Spinal reflexes Flashcards
what is a reflex
reflex is coordinated involuntary movement - initiated by the brain
reflexes can sometimes involve
supraspinal components
what is supra spinal components
something above part of the spine - can be the brain or ligaments or fascia
why do reflexes occur
in response to danger
what is the stretch reflex
a monosynaptic reflex which lengthens the skeletal muscle
how is the stretch reflex evoked
tendon tap
what does a stretch reflex rely on
mechanical response and sensory afferent feedback
how do u abolish the stretch reflex
cutting dorsal root
muscle spindles are receptors that detect changes in the
muscle length during contraction
the stretch in stretch reflex evokes an increase in
spindle firing rate
the sensory signal in the stretch reflex is sent to where
dorsal horn by type 1a afferent neurons
a motor neurons are activated in the spinal ventral horn leading to
muscle contraction of the agonist and synergist muscles
stretch reflex - what muscles are inhibited
antagonist
muscle spindles consist of what
bundles of thin fibres contained within capsule
9spindles) situated in parallel with main intrafusal muscle fibres but
generates no force
muscle spindles wrapped around by what
sensory axons - 1a and 2
muscle spindles have y motor neurons cause active contraction of
spindles
muscle spindle detects - 2
length and stretch of muscle - position
and rate of change - velocity
intrafusal fibres are innervated by what
y motor neurons
what are the 2 types of intrafusal fibres
- nuclear bag fibres - 1a afferents- annulospiral endings
-nuclear chain fibres - both 1a and 2 afferents
what is bigger intrafusal fibres
nc. bag fibres - bc of nuclei bunched together
both types of intrafusal fibres respond to
stretch
stretch reflex-
faster the response means
the fewer neurons and synapses
u can use latency in a reflex to calculate what
how many neurons involved
the earliest onset is what for stretch reflex
<1ms
stretch reflex - the antagonist muscles are inhibited at
slightly longer latencies
reciprocal inhibition
antagonist muscles which may interfere with …
desired movement are suppressed by contraction of the agonist muscle
reciprocal inhibition
co contraction is what
when we want to contract antagonist and agonist at the same time
why is reciprocal inhibition useful
to help stop co contraction and modulates inputs from the brain
what is klippel feil syndrome
a rare condition in which premotor neurons from cortex bifurcate to innervate both sides of the body
moving one hand ipsilateral leads to
mirror movements in other hand
hyperreflexia / spasticity
descending input from the brain normally acts to regulate reflex gain in spinal cord
what can abolish the input for hyperrflexia
sci, stroke and other conditions
what is Intrathecal baclofen
treatment for spasticity
what is the proceedure is intrathecal baclofen -
catheter is placed in spinal fluid and a pump in the abdominal which pumps baclofen - allowing dorsal horn inhibition
what does the treatment for specificity result in
decreased ,muscle spasms and tone
what is the purpose of the stretch reflex
it is a negative feedback loop
preventing major disturbances to regulation of controlled variable - muscle length
what does the stretch reflex maintain
accuracy of movement (in face of small deviations)
voluntary commands come from which part of the brain
motor cortex
the stretch reflex helps correct what
small deviations from desired trajectories caused by unpredictable things
an unpredictable increase in load is a disturbance detected by
muscle spindles and will compensate for deviation from desired muscle length
what is the Hoffman reflex
the finger reflex, which identifies possible problems within the corticospinal tract
what does the hoffman reflex do
evokes a muscle contraction from type 1a sensory nerves
what can hoffman reflex be shown on
EMG
sensory type 1a afferent fibres are activated at a what threshold than motor fibres
lower
how can the hoffman reflex be altered
conditioning a stimulus
what is flexion withdrawal reflex
A reflex which contracts a muscle in response to danger or pain
the flexion withdrawal reflex stimulates what
ipsilateral flexor muscles whilst extensors are inhibited
what type of fibres in withdrawal reflex
thinly myelinated type 3
withdrawal reflex provides extension in
contralateral limb to compensate for unloading in the ipsilateral limb
the reflex withdrawal reflex persists after spinal cord what
transection
reflex adaptability -
golgi tendon input inhibits what
ongoing muscle activity via negative feedback
Golgi tendons are sensitive to tension and force and active what type of afferent neurons
type 1b
what is locomotion
movement or ability to move from one place to another
during lococmotion - golgi tendons input increases extension muscles a activity to produce what
positive feedback
gait phase dependant golgi feedback - GTO reflex contributes to transition between what 2 phases
stance and swing
what type of feedback is during the gait phase of stance
positive
what type of feedback is used for swing gait phase
negative
what is pulmonary stretch receptors
receptors which monitor the mechanoreceptors in the lungs
what is the pulmonary stretch reflex
The reflex which monitors coughing and lung inflation - mediated by the receptors
rapidly adapting receptors lie between what 2 cells
airway epitheial cells and trigger the cough reflex
slowly adapting receptors lie in between what 2 things
airway smooth muscle cells and the trigger the lung inflation reflex
what fibres trigger the cough reflex
RARS activting Ao and C fibres
cough reflex is what
a mechanism for airway defense’s against aspiration
irritatnt receptors are a type of what
nociceptor
mechanical stimuli for cough reflex involves what
bronchoconstriction -dust - food - chemicals - activating type 3 fibres
first step for affernt information travelling to medulla and then to
respiratory central pattern generators in brain stem
effectors for cough reflex is what
inspiratory, expiratory and upper airway muscles
mechanics of breathing
what are the 3 phases for a cough
inspiratory, compression and expiratory
inspiration breathing
what are the 2 steps for cough - inspiratory
deep inspiration with the glottis open
diaphragm external intercostals
what is the compression phase for a cough
expiratory muscle contract - against closed glottis - making pressure
trunk and upper airway compress
what is the phase for expiratory phase for a cough
glottis opens causing a rapid ejection
stretch relfex is caused by what
msucle spindles
