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S&F 1 > Spinal Cord Reflexes > Flashcards

Spinal Cord Reflexes Flashcards

1
Q

What are Reflexes?

A

Automatic Response to sensory stimuli

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2
Q

What are the characteristics of reflexes?

A

Homeostatic responses

Rapid Unconscious (involuntary)

Unlearned S

terotyped (same in every body)

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3
Q

What autonomic (visceral) reflexes

A
  • effector is smooth muscle, cardiac muscle, or glands - generally not consciously perceived
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4
Q

What are somatic reflexes?

A
  • Effector is skeletal muscle
  • Consciously perceived
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5
Q

Pupillary light Reflex What type of reflex is this?

A

Autonomic reflex

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6
Q

Cough Reflex

What type of reflex is this?

A

Mixed reflex (both autonomic and somatic)

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7
Q

Withdrawal Reflex

What type of reflex is this?

A

Somatic Reflex

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8
Q

What are somatic reflex modified by?

A

By higher brain center

  • fundamental circuit for movement (involuntary and voluntary)
  • Provide the building blocks for complex, voluntary behaviors
  • are coordinated and modulated by the cortex and brainstem
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9
Q

Image

A

Image

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10
Q

Stretch reflex, withdrawal reflex, crossed extensor reflex, and plantar response are examples of what type of reflex?

A

Somatic reflex

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11
Q

Stretch Reflex (myotatic)

A

Also called, deep tendon reflex or monosynaptic reflex Knee Jerk Reflex

  1. Sensory receptor - muscle spindle
  2. Sensory neuron- cell body in DRG - Type 1a fiber
  3. Central integration: 1 synapse: 1a to Aa
  4. Efferent Neuron: A- motor neuron
  5. Effector organ: skeletal m.
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12
Q

These two reflexes are coupled

A

Withdrawal Reflex (Flexor) AND Crossed-Extensor Reflex

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13
Q

Plantar (Babincki) Reflex

A

changes with development

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14
Q

What are the components of the reflex are?

A
  • Sensory Receptor
  • Afferent (Sensory) Neuron
  • Central Integrator (spinal cord and synapse)
  • Efferent Neuron (motor neuron)
  • Effector Organ
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15
Q

Sensory Receptor

A

structures that detect and respond to sensory stimuli

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16
Q

Afferent (sensory) neuron

A

conducts impulse from sensory receptor to CNS

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17
Q

Central Integrator

A

Monosynaptic (direct contact between afferent and efferent neuron; no interneurons) vs polysynaptic

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18
Q

Efferent neuron

A

transmitter of impulse from integrating center to effector

Somatic reflexes is always going to involve the motor neuron

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19
Q

Effector organ

A

muscle or gland which responds to the effector

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20
Q

Myotatic units are activated by ?

A

Activated by Spinal Reflexes Myototic units are a group Agonist and antagonist muscle from common spinal reflex response, function together

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21
Q

How do agonist muscles behave?

A

In parallel

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22
Q

How do Muscles around a joint behave?

A

In concert

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23
Q

What establishes a strong neural linkage between muscles acting around a joint so that muscle do not act independent of each other?

A

Divergent connection of spindle afferents

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24
Q

What is Reciprocal Inhibition?

A

Even though the main arc in monosynaptic, you will have a disynaptic unit that synapses with a inhibitory intermotornueron in spinal cord and then makes a synapse with the alpha motor neuron and goes to the antagonist muscle

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25
Q

What are muscle spindles?

A
  • detect stretch
  • located within the muscles
  • initiated rapid contraction of a rapidly stretched muscle
  • innervated by Ia and II fibers
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26
Q

What is a goggle tendon organ (Proprioceptors)?

A
  • detect muscle tension
  • located in tendon at muscle-tendon junction, encapsulated, connected to 10-15 muscle fibers
  • initiates release of tension in contracted muscle
  • innervated by a single large afferent Ib fibers (entwined in the weave of collagen fibers that compose the receptor)
  • in series with muscle fibers
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27
Q

What are twi types of muscle spindles (Proprioceptor)?

A

Some respond to the speed of the stretch and others respond to the strength of the stretch

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28
Q

What are muscle spindle fibers composed off?

A

Intrafusal fibers

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29
Q

Whats are the intramural fibers of a muscles embedded in?

A

Skeletal muscle bundles also known as extrafusal fibers (these are the main cells of contraction.

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30
Q

What are the characteristics of a muscle spindle?

A
  • Encapsulated (collagenous membrane)
  • Within perimysium
  • Spindle shaped
  • coupled to sensory neurons (1a, II)
  • sensory fiber
  • innervated by gamma motor neurons ; regulated at distal end

NO CONTRIBUTION TO MUSCLE TENSION

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31
Q

Intrafusal fibers with Bulbous center region

A

Nuclear bag fibers Types:

  • static bag
  • length of stretch
  • dynamic bad
  • speed of stretch
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32
Q

Intrafusal fibers with Slender one

A

nuclear chain fibers Length of stretch

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33
Q

The sarcomeres/contractile fiber part and the nuclei are located where in the spindle?

A

Distal end and middle, respectively

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34
Q

What modulates the sensitivity of the spindle?

A

Contraction

35
Q

As we age what happens to the muscle spindle/skeletal muscle?

A

You will se more fat within spindle and muscle

36
Q

Group Ia Fibers

A
  • make annulospinal endings around central region of intramural fiber
  • innervate nuclear bag and nuclear chain fibers - Group Aa fibers
  • large, highly myelinated Very responsive when the muscle is initially being stretched and then stabilizes it
37
Q

Group II fibers

A
  • make flower spray endings
  • innervate nuclear chain and static nuclear bag fibers
  • group alpha-beta fibers
38
Q

What are gamma motor neurons?

A
  • cell bodies located in the spinal cord ventral horns (just like alpha motor neurons)
  • make up 30% of motor neurons
  • Type A gamma (5) nerve fibers are smaller than type A alpha (14)
  • innervate intrafusal fibers
  • receive input from higher centers
39
Q

What is the purpose of gamma motor neurons?

A

Adjust spindle sensitivity (they are co-activated with alpha neurons) by stretching the intrafusal fibers during muscle contraction so that they respond to small stretch of muscle = increase gain

40
Q

Static gamma-motor neurons act on which type of intrafusal fiber?

A

Nuclear bag fiber (static)

41
Q

Nuclear chain fibers are acted on by which type of gamma motor neurons?

A

dynamic gamma motor neurons

42
Q

Random addition of load to a stretched muscle causes what?

A

Increase firing of the Ia fiber mainly and II fires mildly-> reflex contraction done by alpha motor neurons This happens because of lack of tension in the muscle

43
Q

What happen when the person is aware of increase in load?

A

They are going prepare themselves -> increase tension to hold load -> nothing happens really

44
Q

What is the firing pattern of Ib fiber?

A

Ib has a dynamic and static response

45
Q

Define a dynamic respinse

A

rate of tension increases induces rapid firing in Ib fibers

46
Q

Define a static response

A

Low level of steady state firing that is closely proportional to the muscle tensio. Firing increases and tension increases

47
Q

Gogli tendon/reverse Myotactic Reflex

A
  1. Tension on tendon activates sensory neuron
  2. Sensory neuron stimulates interneuron
  3. Interneuron inhibits motor neuron
  4. Tension on tendon is reduced
48
Q

What is the Flexion Withdrawal Reflex

A

It is a polysynaptic reflex
- response to stimuli on the skin (often injurious stimuli)

  • elicited by various cutaneous receptors: temperature, pressure, proprioceptors, unexpected stimulus to skin
  • coordinates the contraction of flexor muscles and inhibition of extensor muscles around affected joint
49
Q

Afferent neurons for withdrawal reflex include

A

Touch/pressure fibers (Group I or II) (As, Alpha-beta)

Pain fibers (Group III or IV) ( alpha-delta, C)

50
Q

Steps in Polysynaptic Reflex in respinse to stepping on a sharp tack

A

Activation of group III afferents

Afferents innervate excitatory interneuron in lumbar spinal cord segment

Collateral branches of Group III travel up spinal cord to higher lumbar regions (to flex multi-joints)

Activation of Excitatory Interneurons innervating alpha-motor neurons to flexor muscles in higher spinal segment

51
Q

During a response to stepping on a sharp tack limbs of other parts of the body will be extended to maintain balance and posture. Why is that?

A

Because flexor reflex is coupled to crossed extensor reflex

52
Q

What is the cross extensor reflex?

A

Collateral cross midline on the spinal cord to synapse with alpha motor neuron on the opposite side of the body (from initial reflex) to complete and opposite reaction

53
Q

Why is the withdrawal-crossed extensor reflex prolonged whereas the stretch reflex is quick?

A

Because of reverberating circuits

(They are responsible for maintained flexor activity)

54
Q

What do Reverberating circuits involve?

A

Excitatory interneurons that re-excite each other

55
Q

What is muscle tone?

A

Resting Muscle tension

56
Q

What does muscle tone involve?

A
  • passive partial contraction of muscle
  • resistance to passive stretch during resting state
  • maintained by muscle spindles
  • provides a tonic innervation of muscle required for muscle health
57
Q

How do you measure tone?

A

The excitability of the stretch reflex

58
Q

Dendrastic manœuvre -

A

ask person to contract a body part thats above where you want to elicit the reflex (pull at or right before tap)

59
Q

Lesion in a upper motor neuron causes what?

A
  • weakness (paresis)
  • hyperopia (rigidity or spasticity)
  • Spastic paralysis
  • Hypereflexia
  • Extensor plantar (Babinski) response
  • little or no muscle atrophy
60
Q

Lesion in a lower motor neuron causes what?

A
  • paresis
  • hypotonia (flaccidity)
  • flaccid paralysis
  • hyporeflexia or areflexia
  • fasciculations or fibrillations
  • negative or absent plantar reflex muscle atrophy
61
Q

What is the (Babinski) response

A

Stimulate sensory receptor on the foot laterally -> Adult gets plantar flexion Child gets dorsiflexion

62
Q

Whats the difference between fasciculations and fibrillation?

A

Fasciculations - whole motor unit contracts

Fibrillations - one specific muscle cell contracts

Fasciculations are more noticeable

63
Q

Amyotrophic lateral Sclerosis (Lou Gehrig disease), Brain tumor, Meningitis, MS, Spina cord injury, and stroke are associated with what type of lesion?

A

Lower Motor Neuron lesion

64
Q

Hypertonia involves what two things?

A

Spasticity and rigidity

65
Q

Define Spasticity

A
  • Typical Lesion Site: Typically corticoreticulospinal (pyramidal) tract.
  • Resistance is pronounced in one direction.
  • Resistance is velocity and force dependent.
  • Accompanied by clonus, hyperreflexia, clasp-knife phenomenon
66
Q

Define Rigidity

A
  • Typical Lesion site: Basal ganglia, midbrain
  • Increase in muscle tone with resistance to passive movement
  • No weakness
  • Independent of velocity
  • Resistance is uniform in both directions.
  • Accompanied by tremors (cogwheel)

Seen in Parkinson’s disease

67
Q

What is Clasp Knife Spasticity?

A

Spastic limb initially resists movement and then suddenly releases the tension.

Dysregulated Golgi tendon organ reflex

Loss of regulatory UMNs

68
Q

What is Clonus?

A

Pathological oscillation of muscle reflex

69
Q

How do you test the integrity of the corticospinal tract?

A

The Babinski Reflex (upper motor neuron)

Initiated by nociceptive (pain) fibers

70
Q

What is a Positive Babinski response

A

Abnormal in adults contraction of toe extensors (usually inhibits by Corticospinal tract)

71
Q

What does the Cerebellum control?

A

Cerebellar receives all proprioceptive information from body

Indirectly regulates sensitivity and coordination of spinal reflexes

72
Q

Hypotonia and depressed tendon reflexes are signs for?

A

Cerebellar Lesion

73
Q

T/F Positive Bibinski Response in normal in a 1 year old

A

True.

It is normal in newborns all the way to age 2.

Corticospinal pathways are not fully myelinated in newborns and infants

74
Q

What resembles a lower motor neuron lesion because the signs it presents are similar to lower motor neuron lesion?

A

Cerebellar lesion

75
Q

What are some conditions resulting in PNS/LMN (lower motor neuron) signs?

A

Myasthenia Gravis

Amyotrophic lateral sclerosis (Lou Gehrig disease) Guillain-Barré syndrome

Muscular Dystrophy

Bulbar Palsy

76
Q

Assesment of L1, L3, and L4 is done by?

A

Patellar REflex (knee jerk)

77
Q

Assesment of S1 is done by?

A

Achilles reflex (ankle jerk)

78
Q

Bicep reflex assesses which part of the spinal cord?

A

C5 and C6

79
Q

Assesment of C7 and C8 involves what type of test?

A

Triceps Reflex

80
Q

Brachioradialis reflex test assess which part of the spinal cord?

A

C5 and C6

81
Q

Rating of Deep tendon reflex

A
82
Q

Deep tendon reflexes rated 1+, 2+, or 3+ are normal unless

A
  • Asymmetry (left vs. right)
  • Dramatic difference between the arms and the legs.
83
Q

Reflexes rated as 0 or 4+are usually considered?

A

Abnormal

S&F 1 (25 decks)

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