4. Physiology Flashcards
1
Q
- Mucosa of GI is ____
* Muscular layers involved in movements that propel and mix foods with secretions of mucosa
A
secretory
2
Q
Basic Structures in the G.I. System • \_\_\_\_ muscle fibers – 2-10 mm × 200-500 mm • 1000 parallel fibers • Gap junctions • Low \_\_\_\_ to ion flow from cell to cell • Functional syncytium • Action potential initiates and travels in all \_\_\_\_
• Rich in smooth muscle ○ BSIII material on smooth muscle • Located in \_\_\_\_ layer and the \_\_\_\_ • Work as a synctium ○ When stmulateby AP that stimulates the muscle fiber > it should work as a unit coordinating at the same time ○ Bc of the orientation > propagation of contrction is faster in \_\_\_\_ direction
A
smooth resistance directions muscularis muscular mucosae longitudinal
3
Q
Electrical Activity in the GI System
- Slow waves – Not ____
- 3- stomach, 12 duodenum, 8-9 ileum
- Induced by ____ (electrical pacemakers)
- Spikes – True ____
- Entrance of ____+ through ____ Ca2+/Na+ channels• Two electrical actiivities
○ Slow waves
§ Specific SM celsl that show this change in potentail of their PM > not real AP > just changes in degree of the potential
§ Induced by electrical activity produced by an interstitial cell of cajal
□ Pacemakers embedde din ____ layer
□ In ____ of stimulus, change potential that transmit to muscle fibers
§ Only when the ____ is high > specific stimulus on SM cells is when they can regenerate the real AP and induce the SM cells to contract
A
action potentials
interstitial cells of cajal
action potential
Ca
slow
muscularis
absence
potential
4
Q
Neural Control of the GI System
Two levels:
• Central nervous system (autonomic):
• Parasympathetic – ____, ____.
• Cranial Division: ____–esophagus, stomach, pancreas,
intestines (partial).
• Sacral Division: ____ nerves-distal half of large intestine, external anal sphincter.
• Sympathetic – ____; ____, norepinephrine.
- Enteric Nervous System:
- ____ or Auerbach plexus.
- ____ or Meissner plexus.
• CNS ○ Parasymp stimulates activity ○ Symp is inhibitory • ENS ○ Completely embedded in GI wall, not part of the CNS ○ Two plexuses
A
stimulatory cholinergic vagus pelvic T5-L2 inhibitory
myenteric
submucosal
5
Q
Neural Control of the GI Tract
- Intrinsic controls:
- Nerve plexuses near the ____ initiate ____ reflexes.
- Short reflexes are mediated by local ____ plexuses.
- Extrinsic controls:
- Long reflexes arising within or outside the ____.
- Involve ____ centers and extrinsic autonomic nerves.• Allows presence of two levels of control
○ Intrinsic
§ Short reflexes that take place within the wall of the GI tract in reposns eto local stimuli
§ DO not involve the CNS
§ Local enteric plexuses
□ SI > drop in ____ > receptors that can respond to low pH > trasnmit info through local nerve plexus > plexus induces a repsonse by a specific effector (SM or secretory gland)
® If too acidic - activates a gland that secretes bicarbonate > change in ____ activity
○ Extrinsic
§ ____ is involved
§ ____ may be same (change in pH)
§ Afferent go into the CNS > involved autonomic in response to change in stimulus
§ ____ phase of control > nothing is happening in the GI but our body is repsonding
□ Smell food and hungry > involvement of CNS > GI gets ready for the foodw e’re smelling and we know we’re gonna eat
A
GI tract
short
enteric
GI tract CNS pH secretory CNS stimulation cephalic
6
Q
Function of the Myenteric (Auerbach) Plexus
• Control of muscle activity ____ the GI length.
• Located between ____ and circumferential
musculature.
• Principal effects:
• Increased ____.
• Increased intensity of ____ contractions.
• Slightly increased ____ of rhythmic contractions.
• More rapid movement of ____ waves.
• Plexus is embedded in the \_\_\_\_ layer of the gut ○ All actions are related to muscle functions
A
along longitudinal tonic contraction rhythmic rate peristaltic muscularis
7
Q
Function of the Submucosal (Meissner) Plexus
- Control of function ____ the inner wall.
- Principal effects:
- Control of ____.
- Control of ____.
- Local contraction of the ____ (infolding).• Located in the ____ layer of the wall
○ Control activities in submucosal and mucosal layers
§ Mostly secretion and absorption (main role!)
§ Only in segemnt wtish muscularis mucosae > activation of the SM plexus may have effect on contraction of SM
□ Control degree of infolding of mucosa
A
within local intestinal secretion local absorption muscularis mucosae submucosal
8
Q
Hormonal Control of the GI Tract
- Gastric and intestinal ____, osmolality, texture, pH, affects the motility, secretion and digestion
- Hormones: ____, Ghrelin, Cholecystokinin (CCK); ____; Gastric Inhibitory Peptide (GIP)
A
content
gastrin
secretin
9
Q
Movements in the GI Tract
• Movements require stimulation of the myenteric plexus.
• Movement of segmentation ○ Movement that allows contents of gut to \_\_\_\_ ○ Important in \_\_\_\_ and in SI ○ Induced by contracting a certain region of wall of tract that's not coordinated with a \_\_\_\_ downstream or upstream § Net effect: \_\_\_\_, no movement of material along gut • Peristaltic ○ Contraction > also a \_\_\_\_ somewhere else (usually \_\_\_\_) ○ Food movement is \_\_\_\_ and coordinated § Net effect: \_\_\_\_ of food from oral to uboral side; some \_\_\_\_ as well (not as much)
A
mix stomach relaxation mixing relaxation downstream unilateral movement mixing
10
Q
Secretory activities in the GI tract
TAKE A LOOK!!
A
ya
11
Q
Basic Mechanisms of Gland Secretion Control
- Local stimulation:
- Effect of ____.
- Activation of the ____ system:
- ____ stimulation.
- Chemical irritation.
- ____ of the gut wall.
- Autonomic stimulation:
- Parasympathetic:
- Generally increases ____ of secretion, especially in the ____ (salivary, esophageal, gastric, pancreas and Brunner’s glands).
- Sympathetic:
- Slight to moderate ____ by some glands.
- Reduces overall secretion due to ____.
- Hormonal:
- Increased gastric and pancreatic ____.
A
food
enteric nervous
tactile
distension
rate
upper tract
increase
vasoconstriction
secretions
12
Q
2.1. Digestive Processes in the Mouth and Esophagus.
- Food is ingested.
- ____ digestion begins (chewing).
- Propulsion is initiated by ____.
- Salivary amylase begins breakdown of ____.
- Pharynx and esophagus serve as conduits to pass food from the mouth to the stomach.• No chemical digestion during mechanical digestion (except for thilaine?)
A
mechanical
swallowing
starch
13
Q
Neural Control of the Pharyngeal Phase of Swallowing
- Bolus stimulates pharyngeal sensory receptors that induce a ____ controlled by the motor center in the medulla and pons via the ____, vagus (X) and ____ nerves.
- Goal is to block all passages except to the ____.
- Chewing reflex:
- Presence of ____ → inhibition jaw muscles → lower ____ drop → stretch reflex of jaw muscles → jaw muscle ____ → compression of bolus → ____ → repeat cycle• Chew food > chewing reflex
○ Bc food is in the mouth > mechanoreceptors > feel the oral cavity is filling up > creates a reflex that starts movement of lower jaw > drops > stretch reflex (bc of mechanos in lower jaw) > induces contraction of jaw muscle back up > compresses bolus of food > lower jaw inhibited > back to initial stage
• Once cycle advances enough > bolus is mechanically digested and mixed with ____ secretions > cycle completes; and reflex to swallow bolus of food takes place
○ These are all ____ activities (chewing and swallowing)
§ Nerves involved in these mechanisms are ____, and muscles are ____
• Presence of food when ready to swallow > induce reflex that controlled by ____ > block all passages in oral cavity except the passage to the esophagus (prevent food from going larynx/lungs)
A
reflex
glossopharyngeal
accessory
esophagus
food
jaw
contraction
inhibition
salivary gland voluntary somatic skeletal medulla/pons
14
Q
deglutition
* Food in oral cavity > chewing reflex > \_\_\_\_ is contracted and no food can reach esophagus > \_\_\_\_ is open * When ready to swallow > move tongue retrograde > bolus is pushed > \_\_\_\_ is open (relaxed) > opening esophagus to bolus * After passing sphincter > \_\_\_\_ closes > prevents reflux of food to oral cavity * To ensure reaches stomach > esophagus induces \_\_\_\_ movements > just upstream of food is contracted, and below the esophagus is relaxed > having a wave of contraction going from oral cavity to lower sphincter > wave of contraction/relaxation ensures bolus reaches the stomach * GES opens > bolus reaches the stomach * Initial steps are voluntary, but once food in \_\_\_\_ > involuntary controlled by ANS
A
UES glottis UES UES peristaltic esophagus
15
Q
Neural Control of the Esophageal Phase of Swallowing
- Primary peristalsis: continuation of pharyngeal ____.
- Secondary peristalsis (if food doesn’t reach stomach): esophageal wall ____.
- Receptive relaxation of the ____.
- Receptive relaxation of the ____.• Upper 1/3 of esophagus > muscularis made of ____ voluntary muscles
• Lower 2/3 of esophagus > ____, involuntary autonomic
• In the middle you find both, a transitions
• When swallow food and crosses the UES > involuntary > mediated by ANS
○ Usually one wave of peristalsis > primary peristalsis > continuation of pharyngeal swallowing > ensures bolus reaches stomach in one wave
§ If food gets stuck > new wave of peristalsis induced > secondary peristalsis > reflex to relax the esophageal wall
□ Takes lpace until distention is gone and food reaches the stomach
A
swallowing
distension reflex
lower esophageal sphincter
stomach
skeletal
SM
16
Q
2.2 Digestion in the Stomach
- Digestion of proteins:
- Secretion of ____.
- Secretion of pepsinogen and activation to ____.
- Secretion of Intrinsic Factor for ____ absorption
- ____ absorption.
- Gastric secretions + food = formation of ____.• Digestion of proteins begins > secretion of HCl (denaturant of proteins) and pepsinogen (protease; secreted in stomach and converted to pepsin, only takes place in high acidity)
• Secretory cells in stomach > IF > binds to B12 in order for it to be absorbed
○ Absorption of B12 doesn’t take place in the stomach
○ Only absorption in the stomach > ____ absorption
§ Good > blood levels of alcohol go up quickly > noticing effects quickly
□ If alcohol absorbed in SI/LI > would take hours for alcohol to absorbed
A
HCl pepsin vitamin B12 alcohol chyme alcohol
17
Q
Stomach Secretions
- Stomach glands:
- Cardiac glands: ____.
- Gastric glands:
- Parietal (oxyntic) cells: ____, ____.
- Chief (peptic) cells: ____.
- Mucous neck cells: ____.
- Pyloric glands:
- Mucous cells: ____.
- G-cells: ____.
A
mucins HCl IF pepsinogen mucins
mucins
gastrin
18
Q
Mechanism of HCl Secretion by Parietal Cells
• Parietal are rich in \_\_\_\_ and contain caniliculi > highly secretory; efficient for \_\_\_\_ pumpung • All transporters of ion that contain P > active > ATPases > move ions against graient ○ \_\_\_\_ > drives whole process 1. NaK ATPase > epxorting Na ions thorugh basal domain of cell > simple diffusion is enough to ensure traffick of Na from canaliculis; but cell has an extra ATPase that’s moving Na into the cell > \_\_\_\_ cxn of Na in lumen; at same time cell is exporting Cl- against the gradient into the \_\_\_\_ (into the cavity of the stomach); reason why cell is interested in pumping Na+ in is bc if cell is pumping Cl- out and the cxn the Na+ is high > formatino of NaCl (doesn't want this! Wants HCl!) a. Active pumping of Cl- and Na+ ensures that canilcular side of cell is more \_\_\_\_ charged than the cell in the basal domain (-70 mV) b. A positive ion has to balance the electrical charge > \_\_\_\_ bc the cell wants to produce HCl i. Pump that exhanges H+ for \_\_\_\_ that's located outside ii. Another \_\_\_\_ expense iii. Where are H+ coming from > coming from activity of \_\_\_\_ in the parietal cell > uses CO2 to combine with H2O to produce HCO3 > dissociates into bicarbonate and H+ > H+ pumped into canaliculus > and bicarb is allowed to exit the cell through a transporter in the ECF iv. Source of CO2 to make carb acid is dual > some is from the \_\_\_\_ through simple diffusion, and most of the CO2 is produced \_\_\_\_ by the parietal cell 1) Mitochondria is where a lot of CO2 is made > parietal cell is RICH in \_\_\_\_ bc of pumping activities that require a lot of ATP 2) Formation of HCl in the lumen
A
mitochondria ion NaK ATPase low canaliculus neg K+ energy CA BS intracellularly mitochondria
19
Q
Mechanism of HCl Secretion by Parietal Cells
- ____ Na+ import at the canalicular side.
- ____ Cl- export at the canalicular side (together with [1] creates a negative potential between -40 and -70 mV).
- The negative potential induces the diffusion of ____ to the canaliculus.
- H+ generated from the dissociation of HCO3- by carbonic anhydrase.
- ____ export of H+ to the canaliculus in exchange of K+ by a H+, K+-ATPase.
- ____ follows the osmotic gradient.
- HCO3- generated in step [4] is exchanged for ____ at the interstitial side to balance the electrical potential. HCO3- is used in the protection of the gastric wall. Cl- is used in step [1].
A
ative active K+ active water Cl-
20
Q
Secretion of HCl – Control Mechanisms
• How is secretion controlled: • Antrum ○ In pits > have secretory glands > produced of mucus > speicif population of cells that are endocrine > many different pops based on hormone produce ○ One population > G cell > \_\_\_\_ > respond to presence of \_\_\_\_ in the chyme (in the stomach) > circulates in BS > reaches \_\_\_\_ of stomach > where gastric glands are located > two main pops: § Parietal cells (HCl) § Chief cells (pepsinogen) ○ In gastric glands > endocrine cells > ECL cells > when stim > produce \_\_\_\_, acts as short distance endo activator > acticates secreiton of \_\_\_\_ by parietal cells ○ Activation of chief cells to produce pepinsogen is more unclear § \_\_\_\_ may activate also § \_\_\_\_ may directly activate § Direct activation of \_\_\_\_ system through ACh can activate Chief or ECL cells • Response of parietal/chief is due to \_\_\_\_ which is due to \_\_\_\_ in the chyme • Mechanism to inhibit is mediated by a diff pop in the antrum > \_\_\_\_ cells ○ Repond to high cxn of protons (low pH) by secreting \_\_\_\_ (somatostatin) > inhibits the \_\_\_\_ so they do not produce gastrin > inhibiting productino of HCl and pepsinogen
A
gastrin AA fundus histamin HCl ECL gastrin parasymp
gastrin AA D SST G cells
