digestion - lecture 2

Question 1

what are target cells for excitatory and inhibitory enteric neurons

Answer 1

smooth muscle cell or secretory cell

Question 2

describe ans modulation of ens

Answer 2

cns = parasym (excitatory - vagal nerve ach onto nicotinic receptors) and symp (inhibitory release noradrenaline)
sensory afferent fibers to cns = send info to cns to activate and ans = feedback on system

Question 3

describe activation of ans

Answer 3

Sensory afferents –> parasym = medulla pregang and ans efferents have effect
sensory afferents –> sympa = spinal chord postgang - sympathetic chain of ganglia

efferent sends through vagal nerve

Question 4

describe things that effect cns

Answer 4

afferent neurons with info from chemoreceptors, osomoreceptors and mechanoreceptors
sight, smell and taste of foods = activates directly salivation and also secretion in stomach
emotional state = if anxious = not induce saliva as usual
also cortical pathways
happens outside gut wall = efferent autonomic neuron’s synapse on enteric neurons

Question 5

what doe ans modulation of ens allow for

Answer 5

integrated activity over longer distances along git
long extrinsic reflexes
ps = excites - can excite inhibitory neurons
s = inhibits - can inhibit inhibitory neurons

Question 6

what is neural control of integration by

Answer 6

ens and ans

Question 7

what are non git hormones

Answer 7

may influence growth and development of git

Question 8

what are git hormones

Answer 8

may influence activities outside git

Question 9

what do git hormones do

Answer 9

regulates activities inside git

Question 10

describe hypothalamic feeding center - stimulates hunger

Answer 10

increase appetite
ghrelin released by glands in stomach during fasting

Question 11

describe hypothalamic feeding center - induces satiety

Answer 11

decrease appetite
leptin released by fat cells with overeating

Question 12

what is des

Answer 12

diffuse endocrine system
scattered among other cells in mucosa
largest most diverse endocrine system in body

Question 13

name 5 most important gi hormones

Answer 13

gastrin
cck
secretin
gip
vip

Question 14

name 3 modes of hormonal reg and describe briefly

Answer 14

autocrine = own cell
paracrine = on nearby cell
endocrine = through blood stream capillary and the effects target tissues

Question 15

what type of hormones are git regulatory hormones

Answer 15

mostly peptides

Question 16

describe how git hormones get to target cell

Answer 16

released from mucosa inton portal blood (hepatic portal vein) and goes to liver then to heart then to systemic circ and then to target tissues (tissues of gut)

Question 17

do git hormone have only one target

Answer 17

nooooooooo
multiple targets = diff effects like inhibitory or excitatory

Question 18

what do git hormones interact with

Answer 18

each other and with neurotransmitters
synergistically = potentiate each other so net effect larger then alone
antagonistically = inhibits

Question 19

what does propulsion - flow - in git rely on

Answer 19

gradients of pressure deltaP
Variations in resistance 1/R

Question 20

describe pressure - propulsion in git

Answer 20

muscles produce coordinated contractions of muscular elements in git wall = creates gradient of pressure
circular muscles activated in diff parts = segmentation
activate in each region = peristalsis

Question 21

describe resistance - propulsion in git

Answer 21

normally little to no resistance
sphincters closed at rest
= prevents movement, high resistance but open at right time
stomach acid moves up lower esophageal sphincter = heart burn and damage

Question 22

describe normal flow in git

Answer 22

aboral - away from mouth
meets little to no resistance

Question 23

what are the phases of deglutition - swallowing

Answer 23

oral - voluntary
Pharyngeal
esophageal
gastric

Question 24

Describe pharynx

Answer 24

conveys food from mouth to eso through process known as deglutition = swallowing
connected to nasal passages and to mouth and eso and trachea

Question 25

describe esophagus

Answer 25

transports food into stomach requires relaxation of 2 sphincters = ues and les

Question 26

describe oral phase - mouth--> pharynx

Answer 26

voluntary control can chew or spit out lips closed and use tongue bolus = food in mouth, one sticky mass once choose to swallow = involuntary

Question 27

describe oral phase - anterior mouth --> pharynx

Answer 27

push food up against hard palate bolus moves to back of tongue and soft palate comes up and closes off nose bolus moves to pharynx and epiglottis closes off trachea

Question 28

describe cortical vs medullary centers

Answer 28

Cortical = voluntary, ability to initiate deglutition center = involuntary reflexes driven by coordinate movements- as soon as make decision to swallow - in medulla

Question 29

oral phase definition

Answer 29

transport of bolus (masticated insalivated mass of food) from anterior to posterior of mouth

Question 30

define deglutition center

Answer 30

series of reflexes coordinated in deglutition center in medulla oblongata

Question 31

name and describe 2 important aspects of oral phase

Answer 31

ability to initiate = voluntary --> cortex coordinated movements = reflex involuntary --> medulla

Question 32

describe pharyngeal phase - gen

Answer 32

stretch of pharyngeal receptors once food at back of throat larynx moves close to glottis to protect airways

Question 33

what is pharynx and describe

Answer 33

region where respiratory and digestive tracks cross must be controlled by reflexes if not = food moves into airways and bacteria can lead to infections in lungs, ppl who have stroke have trouble swallowing

Question 34

name and describe 4 important aspects of pharyngeal involuntary phase

Answer 34

1 - passages to nose, mouth and trachea blocked 2 - apnea = stop breathing to decrease chance you pull in air when you swallow 3 - ues relaxes 4 - pharynx muscles contract and push bolus into eso must happen in correct order

Question 35

describe path of air and food

Answer 35

respiratory tract for air going into trachea and git for bolus going to eso both tracts cross in pharynx

Question 36

describe deglutition reflexes - gen

Answer 36

a series of protective reflexes initiated by stimulation of afferent fibers in pharnyx Organized in deglutition center closing off nasal, oral and laryngeal cavities = prevents misdirection of bolus respiration briefly inhibited

Question 37

what is deglutition

Answer 37

swallowing of food

Question 38

describe deglutition reflexes - specific

Answer 38

Pharyngeal receptors send afferents to cns --> deglutition center in medulla - send efferents to do = protective reactions Deglutition apnea relax ues contract pharyngeal constrictor muscles

Question 39

describe upper esophageal sphincter - closure

Answer 39

impulses originate in cns mediated by vagus nerve releases ach (consTANTly) causing muscle contraction striated muscle uper 1/3 eso and smooth muscle lower 2/3 eso

Question 40

describe upper esophageal sphincter - during deglutition

Answer 40

relaxation = impulses stop and muscles relax no ach cricopharyngeus = striated muscle = where ues is

Question 41

describe pharyngeal phase - 4 aspects

Answer 41

involuntary rapid = 1/5th of sec stereotyped = reflex driven same sequence each time temporospatial coordination = same sequence so wont choke, at right time and order

Question 42

describe esophageal phase

Answer 42

gradient of pressure moves down eso vagus somatic = synapses on striated muscle vagus autonomic = synapses on ens then smooth muscle body of eso = in thoracic cavity recall neg pressure in thoracic cavity = -5mmhg - -10mmhg sphincters must be closed all the time

Question 43

describe whole of pharyngeal phase

Answer 43

bolus in pharnyx = reflexes cause it to move downwards as moves down = presses on epiglottis and covers the glottis = secondary effect reflexive contraction of vocal chords = larynx moves upwards and forwards to fit under base of tongue glottis closes and protects lower airways = epiglottis and movement of larynx = deglutition reflex ues relaxes and pharyngeal muscle contracts = push bolus across the released ues into eso