Digestive and Urinary System: Reflexes, Enzymes, and Organ Structure

LAB 5: Reflexes and the Nervous System

Reflexes: Definition and Mechanism

A reflex is an involuntary, rapid response to a stimulus, mediated by the nervous system. Reflex actions help protect the body and maintain homeostasis.

• Character of Reflex Action: Automatic, predictable, and quick responses to specific stimuli.

• Control of Reflex Action: Reflexes are controlled by neural pathways called reflex arcs.

• 5 Basic Components of Reflex Arc:

  1. Receptor

  2. Sensory neuron

  3. Integration center (spinal cord or brain)

  4. Motor neuron

  5. Effector (muscle or gland)

• Example: Patellar Reflex - Tapping the patellar tendon causes contraction of the quadriceps muscle, resulting in knee extension.

Classification of Reflexes

• Based on Integration Center: Spinal reflexes (e.g., withdrawal reflex) and cranial reflexes (e.g., pupillary reflex).

• Based on Effector Organ: Somatic reflexes (involving skeletal muscle) and autonomic reflexes (involving smooth muscle, cardiac muscle, or glands).

Autonomic Nervous System (ANS)

• Sympathetic Nervous System: Prepares the body for 'fight or flight' responses (increases heart rate, dilates pupils).

• Parasympathetic Nervous System: Promotes 'rest and digest' activities (decreases heart rate, stimulates digestion).

• Effects of Sympathetic & Parasympathetic NS: Influence on blood pressure, heart rate, and other body functions.

Reflex Testing Tools

• Sphygmomanometer: Measures blood pressure.

• Stethoscope: Used to listen to heart and lung sounds.

• Reflex Hammer: Used to test deep tendon reflexes.

LAB 6: Digestive System Structure and Function

Organs of the Alimentary Canal

The alimentary canal consists of organs through which food passes and is digested and absorbed.

• Accessory Digestive Organs: Teeth, tongue, salivary glands, liver, pancreas, gallbladder.

• Parts of Stomach: Cardia, fundus, body, pylorus. The stomach wall has several muscular layers for churning food.

• Microscopic Structure: Mucosa, submucosa, muscularis externa, serosa.

• Small Intestine: Duodenum, jejunum, ileum.

• Large Intestine: Cecum, colon, rectum, anal canal.

• Pancreas: Produces digestive enzymes and hormones.

Structural Differences

• Human vs. Rat Digestive System: Differences in size, shape, and some organ arrangements.

• Alimentary Canal Variations: Haustra (pouches), Taenia coli (longitudinal muscle bands), Peritoneum (membrane lining), Omentum (fatty apron), Lesser and Greater Curvature (stomach).

LAB 7: Enzymes and Digestion

Enzymes in Digestion

Enzymes are biological catalysts that speed up chemical reactions, including those involved in digestion.

• Factors Affecting Enzyme Activity: Temperature, pH, substrate concentration.

• Relation Between Enzyme and Substrate: Enzymes bind specific substrates to catalyze reactions.

• Emulsification: Breakdown of large fat globules into smaller droplets (e.g., by bile).

• Enzyme Examples:

  • Carbohydrases (e.g., amylase) for carbohydrate digestion

  • Proteases (e.g., pepsin) for protein digestion

  • Lipases for fat digestion

• Special Gastric Mucosal Layer: Protects stomach lining from acid and enzymes.

• Cells of the Stomach: Chief cells (secrete pepsinogen), parietal cells (secrete HCl), mucous cells (secrete mucus).

Enzyme Activity and Digestion Experiments

• Reagents for Carbohydrate Digestion: Lugol's iodine (tests for starch), Benedict's reagent (tests for reducing sugars).

• Interpretation: Dark blue/black with Lugol's indicates starch; orange/red with Benedict's indicates monosaccharides.

• Reagent for Protein Digestion: Biuret reagent (tests for peptide bonds).

• Sudan Red Stain: Used to detect lipids.

• Phenol Red: pH indicator in lipid digestion experiments.

LAB 8: Urinary System Structure and Function

Organs and Structure of the Urinary System

The urinary system removes waste products from the blood and regulates water and electrolyte balance.

• Main Organs: Kidneys, ureters, urinary bladder, urethra.

• Kidney Structure: Cortex (outer region), medulla (inner region), renal pelvis.

• Nephron: Functional unit of the kidney, responsible for filtration and urine formation.

Blood Supply and Urinary Flow

• Blood Supply: Renal artery brings blood to the kidney; renal vein carries filtered blood away.

• Pathway of Urinary Flow: Nephron → collecting duct → renal pelvis → ureter → bladder → urethra.

Urinalysis

• Features of Normal Urine: Clear, pale yellow, slightly acidic (pH ~6), free of glucose and proteins.

• Abnormal Substances: Glucose (diabetes), proteins (kidney disease), blood (trauma/infection).

Table: Digestive Enzymes and Their Functions

Enzyme	Substrate	Product	Site of Action
Amylase	Starch	Maltose	Mouth, Small Intestine
Pepsin	Proteins	Peptides	Stomach
Lipase	Triglycerides	Fatty acids, Glycerol	Small Intestine
Lactase	Lactose	Glucose, Galactose	Small Intestine
Additional info: Sucrase	Additional info: Sucrose	Additional info: Glucose, Fructose	Additional info: Small Intestine

Key Equations

• Enzyme Reaction Rate:

$\text{Rate} = k[\text{Enzyme}][\text{Substrate}]$

• Urine Formation:

$\text{Urine Output} = \text{Filtration} - (\text{Reabsorption} + \text{Secretion})$

Additional info: These study notes expand upon the brief questions provided, offering definitions, examples, and context for Anatomy & Physiology students.