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Human Systems > Reflex and voluntary movements > Flashcards

Reflex and voluntary movements Flashcards

1
Q

What are reflexes

A

No conscious element; involuntary
* Stereotyped response
* Rapid: short latency (delay)
* Centred on:
-Brainstem (cranial nerves)
-Spinal cord (spinal nerves)
* Monosynaptic circuit

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2
Q

What are the 3 movements we can initiate

A

Involuntary actions - reflexes
Voluntary actions
Semi-automatic actions

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3
Q

Where are motor neurons found

A

spinal chord (somatic - ventral horn)
brainstem (cranial nerves)

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4
Q

What activates motor neurons

A

Influences from cortical regions
Peripheral receptors

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5
Q

What is the stretch reflex pathway (knee jerk)

A

Sensory neuron stimulated group 1a muscle afferent fibre (hammer)

Projectes into spinal chord into ventral horn where it activates and recruites motor neuron

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6
Q

What are muscle spindles composed of

A

Intrafusal fibres wrapped in sensory endings

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7
Q

What type of axons are associated with group 1a muscle afferents

A

A alpha axons

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8
Q

What happens when a muscle is streched

A

intrafusal fibres stretched too which distorts sensory endings within muscle spindles generating AP and when activated fire a high frequency train of action potentials which is conducted along muscle fibre

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9
Q

What happens when muscle is relaxed

A

No generation of AP

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10
Q

What are the steps in the knee jerk reaction

A

Tapping patella tendon causes tendon to pull on quad muscle which activates the muscle spindles, mechanoreceptors then transduce the mechanical signal into an electrical signal and the AP conducts along afferent fibre to ventral horn where it synapses with motor axon and then leads to inervation of muscle and causing a release of ACH which acts upon muscle fibres causing contraction - EXTENSION OF LOWER LEGS

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11
Q

What is the summary of the stretch reflex pathway

A
  • Stimulus
  • Receptor activation (mechanoreceptor)
  • Stimulus transduction
    AP conduction along sensory axon (Aa)
  • Synaptic transmission
  • Motor neuron recruitment
    AP conduction along motor axon (Aa)
  • Synaptic transmission
    (Effector recruitment )
  • Response
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12
Q

What reflexes can we use to test integrity of central nervous system

A

Biceps jerk reflex
Tricep jerk reflex
ankle jerk reflex
rectus abdominis reflex

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13
Q

How does the jaw jerk reflex work

A
  • Hammer tap to chin
  • Stretches spindles of jaw elevator muscles
    (masseter, temporalis, medial pterygoid)
  • Action potentials conducted along
    group 1a muscle afferents to brainstem (Aa)
  • Monosynaptic activation of motor neurons
    of jaw elevator muscles
  • Axon potentials travel along motor axon (Aa)
  • Jaw elevator muscles contract
  • Jaw jerks upwards, mouth closes
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14
Q

What are the steps to the ankle jerk reflex

A
  • Hammer tap to Achilles’ tendon
  • Stretches spindles within gastrocnemius
  • Action potentials conducted along group
    1a muscle afferents to spinal cord (Aa)
  • Monosynaptic activation of motor neurons
    of gastrocnemius muscle
  • Axon potentials travel along motor axon (Aa)
  • Gastrocnemius muscle contracts
  • Foot extends (plantar extension)
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15
Q

What is the lag on an EMG between stimulus and response

A

Latency of response

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16
Q

What are the two features to look for on an EMG

A

Latency of response
Amplitude of response

17
Q

What are the axons in the afferent and efferent in stretch reflex pathways

A

A alpha - no difference in speed of conduction

18
Q

Why is the latency of the jaw jerk reflex less than that for the ankle jerk reflex

A

Because the neural pathway for the jaw jerk reflex is shorter than that for the ankle jerk

19
Q

Which jerk reaction (jaw/ankle) has a greater amplitude of response

A

Ankle - greater recruitment of muscle fibrils in gratrocnemius than masseter

20
Q

What are the components of tendon-jerk reflexes

A

Proprioceceptor endings
Group Ia muscle afferents
Homonymous motor neurons

21
Q

What are the purpose of tendon jerk reflexes

A

Maintenance of posture and muscle tone

22
Q

What type of reflexes use mechanoreceptor and nociceptor endings

A

Cutaneous reflexes

23
Q

What protective mechanisms can reflexes provide

A

Escape mechanism
Prevention of muscle overloading
Prevention of inadvertent ingestion of a foreign body
Digestive aid

24
Q

What is the flexion withdrawal reflex a response to

A

Noxious stimulus

25
Q

Why is the latency of response of the flexion withdrawal relex slower

A

It involves multiple synaptic nodes due to the interneuron splitting to send signals to both the brain and the muscle

26
Q

what sensory endings are found within the tendon

A

Golgi tendon organs - group 1b afferents

27
Q

What activates the golgi tendon organ endings

A

stretching and contraction of the muscle

28
Q

What axons are involved in the inverse myotactuc reflex

A

1b afferents

29
Q

What is the purpose of the inverse myotactic (stretch) reflex

A

Prevents overloading of the muscle - stops overstretching/contraction

30
Q

Are there golgi tendon organs in jaw muscles

A

no

31
Q

How is bite force controlled

A

By increasing loading of the periodontal ligament (base around roots) activating it’s afferent neurons
Afferents inhibit jaw elevator muscle motor neurons

32
Q

What may cause a patient’s bite force to increase

A

Anaesthesie of the molars (afferents cant give the feedback from periodontal ligament) in turn increasing force

33
Q

How does the gag reflex result

A
  • Activation: mechanoreceptor afferent from
    the posterior part of the tongue / soft palate
  • Stimulation of sensory fibres from the
    glossopharyngeal nerve (IX) and/or
    trigeminal (V)
  • Afferents terminate in the brainstem (SpVn)
  • Interneurons project from SpVn to
    nucleus ambiguus (X motor nucleus)
  • X afferents terminate innervate muscles
34
Q

What is the gag reflex called

A

Pharyngeal reflex

35
Q

What muscles contract in the gag reflex

A

Posterior oral and pharyngeal musculature

36
Q

What reflexes involve glands as their effector organs

A

Salivary reflexes

37
Q

What stimulate activate salivary reflexes

A

Gustatory (taste)
Visual/olfactory
Chewing

Human Systems (34 decks)

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