Reflexes Flashcards
(84 cards)
1
Q
List the components of a reflex arc
A
- Stimulus
- Receptors
- Sensory neurone
- Integration centres
- Motor neurone
- Effector
2
Q
What does the sensory neurone do in the reflex arc
A
It transmits afferent information into the CNS
3
Q
What does the motor neurone do
A
It conducts efferent imputes to the effector organ
4
Q
What can an effector organ be
A
Muscle/gland
5
Q
What are Cervical & lumbar enlargements
A
They are enlargements in overstrain areas particularly in the ventral horn
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
7
Q
What do cervical enlargements supply
A
Supplies arms
8
Q
What do lumbar enlargements supply
A
Supplies legs
9
Q
What can the spinal cord be split into
A
Grey and white matter
10
Q
Where is grey matter found
A
- Dorsal horn
- Ventral horn
- Lateral horn
11
Q
What does the dorsal horn contain
A
Sensory relay neurones
12
Q
What does the ventral horn contain
A
Motor neurones
13
Q
Where is white matter found
A
- Dorsal column
- Lateral column
- Ventral column
14
Q
What does the dorsal column do
A
It has ascending axons that carry somatosensory information from dorsal horn to brain stem
15
Q
What does the lateral column do
A
It has ascending and descending axons that innervate interneurones and motor neurones
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
17
Q
Name the 3 different types of reflex pathways
A
- Monosynaptic reflex
- Disynaptic reflex
- Polysynaptic reflex
18
Q
What is a monosynaptic reflex
A
The sensory neurones axon making a direct synaptic connection with the motor neurone
19
Q
What is a Disynaptic reflex
A
A single interneurone receives the sensory output and makes a synaptic connection with the motor neurone
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
21
Q
Name the 2 types of motor neurones
A
Alpha
Gamma
22
Q
What do alpha motor neurones innervate
A
Innervate extrafusal fibres
23
Q
What do alpha neurones do
A
They are the main force generating efferent fibres to muscle body
24
Q
What do gamma motor neurones innervate
A
Innervate intrafusal fibres
25
Describe a motor reflex
A rapid stereotypes repose to a particular sensory stimulus
26
What is a stretch reflex sometimes called
myotatic reflex
27
What are myotatic reflexes specific for
Muscles being stretched/ lengthened
28
What types of reflex is a myotatic reflex?
Monosynaptic reflex
29
What happens when a muscle is stretched
The muscle spindle is stretched and its nerve activity increases
30
Talk through a myotatic reflex
1. Nerve impulse immediately sent to the spinal cord
2. Response to contract the muscle is received
3. Contraction increases muscle tension
31
Describe muscle spindles
They are bundles of modified skeltal muscle fibres enclosed in connective tissue capsule
32
Where are muscle spindles found
Skeletal muscles
33
When is the muscle spindle activated
When a muscle is stretched passively
34
What happens to the muscle spindle when a muscle contracts
It is switched off
35
Give an example of a monosynaptic stretch reflex
The knee jerk reflex
36
What happens in the knee jerk reflex
If you tap on the patellar tendon the tendon deflects and briefly stretches quadricep muscle
37
How does the jerk reflex happen
1. The intrafusal fibres of the muscle spindle in the quadriceps muscle are stretched
2, Results in discharge of sensory nerves
3. These activate 1a afferent sensory fibres which synapse DIRECTLY with the alpha motor neurones
4. Increases firing of the Alpha motorneurones
5. Muscle contracts
38
Summarise how an extensor muscle contracts in a reflex arc
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
Summarise how the flexor muscle relaxes in a reflex arc
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
Describe the Golgi tendon
Small bundles of tendon fibres enclosed in a layered capsule with dendrites coiling between and around the fibres
41
What is the Golgi tendon activated by
Muscles tension
42
Where is the Golgi tendon found
In muscle tendons
43
What reflex is associated with the Golgi tendon
Inverse myotatic reflex
44
What is the the inverse myotatic reflex die to
Tension within muscles
45
What is the result of the Inverse myotatic reflex
The muscle which has increased tension is inhibitd
| The antagonist muscle is activated
46
What is another name for the Inverse myotatic reflex
Tendon reflex
47
Talk through the Inverse myotatic reflex
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
Why is the Inverse myotatic reflex important
It is a protective feedback mechanism to make sure muscle doesn't tense too much that it could get damaged
49
Which is more sensitive the stretch or tendon reflex
Stretch reflex is more sensitive but the tendon reflex can override the stretch reflex when tension is great
50
Summarise how an extensor muscle relaxes in a tendon arc
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
Summarise how a flexor muscle contracts in a tendon arc
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
What is the flexor reflex
A withdrawal reflex stimulated by pain or danger
53
What happens in a flexor reflex
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
As the flexor reflex is happening what else occurs
The cross extensor reflex
55
What makes up the spinal reflex circuit on the head and jaw
1. Sensory input
2. Motor output
3. Interneurones
56
How does sensory input reach the brain
Sensory input travels from skin/tissue mechanoreceptors and joint/muscle proprioceptors, via trigeminal ganglia to the midbrain/brainstem
57
Give an example of a mutation stretch reflex arc relevant to dentists
The jaw jerk reflex
58
Name the stimulus fo red jaw jerk reflex
Tapping the mandible as the mouth is partially open
59
What is the result of he jaw jerk reflex
Masseter muscle jerks the mandible upwards
60
What is the jaw jerk reflex used to test
Used to test the status of a patients trigeminal nerve
61
Name the 3 division of the trigeminal nerve
V1 Ophthalmic division
V2 Maxillary division
V3 Mandibular division
62
What does the ophthalmic nerve do
It carries sensory information from the scalp to the forehead, upper eyelid, the conjunctiva and cornea of the eye, the nose etc
63
What does the maxillary nerve do
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
What does the mandibular nerve do
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
Does the mandibular nerve carry taste sensation
No
66
What doe the periodontal ligament contain
Mechanoreceptors
67
What do the mechanoreceptors in the periodontal ligament DO
They are used for processing level and type of force on teeth
68
What innovates the periodontal ligament
The interior alveolar branch of the mandibular nerve (V3)
69
Nam the different types of mechanoreceptors involved in oral reflexes
1. Muscle spindles
2. Free endings
3. Pacinian corpuscles
4. Meissners or krauses bulbs
5. Ruffini organs
70
Where are muscle fibres found in oral reflexes
Jaw muscles
71
Where are free endings found in oral reflexes
TMK
PDL
Mucosa
72
Where are Pacinian corpuscles found in oral reflexes
TMJ
73
Where are Meissners or krauses bulbs found in oral reflexes
oral mucosa
74
Where are Ruffini organs found in the oral reflex
PDL
75
Give an example of a condition linked to jaw reflexes
Rapid onset dystonia-Parkinsonism
76
What can rapid onset dystonia-Parkinsonism cause
```
Tremors
speech and swallowing problems
muscle spasms
disturbed balance
Some people experience seizures
```
77
What mutation is rapid onset dystonia-Parkinsonism linked to
link to a mutation in one subunit (ALPHA3) of the Na+/K+ ATPase.
78
What are lower motor neurone disorders
Absence of reflexes
79
What are lower motor neurone disorders
exaggerated reflex responses due to reduction in inhibition from “higher” centres
80
What is the jaw jerk reflex
A myotatic stretch reflex
81
What is Trismus
Lockjaw
82
What does Trismus present as
Th inability to open the mouth properly
83
What is Trismus caused by
Spasmodic concentration of the masseter muscle due to:
1. impaction of third molar
2. tetanus
3. radiation therapy
84
State the normal mouth opening range
35mm to 45mm
