Final Flashcards
Name the 6 parts of the CNS that are involved in complex movements
Cerebral Cortex Basal Ganglia Cerebellum Thalamus Brain stem Spinal Cord
What kind of arrangement does the primary cortex have
Somatotopic
What sections of the primary motor cortex is considered premotor
anterior and lateral portions
Where does the premotor area of the primary motor cortex project to?
Primary order motor cortex and basal ganglia
Does the primary motor cortex stimulate movements or contract single muscles?
Stimulate movements
What part of the brain does the supplemental motor area lie in?
Mainly in longitudinal fissure
What are the 4 functions of the supplemental motor area
attitudinal movements
fixation movements
positional movements of head and eyes
background for finer motor control of arms/hands
What are the 3 areas the corticospinal tract originates
Primary motor cortex (30%)
Premotor and supplemental areas (30%)
Somatic sensory areas (40%)
What spinal tract makes up the pyramids and medulla
cotricospinal tract
Where do most corticospinal tract fibers run? Do they all run in same area
They cross midline and form the lateral corticospinal tract
No; some fibers stay ipsilateral and form ventral corticospinal tract
True or false the corticospinal tract lies between the caudate and putamen
True
If all the spinal tracts were cut and the spinal cord was completely separated from brain what would happen?
Flaccidity or “floppy paralysis”
What would happen if spinal cord was cut at mid collicular level? (Decerebrate preparation)
Extensors would be tonically hyperactive “decerebrate rigidity”
What would happen if there was destruction of the cerebral cortex (Decorticate preparation)
Different type of rigidity - “Decorticate spasticity” - tonic excitation from upper area of the reticular formation no longer under inhibitory cortical influence.
What percentage of intracerebral hemorrhages result in decorticate spasticity?
60%
What is decerebration? What does it result in?
Experimental procedure; transection of midbrain at intercollicular level
Loss of sensation; and motor control is profoundly altered
In decerebration does the brain stem control stay intact? Are cortical descending pathways interrupted?
Yes it stays intact
yes they are interrupted
In decerebration what happens to flexion reflexes? What about stretch reflexes?
Flexion reflexes are suppressed
Stretch reflexes are exaggerated
If a patient showed signs of decerebration what would their prognosis be?
Poor
What is “spinal shock”
Initial reaction to cord transection
All cord functions including spinal reflexes are depressed (lack of tonic excitation)
At the onset of clockwise rotation (to the right), what would you expect happens in the VIII cranial nerve on the left side?
Decrease in firing rate
After 20 clockwise (to the right) rotations with the eyes closed on a revolving stool, the subject is abruptly stopped, and the eyes are opened.
What is observed?
Lateral nystagmus with the slow component clockwise
When supine, head tilt is best detected by what?
Saccule
When standing, head tilt is best detected by what?
Utricle
True or false, signals from neck proprioceptors typically augment signals from the vestibular apparatus as the head and neck are rotated and have similar effects on limb flexion and extension. What would make this statement the opposite of the answer?
False
Signals from neck proprioceptors would oppose not augment (assist)
In backward sway, what sequence of contraction of muscles to maintain balance would occur?
Tibialis, then quadriceps, then abdominals
In forward sway, what sequence of contraction of muscles to maintain balance would occur?
Gastrocnemius, then hamstrings, then paraspinals
What would happen to a repetitive simple stretch reflex, if when the muscle contracts it destabilizes posture?
it would be inhibited
What would happen to a repetitive simple stretch reflex, if when the muscle contracts it stabilizes posture?
It would be facilitated
Of the four pathways: striatospinal spinocerebellar nigralstriatal rubrospinal
Which pathway doesn’t exist?
Striatospinal
Which basal ganglia circuit plays a major role in cognitive control of motor activity?
Caudate circuit
Which basal ganglia circuit plays a major role in subconscious control of motor activity?
Putamen circuit
True or false; one’s sense of upright is generally a combination of cues that include both visual and vestibular information
True
What effect does the striatum have on the substantia nigra?
inhibitory GABA projections
What effect does the substantia nigra have on the striatum
inhibitory dopamine projections
Which area acts as a comparator, comparing intention with actual motor performance, and can effect the cerebellum via climbing fiber input?
Inferior olivary nucleus
Strong stimulation of one climbing fiber would elicit what response
complex action potential from a few purkinje cells
Strong stimulation of one mossy fiber would elicit what response?
simple action potential from many purkinje cells
Spontaneous and continuous writhing movements (athetosis) is associated with a lesion in what area?
globus pallidus
Hemibalistic movements are associated with a lesion in what area?
Subthalamus
A patient presents with a resting tremor, lead pipe rigidity in the extremities. Voluntary movements are accurate but slow. Where is a lesion likely to be found?
Basal ganglia
A patient presents with a intention tremor, where is a lesion likely to be found?
Cerebellum
A patient presents with ataxia, upon examination they are unable to perform rapid alternating movements, and unable to check movements (rebound) of the right arm. Where is a lesion likely to be found?
Right side of cerebellum (cerebellum always ipsilateral)
Is the pathway correct?
Corticopontocerebellorubrothalamocorticospinal
yes
Remember: Correct Pathway Certainly Rough, This Could Suck
CorticoPontoCerebelloRubroThalamoCorticoSpinal
Is the pathway correct?
Corticorubrocerebellopontothalamocorticospinal
No
The ventral spinocerebellar tract gains access to the cerebellum primarily via which peduncle?
Superior
The dorsal spinocerebellar tract gains access to the cerebellum primarily via which peduncle?
Inferior
If you administer yohimbine (an alpha 2 receptor blocker) and then stimulate the sympathetic nervous system, what effect do you expect on the amount of norepinephrine released?
Increased
True or false decreased rate of blood coagulation is associated with SNS (sympathetic nervous system)
False, increased rate of blood coagulation is
Denervation supersensitivity is likely associated with what?
Up regulation of receptors by the target tissue
What is the effect of the SNS stimulation on most vascular smooth muscle
constrict
Inhibitory motor neurons from the myenteric plexus release what neurotransmitters?
Dynorphin
Vasoactive intestinal peptide
A patient presents with a slight ptosis of the left eye, but the right pupil appears dilated compared to the left, and they report that the let side of their face never sweats. What’s your opinion doctor?
Interruption of the left sympathetic supply to the face
On EMG (electromyography), what is the clinical significance of an decreased number of motor units activated during a voluntary muslce contraction?
Possible neuropathy (“n” is less)
On EMG (electromyography), what is the clinical significance of an increased number of motor units activated during a voluntary muslce contraction?
Possible myopathy (“m” is more)
In primary cultures of postganglonic SNS neurons, what inhibits the release of norepinephrine?
GABA
If there is a facilitated spinal segment at T6. What would you expect when 3 kg of pressure is applied to the spinous process at T10 which is not in a state of segmental facilitation
Exaggerated response in adjacent paraspinal muscles at only T6
How much pressure can be applied to a normal vertebrae eliciting only a minimal response in the adjacent paraspinal muscles/
7 kg
True or false the CNS coordinates host defense activity
true
In a spinal cord transection how long does it take for spinal cord neurons to regain excitability. Will the reflexes be normal?
days to weeks
some will be hyperactive
What happens in a spinal mass reflex?
Spinal cord becoming excessively active
flexor spasm and evacuation of bladder and colon
What happens to blood pressure during spinal shock? What about skeletal muscle? Sacral reflexes?
Blood pressure falls dramatically
All skeletal muscle reflexes in cord are blocked
Sacral reflexes for bladder and colon evacuation control are suppressed
What tract transmits excitatory signals in the pontine reticular nuclei?
pontine (medial) reticulospinal tract
What does the pontine reticular nuclei stimulate?
axial trunk and extensor muscles that support body against gravity
Where does the pontine reticular nuclei receive stimulation from?
vestibular nuclei and deep nuclei of cerebellum
True or false, the pontine reticular nuclei has a low degree of natural excitability
False, it has a high degree
What tract transmits inhibitory signals in the medullary nuclei? And what muscles does it communicate with?
Medullary (lateral) reticulospinal tract
and it inhibits the same anti-gravity muscles that the pontine reticular nuclei stimulates
Where does the medullary nuclei receive it’s input?
cortex, red nucleus, and other motor pathways
What are 6 roles of the brain stem in controlling motor function?
Controls: Respiration cardiovascular system GI function stereotyped movements equilibrium eye movement
What are 3 very important ipsilateral descending tracts from brain to spinal cord?
Ventral corticospinal tract
Reticulospinal tract
Vestibulospinal tract
What tract are the pontine (medial) reticular formation and medullary (lateral) reticular formation a part of
Reticulospinal tracts
Where does the vestibulospinal tract get it’s origin
lateral vestibular nucleus to extensors
Name 3 very important contralateral descending tracts from brain to spinal cord
Lateral corticospinal tract
Rubrospinal-innervate mainly flexors
Trecto-spinal-innervate cervical musculature only
What are the two lateral motor descending spinal tracts?
Lateral corticospinal and Rubrospinal
What does the rubrospinal tract mainly control?
distal muscles
What are the 4 medial motor descending spinal tracts, what do they mainly control?
Reticulospinal, vestibulospinal, tectospinal and ventral corticospinal
mainly axial and girdle muscles
Which corticospinal tract fibers form the lateral corticospinal tract
contralateral fibers
What percentage of corticospinal tract fibers originate from areas behind the central sulcus, including the primary somatosensory cortex
40%
Greater than 1/2 of the primary motor cortex is devoted to control of what?
hands and speech (homunculus)