Motility Flashcards
How do horses teeth grow, how do they chew?
How can this cause problems
They grow continually
They chew laterally
This can cause sharp and uneven teeth which can make it painful to chew their food
What are 4 indicators to float teeth (horses)
- Dropping feed
- Losing weight
- Head tossing
- Balls of chewed hay (coughed out)
What are the two steps involved in swallowing
- Oropharyngeal phase
- Oesophageal phase
Describe the oropharyngeal phase of swallowing
- bolus pushed back by tongue acting on pressure receptors
- tongue stops return to mouth
- uvula blocks nose
- glottis and epiglottis blocks access to lungs
What structure is pushed back by the tongue when swallowing (what phase is this a part of)
The bolus
The oropharyngeal phase
What stops food from returning to the mouth when swallowing (what phase is structure a part of)
The tongue
What structure blocks the nose when swallowing (what phase is this structure a part of)
The uvula
The oropharyngeal phase
What structures block the lungs when swallowing (what phase is this a part of)
Glottis and epiglottis
Oropharyngeal phase
What coordinates and inhibits the respiratory center (what phase of swallowing is this a part of)
A swallowing center that is found in the medulla
Oropharyngeal phase
What connects the esophagus to the oral cavity (what phase is this a part of)
The pharynogesophageal sphincter opens
Oropharyngeal phase
What are parts of the oesophageal phase (3)
- Peristaltic wave
- Skeletal muscle (involuntary(
- Oesophagogastric/cardiac sphincter opens
What kind of contraction happens with the peristaltic wave (when swallowing)
It is involuntary contraction and it is directional
What does peristalsis mean
What does it do
It means motility
Or rapid purpulsion
- are waves of contraction
What programs the peristaltic reflex
Is this regulated by the brain
It is regulated by the enteric nervous system
No it is not regulated by the brain the only thing that regulated this reflex is the enteric nervous system
What muscles contract during peristalsis? In what order
Relaxation of longitudinal muscle and contraction of circular muscle
Then
Contraction of longitudinal muscle and relaxation of circular muscle
What is the purpose of receptive relaxation
It creates room for food that is entering the system
What induces receptive relaxation (chemicals)
- nitric oxide
- VIP (vasoactive intestinal polypeptide)
- ACh (acetylcholine)
What is the name of the mixing vat in gastric motility
What substances are found in it??
The corpus
- saliva
- food
- gastric secretions
What part of the stomach discriminate the size of food (what does this mean)
The pyloric sphincter (it does not allow food of large sizes into the stomach)
What happens in the antrum for gastric motility
What is this controlled by
- propulsion of food through the pyloric sphincter to the duodenum (discriminates size)
It is controlled by distension and parasympathetic (PNS)
What connects the GI tract to the brain
The vagus nerve
What is involved in filling for gastric motility
- progressive relaxation
- vagus nerve connects GI tract to the brain
What does peristalsis act against
What substances are stirred into food during peristalsis
What is this important for???
The closed pyloric sphincter
HCl and pepsin
Important for protein digestion and lipid droplet formation
What is involved in gastric emptying
What regulates it
-peristalsis
- pyloric sphincter opens
- chyme enters duodenum
Regulation
- force of contraction
- signals from the duodenum
What is another (special) word for digesta
Chyme
What is the rate of emptying dependent on??
The physical and chemical state of the GI tract
What decreases physic contractions
What increases contractions
- vagotomy decreases physic contractions
- stimulation of the vagal nerve increases contractions
What factors increase gastric emptying
Neural control
- distension of the gastric wall
- increased parasympathetic
—) endocrine control (gastric)
What hormone is used for endocrine control of gastric emptying
What does substance does this hormone control
Gastrin (which controls HCl secretion)
What factors decrease gastric emptying
Neural control
- chemoreceptors
- osmoreceptors
- mechanoreceptors at the duodenum
Increased sympathetic
- endocrine control (CCK, Gastric inhibitory peptide and secretin)
What substances/hormones are involved in decreasing gastric emptying
CCK, Gastric inhibitory peptide, and secretin
What is the most common form of motility
Segmentation (alternating contractions of circular muscle)
How does the frequency of segmentation decrease
It decreases distally
What parts of the GI tract are involved in segmentation
How many contractions per minute does each section have
- duodenum (12/min)
- Ileum (9/min)
- colon (2/h)
Is segmentation motility only in one direction
No, segmentation motility is about mixing so there are alternating contractions
What do we call the segmentation movement that occurs in the colon
Haustration
There is also clearing that happens in the colon
What acts as the stimulus in motility regulation
—) what happens after stimulus activation
Chyme receptors distends the duodenum (they swell)
Nerves sense stretching within the gut
Effector (smooth muscle
Vigorous segmentation is induced in the duodenum to help to remove the stimulus
What secretion in the stomach helps to drop pH and communicates all the way to the end of our gut
Gastrin
What happens in the stomach in response to gastrin in the stomach
(What parts does this affect)
Duodenum and the Ileum
- gastro-ileal reflex
- gastro-colic reflex
What happens in the gastro-iléal reflex
- stimulates segmentation
- inhibits ileo-caecal sphincter (opens)/stops contraction
What happens in the gastro-colic reflex
Mass movements in the colon
—) induces deification
This makes more room for additions of food
Describe tonic contraction (what structure does this happen in)
It is constant contraction of the muscle until a stimulus tells it to relax
This happens in all of our sphincters
Give 3 examples of sphincters that use tonic contraction
- esophageal sphincter
- pyloric sphincter
- ileocecal sphincter
What could happen if substances do not leave the small intestine
Bacterial overgrowth could occur
What do the interstitial cells of Cajal (ICC) do
They create constant electrical impulses (depolarization and repolarization)
—) they are not automatically causing contraction
They need a stimulus that makes the action potential to cross the threshold to cause contraction
(Sets the frequency)
What are the stimulants for the activation of the Interstitial cells of cajal
What make it harder (inhibits) activation of the interstitial cells of cajal
Which one is sympathetic and which one is parasympathetic
Acetylcholine ACh (stimulant) parasympathetic
Norepinephrine (inhibitor or depressant) sympathetic
In a fed state what is the main form of motility
What does this do
What regulates it
Segmentation
Mixes luminal content
Regulated by the ENS
What is the complex called when an animal is in a fasting state
What activity is occurring
What are the three phases
- MMC migrating myoelectric complex
- parastaltic activity
1. Quiescent period
2. Intermittent contraction
3. Powerful propulsion sweeps intestinal contents out of
What are two ways that fasting state activities are stimulated
- motillin (stimulates the stomach and the duodenum
- intrinsic nerves stimulate distal duodenum and Jejunum
What is the motility rate like in the large intestine compared to the small intestine (why)
The large intestine is slower than the small intestine since because things are slow for microbial digestion
—) motility and motility rate changes
What are the two main functions of digestion of food in the large intestine??
- Microbial digestion and absorption (of their products)
- Réabsorption of water and electrolytes
What kind of movement are there in the large intestine
- haustral contractions (mixing)
- peristaltic contractions
- antiperistaltic movement
- a oral mass movement (evacuate entire length of colon)
- defecation: voluntary inhibition in trained animals and humans
What do haustral contractions do, where do they occur
They occur in the large intestine
They mix food (substances)
What kind of contraction fills the cecum (what part of the GI tract is this in)
Antiparistaltic movement
It is in the large intestine
What kind of movement evacuates the entire length of the colon
The aboral mass movement
True or False: all animals have voluntary control of defecation
False: only humans and trained animals have voluntary control of defecation
Is the iléal cecal junction open or closed during an antiparastaltic contraction
It is closed that way food can travel back up and enter into the cecum
What in the GI tract can cause altered motility of increases gastric emptying and MMC is reduced with migrating action potential complex???
What does this do?
Parasites in the stomach
Eg: worms
It makes things move faster
When the stomach increases emptying due to parasites or worms, what does it replace MMC with?
MAPC, or migrating action potential complex
What is one of the most common ways that cause us to vomit
Mucosal irritation
What direction do afférent nerves go
What direction do efferent nerves go
Afférent: attract (go towards the brain away from the spinal cord)
Efferent: escape (go away from the brain and to the spinal cord)
What 2 structures close when we vomit, why?
- the soft palet
- the glottis
Prevents vomit from going up our nose and into our lungs
What structure relaxes when we vomit what structures contract
The LES or the lower esophageal sphincter
The diaphragm and the abdominal muscles contract + antiperistaltic contraction
What structure relaxes when we vomit what structures contract
The LES or the lower esophageal sphincter
The diaphragm and the abdominal muscles contract + antiperistaltic contraction
What are the concerns when it comes to vomiting
- It can cause significant water and electrolyte balance
- It can affect our acid base balance
What muscle is found between the longitudinal muscle and the circular muscle in the GI tract
The myenteric plexus (nervous system)
What nervous system has just as many neurons as in our spinal cord
How long are its interneurons
Myenteric plexus (nervous system)
They are really long
For the myenteric and submucosa plexus describe…
What systems affect them (SNS, PNS)
Their interneurons
Amount of neurons
What are they
Myenteric: long interneurons, lots of neurons, affected by both SNS and PNS
Submucosal: minor interneurons, only PNS, less neurons than myenteric plexus
They are groups of neurons
What kind of receptors can “input” or activate the myenteric plexus and the submucosal plexus
- Afférent and efferent neurons
- Mechanoreceptors (wall) and chemoreceptors (lumen)
What are two ways that gut motility can be controlled or respond (main centers or types)
- By direct information from the brain
- From information that comes from the gut
What is the main way that our GI tract is innervated
By the autonomic system (sympathetic and parasympathetic systems)
Give an example of an exocrine secretion and an endocrine secretion
Exocrine: enzymes
Endocrine: hormones
What system inhibits digestion what system promotes digestion
What is secreted in each
Sympathetic inhibits digestion: norepinephrine
Parasympathetic promotes digestion: ACh
What systems can the short reflex interaction with, what about the long reflex
Long reflex: both SNS and PNS
Short reflex: enteric nervous system (does not include CNS)
What is Iléus
When is it common
It is a form of impaired motility
Common post surgery
Blockage can occur
