insulin: Lowers blood glucose; regulated by high glucose levels. Glucagon: Raises blood glucose; regulated by low glucose levels. 18. Other Endocrine Organs Pineal Gland: Hormone: Melatonin. Function: Regulates sleep-wake cycles. Parathyroid Gland: Hormone: Parathyroid hormone (PTH). Function: Raises blood calcium levels. Thymus: Hormone: Thymosins. Function: Maturation of T-cells (immune response). Testes: Hormone: Testosterone. Function: Male secondary sexual characteristics and spermatogenesis. Ovaries: Hormones: Estrogen and progesterone.  Function: Female secondary sexual characteristics and menstrual cycle regulation. 19. Hormonal Changes with Aging Reduced hormone levels (e.g., growth hormone, estrogen, testosterone). Reduced sensitivity to hormones. Increased risk of endocrine disorders. 20. Diseases and Disorders of the Endocrine System Diabetes Mellitus: Insulin deficiency or resistance. Hyperthyroidism: Excess thyroid hormone (e.g., Graves' disease). Hypothyroidism: Insufficient thyroid hormone (e.g., Hashimoto's). Cushing's Syndrome: Excess cortisol. Addison's Disease: Insufficient cortisol and aldosterone. Acromegaly/Gigantism: Excess growth hormone in adults/children. Pituitary Dwarfism: Insufficient growth hormone. Diabetes Insipidus: Deficiency of ADH. Questions and Answers 1. Nervous vs. Endocrine System Control Communication Method: o Nervous: Electrical signals and neurotransmitters. o Endocrine: Hormones in bloodstream. Target: o Nervous: Specific cells (neurons, muscles). o Endocrine: Broad (cells with receptors). Response: o Nervous: Rapid. o Endocrine: Slow.  Effect: o Nervous: Short-term. o Endocrine: Long-term. Duration: o Nervous: Short-lasting. o Endocrine: Prolonged. 2. Three Types of Stimulation Humoral: Blood composition triggers hormone release. Example: Calcium levels stimulating PTH. Neural: Nerves stimulate release. Example: Sympathetic nerves stimulating adrenal medulla. Hormonal: Hormones trigger other hormones. Example: Hypothalamus releasing factors for pituitary hormones. 3. Circulating Hormones Types: o Steroid Hormones: Lipid-soluble (e.g., cortisol). o Peptide Hormones: Water-soluble (e.g., insulin). o Biogenic Amines: Derived from amino acids (e.g., epinephrine). Differences: o Lipid-soluble diffuse into cells, water-soluble bind to surface receptors. 4. Local vs. Circulating Hormones Local: Act nearby (e.g., prostaglandins). Circulating: Travel in blood to distant targets. 5. Target Cell Responsiveness Depends on: o Hormone concentration. o Receptor density. o Influence of other hormones. 6. Hormone Interactions Permissive: One hormone allows another to act (e.g., thyroid hormone for epinephrine). Synergistic: Hormones amplify effects (e.g., glucagon and epinephrine). Antagonistic: Hormones counteract (e.g., insulin vs. glucagon). 7. Hypothalamus Role Synthesizes: ADH, oxytocin. Controls: Pituitary hormone release. 8. Anterior Pituitary Role Hormones: GH, TSH, ACTH, FSH, LH, PRL. Effects: Growth, metabolism, reproduction. 9. Posterior Pituitary Role Stores/releases: ADH, oxytocin. 10. Thyroid Role Hormones: T3, T4, calcitonin. Effects: Metabolism, calcium regulation. 11. Parathyroid Role Hormone: PTH. Effect: Raises blood calcium. 12. Adrenal Cortex Role Hormones: Aldosterone, cortisol, androgens. Effects: Electrolytes, stress response. 13. Stress Response Stages Alarm, resistance, exhaustion. 14. Adrenal Medulla Role Hormones: Epinephrine, norepinephrine. Effects: Fight-or-flight response. 15. Pancreas Role Hormones: Insulin, glucagon. Effects: Glucose regulation. 16. Pineal Gland Role Hormone: Melatonin. Effect: Circadian rhythms. 17. Other Organs Gonads: Sex hormones. Thymus: Immune function. Heart: ANP regulates blood pressure. Kidneys: Erythropoietin for red blood cells. Liver: IGF-1 for growth. Stomach: Gastrin. Small Intestine: CCK, secretin. Adipose: Leptin for appetite. Skin: Vitamin D. 18. Clinical Disorders Hyperthyroidism: High T3, T4 (e.g., Graves'). Hypothyroidism: Low T3, T4 (e.g., Hashimoto's). Cushing's: Excess cortisol. Addison's: Low cortisol/aldosterone.  Acromegaly/Gigantism: Excess GH. Dwarfism: Low GH. Diabetes Insipidus: Low ADH. Diabetes Mellitus: Glucose metabolism issues (Type 1, 2, gestational).