Control of Movement Flashcards
function of alpha motoneurons
activate main (extrafusal) muscle fibers to contract
muscle spindle afferent function
signal muscle length changes
extrafusal
outside the muscle spindle
intrafusal
inside the muscle spindle
golgi tendon organ afferents function
signal muscle force
gamma motoneuron function
increases the sensitivity of muscle spindles to length changes of the parent muscle
how do gamma motoneurons increase spindle sensitivity
by activating intrafusal fibers which stretch spindles and causes sensory afferents to fire more rapidly
what is the gamma loop responsible for
maintaining muscle tension during movement
theory of alpha-gamma coactivation
intrafusal contraction compensates for spindle shortening
- this keeps spindle afferent firing rate constant
reality of alpha-gamma coactivation
spindle afferent firing does decrease, because gamma motoneurons are not enough compensation
2 spinal cord reflexes
- stretch reflex
2. flexor withdrawal reflex
stretch reflex stimulus
muscle stretch
what 2 things simultaneously occur during the stretch reflex
- spindle-afferent-mediated monosynaptic excitation of agonist motoneurons and disynaptic inhibition of antagonist motoneurons
- tendon-organ-mediated disynaptic inhibition of agonist motoneurons and disynaptic excitation of antagonist motoneurons
what opposes change in muscle length
excitation of agonist MN’s and disynaptic inhibition of antagonist MN’s
what opposes change in force
inhibition of agonist MN’s and disynaptic excitation of antagonist MN’s
purpose of stretch reflex
to resists imposed force in a spring-like manner
what causes the flexor withdrawal reflex
stepping on something painful
flexor withdrawal reflex
noxious stimulation (pain) causes flexion of ipsilateral leg and extension of contralateral leg
another name for the primary motor cortex, and why?
sensorimotor cortex, because of the importance of sensory signals
what controls complex movements of extremities
major motor areas of cerebral cortex
somatotopic map
somatotopic representation similar to the topographic map on the somatosensory cortex
where is the somatotopic map located
in the primary motor cortex
how was the somatotopic map established
with electrical stimulation with a probe during brain operations
which regions of the body occupy the largest areas of the somatotopic map
face and hands
how can neurons in the primary motor cortex be activated
with transcranial magnetic stimulation (TMS)
how is TMS stimulating the primary motor cortex useful
useful in spinal cord operations to check for conduction block
what is another name for the pyramidal tract (PT)
the corticospinal tract (CST)
corticospinal tract
axons from neurons in sensorimotor cortex make the tract
- these neurons make monosynaptic connections with spinal alpha motoneurons
what results from CST lesions
spastic hemiplegia
spastic hemiplegia symptoms (5)
- weakness or paralysis of extremities
- exaggerated stretch reflexes
- spasms
- speech deficits
- attentional deficits
paresis
weakness
hypertonus
exaggerated stretch reflex
dysarthria
motor speech disorder
aphasia
disturbance in language comprehension
apraxia
inability to execute learned purposeful movements
hemi-neglect
inability to attend to one side of space
upper motoneuron lesions
another name for CST lesions
Broca’s area function
motor aspects of speech
lesion in Broca’s area
motor aphasia (slurring speech)
Wernicke’s area functions (2)
- comprehension of language
2. association of visual, auditory, and tactile input with words
lesions in Wernicke’s area
sensory aphasia and dyslexia
what would happen if you handed a person with sensory aphasia a pen
they might think it’s a spoon, but proceed to write their name with it
what does sensory aphasia tell us about brain pathways
sensory to motor transformation is separate from sensory to cognitive transformation
2 inputs to cerebellum
- sensory input from spinal cord
2. motor commands from cerebral cortex
4 functional divisions of the cerebellum
- vermis
- intermediate zone
- lateral zone
- flocculondular lobe
vermis
posture, neck and axial musculature
intermediate zone
locomotion
lateral zone
coordinating complex
- skilled movements of arms, hands, and fingers
flocculonodular lobe
balance
what are the basal ganglia
large, deep cerebral nuclei
2 functions of basal ganglia
- involved in initiating movement
2. involved in suppressing activity of muscles that would resist movement
2 possible dysfunctions of basal ganglia
- poverty of movement
2. involuntary movement
poverty of movement
bradykinesia, rigidity, tremor
example of poverty of movement
Parkinson’s disease
involuntary movement
dyskinesia
examples of involuntary movement
chorea, Tourette’s, hemiballismus
bradykinesia
slow movement
4 functions of the brainstem
- control of respiratory and cardiovascular musculature
- control of sleep/wake/arousal
- control of transmission in sensory, motor, reflex, and pain pathways
- initiation of locomotion
which part of the brainstem is responsible for arousal
reticular activating system
which part of the brainstem is responsible for initiation of locomotion
midbrain locomotor area
what inhibits the RAS
sedatives, barbiturates, and other anaesthetics
what activates RAS neurons
visual and other sensory inputs
what results from small lesions in RAS
coma
how do anesthetics work
by inactivating neurons in RAS
what requires input from neurons in RAS? what type of neurons?
pre-optic area of hypothalamus requires input from noradrenergic neurons in RAS
