MBMP2300: Medical Physiology II - Complete Study Guide

# ** --- ## SECTION A: SHORT ANSWER QUESTIONS (SAQs) ### Question 1: Pathophysiology of Protein-Energy Malnutrition **Answer:** Protein-energy malnutrition (PEM) is a systemic condition resulting from inadequate protein and/or energy intake, leading to multiple physiological disruptions. **Key Pathophysiological Mechanisms:** - **Metabolic Adaptation**: Body shifts from anabolic to catabolic state, breaking down muscle proteins for energy - **Hormonal Changes**: Decreased insulin, growth hormone, and IGF-1; increased cortisol and glucagon - **Immune Dysfunction**: Reduced lymphocyte production, impaired cell-mediated immunity, increased infection susceptibility - **Gastrointestinal Changes**: Villous atrophy, decreased digestive enzyme production, malabsorption - **Cardiovascular Effects**: Decreased cardiac output, bradycardia, hypotension **Clinical Manifestations:** - Kwashiorkor: Edema, fatty liver, skin changes (protein deficiency with adequate calories) - Marasmus: Severe wasting, no edema (overall caloric deficiency) - Growth retardation, delayed wound healing, increased mortality risk --- ### Question 2: Gastrointestinal Absorption of Amino Acids **Answer:** [DIAGRAM: Small Intestine Cross-Section] Lumen → Brush Border → Enterocyte → Portal Circulation Proteins → Peptides → Amino Acids → Absorption **Absorption Process:** - **Protein Digestion**: Stomach pepsin and pancreatic enzymes break proteins into peptides - **Final Digestion**: Brush border peptidases convert peptides to amino acids - **Transport Mechanisms**: - **Sodium-dependent transporters**: For neutral, acidic, and basic amino acids - **Sodium-independent transporters**: For some amino acids - **Peptide transporters**: PEPT1 for di- and tripeptides **Location**: Primarily in duodenum and jejunum **Regulation**: Enhanced by insulin, growth hormone, and dietary protein intake **Clinical Significance**: Defects lead to aminoaciduria and malnutrition --- ### Question 3: Migrating Motor Complex (MMC) **Answer:** The MMC is a cyclical pattern of intestinal motility occurring during fasting states, consisting of four distinct phases. **Phase Characteristics:** - **Phase I (45-60 minutes)**: Quiescent period with minimal contractions - **Phase II (30-45 minutes)**: Irregular, intermittent contractions - **Phase III (5-15 minutes)**: Intense, regular contractions ("housekeeper waves") - **Phase IV (5-15 minutes)**: Transitional period between cycles **Functions:** - Sweeps undigested food residues toward colon - Prevents bacterial overgrowth in small intestine - Maintains intestinal hygiene - Propels secretions and debris **Regulation**: Controlled by motilin hormone, vagal stimulation, and enteric nervous system **Clinical Importance**: Disrupted in diabetes, irritable bowel syndrome, and bacterial overgrowth --- ### Question 4: Functions and Regulation of Cholecystokinin (CCK) **Answer:** CCK is a peptide hormone released by I-cells in the duodenum and jejunum in response to fats and proteins. **Primary Functions:** - **Gallbladder Contraction**: Stimulates bile release for fat digestion - **Pancreatic Enzyme Secretion**: Triggers release of digestive enzymes - **Gastric Emptying**: Slows gastric emptying to allow proper digestion - **Satiety Signal**: Acts on brain to reduce food intake - **Sphincter of Oddi Relaxation**: Allows bile and pancreatic juice flow **Regulation:** - **Stimuli**: Fatty acids, amino acids, peptides in duodenum - **Inhibition**: Somatostatin, completed digestion - **Feedback**: Negative feedback from pancreatic enzymes **Clinical Significance**: Deficiency leads to poor fat digestion and gallbladder dysfunction --- ### Question 5: Production of Cortisol **Answer:** Cortisol is a glucocorticoid hormone produced by the zona fasciculata of the adrenal cortex. **Production Pathway:** - **Hypothalamus**: Releases CRH (Corticotropin-Releasing Hormone) - **Anterior Pituitary**: Secretes ACTH (Adrenocorticotropic Hormone) - **Adrenal Cortex**: Produces cortisol from cholesterol via steroidogenesis **Biosynthesis Steps:** - Cholesterol → Pregnenolone → Progesterone → 17α-hydroxyprogesterone → 11-deoxycortisol → Cortisol - Key enzymes: 21-hydroxylase, 11β-hydroxylase **Regulation:** - **Stimulation**: ACTH, stress, hypoglycemia, inflammation - **Inhibition**: Negative feedback on hypothalamus and pituitary - **Circadian Rhythm**: Peak in early morning, lowest at night **Transport**: 90% bound to cortisol-binding globulin (CBG) --- ### Question 6: Pathophysiology of Graves' Disease **Answer:** Graves' disease is an autoimmune hyperthyroid condition caused by thyroid-stimulating immunoglobulins (TSI). **Pathophysiological Mechanism:** - **Autoimmune Process**: TSI antibodies bind to TSH receptors - **Thyroid Stimulation**: Continuous stimulation leads to excess hormone production - **Thyroid Enlargement**: Diffuse goiter formation - **Metabolic Acce