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Gastrointestinal > 6. Motility of the GI Tract > Flashcards

6. Motility of the GI Tract Flashcards

1
Q

3 phases of DEGLUTITION/SWALLOWING

A
  1. ORAL
  2. PHARYNGEAL
  3. OESOPHAGUS
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2
Q

is PHASE 1 (ORAL) of DEGLUTITION voluntary or involuntary

A

VOLUNTARY

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3
Q

is PHASE 2 (PHARYNGEAL) of DEGLUTITION voluntary or involuntary

A

INVOLUNTARY

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4
Q

is PHASE 3 (OESOPHAGEAL) of DEGLUTITION voluntary or involuntary

A

INVOLUNTARY

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5
Q

what happens in PHASE 1 DEGLUTITION

A

ORAL:
- Food BOLUS formed by MASTICATION
- TONGUE moves UP and BACKWARD

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6
Q

Muscles in TONGUE are CONTROLLED by which CRANIAL NERVE

A

12 - HYPOGLOSSAL

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7
Q

what happens in PHASE II DEGLUTITION

A

PHARYNGEAL:
- SOFT PALATE RISES
- EPIGLOTTIS CLOSES (down)
- PHARYNX CONTRACTS
- UPPER OESOPHAGEAL SPHINCTER (UOS) RELAXES (opens oesophagus)

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8
Q

RECEPTORS of the PHARYNX that detect the food and send signals to Brain Stem to UOS to RELAX (and all actions of pharyngeal phase)

A

TACTILE/DISTENSION RECEPTORS

  • MECHANORECEPTORS
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9
Q

What happens in PHASE III DEGLUTITION

A

OESOPHAGEAL:

  • UOS CONTRACTS (reflex after food enters stomach, so oesophagus closed again to prevent gastric reflux)
  • Bolus moved by PERISTALSIS
  • LOWER OESOPHAGEAL SPHINCTER (LOS) RELAXES and opens (LOS is smooth muscle)
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10
Q

CRURAL DIAPHRAGM role in DEGLUTITION

A
  • (skeletal) MUSCLE that SURROUNDS LOS (sling around it)

CONTRACTS to OPEN, so food can pass into stomach

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11
Q

REFLEXES and NERVES used to OPEN LOS

A

VAGAL REFLEX and VAGAL PHRENIC REFLEX

VAGUS NERVE - VAGAL AFFERENT to BRAIN STEM
VAGAL EFFERENT to LOS

PHRENIC NERVE to CRURAL DIAPHRAGM

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12
Q

how does the PHRENIC NERVE stimulate the CRURAL DIAPHRAGM to CONTRACT and OPEN the LOS

A
  • STIMULATES ACETYLCHOLINE RELEASE
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13
Q

how do VAGAL EFFERENT FIBRES cause RELAXATION of LOS

A
  • VAGAL EXCITORY FIBRES (VEF) switched OFF
    (no Ach release)
  • VAGAL INHIBITORY FIBRES (VIF) switched ON
    -> release VASOACTIVE INTESTINAL POLYPEPTIDE (VIP) and NITRIC OXIDE (NO)

therefore relax LOS

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14
Q

to RELAX LOS, VAGAL INHIBITORY FIBRES are SWITCHED ON and RELEASE:

A

VIP (VASOACTIVE INTESTINAL POLYPEPTIDE)
& NO (NITRIC OXIDE)

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15
Q

what causes PERISTALTIC CONTRACTIONS in the STOMACH

A

PACEMAKER ZONE

  • in FUNDIC region (fundus)
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16
Q

order of GASTRIC MOTILITY (how food passes in stomach)

A
  1. FUNDUS : PACEMAKER ZONE for PERISTALSIS - mix and churn
  2. CORPUS (body) : ACID SECRETIONS
  3. ANTRUM : MUSCULAR PUMP - contracts vigorously to further mix
  4. PYLORIC SPHINCTER: OPENS when PRESSURE in PYLORIS INCREASES

-> food to duodenum
4.

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17
Q

the ANTRUM of the STOMACH has what ROLE

A

MUSCULAR PUMP
- contracts vigorously to further mix food before it goes to small intestine

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18
Q

the CORPUS (body) of the STOMACH has what ROLE

A

ACID SECRETIONS

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19
Q

where is the PACEMAKER ZONE in the STOMACH

A

FUNDUS

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20
Q

what is RETROPULSION in the STOMACH

A

when PYLORIC SPHINCTER is still CLOSED, food PUSHED BACK and there is MORE MIXING

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21
Q

which part of the STOMACH acts as a MUSCULAR PUMP

A

ANTRUM

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22
Q

what are the PACEMAKERS of the GUT

A

INTERSTITIAL CELLS of CAJAL

(ICC CELL NETWORK)

(in the circular and longitudinal muscle layers of gut wall and submucosa)
(have gap junctions)

23
Q

what do the INTERSTITIAL CELLS of CAJAL allow for in the GUT

A

SLOW WAVE MECHANISM conducted to smooth muscle
-> SMOOTH MUSCLE CONTRACTION

(ACTION POTENTIALS)

24
Q

what causes DEPOLARIATION of membranes and hence ACTION POTENTIALS in the GUT (depolarisation pacemaker currents)

A

CALCIUM INFLUX (Ca2+)

by L-TYPE CA2+ CHANNELS

25
Q

where does the BASAL ELECTRICAL RYTHM (BER) of the GUT originate and what happens to result in CONTRACTIONS

A
  • In ICC
  • when SPIKE POTENTIALS occur at MAXIMUM DEPOLARISATION of BER due to Ca2+ ENTRY
    -> results in contraction
26
Q

what causes HYPERPOLARISATION/REPOLARISATION in BER

A

OUTWARD K+ CURRENTS
(delayed)

27
Q

ACTION POTENTIAL FREQUENCY can be INCREASED and DECREASED by which NEUROTRANSMITTERS

A

ACH - INCREASE

NORADRENALINE - DECREASE

28
Q

I

A
29
Q

what are the 4 PHASES of the MIGRATING MYOELECTRIC COMPLEX (MMC)

A

I - QUIESCENCE

II - RANDOM CONTRACTIONS

III - BURST of CONTRACTIONS (MAXIMUM AMPLITUDE and DURATION)

IV - RAPID DECREASE of CONTRACTIONS

30
Q

Where does MMC Initiate / Occur

A

79% in ANTRUM of STOMACH (initiates here)

29% in DUODENUM

31
Q

how much of MMC Occurs in the DUODENUM

A

29%

32
Q

2 INTESTINAL MOVEMENTS that take place to move food

A
  1. SEGMENTATION
  2. PERISTALTIC REFLEX
33
Q

what is SEGMENTATION in INTESTINES

A

ALTERNATE CONTRACTION and RELAXATION of ADJACENT SEGMENTS

Back and forth movement

  • causes thorough MIXING of food contents
    fine digestion into SMALLER components that can be ABSORBED
34
Q

as BOLUS passed through INTESTINES what is it RECOGNISED BY to trigger PERISTALSIS

A

DISTENSION / STRETCH

->RELEASES 5-HT (5-hydroxytryptamine) (serotonin)

35
Q

when DISTENSION/STRETCH recognises BOLUS and RELEASES 5-HT what is the SIGNAL PATHWAY

A

signals in Intrinsic PRIMARY AFFERENT NEURONS (IPAN)
(TK/ACH)

-> along INTERNEURONES (ACH)

EITHER
-> EXCITORY MOTOR NEURONES (ACH/TK)
OR
-> INHIBITORY MOTOR NEURONES (VIP/NO)

36
Q

how are the 2 ends of the BOLUS described as it passes through INTESTINES

A

ORAD (BEHIND, Mouth end)

CAUDAD (IN FRONT, Tail end)

37
Q

which END of the BOLUS CONTRACTS in INTESTINES

A

ORAD

38
Q

what happens in CAUDAL END of the BOLUS in the INTESTINES

A

RELAXATION of CIRCULAR SMOOTH MUSCLE

39
Q

what stimulates ASCENDING CONTRACTION of CIRCULAR SMOOTH MUSCLE in the ORAD end of the INTESTINES (behind bolus)

A

PRIMARY AFFERENT NEURONES -> INTERNEURONES (RELEASE ACH)

-> EXCITORY MOTOR NEURONES

RELEASE ACH / TK (tachykinin)

causes contraction

40
Q

what do EXCITORY MOTOR NEURONES RELEASE to cause CONTRACTION of INTESTINES SMOOTH MUSCLE (circular)

A

ACh / TK

41
Q

what causes DESCENDING RELAXATION of the CIRCULAR SMOOTH MUSCLE at the CAUDAD end of INTESTINES (in front of bolus)

A

PRIMARY AFFERENT NEURONES -> INTERNEURONES (ACH)

-> INHIBITORY MOTOR NEURONES

RELEASE VIP (vasoactive intestinal polypeptide)
/ NO (nitric oxide)
- RELAXING FACTORS

42
Q

what RELAXING FACTORS are RELEASED by INHIBITORY MOTOR NEURONES to cause RELAXATION of INTESTINES SMOOTH MUSCLE in front of bolus

A

VIP / NO

43
Q

PERISTALTIC REFLEX in INTESTINES has 2 actions

A
  • ASCENDING CONTRACTION
  • DESCENDING RELAXATION
44
Q

DISTENSTION / STRETCH in the INTESTINES as BOLUS passes causes RELEASE of:

A

5-HT (SEROTONIN)

45
Q

name of the SEGMENTATION action in the LARGE INTESTINE

A

HAUSTRATION

  • mixing, absorption and stool formation
46
Q

Strong PERISTALTIC WAVES SHIFT the INDIGESTIBLE MATERIAL in the COLON (LARGE INTESTINE) TOWARDS RECTUM. called:

A

MASS MOVEMENTS

47
Q

MASS MOVEMENTS in the COLON are STIMULATED by

A

FOOD IN STOMACH and food in DUODENUM

(new food entering)

48
Q

STRETCH of the RECTUM causes:

A

REFLEX:

COLON CONTRACTS to PUSH more indigestible material, RECTUM CONTRACTS

INCREASE PRESSURE

INTERNAL ANAL SPHINCTER RELAXES

49
Q

RELEASE of what RELAXING FACTORS cause the INTERNAL ANAL SPHINCTER to RELAX

A

VIP (Vasoactive Intestinal Polypeptide)
& ATP

50
Q

EXTERNAL ANAL SPHINCTER is under what CONTROL

A

SOMATIC - VOLUNTARY
(striated muscle)

  • RELAXES by PUDENDAL NERVE
51
Q

MASS MOVEMENTS initiate what REFLEX

A

DEFAECATION REFLEX

52
Q

what NERVE CONTROLS EXTERNAL ANAL SPHINCTER

A

PUDENDAL NERVE (S2-S4)

53
Q

how is MOTILITY LEVEL in the COLON (LI) and RECTUM compared to SMALL INTESTINE

A

LOWER MOTILITY

(4-6 waves per min)

Gastrointestinal (19 decks)

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