Chapter 55 Flashcards
True or False: excitation of M1 always causes 1 specific muscle to fire.
False. Excitation of a single motor cortex neuron usually excites a specific movement rather than one specific muscle. This means that it excites a “pattern” of separate muscles, each with its own direction and strength of muscle movement
Stimulation of the primary motor cortex (M1) causes whatresponse?
Point stimulation in these areas, on rare occasion, causes contraction of a single muscle. Most often however, stimulation contracts a group of muscles instead.
Excitation of the premotor area causes hat type of response?
Nerve signals generated in the premotor area cause much more complex ‘patterns’ of movement than the discrete patterns generated in the primary motor cortex.
What is the role of the supplementary motor Cx?
This area functions in concert with the premotor area to provide body-wide attitudinal movements, fixation movements of the different segments of the body, positional movements of the head and eyes
What is Broca’s area for?
lesion would cause inability to speak whole words rather than simple words like “yes” and “no”
A lesion in the voluntary eye movement field would cause what deficits?
lesion would prevent a person from voluntarily moving the eyes toward different objects, causing the person to lock involuntarily onto specific objects. Also controls blinking
What are betz cells?
very large myelinated cells that originate in the pyramid cells of the primary motor cortex. Send short collaterals back to the cortex to inhibit adjacent regions of the cortex in order to sharpen the boundaries of the excitatory signal
What s the role of the caudate and putamen?
control body postural muscle contractions. From here, pathways extend into the brainstem and spinal cord. Will be discussed in more detail in the next chapter.
Pontine nuclei give rise to which fibers?
gives rise to the pontocerebellar fibers (bacon!), which carry signals into the cerebellar hemispheres
What is the role of the corticurubrospinal tract?
The corticorubrospinal pathway serves as an accessory route for transmission of relatively discrete signals from the motor cortex to the spinal cord.
What is the role of the dynamic neurons for the vertical columns?
excessively excited for a short period at the beginning of a contraction, causing the initial rapid development of force
What is the role of the somatosensory system for motor control?
When nerve signals from the motor cortex causes a muscle to contract, somatosensory signals return all the way from the activated region of the body to the neurons in the motor cortex that initiating the action. Most of these somatosensory signals arise in muscle spindles, tendon organs, or the tactile receptors of the skin. These somatic signals often cause positive feedback enhancement of the muscle contraction.
What are the Sx of motor cortical lesions?
The affected area (the contralateral side of the body) will experience hypotonia and muscle spasm due to a lack of inhibitory signals
What is the role of the pontine reticular system?
excite the axial muscles of the body, which support the body against gravity. These include the muscles of the vertebral column and the extensor muscles of the limbs.
What is the role of the medullary reticular system?
inhibit signals to the same antigravity anterior motor neurons. This tract receives strong input collaterals from the corticospinal tract, the rubrospinal tract, and other motor pathways. These tracts normally activate the medullary reticular inhibitory system to counterbalance the excitatory signals from the pontine reticular system, so that under normal conditions, the body muscles are not abnormally tense.
