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CBL neuro > reflexes > Flashcards

reflexes Flashcards

1
Q

Descending motor control

A

VOLUNTARY
Brain
Spinal cord /brainstem
Muscle

Planning

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2
Q

REFLEX coordination

A

INVOLUNTARY
Spinal cord/ brainstem - muscle and vice versa
Reactionary, unplanned

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3
Q

What is a reflex

A

Simple, sterotyped response that couples sensory input and motor output

Relies on functional connections between alpha motor neurones and muscel receptors

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4
Q

Examples of reflexes

A

Myotatic ( stretch) reflex e.g. jaw jerk reflex, knee jerk reflex

Flexor /withdrawal to remove limb from harm

Crossed extensor reflex to maintain postural balance

Cranial nerve reflexes e.g. gag

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5
Q

2 types of neurones in reflex

A

Peripheral

Lower motor

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6
Q

Peripheral neurones in the reflex

A

From receptors in periphery to spinal cord/brainstem

Innervate alpha motor neurones and gamma motor nuerones

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7
Q

Lower motor neruones in hte reflex

A

Brainstem or spinal cord to muscle

Simulate or inhibit muscle contraction via NMJ

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8
Q

Reflex arc

A

Sensory input detected by sensory receptors
Synapse onto a motor neurones in the spinal cord ventral horn
Innervate muscle to cause movement

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9
Q

Divergence

A

Amplifies sensory input and coordinates muscle contractions = movement

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10
Q

CONVERGENCE

A

Messages all come together onto one neurone

On interneurones increases flexibility of response

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11
Q

Inhibition

A

Reciprocal inhibition; interneurones and renshaw cells

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12
Q

Potentiation

A

Mild stretching of the muscle

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13
Q

Sensory system

A

Detects change to enables system to be reactive

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14
Q

Detecting stretch

A

Muscle spindles PROPRIOCEPTORS

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15
Q

What are proprioceptors made from

A

La and II sensory afferents
Monitor the extent of stretch and the rate of change of length
Synapse in spinal cord onto a motor neurons
Intrafusal muscle fibers in parallel surrounded by extrafusal

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16
Q

Mytotatic reflex

A

ONE synapse
Monosynaptic
Stretch reflex

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17
Q

Importance of myotatic reflex

A

Prevents overstretching of muscle
Tested by tapping tendon
Stretches attached muscle
Controls muscle length, maintains muscle tone and prevents muscular damage
Subsequent contraction of same muscle restores muscle length

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18
Q

Reflex pathway of muscle stretch

A 
Weight added
Muscle stretch 
AP firing in afferent neurone 
AP firing in efferent neurone alpha motor neurone  
Muscle shortens
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19
Q

Lower motor neurones

Innervate muscle

A

Alpha motor neurones
Gamma motor neurones
Cell bodies located in ventral horn
Axons exit in ventral root

20
Q

Motor unit

A

alpha motor nuerone + all innervated muscle fibers

21
Q

Alpha motor neurone

A

Large multipolar neurones
Terminate at neuromuscular junctions ( end plate)
Innervate skeletal muscle fibers ( extrafusal muscle fibers )

22
Q

Polysynaptic reflex

A

2 or more synapses
Stimulus is muscle stretch
inhibitory interneurons syanpse onto another alpha motor nuerone

Anatgonisitic muscle relaxes
recipricol innervation
Enables other muscle to contract

23
Q

Gamma motor neurones

A

Smaller neurones
Innervates specialised striated muscle ( intrafusal muscle fibers)
Adjust sensitivity of muscle spindles and increase range of function

24
Q

Detecting stretch via golgi tendon organs ( another proprioceptor )

A

Sensory neurones in tendon
Ib afferent sensory neurones associated with coallgen fibers within hte tendon
Located within tendons each end of a muscle
Monitor and maintain muscle tension
Inhibit further muscle contraction
Funnel like capsule containing collagen fiber bundle and nerve fibers
Arranged in series with extrafusal muscle fibers

25
Q

Function of golgi tendon reflex

A

Prevents overstretching of tendon

Controls muscle tendon

26
Q

How does the golgi tendon reflex(disynaptic (2 synapses )) prevent overstretching of tendon

A

Muscle contraction stretches tendon
Sensory neurones ( 1b afferent) activate interneurones
Inhibit a neurones innervating muscle of origin
Opposite to myotatic reflex

27
Q

How does the golgi tendon reflex control muscle tension

A

Inhibits muscle contraction
Protects muscle from causing damage to tendons
Fine control of tension for grasping fragile objects

28
Q

where do alpha motor neurones receive input from ?

A

Sensory input from muscles ( reflex)

Descending input from upper motor neurones ( initating and controlling voluntary movement)

Interneurons (excitability of inhibitory) form neuronal circuits that produce coordinated movements

29
Q

What do gamma motor neurons do in relation to alpha

A

ADJUST SENSITIVITY OF MUSCLE SPINDLES

30
Q

Weak or absent reflex

A

lower motor neurone lesion

31
Q

Exaggerated reflex

A

upper motor neurone lesion

32
Q

Overriding descending control of reflexes

A

Conditioning the reflex - jendrassick manouvere

EXAGGERATE reflex

33
Q

2 theories of how we override descending control of reflex ( lower limb)

A

alpha neurons receive from upper

Voluntary upper motor neurone innervation overflows to increase excitability of the lower motor neuron pool of the lower extremities , increasing drive to gamma motor neurons

Removes descending inhibition of the reflex arc - modulates inter neuron excitability, removes inhibitory action of stretch reflex

34
Q

Flexion withdrawal reflex

A

Removing something from harmful stimuli
Cutaneous receptors in the skin
Activation of primary afferent neurones - synapse with spinal cord interneurons- activate flexor motor neurones

Disynaptic reflex - inhibitory interneurones excite flexor motor neurons and inhibit extensor motor neurones

35
Q

Crossed extensor reflex

A 
Enables balance during flexion withdrawal reflex 
Simulataneous extension ( strengthening contraction) of contralateral limb

Interneurons from flexion withdrawal activate CONTRALATERAL extensor motor neonres and inhibit contralateral flexor motor neurones, extensor muscles contract adn leg strengthens to support weight

36
Q

Jaw reflexes

A

Jaw jerk reflexes

Jaw unloading reflex

37
Q

jaw jerk reflexes

A

Downward tap on jaw stretches
Activation of trigemeninal nerve
Contraction of masseter muscle

38
Q

Jaw unloading reflex

A

Initiated by Sudden unloading of jaw
Activation of trigeminal nerve
Inhibition and activation of jaw muscles
Stops jaw movement and protects teeth

39
Q

Visual reflexes

A

Pupillary light reflex
Accomodation reflex
Corneal ( blink ) reflex

40
Q

Pupillary light reflex

A 
Pupil constriction(both eyes) in response to light
Activation of optic nerve (CNII)- constriction via oculomotor nerve (CNIII)
Protective = adaption to light levvels
41
Q

Accomodation reflex

A

Adduction of eyes initated by change in focus (CNII)
Activation of optic nerve - change in lens shape (CNIII)
Protective = prevents blurred vision

42
Q

Corneal blink reflex

A

Closure of both eyes initated by foreign object touching one eye
Activation of trigeminal nerve ( CNV) - innervates eyelid by facial nerve ( CNVII)

43
Q

Throat reflexes

A

Gag

Swallowing

44
Q

Gag reflex

A

Object touching posterior wall of pharynx
Activation of glossopharyngeal nerve ( CNIX)
Contraction of sot palate and pharynx
Protects airway

45
Q

swallowing reflex

A

Initiated by food bolus
Causes closure of glottis, elevation of larynx and transient cessation of respiration
Protects airway

46
Q

Postural reflex

A

Tectospinal and vestibulospinal reflex
Initiated by visual or audio stimuli
Coordinates head and eye movement, maintains posture
Protective - responds to changes in surrounding environments

CBL neuro (9 decks)

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