Physio Exam 3 Lec 1

Front 1

Myosing Light Chain-P required for contraction; Myosin Light Chain-DePhosphorylated required for relaxation.
MLC-P catalyzed by MLCKinase; MLC-DP catalyzed by phosphatases.
Level of MLC-P at any time reflects

Back 1

the balance between Mysin Light Chain Kinase
and MLC phosphatase activities.

Front 2

Most of the GI Tract is smooth muscle. But there is also striated muscle in

Back 2

top 1/3 of the esophagus and external anal sphincter

Front 3

contraction of the gut is posible due to the action of what muscles in which layer

Back 3

circular and longitudinal muscles in the muscularis externa.

Front 4

Enteric Nervous System composed of

Back 4

Myenteric Auerbach's Plexus and Submucosal (Meissner's) plexus

Front 5

Myenteric Auerbachs plexus located in and action

Back 5

between the smooth muscle layers in gut and primarily regulate smooth muscle contraction

Front 6

Submucosal Meissner location and action

Back 6

In submucosa, it senses the environment within the gut(stretch receptors) and regulates blood flow and epithelial cell function

Front 7

Peristalsis main characteristic

Back 7

it creates a pressure difference in which proximal segements of esophagus are contracted while distal segments are relaxed.

Front 8

Integration of enteric reflexes leading to GI motility caused by bolus of food

Back 8

-Bolus activates chemoreceptors in submucosal plexus and stretch sensitive neurons in myenteric plexus
-Motor nerves activated by sensory neurons stimulate inhibitory or excitatory receptors on SMC
-Sensory neurons also stimulate cells that secrete mediators that inhibit or excite smooth muscle

Front 9

Whats the general effect of integration of enteric reflexes?

Back 9

to contract orally and relax distally

Front 10

The stomach and intestines use a vary energy saving mechanism when ingesting food

Back 10

Stomach or intestines will stretch in response to food, but relax at new length without changing length. This is a property of smooth muscle that makes it really energy saving

Front 11

Another reason why smooth muscles are energetically economical is because they exert force that can be mainted with

Back 11

fewer active cross-bridges and low ATP consumption because smooth muscles have tonic contraction

Front 12

Tonic contraction

Back 12

-Sustained stimulation --> Ca2+ and MLC-P peak to produce rapid contraction, then fall to reduced level.

Front 13

SMC membrane potential fluctuates spontaneously, a contraction is generated when

Back 13

the basal electrical rhythm (BER) depolarization is above the threshold.

Front 14

Rhythm and extent of tone in SMC is determined by

Back 14

Frequency and magnitude of BER

Front 15

Spike activity of SMC can be generated by

Back 15

hormones, nervous system, and pacemaker activity

Front 16

Maximal contraction of SMC requires

Back 16

spike activity and BER

Front 17

As opposed to skeletal muscles in which their contractions are all or nothing, smooth muscle contractions are

Back 17

graded

Front 18

Which type of graded contraction generates rapid, maximal contraction

Back 18

when APs are closer together. Achieved by AP and BER combination.

Front 19

Spikes activity occur because

Back 19

neural stimulation, activation of stretch receptors etc.

Front 20

Parasymp action on smooth muscle

Back 20

depolarize and contract

Front 21

Sphincters experience what type of contraction?

Back 21

sustained depolarization and contraction

Front 22

NE and symp action on SMC

Back 22

Hyperpolarize and relax

Front 23

While swallowing, the trachea and epiglottis

Back 23

are closed

Front 24

Swallowing proccess initiates as

Back 24

a voluntary action and procceeds reflexively, once it starts it wont stop

Front 25

Cephalic phase refers to

Back 25

preparation of GI tract for a meal...smell..thinking about food etc

Front 26

Is mastication (breakdown of food) essential for digestion?

Back 26

no

Front 27

Saliva role in mastication

Back 27

lubricates
antibacterial factors and immunoglobins

Front 28

Swallowing centers characteristics

Back 28

collection of cells not a discrete nuclei

Front 29

Swallowing is divided into 3 phases

Back 29

oral, pharyngeal and esophageal

Front 30

Muscles involved in Phase I (oral) of swallowing

Back 30

mylohyoid, geniohyoid, and digastric and tongue

Front 31

How does involuntary swallowing occurs in phase I

Back 31

receptors in the oropharynx relay impulses to swallowing center in medulla and lower pons to initiate involuntary reflex

Front 32

Swallowing Phase II (pharyngeal) main characteristics

Back 32

Epiglottis covers trachea
breathing stops
Superior pharyngeal constrictor muscles contract to push bolus into esophagus
Peristaltic wave is initiated in the pharynx and moves down the esophagus

Front 33

Swallowing Phase III (esophageal) controlled by

Back 33

swallowing center

Front 34

Swallowing Phase III characteristics

Back 34

-Upper Esophageal Sphincter contracts, larynx, glottis and epiglottis return to normal position once food has passed
-Process becomes involuntary once bolus reaches smooth muscle
-Increase in pharyngeal pressure pushes bolus into esophagus

Front 35

During Swallowing Phase III food further entry and reflux is block by

Back 35

increase of pressure in Upper esophageal sphincter

Front 36

1st peristalsis

Back 36

initiated and regulated by swallowing center, starts below UES due to sequential activation of muscles in pharynx and esophagus

Front 37

2 peristalsis

Back 37

: Initiated by distention
if 1 peristalsis is not sufficient to
clear food; Pushes remnants of food out of esophagus; Locally regulated

Front 38

3 peristalsis

Back 38

: Generally non-propulsive, develops with age; Can lead to pain after swallowing

Front 39

Swallowing center in medulla is activated by

Back 39

sensory input from the pharynx

Front 40

Swallowing center activation inhibits

Back 40

vomit, respiration

Front 41

Pharynx and striated esophagus receive innervation from

Back 41

nucleus ambigous via vagus

Front 42

smooth muscle in esophagus activated by

Back 42

vagus coming from dorsal motor nucleus

Front 43

While food is propelled by peristalsis, liquids move by

Back 43

gravity. So liquids cant be swallow while upside down

Front 44

Basal tone of Lower Esophageal Sphincter (LES) may be all

Back 44

myogenic

Front 45

contraction/relaxation of LES is controlled by

Back 45

vagus but modulated by different agents

Front 46

Agents that increase LES pressure

Back 46

Hormones: gastrin, cholinergics, a2-adrenergics, PGF 2, Substance P, metenkephalin, motilin.
-Protein meal, gastric pH, intra-abdominal pressure

Front 47

Agents that decrease LES pressure

Back 47

-Hormones: VIP, NO, glucagon, female sex hormones (progesterone during pregnancy increases heartburn).
-Dietary fat, nicotine, xanthines (from chocolate), alcohol, gastric distension

Front 48

Vagus regulates LES via

Back 48

visceral motor fibers (Vagal inhibitory, Vagal Excitatory fibers) from dorsal motor nucleus

Front 49

At high pressures, LES

Back 49

Relaxes and recontracts to prevent reflux

Front 50

Reflux is caused by

Back 50

Pressure in the esophagus, which is in the chest, is less than in the stomach, which is in the abdomen (eg: defecation).

Front 51

Belching (Eructation):

Back 51

-Distension of stomach by introducing gas into stomach (coke, beer).
-Distends stomach without increasing pressure.
-LES RELAXES, but gas pushed back into stomach by secondary peristalsis.
-Repeated until there is conscious awareness of distension.
-Breathe against closed glottis, contract abdominal muscles, increase gastric and decrease esophageal pressure ---> Belch

Front 52

Vomiting (reverse peristalsis)

Back 52

-Reflex behavior controlled by vomiting center in medulla.
-Physical stimuli (stuff in duodenum), activate duodenal receptors.
-Cephalic stimuli: toxins, emetics, impulses from higher centers.
-Decreased regulation of vomiting center by swallowing center.
-Widespread autonomic discharge leads to copious salivary secretion, rapid
and shallow breathing, rapid heartbeat, dilation of pupils and sweating.
-The retching part of vomiting is similar to belching with fluid involved.

Front 53

The fundus of the stomach has receptive relaxation meaning

Back 53

Thin
muscle + lots of connective
tissue = volume increase to
accommodate food at low
pressure. Reduces refux.

Front 54

Body of the stomach starts

Back 54

chymification

Front 55

Total transit time in the stomach

Back 55

4-6 hrs

Front 56

Stomach is innvervated by

Back 56

vagus, and enteric nervous system

Front 57

Stomach is somewhat unique because it contains

Back 57

a defined pacemaker zone that sets the BER at ~3/min

Front 58

Conduction of the stomach

Back 58

BER (gastric slow wave)
flows as wave towards antrum.
Gastric slow wave is triphasic

Front 59

slow, sustained contraction of stomach achieved by

Back 59

AP on top of slow wave

Front 60

in the stomach, Electrical and mechanical activity are different and slightly offset

Back 60

as you go down the stomach

Front 61

contraction patterns in stomach

Back 61

Waves of contraction slightly offset in time, strongest near antrum, propel food down and out of stomach

Front 62

Antral motility or systole characteristics

Back 62

Contractions begin in mid-stomach and push contents towards duodenum.

Front 63

Force of antral contraction strong enough to close distal antrum. Called

Back 63

antral systole

Front 64

Antral contractions segment (segmentation) pushes

Back 64

part of the contents back into stomach (retropulsion)

Front 65

Gastric emptying determined by

Back 65

ratio of intensity of antral contractions to pyloric resistance (pyloric sphincter has to relax to get emptying).

Front 66

Increased (more emptying) by

Back 66

: Acetylcholine > starch in food > liquid consistency > hypotonicity and pressure

Front 67

Decreased (less emptying) by

Back 67

Adrenergic agents, CCK, GIP, VIP, secretin > fat > semi-solid consistency > hypertonicity and pH < 3.5

Front 68

gastric emptying net result

Back 68

Neutralize pH and maintain osmolarity
in duodenum.
-Fat is emulsified (churned into fine
droplets so that they can combine
with bile salts in the gut).
-Protein and lipid greatly decrease gastric
emptying.
-Gastric emptying is fast for liquid meal
and slow for large meal with more solids

Front 69

Small intestine waves

Back 69

slow waves (mainly due to BER) (higher in duodenum and declines down the intestine) that result in peristalsis

Front 70

Segmentation

Back 70

: Get annular contractions and relaxations that break up and move bolus back and forth (eg: antrum). Like kneading bread.
Segmentation mostly for mixing but can result in propulsion

Front 71

Rate of segmentation decreases down

Back 71

the small intestine

Front 72

Most mixing of food with intestinal juices takes place in

Back 72

proximal small intestine.because proximal gut is more active [has more slow waves and spike potentials

Front 73

Propulsion generally increases as segmentation (ie: mixing)

Back 73

decreases

Front 74

high segmentation and pressure in proximal gut, low segmentation and pressure in

Back 74

distal gut = change in P for movement

Front 75

Intense electrical/contractile activity followed by long quiescent periods (migratory myoelectric complexes MMC)
Seen during

Back 75

fasting and between meals (hunger pangs

Front 76

MMC interrupted by

Back 76

eating. Get segmentation and peristalsis instead.

Front 77

Gastric secretions and gut blood flow increase in concert with

Back 77

MMC

Front 78

Eating and surgery on gut prevent

Back 78

MMC

Front 79

MMC generate bowel sounds, and they have to be heard usually after

Back 79

-surgery before giving solid food

Front 80

Distension of ileum relaxes

Back 80

ileocecal sphincter

Front 81

distension of the cecum

Back 81

contracts ileocecal sphincter

Front 82

Ileum transit time

Back 82

6 hrs to 60 days!

Front 83

Colon job

Back 83

reabsorbs water and electrolytes and maintains bacterial population at minimum

Front 84

Electrical activity of colon

Back 84

More variable than in small
intestine and BER lower in ascending
colon.

Front 85

colon's Lower BER frequency allows for

Back 85

for more absorption of water and electrolytes.

Front 86

Myenteric plexus in colon generates AP that regulate

Back 86

longitudinal muscles

Front 87

Stimulation of sympathetic nerves towards colon

Back 87

stops colonic movement

Front 88

Stimulation of vagus in the colon

Back 88

causes segmental contractions

Front 89

Stimulation of pelvic nerve in the colon causes

Back 89

expulsive contractions of distal colon

Front 90

Segmented contractions in colon known as

Back 90

Haustra and has 2 functions, Haustral shuttling and systolic multihaustral propulsion

Front 91

Haustral Shuttling

Back 91

Random movements that knead the poop

Front 92

Systolic Multihaustral Propulsion

Back 92

Contractions of adjacent haustra propel the poop.

Front 93

Peristaltic Propulsion

Back 93

Also have peristalsis and haustra have to relax in front of them

Front 94

Increase in pressure in rectum decreases pressure in internal anal sphincter and increases pressure

Back 94

pressure in external anal sphincter. Filling of rectum --> defecation reflex.

Front 95

Defecation Reflex because

Back 95

it involves the brain and parasympathetic (ie: voluntary) control of the EAS. Initiated by rectal distention

Front 96

Hirschsprung’s Disease or Megacolon

Back 96

Patients lack enteric neurons to the colon and EAS. EAS does not relax when rectum is full. Serious constipation that is not good