L5 - smooth muscle

Question 1

functions of GIT

Answer 1

digestion, absorption , secretion and motility

Question 2

where can you find the skeletal muscle in the GIT

Answer 2

Pharynx, upper third of oeso and external anal sphincter

Question 3

types of SM in GIT

Answer 3

PHASIC AND TONIC

Question 4

what is phasic muscle

Answer 4

conttract and relaxed in seconds

- in oeso, stomach antrum and small intesine

Question 5

function of phasic muscle

Answer 5

empties food rapidly into intestine

Question 6

what is tonic muscle

Answer 6

contraction sustanined for longer

Question 7

function of tonic muscle

Answer 7

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

Question 8

how is smooth muscle controlled by controlling APs

Answer 8

• 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

Question 9

what factors leads to depolarisation of pacemaker cells

Answer 9

• stretching
• ACH
• PNS

Question 10

what factors leads to hyper depolarisation of pacemaker cells

Answer 10

-NA and SNS

Question 11

What happens when the amplitude of the depolarisation reaches threshold ?

Answer 11

• 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

Question 12

mechanism of Ca in SM contraction

Answer 12

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

Question 13

how to stop contraction ? just a guess tho

Answer 13

the myosin is dephosphorylated by MLCP phosphostase

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

Question 14

innervation of the GIT

Answer 14

• extrinsic nerves of the ANS

- intrinsic nerves of the ENS

Question 15

what does ENS controls in the digestive system

Answer 15

-motility, secretion and blood flow

Question 16

what plexi is ENS made up of

Answer 16

-myenteric plexus and submucous plexus

Question 17

what happens if myenteric plexus is activated

Answer 17

-increases tonic contraction, intensity and rate of contractions

Question 18

what happens if submucousal plexus is activated

Answer 18

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

Question 19

pathway of the activity in the ENS

Answer 19

• sensory neuron>interneuron>motor neuron> smooth muscle in GIT

Question 20

types of motor neurons in ENS

Answer 20

• excitatory - contracted

- inhibitory - relaxed

Question 21

types of enteric sensory neurons

Answer 21

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

Question 22

which gangelionic fibres does extrinsic PNS innervation conducted by

Answer 22

pregangelionic fibres ]

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Question 23

what nerve innervates the upper organs in the digestive system

Answer 23

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

Question 24

what nerve innervates the lower organs in the digestive system

Answer 24

lower 2 thirds of large intestine, rectum and anus

Question 25

what are activatory relflexes in the GIT

Answer 25

• 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

Question 26

what are inhibitory relflexes in the GIT

Answer 26

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

-intestino-intestinal, ileum to duodenum

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Question 27

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

Answer 27

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

Question 28

what is chagas disease, what’s the cause

Answer 28

• due to a parasite

- decreased no of intrinsic myenteric neurons and smooth muscle cells

Question 29

what is achalasia , what’s the cause and symptoms

Answer 29

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