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3rd yr- CSB- Occlusion > Reflexes > Flashcards

Reflexes Flashcards

1
Q

List the components of a reflex arc

A
  1. Stimulus
  2. Receptors
  3. Sensory neurone
  4. Integration centres
  5. Motor neurone
  6. Effector
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2
Q

What does the sensory neurone do in the reflex arc

A

It transmits afferent information into the CNS

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3
Q

What does the motor neurone do

A

It conducts efferent imputes to the effector organ

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4
Q

What can an effector organ be

A

Muscle/gland

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5
Q

What are Cervical & lumbar enlargements

A

They are enlargements in overstrain areas particularly in the ventral horn

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6
Q

What are Cervical & lumbar enlargements due to

A

Expansion of grey matter in the ventral horns to accommodate the large groups of motor neurones supplying the muscles of the fore and hind limbs

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7
Q

What do cervical enlargements supply

A

Supplies arms

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8
Q

What do lumbar enlargements supply

A

Supplies legs

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9
Q

What can the spinal cord be split into

A

Grey and white matter

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10
Q

Where is grey matter found

A
  1. Dorsal horn
  2. Ventral horn
  3. Lateral horn
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11
Q

What does the dorsal horn contain

A

Sensory relay neurones

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12
Q

What does the ventral horn contain

A

Motor neurones

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13
Q

Where is white matter found

A
  1. Dorsal column
  2. Lateral column
  3. Ventral column
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14
Q

What does the dorsal column do

A

It has ascending axons that carry somatosensory information from dorsal horn to brain stem

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15
Q

What does the lateral column do

A

It has ascending and descending axons that innervate interneurones and motor neurones

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16
Q

What dos the ventral column do

A

It has ascending axons that convey information about pain and thermal sensation
It also has a deceasing pathway which controls muscles and posture

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17
Q

Name the 3 different types of reflex pathways

A
  1. Monosynaptic reflex
  2. Disynaptic reflex
  3. Polysynaptic reflex
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18
Q

What is a monosynaptic reflex

A

The sensory neurones axon making a direct synaptic connection with the motor neurone

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19
Q

What is a Disynaptic reflex

A

A single interneurone receives the sensory output and makes a synaptic connection with the motor neurone

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20
Q

What is a Polysynaptic reflex

A

A reflex pathway involving a chain of 2 or more interneurones between the sensory neurone and the motor neurone

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21
Q

Name the 2 types of motor neurones

A

Alpha

Gamma

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22
Q

What do alpha motor neurones innervate

A

Innervate extrafusal fibres

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23
Q

What do alpha neurones do

A

They are the main force generating efferent fibres to muscle body

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24
Q

What do gamma motor neurones innervate

A

Innervate intrafusal fibres

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25
Q

Describe a motor reflex

A

A rapid stereotypes repose to a particular sensory stimulus

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26
Q

What is a stretch reflex sometimes called

A

myotatic reflex

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27
Q

What are myotatic reflexes specific for

A

Muscles being stretched/ lengthened

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28
Q

What types of reflex is a myotatic reflex?

A

Monosynaptic reflex

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29
Q

What happens when a muscle is stretched

A

The muscle spindle is stretched and its nerve activity increases

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30
Q

Talk through a myotatic reflex

A
  1. Nerve impulse immediately sent to the spinal cord
  2. Response to contract the muscle is received
  3. Contraction increases muscle tension
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31
Q

Describe muscle spindles

A

They are bundles of modified skeltal muscle fibres enclosed in connective tissue capsule

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32
Q

Where are muscle spindles found

A

Skeletal muscles

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33
Q

When is the muscle spindle activated

A

When a muscle is stretched passively

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34
Q

What happens to the muscle spindle when a muscle contracts

A

It is switched off

35
Q

Give an example of a monosynaptic stretch reflex

A

The knee jerk reflex

36
Q

What happens in the knee jerk reflex

A

If you tap on the patellar tendon the tendon deflects and briefly stretches quadricep muscle

37
Q

How does the jerk reflex happen

A
  1. The intrafusal fibres of the muscle spindle in the quadriceps muscle are stretched
    2, Results in discharge of sensory nerves
  2. These activate 1a afferent sensory fibres which synapse DIRECTLY with the alpha motor neurones
  3. Increases firing of the Alpha motorneurones
  4. Muscle contracts
38
Q

Summarise how an extensor muscle contracts in a reflex arc

A
  1. Tendon is stretched briefly
  2. Muscle is stretched
  3. This activates 1a fibres via muscle spindle receptors
  4. Excitation of alpha motor neurones
  5. Extensor muscle contracts
39
Q

Summarise how the flexor muscle relaxes in a reflex arc

A
  1. Tendon is stretched briefly
  2. Muscle is stretched
  3. This activates 1a fibres via muscle spindle receptors
  4. Excitation of interneurones
  5. inhibitor of alpha motor neurone
  6. Flexor muscle relaxes
40
Q

Describe the Golgi tendon

A

Small bundles of tendon fibres enclosed in a layered capsule with dendrites coiling between and around the fibres

41
Q

What is the Golgi tendon activated by

A

Muscles tension

42
Q

Where is the Golgi tendon found

A

In muscle tendons

43
Q

What reflex is associated with the Golgi tendon

A

Inverse myotatic reflex

44
Q

What is the the inverse myotatic reflex die to

A

Tension within muscles

45
Q

What is the result of the Inverse myotatic reflex

A

The muscle which has increased tension is inhibitd

The antagonist muscle is activated

46
Q

What is another name for the Inverse myotatic reflex

A

Tendon reflex

47
Q

Talk through the Inverse myotatic reflex

A
  1. As the tension applied to a tendon increases, the Golgi tendon organ is stimulated
  2. Nerve impulses arise and propagate into th apsidal cord also 1b afferent sensory fibres
  3. Sensory neurone activate an inhibitory interneurone that makes. synapse with an alpha motor neurone
  4. Inhibitory neurotransmitter is released which inhibits the motoprneruone
  5. This generated fewer nerve impulses along th efferent fibre to the muscle
  6. So the muscle relaxes relieving excess tension
48
Q

Why is the Inverse myotatic reflex important

A

It is a protective feedback mechanism to make sure muscle doesn’t tense too much that it could get damaged

49
Q

Which is more sensitive the stretch or tendon reflex

A

Stretch reflex is more sensitive but the tendon reflex can override the stretch reflex when tension is great

50
Q

Summarise how an extensor muscle relaxes in a tendon arc

A
  1. Extensor muscle contracts
  2. Tension builds up in tendon
  3. Afferent 1b fibres activated via Golgi tendon organ
  4. Excitation of interneuron (inhibitory)
  5. Inhibition of alpha motor neurone
  6. Extensor muscle relaxes
51
Q

Summarise how a flexor muscle contracts in a tendon arc

A
  1. Extensor muscle contracts
  2. Tension builds up in tendon
  3. Afferent 1b fibres activated via Golgi tendon organ
  4. Excitation of interneuron (excitatory)
  5. Excitation of alpha motor neurone
  6. Flexor muscle contracts
52
Q

What is the flexor reflex

A

A withdrawal reflex stimulated by pain or danger

53
Q

What happens in a flexor reflex

A
  1. pain receptors (nociceptors) in the skin are stimulated
  2. This triggers a sensory impulse that travels in a-delta fibres to the spinal cord
  3. Sensory neurone synapses with spinal interneurons that synapse with motor neurones
  4. Some motor neurones stimulated and send motor impulses to stimulate flexor muscles
  5. Leads to action eg withdrawal of limb from hot object
54
Q

As the flexor reflex is happening what else occurs

A

The cross extensor reflex

55
Q

What makes up the spinal reflex circuit on the head and jaw

A
  1. Sensory input
  2. Motor output
  3. Interneurones
56
Q

How does sensory input reach the brain

A

Sensory input travels from skin/tissue mechanoreceptors and joint/muscle proprioceptors, via trigeminal ganglia to the midbrain/brainstem

57
Q

Give an example of a mutation stretch reflex arc relevant to dentists

A

The jaw jerk reflex

58
Q

Name the stimulus fo red jaw jerk reflex

A

Tapping the mandible as the mouth is partially open

59
Q

What is the result of he jaw jerk reflex

A

Masseter muscle jerks the mandible upwards

60
Q

What is the jaw jerk reflex used to test

A

Used to test the status of a patients trigeminal nerve

61
Q

Name the 3 division of the trigeminal nerve

A

V1 Ophthalmic division
V2 Maxillary division
V3 Mandibular division

62
Q

What does the ophthalmic nerve do

A

It carries sensory information from the scalp to the forehead, upper eyelid, the conjunctiva and cornea of the eye, the nose etc

63
Q

What does the maxillary nerve do

A

It carries sensory information from the llower eyelid and cheek, the nares and upper lip, the upper teeth and gums, the nasal mucosa, the palate and roof of the pharynx, the maxillary, ethmoid and sphenoid sinuses and parts of the meninges.

64
Q

What does the mandibular nerve do

A

nerve carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw parts of the external ear, and parts of the meninges.

65
Q

Does the mandibular nerve carry taste sensation

A

No

66
Q

What doe the periodontal ligament contain

A

Mechanoreceptors

67
Q

What do the mechanoreceptors in the periodontal ligament DO

A

They are used for processing level and type of force on teeth

68
Q

What innovates the periodontal ligament

A

The interior alveolar branch of the mandibular nerve (V3)

69
Q

Nam the different types of mechanoreceptors involved in oral reflexes

A
  1. Muscle spindles
  2. Free endings
  3. Pacinian corpuscles
  4. Meissners or krauses bulbs
  5. Ruffini organs
70
Q

Where are muscle fibres found in oral reflexes

A

Jaw muscles

71
Q

Where are free endings found in oral reflexes

A

TMK
PDL
Mucosa

72
Q

Where are Pacinian corpuscles found in oral reflexes

A

TMJ

73
Q

Where are Meissners or krauses bulbs found in oral reflexes

A

oral mucosa

74
Q

Where are Ruffini organs found in the oral reflex

A

PDL

75
Q

Give an example of a condition linked to jaw reflexes

A

Rapid onset dystonia-Parkinsonism

76
Q

What can rapid onset dystonia-Parkinsonism cause

A 
Tremors
speech and swallowing problems
muscle spasms 
disturbed balance 
Some people experience seizures
77
Q

What mutation is rapid onset dystonia-Parkinsonism linked to

A

link to a mutation in one subunit (ALPHA3) of the Na+/K+ ATPase.

78
Q

What are lower motor neurone disorders

A

Absence of reflexes

79
Q

What are lower motor neurone disorders

A

exaggerated reflex responses due to reduction in inhibition from “higher” centres

80
Q

What is the jaw jerk reflex

A

A myotatic stretch reflex

81
Q

What is Trismus

A

Lockjaw

82
Q

What does Trismus present as

A

Th inability to open the mouth properly

83
Q

What is Trismus caused by

A

Spasmodic concentration of the masseter muscle due to:

  1. impaction of third molar
  2. tetanus
  3. radiation therapy
84
Q

State the normal mouth opening range

A

35mm to 45mm

3rd yr- CSB- Occlusion (7 decks)

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