Shared Flashcard Set

Details

Chapter 22
The Motor Cortical Areas & Descending Pathways
61
Other
Undergraduate 3
10/13/2015

Additional Other Flashcards

 


 

Cards

Term
Where are the cell bodies of the corticospinal tract located?
Definition
in the cerebral cortex
Term
pyramid
Definition
part of the medulla which is formed by the fibers of the corticospinal tract; gives the name to the pyramidal tract
Term
5 places where the cell bodies of the pyramidal tract are located
Definition
1. precentral gyrus (Brodmann's area 4)
2. area 6
3. SI
4. SII
5. posterior parietal cortex
Term
What are elicited by the primary motor area (precentral gyrus/Brodmann's area 4)?
Definition
muscle contractions
Term
How is the MI organized?
Definition
somatotopically
Term
giant cells of Betz
Definition
the cells with the largest cell bodies of the pyramidal tract
Term
Where do the fibers of the SI that go into the pyramidal tract come from within the SI?
Definition
area 3a (the part of the SI adjacent to area 4 & receives input from muscle spindles)
Term
Where to the pyramidal cells (cells of the pyramidal tract) lie?
Definition
the cortical fifth layer
Term
Where does the pyramidal tract pass downward?
Definition
through the internal capsule
Term
What is the difference in location of the pallidothalamic fibers of the internal capsule & the optic radiation of the internal capsule?
Definition
pallidothalamic fibers: lie anteriorly
optic radiation: pass through posteriorly on its way to the occipital lobe
Term
Can damage to the internal capsule produce sensory & other deficits in addition to pareses of the muscles of the opposite body half?
Definition
yes!
Term
What happens to the pyramidal tract fibers in the mesencephalon?
Definition
they distribute over the middle 2/3 of the crus & mix with other descending fibers
Term
What type of fibers are collected in the medullary pyramid?
Definition
corticospinal
Term
What happens to the corticospinal fibers after they cross the midline at the caudalmost level of the medulla?
Definition
they continue in the lateral funicle of the cord as the lateral corticospinal tract
Term
What mediates pyramidal-tract actions on the muscles of the distal extremities?
Definition
fibers that cross in the lower medulla
Term
What mostly influences axial muscles (muscles of the back, thorax, & abdomen)?
Definition
the small contingent of uncrosses fibers
Term
What is the path of the pyramidal tract fibers that control the muscles of the head?
Definition
they leave the corticospinal fibers in the brain stem to end in or close to the motor & sensory cranial nerve nuclei
Term
Are glutamatergic corticospinal neurons excitatory or inhibitory?
Definition
excitatory
Term
Do some of the pyramidal tract fibers coming from MI end monosynaptically on the motoneurons?
Definition
yes!
Term
Muscles from what part of the body generally have monosynaptic connections from the MI to the motoneurons?
Definition
motoneuron groups that control the distal muscles of the extremities (in particular, the intrinsic muscles of the hand)
Term
Are monosynaptic connections of particular importance for the movements that require the highest or lowest degree of voluntary control (least or most autonomic)?
Definition
highest degree of voluntary control (least autonomic) (ex. independent or fractioned finger movements)
Term
Does a single pyramidal tract axon have narrow or widespread ramifications?
Definition
widespread; it is enables to contact numerous motoneurons in different segments of the cord that supply several muscles
Term
Does contact with inhibitory interneurons increase or decrease the specificity of actions?
Definition
increase
Term
Do commands from the motor cortex elicit reciprocal inhibition in the cord?
Definition
yes!
Term
Do flexors of the thumb have a higher or lower threshold for activation than the extensors?
Definition
lower
Term
Can the pyramidal tract control the sensitivity of the muscle spindle?
Definition
yes!
Term
Can the strength of the long-latency strength reflex be increased or decreased?
Definition
yes! depending on what is appropriate during motor learning
Term
Why is it significant that the Renshaw cells are subject to supraspinal control?
Definition
the strength of the recurrent inhibition can be increased or decreased selectively in various motoneuronal groups
Term
Can the autogenic inhibition elicited by stimulation of tendon organs be reversed to excitation during voluntary contraction of the muscle?
Definition
yes!
Term
After a unilateral transection of the pyramid, can you move around apparently normally?
Definition
yes!
Term
After a unilateral transection of the pyramid, can you move your fingers independently of each other (fractioned movements)?
Definition
no!
Term
What is the most enduring symptom of damage of the motor cortex or the pyramidal tract?
Definition
difficulty with tasks that require precise, fractioned finger movements (writing, tying shoelaces, buttoning a shirt, & picking up small objects)
Term
Are there indirect pathways (synaptically interrupted in the brain stem) that transmit signals from the cortex to the motoneurons?
Definition
yes!
Term
Where do reticulospinal fibers come from?
Definition
the reticular formation of the pons & the medulla
Term
3 things reticulospinal tracts are important for
Definition
1. maintaining the upright position
2. orienting movements of the body toward external events
3. fairly crude, stereotyped voluntary movements of the extremities
Term
Where do fibers from the tectospinal tract come from?
Definition
the superior colliculus
Term
Where do most descending fibers of the tectospinal tract that cross the midline shortly below the superior colliculus terminate?
Definition
cervical levels of the cord
Term
3 places that the superior colliculus gets signals from that are important for control of conjugate eye movements
Definition
1. retina
2. visual cortex
3. frontal eye field
Term
What does electrical stimulation of the superior colliculus cause?
Definition
coordinated movements of the eyes & the head
Term
What reflex is influenced by the tectospinal tract?
Definition
optic reflexes (moving the head & eyes toward something in the visual field)
Term
Where do primary sensory fibers from the vestibular apparatus terminate?
Definition
in the vestibular nuclei (in the pons & medulla)
Term
Where does the lateral vestibulospinal tract come from? Where does it reach?
Definition
comes from: lateral vestibular nucleus
reaches: all levels of the spinal cord
Term
What funicle does the vestibulospinal tract lie in?
Definition
ventral funicle
Term
What is the medial vestibulospinal tract important for?
Definition
mediation of reflex head movements in response to vestibular stimuli
Term
What does the medial vestibulospinal tract use as a neurotransmitter?
Definition
glycine (inhibitory!)
Term
What neurotransmitter is used in raphespinal fibers? What about in coeruleospinal fibers?
Definition
raphespinal: serotonin
coeruleospinal: norepinephrine
Term
When do descending monoaminergic neurons show their lowest activity?
Definition
in deep sleep when all movements are suppressed
Term
How do monoaminergic pathways contribute to the effects of motivation on the performance of voluntary movements?
Definition
increased speed & force
Term
What does the "plateau potential" of monoamines do?
Definition
alters the excitability of the motoneurons
Term
Why are constant corrections necessary for maintaining an upright position?
Definition
it is liable (a small supporting area & a high center of gravity)
Term
4 types of receptors that provide information used for postural control
Definition
1. proprioceptors in the legs, the spine, & the neck
2. cutaneous receptors on the sole of the foot
3. vestibular receptors in the inner ear
4. photoreceptors in the retina
Term
Does the final motor command depend only on sensory signals?
Definition
no! also on the context in which they arise
Term
On what type of basis do postural reflexes operate?
Definition
feedback (they are responses to movements that have already started)
Term
Are commands about postural adjustments issued in advance in conjunction with voluntary movements?
Definition
yes!
Term
What do rhythm generators do for the legs?
Definition
they produce rhythmic, alternating leg movements in the absence of any command signals from higher levels
Term
What make up rhythm generators?
Definition
fairly complicated spinal networks of interneurons with excitatory & inhibitory interconnections which eventually control the activity of motoneurons
Term
pacemaker properties
Definition
neurons that fire brief trains of action potentials with silent periods between, without receiving a rhythmically alternating input
Term
Where is the mesencephalic locomotor region located?
Definition
just ventral to the inferior colliculus on the pontomesencephalic junction
Term
What causes the gait disturbance in Parkinson's disease?
Definition
dysfunction of connections between the basal ganglia & the PPN
Term
How long before a movement does the readiness potential start?
Definition
850 msec
Term
4 places of increased neuronal activity before a voluntary movement
Definition
1. cerebellum
2. basal ganglia
3. thalamus
4. limbic structures
Supporting users have an ad free experience!