spinal reflexes Flashcards
name the three types of movement classifications
- simple reflexes
- rhythmic motor patterns
- voluntary
what are examples of simple reflex types (generalised)
involuntary
rapid
stereotyped
what are examples of rhythmic motor patterns
combines voluntary + reflexive acts - walking, running, chewing
once initiated they are reflexive
what are examples of voluntary actions
complex- reading, writing
learned + purposeful
what three horns make up the grey matter of the spinal cord
dorsal horn
lateral horn
ventral horn
is the dorsal horn or ventral horn on the anterior side
ventral horn
does the dorsal root have a ganglion?
yes
which is responsible for flexion - the dorsal nerves or ventral nerves
dorsal
which is responsible for extension - the dorsal nerves or ventral nerves
ventral
what are Renshaw cells
interneurons involved in recurrent or feedback inhibition
-suppress weakly firing motor neurons
-dampens strongly firing ones to produce economical movement
what is the muscle spindle involved in (what is its role)
it identifies stretch
doesnt allow muscle to overstretch
what happens if a muscle stretches too far
gets damaged
how is the muscle spindle involved in proprioception
muscle spindle understands length of muscle and sends it to CNS so you know where limbs are at all times
what do afferent axons do
identify length and rate of stretch
what do gamma motor neurons do
modify set point of muscle spindle - change length not force!
sends it to spinal cord
what type of reflex is a myotatic (knee jerk) reflex
monosynaptic stretch reflex
what is a myotatic reflex
knee jerk reflex
what is the name of the afferent neuron involved in myotatic reflex (reflex)
la afferent
describe the pathway of a myotatic reflex (knee jerk) - there are 4 steps
- tap of patellar tendon stretches quadriceps muscle
- stimulates dynamic nuclear bag receptors of muscle spindle
- increases rate of firing of la afferent leads to contraction of quadriceps muscle
- la fibers also stimulate inhibitory interneurons which inhibits antagonistic (flexor) muscles of knee joint
the knee jerk reflex is lost if ______ are damaged
lower lumbar dorsal roots of spinal cord are damaged
what direction do reflexes travel through the spinal cord
in through the ganglion into the dorsal root, through into the ventral root
what are the two phases in the gait cycle?
right stance phase
right swing phase
what happens during the stance phase
foot touches the ground, flexion of knee and ankle
finishes with extension of all joints ready for forward movement
what happens during the swing phase
flexion of hip, knee + ankle
then knee and ankle extend
what is the definition of a central pattern generator
use lots of reflexes together to run in a repetitive motion
how are central pattern generators modulated
via proprioceptive input
is the central pattern generator capable of autonomous signals
yes
where is the central pattern generator initated
in the mesencephalic locomotor region
what does the output leave the central pattern generator through
reticular nuclei
reticulospinal tracts
as a muscle extends, what does the muscle spindle inhibit
flexor muscles
in the central pattern generator describe the pathway how flexor muscles are activated, starting from la afferent nerve
la afferent brings information from dorsal column to central pattern generator
activates the flexor MN pool
then the la inhibitory interneuron inhibits the extensor MN pool (crosses the ventral spinocerebellar tract)
.. also renshaw cells provide negative feedback, inhibit the flexor MN pool and extensor MN pool
then impulse travels to flexor muscles via dorsal column
in the central pattern generator describe the pathway how extensor muscles are activated, starting from la afferent nerve
la afferent brings information from dorsal column to central pattern generator
activates the extensor MN pool
then the la inhibitory interneuron inhibits the flexor MN pool (crosses the ventral spinocerebellar tract)
.. also renshaw cells provide negative feedback, inhibit the extensor MN pool and flexor MN pool
then impulse travels to extensor muscles via dorsal column
does the primary motor cortex (M1) supply muscles from the same side, opposite side, or both sides of the body
opposite side of the body
what are the names of the 4 premotor cortical areas
- supplementary motor area (SMA)
- cingulate gyrus
- ventral premotor cortex
- dorsal premotor cortex
does the supplementary motor area (one of the 4 premotor cortical areas) supply muscles from one or both sides of the body
both
where does the basal ganglia receive excitatory input from
cerebral cortex
where does the basal ganglia outputs go to
thalamus
spinal cord
cerebral cortex
name the 5 parts of the basal ganglia
caudate
globus pallidus
subthalamic nucleus
substantia nigra
putamen
what is the hyperdirect pathway - there are 4 steps
initial planned info from motor cortex → subthalamic nuclei → globus pallidus → inhibits thalamus to allow initiation of movement to occur
describe the direct pathway
the striatum inhibits 1) the INTERNAL segment of globus pallidus 2) pars reticulata of substantia nigra
substantia nigra inhibits thalamus
thalamus stimulates motor cortex
!!! OVERALL input is EXCITATORY
describe the indirect pathway
striatum inhibits the EXTERNAL segment of globus pallidus + subthalamic nucleus
subthalamic nucleus projects excitatory input to internal segment of globus pallidus, pars reticulata of substantia nigra -> the thalamus is inhibited
thalamus gives excitatory input to motor cortex
!!! OVERALL input is INHIBITORY
what does the cerebellum do - what is its role
adjusts motor responses by comparing the intended output with sensory signals and to update movement commands if they deviate from the intended trajectory
where does the cerebrocerebellum get its info from and what does it control
receives input from cerebral cortex, movement planning and initiation of movement
where does the spinocerebellum get its info from and what does it control
receives input from the spinal cord about limb position, touch and pressure
what does the vestibulocerebellum control
balance and eye movements
what are the 3 peduncles names
superior
middle
inferior
—- peduncles
the superior peduncle connects the ________ to the ________
the superior peduncle connects the CEREBELLUM to the MIDBRAIN
what do the cerebellar peduncles all contain
efferent and afferent axons between cerebellum and CNS
the middle peduncle connects the ________ to the ________
the middle peduncle connects the CEREBELLUM to the PONS
the inferior peduncle connects the ________ to the ________
the inferior peduncle connects the CEREBELLUM to the MEDULLA
the majority of afferent signals use which two peduncles for passage
middle and inferior peduncles
the majority of efferent signals use which peduncles for passage
superior peduncle
what is an afferent neuron
bring sensory info from the outside world to the brain
what is an efferent neuron
carries signals from the brain to the PNS to initiate an action
where do all descending motor pathways originate (except the corticospinal tract)
brain stem
what are the 3 types of nuclei for postural control and locomotion
- vestibular nuclei
- red nucleus
- reticular nuclei
what are the names of the 5 brain areas that give rise to descending tracts
cerebral cortex
brainstem + medulla
— reticular formation
— vestibular nuclei
— red nucleus
— tectum
what descending tract does the cerebral cortex give rise to
the corticospinal tract
in the brainstem + medulla, what descending tracts do:
— reticular formation
— vestibular nuclei
— red nucleus
— tectum
give rise to. (there is 1 for each bullet point)
- reticular formation
reticulospinal - vestibular nuclei
vestibulospinal - red nucleus
rubrospinal - tectum
tectospinal
muscle motor pathway lesion what is it involved in and what change occurs if it goes wrong
- normal reflexes
- weakness/wasting
eg - myositis, muscular dystrophy
neuromuscular junction (motor pathway lesion) what is it involved in and what change occurs if it goes wrong
- normal reflexes
- normal muscle bulk
- fatigable weakness
eg - myasthenia gravis
how are upper motor neurons most likely to be damaged
cerebral vascular accident, spinal cord trauma
how are lower motor neurons most likely to be damaged
motor neurone disease, neuropathy
cerebellum (motor pathway lesion) what is it involved in and what change occurs if it goes wrong
normal reflexes, strength,
- slight decrease in tone
-incoordination, multiple sclerosis
basal ganglia (motor pathway lesion) what is it involved in and what change occurs if it goes wrong
movement changes
- parkinson’s, huntington’s
