L5 - smooth muscle Flashcards

1
Q

functions of GIT

A

digestion, absorption , secretion and motility

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2
Q

where can you find the skeletal muscle in the GIT

A

Pharynx, upper third of oeso and external anal sphincter

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3
Q

types of SM in GIT

A

PHASIC AND TONIC

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4
Q

what is phasic muscle

A

conttract and relaxed in seconds

- in oeso, stomach antrum and small intesine

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5
Q

function of phasic muscle

A

empties food rapidly into intestine

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6
Q

what is tonic muscle

A

contraction sustanined for longer

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7
Q

function of tonic muscle

A

keeps the sphincters closed to carefully control the movement of the food and chyme

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8
Q

how is smooth muscle controlled by controlling APs

A
  • the cells are electrically coupled with pacemaker cells

- when an AP occur inthe pacemaker cells, it’s transmitted throughout the muscle sheet of the cells

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9
Q

what factors leads to depolarisation of pacemaker cells

A
  • stretching
  • ACH
  • PNS
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10
Q

what factors leads to hyper depolarisation of pacemaker cells

A

-NA and SNS

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11
Q

What happens when the amplitude of the depolarisation reaches threshold ?

A
  • AP conducted, causing Ca ion inlfux and contraction of the smooth muscle
  • the force of the contraction is proportional to the freq of AP and Ca conc
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12
Q

mechanism of Ca in SM contraction

A
  1. Ca2+ influx leads to calcium binding with calmodulin to make calmodulin-Ca complex
  2. the complex activates the inactive myosin light chain kinase into active one
  3. ATP phosphorylates the myosin and ATP is converted into ADP in that process
  4. myosin - P binds with actin and becomes phosphorylated through ATP to initiate contraction
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13
Q

how to stop contraction ? just a guess tho

A

the myosin is dephosphorylated by MLCP phosphostase

- Ca ions uptake by the SAR in the muscle cell to restore the intracellular Ca levels

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14
Q

innervation of the GIT

A
  • extrinsic nerves of the ANS

- intrinsic nerves of the ENS

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15
Q

what does ENS controls in the digestive system

A

-motility, secretion and blood flow

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16
Q

what plexi is ENS made up of

A

-myenteric plexus and submucous plexus

17
Q

what happens if myenteric plexus is activated

A

-increases tonic contraction, intensity and rate of contractions

18
Q

what happens if submucousal plexus is activated

A

increases secretory activity and modulates intestinal absorption
- controls secretion and blood flow

19
Q

pathway of the activity in the ENS

A
  • sensory neuron>interneuron>motor neuron> smooth muscle in GIT
20
Q

types of motor neurons in ENS

A
  • excitatory - contracted

- inhibitory - relaxed

21
Q

types of enteric sensory neurons

A
  • mechano reception so produces a contractile response if stretched
  • chemo reception - detects chemical stimuli like low pH or FAs
22
Q

which gangelionic fibres does extrinsic PNS innervation conducted by

A

pregangelionic fibres ]

-

23
Q

what nerve innervates the upper organs in the digestive system

A

vagus nerve for oeso, stomach, small intestine aand upper third of large intestine

24
Q

what nerve innervates the lower organs in the digestive system

A

lower 2 thirds of large intestine, rectum and anus

25
Q

what are activatory relflexes in the GIT

A
  • gastro -enteric, stomach to small intestine
  • gastro- ileal, stomach to lower small intestine
  • gastro-colic, stomach to large intesine
  • duodeno-colic, duodenu to colon
  • the signal is passed throughout to move the food along the system
26
Q

what are inhibitory relflexes in the GIT

A

-ileo-gastric, ileum to sotmach
signal sent to the stomach to stop emptying to absorb the nutrients

-intestino-intestinal, ileum to duodenum

-

27
Q

what is hirschsprung disease, what’s the cause and symptoms

A
  • lack of gangelionic cells in the ENS plexi
  • prevents propulsion of the feceaes
  • vomiting, constipation
28
Q

what is chagas disease, what’s the cause

A
  • due to a parasite

- decreased no of intrinsic myenteric neurons and smooth muscle cells

29
Q

what is achalasia , what’s the cause and symptoms

A

lack of inhibitory motor neurones on the lower part of OESO and its lower oeso sphincter
-chest pain, weight loss