Usmle 1 GI

• ▪ Cephalic
• ▪ Oral
• ▪ Pharyngeal
• ▪ Esophageal
• ▪ UGI
• ▪ LGI

▪ Role of the brain

▪ Responsible for basic urges (Controls)

▪ Hippocampus – long term memory

▪ Amygdala- reward and fear, mating

• Can overcome limbic system (cortex)

• • Measures circadian rhythms in response to light
•    • Low Melatonin with light
•    • High Melatonin with dark 
•    • Melatonin (tryptophan) milk and turkey

• • 1st 8 hours:     
• • Catabolism in the morning       
•    • Take vitamins       
•    • Exercise in the A.M. to burn most fat 

• • 2nd 8 hours      
•    • Mixture of catabolism and anabolism 

• • 3rd 8 hours: (Night time)     
•    • Catabolism is off     
•    • Anabolism is on 

• • Getting ready to fall asleep.      
•    • Explains “Jet lag”, gain weight if eat in evening…

• Hunger Center (lateral nucleus of hypoth)

• Controlled by low glucose

• • Low glucose (Hypoglycemia) ↑Firing of hunger center
•    • This center can be stimulated by the sight of food: therefore can always feel hungry

• • Stimulated 20% of the time
•    • Lesion:
•      • anorexia → because no longer have “hunger signal”
•    • Could be associated with Anorexia Nervosa/Body dysmorphic
•      • Anorexics feel they are not thin enough
•      • Patient trying to please the mom – look for executive mom type- hard to please.
•      • Treat with SSRI to get at hunger center
•         Selective serotonin reuptake inhibitors

• Satiety Center (medial nucleus of hypoth)

• ↑Glucose (Hyperglycemia) ↑firing of satiety center

• • Stimulated 80% of the time
•    • Lesions/Abnormalities:
•      • Die of Hyperphagia = overeating.
•      • Could be associated with Bulimia
•        • Girl trying please boyfriend.
•        • Signs to look for:
•        • Abrasion of knuckles
•        • Loss of enamel on teeth

• • Controls MENSES
•    • progesterone stimulates hunger system

• Pregnancy due to corpus lutetium

• • Controls TEMPERATURE:
•    • ANTERIOR Hypothalamus: cools (inhibits NE)
•      • Lesion anterior- die from: hyperthermia
•    • POSTERIOR Hypothalamus: warms
•      • Lesion posterior- die from hypothermia

• • Acetaminophen: for use with fever
• (stimulate anterior hypothalamus- cools), then it
• blocks posterior so you do not go back up again

• • Toxicity- microsteatosis (small fat cells in liver)
•    • Reye syndrome in children

• • Tx: N-acetylcystine-reducing agent
•    • 4 hour level will determine if you use it

• • Men: 5 feet = 106 lbs
• • Women: 5 feet= 100 lbs

• Add 5 lbs for per inch past that…

• • Small frame: add 15 lbs
• • Large frame: add 30 lbs

• (i.e. male 5’10”: 106 + 50 +30 = 186 lbs)

• Obesity is considered 20% over ideal body weight

• • Neurotransmitters in the hypothalamus are NE and Serotonin
•   • NE & Serotonin can contribute to both centers

• Amphetamines will cause ↑release of preformed catecholamines so NE and Serotonin levels will go up and hit satiety center: won’t be hungry.

• Lesion of the satiety center (Ventromedial)

• Trinucleotide repeats

• • Genomic imprinting 
•    • Uniparental disomy (one parent genes, both chromo)

• Chromosome 15

• • Huge Appetite
•    • Die due to over eating

• • Anytime the body senses stress, sets off the same reflex
•   • 1st Parasympathetic then 2nd Sympathetic discharge

• • Sympathetic ↑vasoconstriction in GI and skin
•   • Stress ulcer (GI doesn’t have blood supply to protect itself)
•   • Ex. Hospital protocol- Patients in the ICU need to be on H2 blockers.

• Sympathetic for Ejaculation.

• 1st Parasympathetic then 2nd Sympathetic discharge

• • “You scared the crap out of me!!!”
• ­ • ↑GI motility
• ­ • ↑GI acid output

• • Parasympathetic ALWAYS precedes SYMPATHETIC
•   • Ex. Point and Shoot:

• Parasympathetic for erection

• Put food into mouth- salivary glands respond

• • SALIVARY GLANDS
•    • Parotid [ in front of ear ](serous)-water - CN 9
•    • Lingual [ on tongue ] (most serous) CN 7
•    • Sublingual [under tongue] (most mucus) CN 7
•    • Submandibular [jaw] (mucus) CN 7

• • Saliva in your mouth has to be HYPOTONIC (cracker)
• • Food on your cheek- food will get stuck (gummy bear)

• • Saliva needs to be basic for 3 reasons:
•   • Acidic Food
•   • Bacteria fermenting glucose to lactic acid
•   • reflux

• • Isotonic Plasma
•   • 1° saliva

• • Saliva needs to be BASIC ↑↑↑ HCO3 Production
• • Exchange
•   • 3 Na out
•   • 1 Cl out
•   • 2 K in
•   • HCO in

• • 2° Saliva = hypotonic
•    • Saliva has more Na and Bicarb → Very Alkalotic

• • Reflux → Normal phenomenon
•   • GERD –with symptoms

• • Esophagitis
•   • What you see on a scope
•   • look for T cells, macrophages in raw spots

• • BARRETT’S ESOPHAGUS
•   • short to long columnar

• • MALORY WEIS SYNDROME
•   • tears in submucosa (ETOH, vomiting)

• • BOORHAAVE’S SYNDROME
•   • Rupture of esophagus

• IgA

• Lipase- little fat break down

• Amylase: breaks alpha 1,4 bonds

• Lysozyme: a detergent

• • HCO3: three sources of acid
•    • From food (drinks)
•    • Produced by bacteria ( strep mutans)
•    • Reflux

• will produce more saliva

• • this saliva will have ­↑osmolarity, (more salt)
•   • No more than 300 mOsm
•   • Can’t be hypertonic (Because saliva goes through very fast)

• same as parasympathetic stimulation

• • Acetylcholine 
•   • CNS: excitatory
•   • PNS: activates muscles

• • Methacholine
•   • dx asthma (old)
•   • beta 2 agonist to bring you out

• • Pilocarpine
•   • sweat test ( > 60)
•   • open angle glaucoma (chronic)

• • Carbachol-
•   • post op urinary retention (stimulate bladder emptying)

• • Bethanechol
•   • post op urinary retention

• Vasoconstriction = ↓ salivary production because blood is being shunted away, however, the blood will be thick and ↑ Na concentration

• NE → α>β

• • Epi → β>α
•   • Pseudoephedrine → stress incontinence
•   • Phenylephrine → tx: for neurogenic shock
•      • vasoconstricts arteries

• • Saliva also secretes IgA
•    • Used to coat bacteria in the mouth from food you eat → provides protection

• • Also secretes Lysozyme
•    • Acts as a detergent
•    • Prevents adhesion to the teeth

• • Lipase
•    • Fat digestion begins in mouth, but that is negligible

• • Start Carbohydrate digestion
•   • Lactase
•     • Most common SECONDARY dissacharidase deficiency.
•     • 1st enzyme to disappear with diarrhea.
•     • Will stop producing at age 4 
•       • lactose intolerance

•   • Sucrase
•     • The most common PRIMARY (congenital) dissacharidase deficiency

•   • Maltase
•   • α- dextranase

• Lactose = glu and gal

• Sucrose = glu and fru

• Maltose = 2 glucose and α 1,4 linkages

• α– dextrins = 2 glucose w/ α 1,6 linkage

• • MCC: of malabsorption in children
•    • meconium ileus (bowel obstruction)

• Autosomal recessive inheritance

• CFTR gene on chromosome 7

• • Defective CHLORIDE transport
•    • Chloride traps sodium, increasing the salt
• content and thickness of secretions

• Staph Aureus and Pseudomonas Aeruginosa

• MUST cover Staph Aureus with one antibiotic and Pseudomonas Aeruginosa with two antibiotics

• • Dx: Pilocarpine
•    • Cl sweat test
•      • < 40 Normal
•      • 40 – 60 Heterozygous
•      • > 60 CF

• Meconium ileus: first presentation in neonate

• Predispose to Oxalate kidney stones

• lungs (thick mucus)

• Steatorrhea = fatty stools/ oily diarrhea

• • Malabsorption develops as pancreatic ducts
• become clogged

• sweat glands and epididymis (men infertil)

• A normal phenomenon: GERD

• • ESOPHAGITIS-
•   • tissue inflammation (T-cell/Mac)

• • BARRETT’S ESOPHAGUS-
•   • short to long columnar

• • MALORY WEIS SYNDROME-
•    • tears in submucosa (ETOH, vomiting)

• • BOORHAAVE’S SYNDROME-
•    • Rupture of esophagus

• • Masseter- (cheek) closes
• • Temporalis- (closes) moves jaw forward and back
• • Medial Pterygoids (closes)
• • Lateral Pterygoids- (opens) lowers jaw

• • Innervated by cranial nerve 5 (Trigeminal)-
• mandibular V3

• Develop from first branchial arch

• • Tip of tongue rises 
• • Sides of tongue rise and fold medially 
• • Tip of tongue rises to hard palate 
• • Gravity begins bolus rolling 
• • When bolus approaches trachea, epiglottis
• • Closes off glottis 
• • Bolus rolls over epiglottis/touches the pharynx
• • CN 9, 10 sense the bolus 
• • UES opens relaxes 
• • Bolus drops into esophagus

• • Upper 1/3 has skeletal muscle
•    • Voluntary activity
•    • made up of 4 muscles
•    • Superior and middle pharyngeal constrictors 
•    • Gag reflex controlled by CN IX and X

• Smooth muscle bottom 2/3

• Nucleus Ambiguus: innervates the UES efferent vagus (motor CN 10)

• Dorsal motor nucleus: innervates the rest of GI – efferent vagus (motor CN 10)

• Primary peristalsis: requires vagus nerve and Auerbach’s plexus; begins just distal to the UES only

• Secondary peristalsis: intrinsic to smooth muscle; can begin anywhere in GI

• 
• 

• They are small, bulging pouches that can form in the lining of your digestive system

• • Zencker's
•    • Above UES = Congential

• • Traction
•    • Below UES and below LES → traction

• • Presentation:
•    • Coughing up undigested food.
•    • Malodorous halitosis

• • Esophageal atresia with distal TE fistula
•    • Blind pouch at top of esophagus.
•    • M/C congential esophageal problem
•    • Presentation:
•      • vomiting with first feeding
•      • Look for big gastric bubble on X-Ray

• membrane that connects to pharynx does not dissolve

• Choanale- space between nostrils and pharynx

• • Presentation
•   • turn blue when they feed
•   • turn pink when they cry

• Lack of aurebachs plexus (ganglia) in lower esophagus

• GI tract will contract but won’t relax

• • Presentation:
•   • Will start chocking and gagging when start on cereal (but ok with milk)
•   • Look for Bird’s beak on Barium Swallow

• • Diagnosis
•   • Monometry: ↑ pressure across the LES

• • Treatment:
•   • Bougie used to dialate esophagus
•   • partial Vagotomy (the nerve causes the narrowing)
•   • Myotomy (to split tightened muscle fibers)

• • Sudden loss of Ganglia in adult causing Achalasia
•   • indicates Chagas disease (6 months trip from S. America)

• Same diseases in the rectum → loss of both Auerbach’s and Meissener’s

• Rectum won’t be able to relax

• • Presentation:
•   • Constipation

• Diagnose with Barium

• Treatment: remove part of the rectum that’s affected.

• Strips of mucosa going across esophagus (congenital)

• • They can start bleeding after burns hot liquids
•    • Fe deficiency anemia:Plummer-Vinson

• Diagnose with Barium swallow

• Gastroesophageal reflux disease (GERD) occurs when stomach acid repeatedly flows back into the tube connecting your mouth and stomach (esophagus).

• This backwash (acid reflux) can irritate the lining of your esophagus.

• is a method to reproduce symptoms of heartburn. (GERD)

• A nasogastric (NG) tube is passed through one side of your nose and into your esophagus. Mild hydrochloric acid will be sent down the tube, followed by salt water (saline) solution.