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BDS2 OCB > OCB04-2015 > Flashcards

OCB04-2015 Flashcards

1
Q

What factors affect chewing in humans?

A

Dentition

Salivary flow

Muscle strength

Food consistency/structure

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2
Q

What muscles are involved in jaw closing?

A

Masseter

Temporalis

Medial pterygoid

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3
Q

What muscles are involved in jaw opening?

A

Digastric (pulls against hyoid)

Sub-hyoid muscles help in stabilisation

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4
Q

What are the four phases of mammalian masticatory movement?

A
  1. Fast closing
  2. Slow closing
  3. Slow opening
  4. Fast opening
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5
Q

Which phase of masticatory movement is not present when ingesting soft foods?

A
  1. Slow closing
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6
Q

What factors affect the time spent in each phase of masticatory movement?

A

Species

Food consistency

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7
Q

How does the tongue move during the phases of masticatory movement?

A

Fast opening and closing = retraction to allow food into mouth

Slow closing and opening = protraction (elongates below food)

  1. Fast closing = retraction

2, Slow closing = protraction

  1. Slow opening = protraction
  2. Fast opening = retraction
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8
Q

What do the styloglossi and genioglossus do during the opening stages of mastication?

A

Form the longitudinal trough in tongue dorsum

Can push food to posterior oral cavity if both styloglossi contract

Can push food towards teeth if one styloglossus contracts

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9
Q

What does the tongue do pre-swallowing?

A

Tongue presses food against hard palate, squeezing it posteriorly

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10
Q

What detects the texture and properties of food?

A

Mucosal mechanoreceptors (gingival, PDL, etc)

Principally on soft palate to the back of the throat

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11
Q

Which neurons innervate the jaw muscles?

A

α and β motoneurons of trigeminal motor nerve

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12
Q

What are jaw-opening α-motoneurons primarily excited by?

A

Inputs from central pattern generator that drives chewing

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13
Q

What are jaw-closing α-motoneurons excited/inhibited by?

A

Excited by inputs from central pattern generator that drives chewing and the muscle spindles

Inhibited by strong stimuli to mucosal and PDL afferents (ie very hard food)

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14
Q

Describe the hypoglossal motor nucleus function in masticatory movement.

A

Controls tongue

Some crossover to contralateral sides allows asymmetrical movement

Some input from central pattern generator to coordinate tongue movement with jaw opening/closing

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15
Q

Describe the facial motor nucleus function in masticatory movement.

A

Controls facial muscles including buccinator and circum-oral muscles needed to contain food in the mouth

Controls posterior digastric which needs to contract with the anterior digastric during jaw opening

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16
Q

What is the origin of the signals that elicit muscle activity in chewing?

A

Reflex

Central pattern generator in brainstem

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17
Q

What is the masticatory CPG influenced by?

A

“Drive” from motor cortex and peripheral receptors

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18
Q

What is the masticatory CPG?

A

Interconnected neural circuits producing a neural oscillatory network capable of generating simple patterns of masticatory movement

Has rhythm and pattern generator functions

19
Q

Where is the masticatory CPG located?

A

Probably in the reticular formation and parts of the pons that contain the trigeminal nucleus

20
Q

How does a CPG work?

A

2 pathways/circuits interconnected by inhibitory pathways

Bias where one circuit starts after receiving a signal

Mutually reinforcing circuits help to propagate and maintain signal for each circuit

Active circuit sends an inhibitory signal to prevent second circuit from working at the same time

Circuit works for a while before tiring which decreases the inhibitory signal to allow the second circuit to work

21
Q

Why is a CPG alone insufficient for normal life?

A

Basic rhythmical movement cannot be modulated by higher centres and afferent input to meet the variety challenges involved in normal mastication (eg hard foods)

22
Q

What role does the cortex have in mastication?

A

Initiate feeding and tongue posture

Motor cortex essential for coordination and modulation of all motor systems in response to afferent input

23
Q

What is stage 1 transport in mastication and swallowing?

A

On tongue to molars to assess whether bolus is suitable for swallowing or needs further chewing

24
Q

How many chews is typically required before swallowing?

A

7-10

25
Q

What is stage 2 transport in mastication and swallowing?

A

Transport to back of tongue and swallowing

26
Q

What phase of masticatory movement is elongated during stage 2 transport?

A

Longer slower opening to allow time for pharyngeal swallow

27
Q

What is swallowing?

A

Sequence of muscle contractions and relaxations which move material from oral cavity to stomach

~2mins

28
Q

How many swallows does the average adult do per day? How many of these are done with eating?

A

Up to 1000/day

~150 swallows with eating

29
Q

What are the 3 main stages of swallowing?

A
  1. Oral
  2. Pharyngeal
  3. Oesophageal
30
Q

Describe the oral stage of swallowing.

A

Conscious/voluntary

Food bolus moved back to a “glossopharyngeal-innervated” area

31
Q

Describe the pharyngeal stage of swallowing.

A

Reflex/involuntary (can be controlled a little)

Elicited by bolus stimulation of glossopharyngeal receptors

32
Q

Is the oesophageal stage of swallowing conscious or reflex?

A

Reflex/involuntary

33
Q

In what order do the pharyngeal muscles contract during a swallow?

A

Superior constrictor –> middle constrictor –> inferior constrictor

34
Q

What muscles pull on the hyoid to change tongue position during swallowing?

A

Anterior and posterior bellies of digastric

Sternohyoid

35
Q

What is the vallecula?

A

Pouch between base of tongue and epiglottis

36
Q

What role does the vallecula have in swallowing?

A

Highly innervated so when food or saliva touches this space, it will help to elicit a swallow and suppress respiration

37
Q

Which parts of the brainstem control the stages of swallowing?

A

Higher centres for preparatory and oral phases

Brainstem for pharyngeal and oesophageal stages

38
Q

Where is the CPG for swallowing?

A

Brainstem

  • nucleus tractus solitarius = dorsal swallowing group
  • nucleus ambiguus = ventral swallowing group
39
Q

Describe what happens in the CPG for swallowing.

A

Dorsal swallowing group (NTS) receives inputs from higher centres and peripheral afferents to generate the trigger, shape and timing of the rhythmic swallowing patterns

Ventral swallowing group (NA) contains cell bodies of motoneurons that are activated by dorsal swallowing group and directly innervate the muscles

40
Q

What reflexes can interrupt swallowing?

A

Sneezing

Coughing

Gagging

Choking

41
Q

What are the 4 mechanisms that protect the lower airway?

A

Closure of glottis (prevents aspiration)

Flexionof epiglottis over laryngeal inlet

Interruption of respiration

Swallows times to occur near end of inspiration

42
Q

Why are swallows naturally timed to occur near the end of inspiration?

A

Ensures that if an object is aspired:

  • there is an escape of air at first opening of the glottis to help clear the laryngeal opening
  • there would be an adequate volume of air in the lungs to permit a forceful cough to dislodge the object
43
Q

What medical conditions interfere with swallowing and reflexes that protect the airway?

A

Stroke

Parkinson’s disease

Myaesthenia gravis

Motor neuron disease

Recurrent laryngeal, superior laryngeal or main vagus nerve palsies

Severe chronic obstructive pulmonary disease (COPD)

BDS2 OCB (22 decks)

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