Movements of GIT

Question 1

List the 4 function of the GIT movements.

Answer 1

Propel ingesta, digest and absorb ingesta, break up ingesta, circulate ingesta

Question 2

How are smooth muscle fibres connected to each other?

Answer 2

Tight junctions or ‘nexuses’

Question 3

What do the nexuses of smooth muscle cells allow for? what muscle is this similar to?

Answer 3

Transport of ions -> membrane potential spread. Similar to cardiac muscle

Question 4

What are the fluctuations of the GI smooth muscle (in mV) and what causes these?

Answer 4

20-30mV, caused by changes in intracellular Ca2+

Question 5

What is the term used to describe the rhythmic changes in Ca2+ intracellular concentration

Answer 5

Slow waves

Question 6

What are the factors contributing to a difference in the frequency of slow waves?

Answer 6

region of GIT, species

Question 7

In the dog, how often to slow waves occur in the small intestine, stomach and LI

Answer 7

SI: 20x/min
LI/ stomach: 5x/min

Question 8

What cells initiate/ control the slow waves?

Answer 8

Interstitial cells of Cajal (ICC)

Question 9

How do the ICC transport their ‘message’

Answer 9

Via nexuses with circular and longitudinal layers of the GUT

Question 10

What is the approximate region (mV) that a depolarising over will cause a muscle contraction?

Answer 10

-40mV

Question 11

Will stimulation of the sympathetic NS result in depolarisation or hyperpolarisation of the cell membrane? why?

Answer 11

Will result in hyperpolarisation. The sympathetic NS wants to decrease motility, therefore reduces the likelihood of a muscle contraction by forming the action potential in a more negative direction than the required threshold to cause a muscle contraction

Question 12

Will stimulation of the parasympathetic NS result in depolarisation or hyperpolarisation of the cell membrane? why?

Answer 12

Will result in depolarisation. The parasympathetic NS wants to increase motility (rest and digest), therefore increases the likelihood of the cell membrane reaching the required threshold to cause a muscle contraction.

Question 13

What is the term for a muscle becoming more excitable after being depolarised?

Answer 13

Primed

Question 14

What nerves contribute to prehension/ mastication?

Answer 14

Facial (7), glossopharyngeal (9), trigeminal (5)

Question 15

What are 2 issues likely causing problems with deglutition?

Answer 15

Lesion in brainstem/ cranial nerves