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reflexes Flashcards

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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

Study These Flashcards
A

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

20
Q

Motor unit

Study These Flashcards
A

alpha motor nuerone + all innervated muscle fibers

21
Q

Alpha motor neurone

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A

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

22
Q

Polysynaptic reflex

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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

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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 )

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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
Function of golgi tendon reflex
Prevents overstretching of tendon | Controls muscle tendon
26
How does the golgi tendon reflex(disynaptic (2 synapses )) prevent overstretching of tendon
Muscle contraction stretches tendon Sensory neurones ( 1b afferent) activate interneurones Inhibit a neurones innervating muscle of origin Opposite to myotatic reflex
27
How does the golgi tendon reflex control muscle tension
Inhibits muscle contraction Protects muscle from causing damage to tendons Fine control of tension for grasping fragile objects
28
where do alpha motor neurones receive input from ?
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
What do gamma motor neurons do in relation to alpha
ADJUST SENSITIVITY OF MUSCLE SPINDLES
30
Weak or absent reflex
lower motor neurone lesion
31
Exaggerated reflex
upper motor neurone lesion
32
Overriding descending control of reflexes
Conditioning the reflex - jendrassick manouvere | EXAGGERATE reflex
33
2 theories of how we override descending control of reflex ( lower limb)
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
Flexion withdrawal reflex
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
Crossed extensor reflex
``` 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
Jaw reflexes
Jaw jerk reflexes | Jaw unloading reflex
37
jaw jerk reflexes
Downward tap on jaw stretches Activation of trigemeninal nerve Contraction of masseter muscle
38
Jaw unloading reflex
Initiated by Sudden unloading of jaw Activation of trigeminal nerve Inhibition and activation of jaw muscles Stops jaw movement and protects teeth
39
Visual reflexes
Pupillary light reflex Accomodation reflex Corneal ( blink ) reflex
40
Pupillary light reflex
``` Pupil constriction(both eyes) in response to light Activation of optic nerve (CNII)- constriction via oculomotor nerve (CNIII) Protective = adaption to light levvels ```
41
Accomodation reflex
Adduction of eyes initated by change in focus (CNII) Activation of optic nerve - change in lens shape (CNIII) Protective = prevents blurred vision
42
Corneal blink reflex
Closure of both eyes initated by foreign object touching one eye Activation of trigeminal nerve ( CNV) - innervates eyelid by facial nerve ( CNVII)
43
Throat reflexes
Gag | Swallowing
44
Gag reflex
Object touching posterior wall of pharynx Activation of glossopharyngeal nerve ( CNIX) Contraction of sot palate and pharynx Protects airway
45
swallowing reflex
Initiated by food bolus Causes closure of glottis, elevation of larynx and transient cessation of respiration Protects airway
46
Postural reflex
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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