Unit 2 Exam Flashcards
Which cortiocospinal tract fibers form the ventral corticospinal tract?
Ipsilateral
Which corticospinal tracts form the lateral corticospinal tracts?
Contralateral
What percentage of corticospinal tract fibers originate from areas behind the central sulcus, including the primary somatosensory cortex?
40%
What percentage of fibers from the corticospinal tract originate in front of the central sulcus?
60%
Greater than 1/2 of the primary motor cortex is devoted to control of which areas?
Hands and speech
A stroke that lesions the posterior limb of the internal capsule would be associated with?
Loss of voluntary movement
A high brain stem lesion gives what clinical finding?
Spacticity
A mid brain lesion gives what clinical finding?
Rigidity
A low brain stem lesion gives what clinical finding?
Flaccidity
What brainstem area receives stimulation from the vestibular nuclei and transmits excitatory signals to stimulate the axial trunk and extensor muscles that support the body against gravity?
Pontine nuclei
What brainstem area receives stimulation from the vestibular nuclei and transmits inhibitory signals to allow muscles tones to be increased or decreased depending on need?
Medullary reticular nuclei
If descending cortical signals are blocked what is the expected result?
Increased extensor tone
Flexion reflexes suppressed; stretch reflexes are exaggerated
What is the function of a dynamic signal from pyramidal cells to alpha motor neurons?
Initiation of skeletal muscle contraction
What is the function of a static signal from pyramidal cells to alpha motor neurons?
Maintain muscle contraction after initiation has occurred
Explain neck rotation to the right as far as extensor and flexors are concerned.
Flexors are facilitated on the right, and extensor inhibited on the right
With clockwise rotation (to the right), what would you expect to happen in the VIII cranial nerve on the left side?
Decrease in firing rate
-stimulation of semicircular canals on side rotation is into (clockwise stimulates canals on that side)
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 would be observed?
Lateral nystagmus with the slow component clockwise
Nystagmus occurs when the semicircular canals are being stimulated while the head is not in motion
When supine, head tilt is best detected by which of the following?
Saccule
-saccule deals with the vertical plane (important when one is LYING DOWN)
When upright, head tilt is best detected by which mechanisms?
Utricle
-utricle deals with the horizontal plane (important when one is UPRIGHT)
Signals from the neck propioception typically ______ signals from the vestibular apparatus as the head and neck are rotated and have similar effects on limb flexion and extension.
Oppose
In sway, contraction of muscles to maintain balance occurs in?
Distal to proximal sequence
What would happen to a reptitive simple stretch reflex, if when the muscle contracts it destabilizes posture?
It would be inhibited
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 execution of learned patterns of movement?
Putamen
Ones sense of upright is a combination of what?
Visual and vestibular information
Effects of Striatum on substancia negra
Inhibitory (GABA)
Effects of substancia nigra on the striatum?
Stimulatory (DOPAMINE)
Which area acts as a comparator ?
Inferior olivary nucleus
- Comparing intention with performance
- effects the cerebellum via climbing fibers
- alter cerebellar activity -> alter decending corticalspinal traffic
Purkinje fibers
- Major inhibitory in the cerebellar cortex
- inhibit deep cerebellar nuclei
Complex AP
- climbing fiber input from inferior olicary nucleus
- 1:1 ratio of climbing fibers to purkinje fibers
Simple AP
- mossy fibers input via granule cells
- 1 mossy fibers excites 100-1000 of purkinje fibers
- found everywhere but inferior olivary nucleus
Lesions to the globus pallidus?
Spontaneous and continuous writhing movements
Lesion to subthalamus?
Hemiballismus = sudden violent flailing movements of the limbs
Lesion to the substantia nigra?
Parkinson’s = rigidity, acinesia, resting tremors
Lesion to the putamen?
Chorea = flicking movements in hands, face
Cerebellar lesions are demonstrated on which side?
Ipsilateral
-(dysmetria, ataxia, past pointing, dysdiadochokinesia, dysarthria, international tremor, nystagmus)
Longest pathway name
Corticopontocerebellarubrothalamocorticospinal
Impulses from motor cortex ->pontine -> purkinje cells -> dentate nucleus -> red N of midbrain ->thalamus ->motor cortex
Superior peduncle
Ventral spinocerebellar
contains most efferent projections
Middle peduncle
Pontocerebellar
Inferior peduncle
Dorsal spinocerebellar
Yohimbine
Increases Norepinephrine release
NE can regulate its own release release (negative feedback)
SNS Preganglionic release?
Release Acetylcholine
SNS Postganglionic release?
Release NE
- NE binds to alpha or beta receptors which effect G protein
- NE has equal affinity for Alpha and Beta receptors
- E has a greater affinity for Beta
PNS pregnaglionic release?
ACH
PNS Postganglionic release?
ACH
-ACH binds to muscarinic receptor, which effect G protein
Denervation supersensitivity
Sharp increase of sensitivity of post-synaptic membranes to a chemical transmitter after DENERVATION. It is a compensatory change
SNS stimulation effects?
Vascular smooth muscle = constrict
Ducts = dilation
Blood vessels = constriction
Inhibitory motor neurons form the myenteric plexus release what neurotransmitter?
Dynorphin & vaso active intestinal peptide
Excitatory motor neurons form the myenteric plexus release what neurotransmitter?
ACH & Substance P
What facilitates the release of NE?
ACH, E, Ang II, corticotropin, PACAP
Inhibit release of NE?
GABA, adenosine, NPY, somatostatin, opioids, PGE, NO, dopamine
Amount of pressure applied to a normal vertebrae eliciting a minimal response?
7Kg.
Less than half of the primary motor cortex is devoted to?
Trunk and equilibrium
How much pressure can be applied to an abnormal vertebrae eliciting a minimal response?
1-3 Kg
