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Human Systems and Anatomy > Reflexes > Flashcards

Reflexes Flashcards

1
Q

what are the three types of movement

A

involuntary actions
semi automatic actions
voluntary actions

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2
Q

what is involved in involuntary actions

A

these are reflexes that are centred in the spinal cord and brain stem that have no conscious element

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3
Q

what is the reflex action centred on

A

spinal cord for the spinal nerves and cranial nerves are in the brainstem

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4
Q

what type of pathway is involved in reflexes

A

monosynaptic circuit

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5
Q

what is the speed of reflexes

A

they are rapid, and have short latency

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6
Q

what is latency

A

the time between the stimulus and the response

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7
Q

what is the common final pathway of a reflex

A

motor neurons

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8
Q

where are somatic motor neuron bodies found

A

the spinal cord

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9
Q

where are cranial nerve cell bodies found

A

brainstem

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10
Q

what activates motor neurons in a reflex

A

various brain regions and various peripheral receptors

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11
Q

what is stimulated in the knee jerk response

A

group 1a muscle fibres that link the dorsal and ventral roots at spinal level

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12
Q

what initiates the reflex response

A

activation of mechanoreceptors that are muscle spindles in the belly of the muscle that respond to the stretch of the muscle itself

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13
Q

what is the muscle afferent in reflexes

A

1a

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14
Q

are mechanoreceptors in the muscle always active

A

yes - there is always a steady rate of activity from mechanoreceptors to give an indication of the tone of the muscle itself. when they are stretched further than what is normal, there is generation of action potential

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15
Q

what spinal afferents alwyas active when muscle is contracting

A

no

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16
Q

describe the knee jerk reflex

A
  • mechanical stimulus applied to the patella tendon in the knee
  • tendon pulls on the quadriceps to activate muscle spindles
  • generation of action potential that is conducted along the a alpha axon
  • into the ventral horn of the spinal cord
  • synaptic transmission between the central terminals and the motor neurons they are innervating
  • action potential conducted along motor axon as it exist via the ventral roots
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17
Q

why are reflex actions so short

A

the 1a alpha axon is large and has strongly myelination.
only involves one synapse

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18
Q

list the components of the stretch reflex pathway in order

A
  • stimulus
  • receptor activation
  • stimulus transduction
  • action potential conduction along sensory axon
  • synaptic transmission
  • motor neuron recruitment, action potential conduction along motor axon
  • synaptic transmission for effector recruitment
  • response
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19
Q

what is the muscle efferent axon in reflexes

A

a alpha, same as the sensory afferent

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20
Q

describe the reflex pathway for the jaw jerk reflex

A
  • hammer tap to chin
  • stretches spindles of jaw elevator muscles
  • action potentials conducted along group 1a muscle afferents to brainstem
  • monosynaptic activation of motor neurons of jaw elevatory muscles
  • axon potentials travel along the motor axon
  • jaw elevatory muscles contract
  • jaw jerk upward, mouth closes
21
Q

what are the jaw elevator muscles

A

masseter
temporalis
medial pterygoid

22
Q

describe the reflex pathway of the ankle jerk reflex

A
  • hammer tip to achilles tendon
  • stretches spindles within gastrocnemius
  • action potentials are conducted along group 1a muscle afferents to the spinal cord
  • monosynaptic activation of motor neurons of the gastrocnemius muscle
  • axon potentials travel along the motor axon
  • gastrocnemius muscle contracts
  • foot extends
23
Q

what is plantar extension

A

the extension of the foot

24
Q

what is the measure of electrical activity within skeletal muscle

A

bidirection of the electromyogram

25
Q

what are the key features on the myogram to look for when looking at reflexes

A

latency and amplitude of response

26
Q

why is the latency for the jaw jerk reflex less than that for the ankle jerk reflex

A

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

27
Q

what is the amplitude of a reflex

A

the measure of electrical activity in skeletal muscle

28
Q

why is the amplitude for the jaw jerk reflex smaller than in the ankle jerk

A

the masseter is a small muscle and there are less muscle fibrils that have to be recruited.

29
Q

what is the muscle activated in the ankle jerk reflex

A

the gastrocnemius

30
Q

which neurons are involved in maintenance of posture and muscle tone

A

proprioceceptor endings
group 1a muscle afferents
homonymous motor neurons

31
Q

which receptors are involved in cutaneous reflexes

A

mechanoreceptor endings and nociceptor endings

32
Q

what are the protection mechanisms of somatic reflexes

A
  • escape mechanism
  • prevention of muscle overloading
  • prevention of inadvertent ingestion of a foreign body
  • digestive aid
33
Q

what kind of pathway is the flexion withdrawal reflex

A

disynaptic

34
Q

describe the flexion withdrawal reflex

A
  • interneuron is recruited
  • interneuron axon splits and sends a branch to the higher centres for the perception of pain to reinforce that input via the spinothalamic pathway
  • input projects directly to the motor neurons to initiate the withdrawal reflex
35
Q

what are golgi tendon organs

A

a population of nerve endings in the tendon that prevent muscle overloading, that give rise to group 1b muscle afferents

36
Q

how are golgi tendon organs activated

A

stretching and contraction of the muscle itself, they act to prevent overwork of the muscle by recruiting 1b afferents to inhibit the motor neurons that innervate the muscle group

37
Q

what is the inverse stretch reflex

A

this is when the golgi tendon organ inhibit the contraction of muscle to prevent it overloading

38
Q

what is another name for the inverse stretch reflex

A

the inverse myotactic reflex

39
Q

describe how muscle overloading occurs in the rest of the body

A

there are no golgi tendons in the jaw muscles
bit force is instead controlled through the loading of mechanoreceptors in the periodontal ligament
the afferents inhibit jaw elevator muscle motor neurons

40
Q

why is it important to consider periodontal ligament when anaesthetising a patient

A

anaesthetising the sensory afferents in the periodontal ligament can increase the bite force of the patient which can damage their jaw as they are unaware of how hard they are biting down

41
Q

what activates the pharyngeal refledx

A

mechanoreceptor afferents from the posterior part of the tongue and soft palate
there is stimulation of sensory fibres from the glossopharyngeal nerve and trigeminal nerve which terminate in the brain stem

42
Q

where do the IX and V sensory afferents terminate

A

the brain stem is the SpVn

43
Q

what happens once IX and V terminate in the SpVn

A

interneurons will project from here to go to the nucleus ambiguus to the vagus nucleus
the vagus afferents will terminate and innervate muscles

44
Q

what contracts in the gag reflex

A

there is mass contraction of both sides of the posterior oral and pharygneal musculature

45
Q

what does SpVn mean

A

the spinal trigeminal nucleus in the brain stem

46
Q

why is there bilateral contraction in the gag reflex even if stimulus is on one side

A

to increase the chance of expelling the foreign particle

47
Q

what is the stimulus of the salivary reflex

A
  • gustatory stimuli
  • visual
  • olfactory
  • chewing forces
48
Q

what is the outcome of the salivary reflex

A

increased salivary flow

Human Systems and Anatomy (57 decks)

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