Physiology Flashcards
How does CNS regulate GI function?
Vago-vagal reflex (increases GI motility)
What are the 2 paracrine hormones?
Somatostatin + Histamine
What does somatostatin do?
(anti-growth hormone)
Reduces gastric secretion and the emission of gastrointestinal hormones, such as secretin and gastrin.
What does histamine do?
Stimulates acid production
What are the 4 endocrine hormones?
- Gastrin
- CCK
- Secretin
- GIP
Gastrin stimulates the growth of gastric mucosa via?
Increasing Gastric H+ secretion
What does CCK do?
Inhibits gastric emptying via trophic effect (cells divide a lot)
Also, increases pancreatic enzyme secretion and pancreatic HCO3- secretion
What does secretin do?
Inhibits trophic effect
Decreases Gastric H+ secretion
Does same thing as CCK w/ pancreas
What does GIP do? What stimulates it?
Increases insulin secretion (Incretin effect)
Decreases Gastric H+ secretion
Stimulated by taking oral glucose
What is the incretin effect?
It is better to take oral glucose than IV glucose for diabetes treatment.
These neurotransmitters (NE, VIP, NO, GRP, Neuropeptide Y) cause what?
Relaxation
These neurotransmitters (ACh, Substance P, Enkephalins) cause what?
Contraction
Parasympathetic Nerves + Hormones
Vagus (Brainstem) + Pelvic N.’s (sacral spinal cord)
Gastrin + Motilin
Sympathetic Nerves + Hormones
Spinal cord
Secretin + GIP
What generates spontaneous slow wave activity?
ICC (Interstitial cells of cajal)
“pacemaker of GI smooth muscle”
The mastication “chewing reflex” is innervaed by which cranial nerve?
5th cranial nerve
Where are ICC cells located?
Myenteric Plexus
What are the three swallowing phases? And what are they controlled by? What nerves give afferent sensory input?
- Oral
- Esophageal
- Pharyngeal
THE MEDULLA
Vagus N. + Glossopharyngeal N.
Which peristaltic wave cannot occur after vagotomy?
Primary peristaltic wave
What is the function of the migrating myoelectric complex? What is it mediated by?
“Stomach Cleaning”
It sweeps undigested food to the colon via periodic peristaltic contractions
Medated via motilin
What reflex kicks in as negative feedback from the duodenum to slow down the rate of gastric emptying?
Entero-gastric reflex
What is gastroparesis?
Slow emptying of the stomach (common in diabetes)
-normal time = 3 hrs-
What part of the stomach “mixes” and digests food? What is this called?
The caudad part, this is called retropulsion (accomplished via parastaltic contractions)
What part of the stomach functions in “receptive relaxation”?
The orad part. This decreases pressure + increases volume via vago-vagal reflex. CCK contractions and increases gastric distensibility.
What is achlasia?
LES can’t relax and food gets stuck
What increases the entero-gastric reflex, slowing down gastric emptying?
Acid/Fat in duodenum and hypertonicity
What type of contractions “mix” the stomach?
Segmentation contractions
What type of contraction push food forward?
Peristaltic contractions (via myenteric plexus)
Serotonin, Prostaglandins, Gastrin, CCK, Motilin, and Insulin ____ contractions.
stimulate
Epi, Secretin, and Glucagon ______ contractions?
Inhibit
A spinal cord injury can inhibit which reflex and cause you to have no control of defecation?
Retrosphincteric reflex
What center coordinates the vomiting reflex?
medulla
Vagus N. innervates…
cecum, ascending + transverse colon
Pelvic N. innervates…
descending colon + rectum
Somatic pudendal N. innervates…
External Anal Sphincter
Peristaltic contraction flow chart
Signal (stimulation of mucosa) –> enterochromaffin cells –> release serotonin –> bind to IPANs –> initiates peristaltic reflex –> interneuron –> motor neuron –> signal (distension of muscle)
