Student Feedback and Final Exam Prep

Student Feedback Exercise

• Students' feedback is important for improving learning experiences and modules.
• Constructive comments are valuable to increase the value of feedback.
• Feedback should be specific and describe how teachers or module organization have helped (or not helped) learning.
• Inappropriate language or personal comments undermine feedback and are not acceptable.
• Abusive comments will be discarded.
• Feedback is confidential; professors will only see an aggregate report after exam results are released.
• Feedback can be completed on-campus, at home, or on the go using a mobile-friendly platform.

Final Exam Information

• The final exam is scheduled for Saturday, November 30, 2024.
• The exam venue is MPSH2-A, starting at 1 pm.
• The exam format includes multiple-choice questions (MCQs) and open-ended questions.
• The exam covers material from weeks 8 to 13.
• Section 1: Respiratory Physiology (14 MCQs and 1 open-ended question; 20 points).
• Section 2: Neural Physiology (24 MCQs and 2 open-ended questions; 44 points).
• Section 3: Gastrointestinal Physiology (22 MCQs and 2 open-ended questions; 36 points).
• The overall exam consists of 60 MCQs and 5 open-ended questions (100 points total).
• Students can use one A4 size sheet of paper (double-sided) for notes.
• Electronic calculators are permitted.

Recap: Neural Stimulation Threshold Current

• IthresholdI_{threshold}Ithreshold​ = IrheobaseI_{rheobase}Irheobase​ (1 + tchronaxietpulse\frac{t_{chronaxie}}{t_{pulse}}tpulse​tchronaxie​​)

Recap: Divergence in a Neural Circuit

• The question asks to identify an example of divergence in a neural circuit
• The provided options include stretch reflex scenarios and neuron responses to stimuli
• In a stretch reflex, a single sensory neuron might connect to multiple motor neurons, a type of divergence
• other provided answers are not example of divergence

A True Story: Competitive Eating Effects on GI System

• A video showing effects of competitive eating

BN2201: Gastrointestinal Physiology I

• This is a course name

Part I: General GI Introduction and Motility

• Topics include the general introduction to the GI tract, motility of esophagus, stomach, small intestine, and large intestine.

GI Tract - Hollow Tube Components

• Structures within the GI tract include mouth, salivary glands, esophagus, stomach, pancreas, liver, gallbladder, small intestine, and large intestine.

GI Terminology

• Oral/Orad direction: Towards the mouth
• Aboral/Anal/Caudal direction: Away from the mouth/towards the anus
• Gut: General term for the stomach and intestine
• Bowel/Enteric: Related to the intestine
• Hepatic: Associated with the liver
• Visceral: Related to internal organs of the body

The Alimentary Canal: Anatomy

• Structures and locations within the digestive tract (Mouth, esophagus, Stomach, Small Intestine, Large Intestine)

GI Compartmentalization: Sphincters

• Muscular structures controlled by nervous and hormonal systems.
• Contraction prevents food movement.
• Lower esophageal sphincter (LES) prevents acid reflux.

Tissue Organization in the GI Wall

• Mucosa, submucosa layers include different tissues- epithelium, lamina propria, muscularis mucosae, glands in submucosa, duct of gland (outside tract), lymphatic tissue & lumen
• Muscularis, Serosa layers include different tissues, blood vessels- Myenteric plexus, arteries, veins.

Regulation Mechanism in GI Tract

• Endocrine: Hormones released into blood, enterochromaffin-like cells (ECL)
• Neurocrine: Extrinsic nervous system (e.g., vagus nerve; parasympathetic and sympathetic); Intrinsic nervous system (enteric nervous system): Myenteric plexus and submucosal plexus
• Paracrine: Local signaling molecules (eg serotonin), smooth muscle function, absorption

Integrated Response to a Meal

• GI activities during ingestion, propulsion, mechanical digestion, secretion, absorption of nutrients, and defecation.

Involuntary Muscle

• Smooth muscle and cardiac muscle are involuntary muscles responsible for body functions.

Types of Muscles

• GI organs are mostly composed of smooth muscles.
• Smooth muscles exhibit slower, involuntary contractions compared to skeletal muscles.
• Action potentials in GI smooth muscle are longer than those in skeletal muscle and lack overshoots.

Types of Contractions (Smooth, Cardiac, Skeletal)

• Smooth muscles perform two main types of contractions: phasic (fast and strong) and tonic (slow and sustained).
• These contractions are involved in motility patterns like mixing, propulsion, and pendular movement.

Skeletal vs Smooth Muscles

• Skeletal muscles require neural input for contraction, whereas smooth muscles in the gut can contract spontaneously.
• "Slow waves", a type of spontaneous fluctuation in membrane potential, are common in smooth muscle tissue (except the esophagus).

Electrophysiology of the GI Tract

• Interstitial cells of Cajal (ICCs) initiate slow waves but are not involved in action potentials.
• ICC pacemaker activity differs across the GI tract; specifically in the stomach, duodenum, ileum, and colon.

ICC, ENS, and Smooth Muscles

• ICCs—the pacemakers—electrically couple to smooth muscle cells through gap junctions.
• Slow waves in ICCs cause smooth muscle contractions through calcium channel opening, calcium accumulation, and activation of Myosin Light Chain Kinase (MLCK).

Contraction in the Gut

• Slow waves (from ICCs) and appropriate ENS input cause contraction.
• Slow waves reaching threshold amplitude trigger contraction and release of neurotransmitters from enteric neurons.
• Nonzero resting tension/tone in smooth muscle.

Motility of the Esophagus: Propulsive and Protective Functions

• The esophagus transfers food from the pharynx to the stomach.
• It has upper and lower esophageal sphincters (UES, LES) that prevent reflux and protect the airway
• The esophagus is 18-25 cm long and contains skeletal and smooth muscles.
• Motility is controlled by somatic and autonomic nerves.

Relaxation of LES

• Swallowing causes neural reflex relaxation of the LES and the proximal stomach.

Motility of the Stomach

• 15-25 cm long in adults
• empty stomach ~50 ml and fully distended ~4 liters
• Types include mixing, grinding, emptying

Motility of the Stomach: Fed State

• Mixing, grinding, and emptying occur after eating.
• Jetlike retropulsion moves solids through the stomach outlet.

Motility of the Stomach: Fed State

• Small openings allow liquids to pass through the pylorus quickly, but larger particles to proceed more slowly.

Motility of the Stomach: Fasting State

• Migrating Motor Complex (MMC) clears the stomach, approximately every 100 minutes, unless food arrives, with 5-10 minutes of luminal occlusive contractions.
• Strong phasic contractions occur throughout the stomach.

Motility of the Small Intestine

• The small intestine (2.5–4 cm diameter, ~25 cm duodenum, 2.5 meters jejunum, 3.6 meters ileum)
• It takes approximately two hours for food to pass through the small intestine, clearing up the entire structure through various contractions (primarily smooth muscle contractions).

Motility of the Small Intestine: Migrating Motor Complex

• Electrical activity patterns occur in the regular cycle of fasting.

Motility of the Small Intestine: Patterns

• Segmentation (mixing), peristalsis, pendular movement are important for mixing and propulsion

Motility of the Large Intestine

• 6 cm diameter and ~1.5 meters long.
• The large intestine is involved in reabsorbing water and some electrolytes.
• Its musculature involves smooth muscle and some striated voluntary muscle cells, primarily present in the outer anal sphincter

Motility of the Large Intestine: Patterns

• Segmental propulsion – content moves back and forth between haustra.
• Mass movement – a clearing mechanism similar to MMC.

Part I Summary

• This is a summary of the parts of the GI intro and motility

Part II Summary

• This section summarizes the stats on GI disorders, esophagus and Dr Clouse, accessibility of the stomach, and methods to look from the inside.

GI Disorders

• Functional gastrointestinal disorders (FGIDs) are defined as a combination of motility disturbance, visceral hypersensitivity, Altered Central Nervous System processing and immune function, gut microbiota and altered central nervous system processing.
• They occur in about 40% of the population.

GI Disorders – Why is BME Needed?

• Numerous underlying diseases can cause gastrointestinal disorders, including diabetic gastroparesis, idiopathic gastroparesis, cyclic vomiting syndrome, intestinal pseudo-obstruction (a functional disorder), functional dyspepsia, achalasia, and gastroesophageal reflux disease (GERD).

Esophageal Manometry

• Assessing esophageal function and motility via esophageal manometry

Clouse Plots

• Analysis of esophageal function and pressures during swallowing.

GERD: An Extremely Prevalent Disease

• Gastroesophageal reflux disease (GERD) happens when the lower esophageal sphincter (LES) malfunctions.
• Stomach acid, then enters the esophagus, causing symptoms in about 18-27% of the population.

GERD: Treatment Options

• Treatment options for GERD include lifestyle modifications, drug therapies, surgical interventions (e.g., the Linx device).
• The Linx device is a surgical approach with roughly 80% effectiveness in treating chronic GERD despite medical therapy in some cases.

Assessing Gastric Motility

• X-ray fluoroscopy (Barium sulfate) is used to observe the proportion of the meal in the stomach over time and the walls of the nearby adjacent GI organs.
• Y-scintigraphy: A method used for detecting the time it takes for the meal to clear the stomach by using a radiolabeled meal.

Assessing Gastric Motility- y-scintigraphy and liquid/capsule y-scintigraphy

• A radiolabeled meal (either solid, liquid, or capsule form) is given.
• The amount of meal in the stomach over time is tracked (gastric emptying) via external detection of emitted radiation.
• Liquid or capsule-type forms are commonly used.

Quantifying Gastric Emptying: The Siegel Model

• Mathematical model (y= 1-(1-e-kt)β) describes how much food remains in the stomach over time.
• Parameters (β and k) are dependent on food type and patient's gastric motility.

Visualizing Gastric Emptying

• X-rays can visualize the different parts of the stomach, including the duodenum, pylorus, the gastric body, and more.

Regulation of Gastric Emptying

• The chemical signals from the food (liquids like glucose and protein solutions) dictate how and when the pylorus regulates the opening/closing/flow.
• Downstream receptors detect this composition and send signals back to the stomach.

Gastroparesis

• This is a disease in which the stomach has difficulty emptying.
• This causes an endless search for answers when trying to determine the cause.
• This includes different diagnostic methods and investigations such as CT, MRI, endoscopies, and ultrasound scans, as well as gastric emptying scans.

Therapeutic Options (1): Drugs

• Prokinetic drugs are used to stimulate enteric neurons, increasing neurotransmitter release and stimulating receptors in the chemoreceptor trigger zone (CNS)

Therapeutic Options (2): Enterra Device

• Enterra device is a surgical device that stimulates the enteric nervous system for treating certain gastrointestinal conditions.
• The actions and mechanism are not entirely known.
• This device induces neural neuromodulation of parasympathetic nerves or ganglia which regulate gastric motility.

Other Stomach Diagnostics: Electrogastrography (EGG)

• Recording of slow wave activity in the stomach from the detection of the electrical output of the stomach via skin electrodes.

Looking from Inside: Colonoscopy

• Colonoscopy is a procedure that allows visualization of the colon and rectum.
• Biopsies can be taken during colonoscopy.
• It is used for colorectal cancer screening for average-risk individuals over 50 years old.

Looking from Inside: Upper GI Endoscopy

• Visualization of the upper GI tract (including esophagus, stomach, duodenum)
• Can aid in tissue biopsy, aiding in the diagnosis of abnormalities.

Looking from Inside: Small Intestine Endoscopy

• Small intestine is difficult to visualize anatomically.
• Different techniques include double balloon and capsule endoscopy
• Various types of imaging (i.e. Pillcam and more) are available to visualize the structure of the small intestine,

Video Capsule Endoscopy vs Traditional Endoscopy

• Advantages of video capsule endoscopy (VCE) over traditional techniques include non-invasiveness and the ability to detect certain types of bleeding.

Beyond Camera - Ingestible Bacterial-Electronic System

• Genetically encoded bacteria detect inflammation-associated molecules.
• Wireless capsule records GI bleeding

Your Gut - the Second Brain?

• Shows the connection between the gut and mental wellbeing.
• The gut may affect appetite, anxiety, and Parkinson's disease

This quiz covers important guidelines for student feedback and details regarding the upcoming final exam scheduled for November 30, 2024. It emphasizes the importance of constructive feedback and provides insights into the exam format and content. Prepare effectively with this comprehensive overview.