Theme 5: Neurophysiology Flashcards
what fibre types are associated with muscle spindle and Golgi tendon organs?
muscle spindle- type Ia/ A-alpha and type II/ A-beta
Golgi tendon organs- type Ib/A-alpha
which fibre type is associated with the withdrawal reflex?
type III/ A-delta
which fibre type is responsible for pain and temperature sensation?
type IV/ C
where is the emotional response to pain produced?
the cingulate gyrus in the limbic system
what is the purpose of the crossed extension reflex?
occurs at the same time as the withdrawal reflex to compensate and enhance postural support
what function do the type Ia and type II fibres have in the stretch reflex?
type Ia- respond to the velocity of stretch (phasic response)
type II- respond to the degree of stretch (sustained response, tonic firing)
what is the purpose of gamma motor neurones in the muscle spindle?
they maintain contraction of the muscle spindle when the stretch reflex occurs snd the muscle contracts so that the muscle spindle remains the same length despite the new length of the muscle. this allows tonic firing to be maintained so it is still sensitive to stretch
what is recurrent inhibition?
Alpha motor neurones feedback onto themselves via the renshaw cell (inhibitory interneurone) causing the alpha motor neurone to be inhibited. this prevents the neurone from firing for too long/too often and causing too much contraction
what is reciprocal inhibition?
one set of muscles is excited whilst another set is inhibited
what is pre-synaptic inhibition?
upper motor neurones act on pre-synaptic neurones via interneurones to inhibit the pathway. occurs in reflex pathways- UMN lesion causes hyperreflexia
what is the function of the corticospinal pathway?
voluntary control of musculature
what is the function of the corticobulbar pathway?
innervate the motor nuclei of cranial nerves
what is the function of the rubrospinal pathway?
excite flexor activity and inhibit extensor activity
what is the function of the reticulospinal pathway?
control axial muscles (muscles of the tail trunk and head)
what is the function of the vestibulospinal pathway?
assist in postural adjustments and positioning of the head in response to acceleration
what is the function of the tectospinal pathway?
control neck movements in response to visual stimuli
what are signs of an upper motor neurone lesion?
weakness
spasticity- velocity dependent resistance
hypertonia
hyperrelfexia
what are the signs of a lower motor neurone lesion?
weakness hypotonia flaccid paralysis hyporeflexia fasciculation's atrophy
what causes decorticate posturing?
damage to motor pathways above the level of the red nucleus- midbrain, internal capsule, cerebral hemisphere
what causes decerebrate posturing?
damage at or below the red nucleus- brainstem, cerebellum, pons
what is decorticate posturing?
involuntary flexion of upper extremities caused by excess red nucleus influence
arms are flexed and bent inwards, hands clenched, legs extended and feet turned inward
what is decerebrate posturing?
involuntary extension of upper extremities head is arched back arms extended and internally rotated wrists extended patient is rigid with teeth clenched
what is a vegetative state?
wakefulness but absent awareness
what is a minimally conscious state?
wakefulness with minimal awareness
