Digestion 5 Flashcards
Vomiting results from ____ due to ________
an increase in intraabdominal pressure
the action of the diaphragm and abdominal muscles
What is the role of the GIT in vomiting?
It is passive and does nat have any major implications
What happens to the upper stomach and the upper duodenum during vomiting?
Upper stomach: relaxes
Duodenum and lower stomach: contracts
When the intraabdominal pressure increases, the pressure ____ which induces vomiting.
overcomes the resistance of the LES
What are the afferent activities that can activate the vomiting centre? (6)
Pharyngeal stimulation
Pain
GIT/ urogenital distension
Biochemical disequilibrium
Vestibular signals
Psychogenic factors
What will be the efferents sent by the vomiting centre? (2)
There is going to be a widespread autonomic discharge of PS and SYM signals with alternating effects preceding and during vomiting (cold sweats, brady- and tachycardia)
as well as nausea
What happens before vomoting?
Retching: incomplete vomiting
What happens during emesis? (2)
- Relaxation of upper GIT and spams (complete contraction) of the pyloric antrum and duodenum
- Contraction of the abdominal muscles and diaphragm
Apart from the vomiting centres, what can initiate vomiting?
Agents in the bloodstream can act on the Chemoreceptor Trigger Zone (CTZ)
Why can toxin activate the CTZ and not the vomiting centres directly?
The CTZ is outside of the blood-brain barrier, meaning toxins are not filtered out before reaching this zone
What are examples of circulating emetic agents (toxins that can activate the CTZ)
Chemotherapeutic drugs
Vomiting inducing drugs
Food poisoning causing toxins
The emesis is completed with _____
reversal of the thoracic pressure from negative to positive as the diaphragm is displaced upwards
What is the main role of the small intestines?
Most of the digestion and all of absorption
What are the 4 functions of the UPPER small intestines? (2 you already know)
Osmotic equilibrium (previously hypertonic chyme becomes isotonic)
Neutralisation
Digestion
Absorption
What are the 2 MOTOR activities of the small intestines? define if needed
-Effective mixing (with enzymes and to make contact with the walls
-Slow propulsion (2-6h)
Intestinal frequency contractions are governed by ________ which is _________ than the gastric one.
the intestinal BER
faster
Like in the stomach, intestinal contractions are
- Phased-locked to _____
- Initiated by ____ or _____
- related to the _____ for amplitude
BER
ACh or stretch
number of spikes
T of F
BER and so intestinal contraction is the same throughout the small intestine.
F
Different pacemaker cells will follow a different frequency depending on their position along the intestine. The frequency decline systematically from proximal to distal (12/ min to 8/min)
BER frequency is greater in the proximal intestine as well as _________ and ________
Therefore, _____ and _______ of contractions are _______ in the proximal intestine
Excitability of the smooth muscle
Thickeness of the smooth muscles
Frequency and amplitude
greater
What is the most common type of contractile activity in the SI?
What is it a response to?
What is it controlled by?
What is it modulated by?
Segmentation
Myogenic response of the circular muscle due to distension
Coordinated and organised by a LOCAL ENS response
The ANS and hormones modulate (PS and SYM)
If there are more and stronger contractions in the proximal intestine, will there be more movement in the proximal or distal intestine? Why?
The proximal intestine will have slower movements because of increased resistance
Distal has more movement (net aboral movement)
Unless in the presence of a pathological condition, peristalsis in the SI is …. (3)
Irregular
Weak
Over short distances
SI peristalsis is mediated by _____ and modulated by ______. Frequency can’t exceed ________
local reflexes
ANS and hormones
BER
How do longitudinal and circular muscles interact during SI peristalsis?
AHEAD OF BOLUS: Contraction of longitudinal m., relaxation of circular m
BEHINF BOLUS: Contraction of circular m. and relaxation of longitudinal m.
Colon contractile activity is _______
slower and irregular
What are the functions of the colon?
Absorption of H2O and ions since the digestion and absorption of nutrients is over
How much water is absorbed in the colon?
about 1.5L goes in
about 0.2L comes out
1.3L is absorbed
The large colon empties its contents corresponding to ________, increasing activity in ________ and _______
intake of a new meal
the colon and distal SI
Explain how the activity of the mid and hindgut is increased after the intake of a meal.
Stretch receptors of the stomach activate the….
1. Gastroileal reflex: opening of the ileocecal sphincter. to move contents into the colon (which triggers the ileocolic reflex, and increases sigmoid colon activity)
- Gastrocolic reflex: increases movement of contents from the sigmoid colon into the rectum. If there is enough, there will be defecation
