Motility Physiology Flashcards
(49 cards)
circular vs longitudinal muscle, what does each do with contraction?
circular = lowers diameter of segment
long = lowers length of the segment.
what happens in the GI that is a unique feature
slow waves done by the smooth muscle!!! they are NOT AP’s!
the membrane potential goes up and down by the cells of cajal. as it gets higher, it is easier for APs to happen, thus the slow waves are determining the contraction.
When does tension happen?
slow waves influence contraction, and tension is contraction which happens after the action potentials.
essentially mechanical response follows the electrical response?
how do you increase contraction of the GI?
neural and hormonal activity.
What’s the difference between phasic and tonic contractions? examples?
Tonic contraction = constant level of contraction without regular periods of relaxation (e.g. spinchters)
phasic = periodic cont reactions followed by relaxation (pretty much everywhere)
Greater APs means what? How does this happen?
what does the opposite of this?
larger contractions
so if the slow wave is more + there would be more APs. This is done by ACh, which increases amplitude of slow waves.
NE, which decreases the amplitude of slow waves.
What stimulates slow waves and APs
hyper polarization of slow waves?
stretch, acetylcholine, PNS
NE, sympathetics
What are the pacemaker regions in the enteric nervous system? why does this work?
myenteric plexus + submucosal plexus
doesn’t need the CNS to generate slow wave activity.
What are the two parts of the ENS and what does it control?
submucosal plexus –> mainly controls GI secretions and local blood flow
myenteric plexus (Auerbach) –> controls GI movements
Where are the slow waves generated?
Interstitial cells of Cajal –> generate the slow wave
What do Interstitial cells of Cajal do?
generate the slow waves and pass conduction to smooth muscle via gap junctions
What is mastication?
what innervates it?
voluntary or involuntary?
what is it controlled by?
chewing the food and prepping it to go onto the esophagus.
5th cranial nerve (trigeminal)
It’s voluntary and involuntary (chewing reflex)
nuclei in the brain stem
What are the three phases of swallowing?
Oral phase (voluntary) Pharyngeal phase (involuntary) Esophageal phase (involuntary)
From the pharynx to the LES, what is the esophagus composed of?
from the pharynx to the esophagus (after the UES), it’s voluntary so striated muscle.
below that is smooth muscle
which is longer, pharyngeal or esophageal?
esophageal
The involuntary swallowing reflex is controlled by what?
pathway?
the medulla
food in pharynx -> afferent sensory input via vagus –> swallowing center (medulla) –> brainstem nuclei –> efferent input to the pharynx
What are the two peristaltic waves? where are these present??
esophagus!
primary = controlled by the medulla, continuation of pharyngeal peristalsis. Vagotomy destroys this.
secondary: occurs if primary wave fails to empty the esophagus or if gastric contents reflux. occurs even after a vagotomy (doesn’t rely on the vagus like primary)
Why is there a drop in pressure at the UES at first and then it goes super high?
it relaxes and then the bolus goes through and it needs to close really quickly so that’s why it goes back up really fast.
What’s important to note about the LES and Fundus during the swallowing reflex?
they both relax before the bolus even gets there.
Why is the intrathoracic location of the esophagus a challenge?
how is it solved?
we need to keep air out of the esophagus at the upper end and the lower end needs to keep gastric juice out.
UES and LES are always closed unless bolus is passing.
Achalasia?
impaired peristalsis, incomplete LES relaxation during swallowing, so elevated LES resting pressure.
so food gets stuck because the enteric nervous system is not good. back flow of food, chest pain, dysphagia.
What is GERD?
LES is relaxing more than it should. contents come up to the esophagus. if chronic it’s. Barrett’s esophagus.
happens because of motor abnormalities that result in abnormally low pressure of the LES.
What tests do you do for achalasia to check?
barium swallow test and esophageal motility studies (manometry)
What is receptive relaxation? what part of the stomach is doing this?
what hormone lowers contractions and increases gastric distensibility of this?
Orad… lower pressure and higher volume of the road region (vasovagal reflex!)
the orad exhibits little contractile activity.
CCK
