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Neuro Anatomy > Reflexes > Flashcards

Reflexes Flashcards

1
Q

What are the types of muscles ?

A
  • striated involuntary (cardiac muscles)
  • striated voluntary (skeletal muscles)
  • non-striated involuntary (smooth muscles)
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2
Q

What are the 5 properties of skeletal muscles ?

A
  • extensibility
  • elasticity
  • contractility
  • excitability
  • conductivity
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3
Q

What are the four functions of skeletal muscles ?

A
  • generate movement
  • maintain posture
  • generate heat
  • stabilize joints
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4
Q

What composes the «thick filaments»

A

Each thick filament consists of myosin molecules whose head protrude at opposite end of filament

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5
Q

What composes the «thin filaments»

A

A thin filament consists of 2 strands of actin subunit twisted into a helix plus two types of regulatory proteins : troponin and tropomyosin

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6
Q

Describe the physiology of skeletal muscles fibers

A
  • AP arrives at neuromuscular junction
  • Ach liberation and binding on sarcolemma
  • ion permeability change
  • depolarization
  • ignition of AP in the sarcolemma

Exitation-contraction coupling phase

  • AP travels along the whole sarcolemma
  • AP travels along the T-tubules
  • sarcoplasmic reticulum liberates Ca 2+
  • Ca 2+ binds to troponin
  • myosin binding sites on actin are exposed
  • myosin heads bind to actin
  • contraction
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7
Q

What is a motor unit

A

It is the functional unit of the neuromuscular system that allows the production of force and movement.
It is composed of the alpha motor neuron in the ventral horn of the spinal cord and the muscle fibers it innervates

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8
Q

What are the four types of motor units ?

A
  • slow motor unit : for sustained muscular contraction
  • large motor unit : easily fatigable
  • fast fatigable motor unit : for brief exertion that requires large force
  • intermediate : fast fatigable resistant motor unit : not as fast as FF but develops 2X the force of slow motor unit
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9
Q

What are the different muscles fibers ?

A
  • slow twitch (type I) : slow oxidative fibers - contracts slowly but resistant to fatigue
  • fast twitch (type II) : fast glycolytic fibers - generates fast powerful contractions but quickly fatigable
  • intermediate : fast oxidative glycolytic fiber - will adapt to body demand

The ratio of each is genetically determined, different in everyone and different in every muscle

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10
Q

What is the order of recruitment of MNs ?

A

From the weakest to the strongest during contraction. It is the size recruitement principle or Henneman principle.

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11
Q

What are the 3 phases of muscle twitch

A

Lag/latent : excitation contraction
Contraction phase : cross bridges activity
Relaxation phase : Ca 2+ re-enter the SR

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12
Q

What are the 3 muscular metabolic pathways

A
  • direct phosphorylation
  • anaerobic
  • aerobic
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13
Q

What is the difference in eccentric and concentric contraction regarding the Henneman’s principle ?

A
  • in concentric contraction MU1 is activated before MU2
  • in eccentric contraction MU2 is activated before MU1
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14
Q

What is muscle tone ?

A

Even when considered to be relaxed, skeletal muscles are slightly contracted due to spinal reflexes. There is no production of movement but it allows the stabilization of joints.

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15
Q

Define hypotonia

A

Absence of low level muscle contraction that leads to muscle tone
It causes a flaccid appearance with functional impairments and weak reflexes
Can result from damage to cerebellum or loss of innervation in skeletal muscles

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16
Q

Define hypertonia

A

Excessive muscle tone accompanied with hyperreflexia
Can result from a damage to UMN in the CNS

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17
Q

Classify the body receptors by the type of stimuli they detect

A
  • mechanoreceptors
  • thermoreceptors
  • nociceptors
  • chemoreceptors
  • photoreceptors
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18
Q

Classify the body receptors according to their location

A
  • exteroceptors
  • anteroceptors
  • proprioceptors
19
Q

Classify body sensory receptor according to their complexity

A
  • complex receptors
  • simple receptors
20
Q

What is a reflex ?

A

Reflexes are automatic responses to a stimulus, unconscious of changes inside or outside the body
Reflex are involuntary, poly synaptic or monosynaptic

21
Q

What are the 4 spinal reflexes

A
  • stretch reflex
  • golgi tendon reflex
  • flexor and crossed extensor reflex
  • superficial reflexes
22
Q

What is the information provided by muscle spindles ?

A

Muscle length

23
Q

What is the information provided by golgi tendon organ ?

A

Amount of tension in the muscle

24
Q

What is a muscle spindle ?

A

Intra fusal muscle fiber enclosed in connective tissue capsule
- type Ia fiber : center of the fiber- rate and degree of stretch - heavily myelinated : allows for fast conduction- very high sensitivity
- type II fiber : end of fiber - degree of stretch - myelinated - low dynamic sensitivity only sends signal about the actual length of the muscle

25
Q

What happens during alpha-phy coactivation ?

A

Both extrafusal and intrafusal muscle fibers contract.
Muscle spindle tension is maintained and it can still signal changes in length

26
Q

Briefly describe the stretch reflex

A
  • muscle spindles are activated by stretch
  • sensory afferent neuron sends impulse to spinal cord
  • sensory afferent neuron synapses to alpha motor neuron which excites extrafusal muscles fibers
  • sensory afferent neuron also synapses to interneuron that inhibits motor neuron of the antagonist muscle
  • efferent impulse of motor neuron cause muscle to contract in order to resist to stretch
  • efferent impulse of motor neuron to antagonist are inhibited
  • synergists is also contracted
27
Q

Give a specific example of stretch reflex

A

The patellar or knee jerk reflex

28
Q

Describes what happens during the patellar/ knee jerk reflex

A

1) tapping the patellar ligaments excites the quadriceps’ muscle spindles
2) sensory afferent impulse travels to the spinal cord were synapse occurs with the alpha motor neuron and interneuron
3) motor neuron activates the contraction of quadriceps to resist the stretch (this causes the knee to extend)
4) interneuron inhibits the motor neuron causing the hamstrings to relax and not resist the contraction of quadriceps (reciprocal inhibition)

29
Q

Define golgi tendon organ

A

Mechanoreceptor that informs about muscle tension via In afferent in the tendon
The efferent impulses to muscle with stretched tendon are damped causing it to relax thus reducing tension

30
Q

What are superficial reflexes ?

A

They are elicited by gentle cutaneous stimulation

31
Q

Give examples of 2 superficial reflexes

A
  • plantar reflex : Babinski sign
    Integrity of L4 to S2
    Integrity of cortico spinal tract
  • abdominal reflexes:
    Integrity of spinal cord
    Integrity of ventral rami from T8 to T12
    Integrity of cortico spinal tract
32
Q

Define pre-synaptic inhibition

A

Mechanism of inhibition that modulate the influx Ia before this one is transmitted to the alpha motor neuron
The decrease in the release of excitatory neuro transmitters is caused by GABA synapses which reduces the size of pre synaptic potentials

33
Q

Define recurrent inhibition

A

Recurrent inhibition of alpha motor neurons via motor axon collaterals and Renshaw cells

34
Q

What is the H reflex

A

Electrical analogue to stretch reflex : low intensity electrical stimulation of the afferent nerve observed in the EEG. Results in monosynaptic excitation of alpha motor neuron

35
Q

What is the difference between H reflex and T reflex ?

A

H reflex gives information about MNs excitability and synaptic transmission
While T reflex (myotatic reflex) gives information on the muscle spindle solicitation

36
Q

Describe the H-reflex modulation

A

Changes in the amplitude of H-reflex gives and indication on the efficacy of Ia afferent (muscle spindles) to discharge spinal MNs
Increase in H-reflex : increased efficacy between Ia afferent and MN
Decrease in H-reflex : decrease efficacy between Ia afferent and MN

37
Q

Which nerve is tested by the biceps stretch reflex

A

(Strike on the biceps tendon)
Musculocutaneous nerve
C5 (C6) level

38
Q

What nerve is tested by the triceps stretch reflex

A

(Percussion above the oleocranon on triceps tendon)
Radial nerve
C7 (C8)

39
Q

What nerve is tested by stylo-radial stretch reflex test ?

A

(Percussion over the radial styloïde)
Radial nerve
C6

40
Q

What nerve is tested during the cubito pronator stretch test ?

A

(Percussion over the ulnar styloïde)
Ulnar nerve
C8

41
Q

What nerve is tested in the finger flexor stretch reflex test

A

(Percussion over the distal interphalangeal joint)
Ulnar and median nerves
C8

42
Q

What nerve is tested during the quadriceps stretch reflex ?

A

(Percussion over the patellar tendon)
Femoral nerve
L4 (L3)

43
Q

Which nerve is tested during the Achilles’ tendon stretch reflex ?

A

(Percussion over the Achilles’ tendon)
Sciatic nerve (tibial branch)
S1 (S2)

Neuro Anatomy (15 decks)

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