Physio GIT-2 - Summary Psychology PDF

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PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

GIT 2: MOTOR FUNCTION TWO TYPES OF MOVEMENT Defecation reflex is the end point

MIXING MOVEMENT 

PROPULSIVE MOVEMENT  Basic propulsive movement is peristaltic movement (prototype movement)  Movement of the GI content from the mouth to the anus (analward/aboralward) - peristalsis is observed from the esophagus to the anus requires intact myenteric plexus (controls the motor movement of GIT) - initiated by stretching the gut wall - peristalsis is a ring-like contraction above, proximal and at the back of the stimulus and relaxation below, in front and distal oralward is abnormal  vomiting Why do you have that kind of contraction? - arrangement of neurons in the GIT *serotonin inhibitors and agonist are important GI drugs

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observed in the small intestine also requires intact Myenteric plexus but unlike the peristaltic (contraction above, relaxation below) it is an alternate contraction-relaxationcontraction-relaxation. the contracted will relax and the relaxed will contract. Once it contracts it either moves the GI content to right or left  slowed GI content movement (allows mixing) INGESTION OF FOOD

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• Peristaltic or Myenteric Reflex - Local stretch  releases SEROTONIN  activates sensory neuron  activates myenteric plexus - myenteric plexus is activated by the activated neurons NOT the local stretch - Cholinergic neuron (Retrograde direction)  activates neurons  releases Ach & Substance P  contraction (behind, proximal or above the stimulus) - Ach and substance P - excitatory NT - Cholinergic neuron (Anterograde direction)  activates neurons  releases VIP and NO  relaxation (in front, distal, below) Let’s say you have the whole small intestine and you cut it then decided to reanastomose it again. Then, you have to and suture it in proper position •

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GI content mixes with GI secretions for optimal digestion and absorption Prototype movement: Segmentation contraction retard the movement to make it slow for optimal digestion and absorption

2 – 25 cm/sec – rate of peristaltic movement

Hunger – intrinsic desire for food Appetite – seeking a specific food that you want When we ingest food, the responses are: Cephalic Phase  before you start eating, you already have secretions  activation of GI tract in response to meal (main feature)  stimuli involved cognitive and anticipation of thinking about food (salivation) - olfactory input (smell of food) - visual input (sight of food) - auditory (listening about food) Motor Function: • • • • • •

MASTICATION (CHEWING) activity of the mouth voluntary as well as reflex behavior (involuntary) food, chewing into smaller particles number of chews (optimum): 20-25 Most important structure: teeth Force: 55 dynes (incisors) – cutting action 200 dynes (molars) – grinding action Page 1 of 10

PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

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Muscle Innervation – CN V (trigeminal) no muscles and nerves  no mastication once you put food in your mouth, you automatically depress your jaw  contraction of the muscles the muscles are the most important components for mastication (temporalis and Masseter) teeth are needed but mastication is possible even w/o them, but is difficult

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When you masticate or chew, some are already mechanically digested. Events in the Oral Stage: 1. The tip of the tongue will separate the bolus from the rest of the food in the mouth – voluntary initiation. (Separates properly chewed and incompletely digested food) 2. The tongue will separate the bolus of food from the mass of the food in the mouth. It starts with the tip and eventually it goes to the posterior part. 3. Posterior will push it to the hard palate, move it upward and backward. Then the food is already in the pharynx (swallowing reflex).

DEGLUTITION (SWALLOWING)  

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activity of the mouth (voluntary), pharynx (involuntary) and esophagus (involuntary) Purpose: To transport food into the stomach Note: When the food is swallowed and not yet digested in the stomach, swallowing is not yet completed. Complete Swallowing – presence of food in the stomach Propulsion of food into the stomach Partly voluntary, mostly reflex response Regulated by CN V, VII, IX, X and XII Afferent fibers – CN V, IX and X Centers – tractus solitarius and nucleus ambiguous Present in the pons but primarily in the medulla Efferent fibers – CN V, VII and XII 600 swallows per day Awake without food: 350 Sleeping: 50 Eating: 200

swallowing is voluntarily initiated but eventually becomes a reflex response or involuntary tongue: functionally important organ

Process:

STAGES OF SWALLOWING Mastication- mixing movement Swallowing- propulsive movement ORAL STAGE  

motor activity of the mouth primarily a voluntary response sometimes becoming involuntary

PHARYNGEAL STAGE   

swallowing reflex exclusively involuntary it is pushing up and then posteriorly then the food now enters the pharynx

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PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

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To test for gag reflex of stroke patients use a tongue depressor to stimulate the uvula. (+) gag reflex –act of vomiting (-) gag reflex – no act of vomiting; you must place NGT. You cannot let the patient have oral intake because there is a chance the patient will have aspiration

most dangerous stage because the pharynx is both the passage of food and air respiration is reflexly inhibited this is where you have the reflex at the opening of the pharynx there are some touch receptors. So, once the food touches that area, the touch receptors are activated. Once you activate the touch receptors, what will happen? - CN V, IX and X. These afferent nerves will send impulses to the center (medulla: tractus solitarius and nucleus ambiguous). It is integrated in the medulla  send impulses through the efferent  going to the structures of the Pharynx

2. Anesthetized Patients  Anesthesia causes incomplete closure of the airway  Px’s are not allowed to eat food 6 hours before operation  Why 6 hours? because anesthetic agents are emetic agents that can trigger vomiting.  Vomiting when airway is incompletely closed, contents may enter the airway  Mouth to colon: 6 hours 3. Comatose Patients • Under NGT in feeding unconscious px’s

Events in the Pharyngeal Stage: 1. Movement of soft palate upward 2. Movement of Palatopharyngeal inward and towards each other. Purpose: make it narrow to avoid reflux of food into the nasopharynx 3. Movement of vocal cords toward each other This will cause adduction to close the airway. Then moves upward and forward against the epiglottis to close the airway. 4. Opening of the upper esophageal sphincter 5. Contraction of superior constrictor muscles strongly to push the food into the esophagus. 6. Respiration is reflexly inhibited. This is the reason why you cannot swallow and inspire at the same time.

After this there is relaxation of esophageal sphincter; so the food enters the esophagus and it is pushed down. ESOPHAGEAL STAGE Peristaltic movement – causes movement of food into the stomach 2 types of peristaltic movement: 1. Primary peristalsis – moves food into the stomach. (moderate to mild) 2. Secondary peristalsis – when there is still some food left in the esophagus another strong contraction will happen.

End point: food to the esophagus

When food is already in the stomach, lower esophageal sphincter will close.

Aspiration – GI content goes to the airways and causes sudden death

End-point of swallowing – food in the stomach

Conditions where there is incomplete closure of airway during swallowing 1. Patients with Stroke • Gag reflex is affected • Required to put NGT before feeding

STOMACH -

Stomach does not contract because food is temporarily stored Three important motor movements: Page 3 of 10

PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

- Receptive Relaxation (fundus) - Mixing and Grinding (antrum) - Gastric emptying (pylorus) STRESS/RECEPTIVE RELAXATION • •

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What type of movement? No movementrelaxation a.k.a. temporary storage There are layers of food in the stomach which are arranged with the highest density are carbohydrates in the bottom followed by proteins and fats are on top. Motor function of the proximal stomach which is the fundus and body of stomach is called temporary storage, because once you are swallowing the response of the stomach is to relax the fundus and the body its purpose is to temporary store food. volume adaptation phenomenon  adapts to large volumes with little increase in intragastric pressure (1-1.5L) vagally mediated ---- vagovagal reflex --abolished by vagotomy Once you are swallowing, your stomach will not contract until you stop swallowing, because as food passes in the esophagus, the vagal fiber will send an impulse to the fundus and stomach causing relaxation and will send an impulse to the vagal fiber which is why it is called vagovagal reflex. (Integrated not only in the enteric but also in the autonomics) Stomach contracts when you stop swallowing Normally you stop swallowing when the amount of food in the stomach is 1-1.5L, it will distend the stomach which will send a neural impulse to the hypothalamus activating satiety center, and once activated, appetite decreases and you stop swallowing. Once stomach is distended, some of the anorexigenic agents that will increase is proopiomelanocortin and corticotropinreleasing hormone.

 Cocaine amphetamine transcriptase – decrease appetite, it is an anti-obesity drug *non-propulsive and non-mixing Effective method of weight loss • Diet restriction – you do not release anorexic substance. If your stomach is not extended because you’re on diet a hormone ghrelin is very high. • Ghrelin – this reactivate your appetite center, calling it anorexigenic substance. • Most effective way of losing weight – bariatic surgery (remove some portion of your stomach); gradual diet restriction MIXING AND GRINDING • The motor function of the distal stomach (primarily the antrum). • Grinding and Mixing function of the antrum. - Because it has the thickest muscle and secondary to the slow wave or BER which will cause contraction in stomach, once stop swallowing, - You have the food in the proximal stomach you stop swallowing, receptive relaxation is already gone. - The slow wave in the stomach will cause a weak contraction/weak constrictor/mixing waves the fundus and proximal stomach. Secondary to slow waves or BER • Spike potential - that is controlled by the slow wave. Will cause an ↑ intensity of contraction in the antrum, now since antrum is very thick plus you have spike potential in a strong contraction you grind the food. • In the antrum, spike potential will be present which will cause a stronger contraction and the food will be grind and will mix it with secretions which is called mixing and grinding. • So weak contraction is followed by a higher intensity caused by spike potential in the antrum and that will now cause the grinding. • Once food is grind in the distal stomach, the pyloric sphincter is very narrow so it will not

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PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

• If the factors are present in the stomach it will promote gastric emptying and if they are present in duodenum it will mostly inhibit gastric emptying.

allow the passage of solids but only fluid semifluid substances. • Hence, the solid food is hurdled backward to the proximal stomach with the process known as retropulsion (mixing). • Once food is adequately mixed and ground, it will become chyme – very acidic (semiliquid).

*If the factors are coming from the stomach it is usually promotion. *If the factors are coming from the duodenum it usually for delay. Factors that regulate gastric emptying: Gastric Factors: promotes gastric emptying  gastric volume (distention) ↑gastric volume  gastric emptying  physical and chemical composition of gastric content  effect of gastrin  ↑ activity of pyloric pump Types of food  CHO – fastest; CHON – second; Fats – slowest  That’s why you take alcohol with fatty foods,  because fatty foods delay gastric emptying.  Gastric factors promote gastric emptying.  (gastric irritation and gastric distension)

GASTRIC EMPTYING • • •

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motor function primarily by the pylorus promoted by intense antral contraction (pyloric pump) and prevented by the pylorus You empty the gastric content to the small intestine (duodenum) which is regulated by the pyloric sphincter. It is very important to regulate gastric emptying as failure to do so may cause damage to the duodenal wall. The most common type of ulcer is duodenal ulcer  not as well protected as the stomach. The stomach is not damaged due to bicarbonate and mucus in its walls. If it is too slow  feeling of bloatedness If it is too fast  duodenal ulcers promoted by intense antral contraction (pyloric pump) & prevented by the pylorus contracting. propulsive type of movement

Physical state of food: • Gas/Fluid – fast • Solid – slow Chemical Composition of Food • Osmolality: - fast= isoosmolar (promote gastric emptying) - slow= hypo/hyper(delays gastric emptying) • pH: - alkaline chyme– promote gastric emptying - acidic chyme– delays gastric emptying 

Inhibit gastric emptying: - high lipid - high H+ ion - increased osmolality Page 5 of 10

PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

- tryptophan Decrease gastric emptying Acidic environment (↑H+ or ↓pH) Hypo/Hyperosmolarity ↑ lipid content ↑ tryptophan in food

Increase gastric emptying Gastric distention ↑ gastric volume Chemicals in gastric area Gastrin ↑ pH Isosmolar stomach

Duodenal Factors • inhibit gastric emptying time - duodenal distension - chemical irritation of duodenal mucosa acidity of the chime (↓3.5 to 4) - osmolality of the chime (hyper or hypo) type of breakdown products fats  proteins carbohydrates - hormones (CCK, gastrin, secretin and GIP) - if the hormone is in the stomach: gastrin - If the hormone is in the intestine: CCK, secretin, GIP - Gastrin: Promotes gastric emptying  Direct: promotes  Indirect: inhibits  Gastrin increase acid secretion= gastrin will inhibit=indirect action - Grumbling sound of stomach “hunger..”

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HUNGER PANGS forceful rhythmic peristalsis in body 12-24 hrs, peak 3-4 days starvation SMALL INTESTINE

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3/4 of the length of the gut Duodenum – 5% Jejunum – 40% Ileum – 55%

Gastric emptying is propulsive • Frequency of peristalsis is not uniform in small intestine the frequency is higher in proximal than distal. (opposite for the colon) • Most important motor function in the small intestine: Segmentation contraction

• First food to enter the cecum: 4 hours; ascending colon: 6 hours; transverse: 9 hours; descending: 12 hours; it takes 12 hours for food to enter the rectum • Mixing contraction – mix food with intestinal secretions • MMC (Migrating motor complexes) - occurs in fasted state, modified motor activity observed from stomach down to your ileum. Modified because it is cyclic contraction. - Remove leftovers in the GIT in between meal. Mediated by modulin secreted by MO cell.

Peristalsis Enhanced by: Gastrin, Insulin, CCK & Serotonin Inhibited by: Glucagon Six hours after operation in the abdominal area, no movement of GIT: Dynamic/Paralytic Ileus • pain  release of opiods decrease gastrointestinal motility • irritation of peritoneum, increase discharge of adrenergic  inhibits gastrointestinal motility • Resumes after 6 hours Migrating Motor Complexes Modified Motor Activity • occurs in fasted state (intermeal period) just like hunger pangs • cyclical contraction pattern (stomach – distal ileum) Page 6 of 10

PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

• strong antral contraction with relaxed pyloric sphincter • migrates down entire bowel • “Interdigestive housekeeper”  MOTILIN • Breakfast (mix and grinding) quiet within 90 minutes because of absence of spike potential, no contraction/period of dormancy (Phase 1) after phase 1/ after a meal, irregular contraction because of irregularly formed spike potential (phase 2)  spike potential produced causing stronger contraction (phase 3)  quiet  2 & 3  quiet  2 & 3  quiet  meal (cylical) • Migrating – because it migrates to the terminal ileum • Modified- because it is cyclical Peristaltic Rush • Powerful and rapid contraction (to get rid of toxins and irritants • Peristaltic contraction due to intense irritation of the intestinal mucosa • Experienced during diarrhea • Metallic sound – heard under the stethoscope Ileocecal Valve • Prevents the backflow of fecal material from the colon into the small intestine • One way Valve: prevents backflow of fecal material. Ileocecal Sphincter • Responsible for the slow emptying of ileal contents LARGE INTESTINE • •

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Receives 500 mL- 1500 mL/day Slower contraction than the small intestine to give time for water, minerals, and electrolytes to be absorbed Functions: - Absorption of H20 and electrolytes (proximal portion (ascending and half of transverse)) - Storage of fecal material (distal portion)

- 1/2 is dedicated to storage of fecal material Difference between large and small intestine? Aside from the diameter, there is a whole coverage of longitudinal muscles in the small intestine, while in the large intestine they are oriented in one area (teniae coli) Do you have peristaltic movement in your Large intestine?: Yes because peristalsis occurs from esophagus to rectum Do you have segmentation contraction in Large intestine?: YES a.k.a Haustration which is a mixing movement Three Types of Colonic Movement: 1. Haustrations - Mixing movement - Same as segmentation (when one portion contracts, the other portion relax then you form the haustra – bulging) - Cecum  transverse colon - Purpose: Retard the movement for absorption - Primary motor function occurring in the proximal area of large intestine is segmentation contraction for absorption 2. Mass movement (only observed in the colon) - Propulsive type of movement - Modified peristaltic movement - Usually occurs 1 to 10x a day (most active in the morning and in the afternoon) - Facilitated by gastrocolic & duodenocolic reflexes (transverse colon  sigmoid colon) - Distal area Why do we need mass movement? - Because before you have defecation, fecal material should be in the rectum. But rectum is empty of feces most of the time. Don’t do rectal examination when there is an urge to defecate. - Anorectal angle will prevent entry of fecal material into the rectum. - you need to have a strong force in order to move fecal material into the rectum (mass movement)

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PHYSIO GIT2-2P DR. CARINA GOMEZ NOV. 22, 2018

External Anal Sphincter Tone

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Peristalsis - Motor function for the remaining part of the large intestine are mass movement and peristalsis. - Becomes stronger in the distal area (to push the fecal material)

*Distention of the stomach will cause contraction of the ileum  contents go to the colon (gastroileal reflex) • Rectum is empty of feces (most of the time), reasons why are as follows: - Angulations / very acute anorectal angle; very acute that it goes up then down - this acuteness will prevent the fecal material to enter the rectum - Due to a weak functional sphincter that exists 20 cm from the anus at the juncture between the sigmoid colon and the rectum that p...