Movement Flashcards

Question

Inhibition of Movements

Answer 1

* Antisaccade task: inhibits a saccade (a voluntary eye movement from one target to another) – e.g. stare at finger, wiggle the other (you want to make a saccade to moving finger, but in antisaccade task you have to inhibit that urge) – if you inhibit it well = parts of PFC + basal ganglia activity BEFORE seeing stimulus. * Performing this task well requires sustained activity in parts of the prefrontal cortex and basal ganglia before seeing the moving stimulus * Ability to perform this task matures through adolescence (children younger than 7 have lots of challenge with this task + ADHD impaired too, suggesting these individuals may have some disorder affecting PFC or basal ganglia structures from inhibiting unwanted action) + deteriorates at old age because PFC is highly vulnerable to damage.

Answer 2

* Active during in preparation of a movement and while watching someone perform the same movement * important for understanding, identifying, and imitating * social behaviors * Unknown whether they cause or result from social behavior * Develop properties by learning * Really exciting because they provide possible mechanism for social cognition (e.g. understanding/imitating others) – but unknown if they CAUSE social behavior, or is result of behavior. there is some evidence of mirror neurons being innate (newborns showing face reactions when seeing that face reaction (above what we would expect at chance level) Several types of evidence suggest that mirror neurons develop their properties by learning. In both monkey and human infants, many mirror neurons do not respond to observations of others’ movements until after the infants have practiced making those movements themselves

Answer 3

* Messages from the brain are sent to the medulla and spinal cord to control the muscles * Corticospinal tracts are paths from the cerebral cortex to the spinal cord - they are white matter tracts (myelinated axons)! * Both tracts contribute in some way to nearly all movements, but certain movements rely on one tract more than the other * Two such tracts: * Lateral corticospinal tract * Medial corticospinal tract

Answer 4

• A set of axons from the primary motor cortex, surrounding areas, and red nucleus go to the spinal cord • These areas are important for Control of movement in peripheral areas (hands and feet) • Red nucleus: a midbrain area with output mainly to the arm muscles Axons of the lateral tract extend directly from the motor cortex to their target neurons in the spinal cord. • Axons extend from one side of the brain to the opposite side of the spinal cord, and control opposite side of the body • Crossover happens at “pyramids of medulla” – also called “pyramidal tract” – cross over to affect movement on contralateral side. = handles LATERAL body

Answer 5

• A set of axons from many parts of the cortex (not just primary motor area and surrounding areas) • Incl. Reticular formation, midbrain tectum, and vestibular nucleus • Vestibular nucleus is a brain area that receives information from the vestibular system (used in balance, combining movement with balance) • The medial tract controls the muscles of the neck, shoulders, and trunk • Axons of the medial tract go to both sides of the spinal cord, not just to the contralateral side. (10% ipsilateral, 90 % contralateral) • moves muscles of midline / trunk of body. • Responsible for bilateral movements like walking, turning, bending, standing up, and sitting down =handles MEDIAL body

Answer 6

• Brainstem: organizes many adaptive movements • Maintaining posture, standing upright, coordinating movements of the limbs, swimming and walking, grooming the fur, and making nests controls lot of involuntary behaviors

Answer 7

* Voluntary movements difficult to make, whereas conscious behavior controlled by the cortex may remain intact * Caused by brainstem trauma * Often occurs during pregnancy or childbirth – can occur from lack of oxygen to brain, or trauma (trauma in brainstem) – conscious behaviors (by higher cortical functions) remain intact.

Answer 8

* Condition in which a patient is aware and awake but cannot move or communicate verbally because of complete paralysis of nearly all voluntary muscles except the eyes (sometimes FULL paralysis, ocular paralysis more rare though) * Due to brainstem damage (signals from cortex cannot get through to spinal cord)

Answer 9

* Spinal cord important for movement to occur - example: * Christopher Reeve’s spinal cord was severed near its upper end (C1–C2 level). (topmost portion) – from horseback riding accident. = became quadroplegic. * Left his brain intact and functioning; his remaining spinal cord intact and functioning, too; but his brain and spinal cord were no longer connected. * He was completely paralyzed and unable even to breathe without assistance * In humans and other animals with a severed spinal cord, spinal reflexes still function even though the spinal cord is cut off from communication with the brain. * Paralyzed limbs may display spontaneous movements or spasms. * The brain can no longer guide the timing of these automatic movements

Answer 10

Inability for voluntary movement in part of the body cause: Damage to motor neurons or their axons in the spinal cord

Answer 11

Loss of sensation and voluntary muscle control in the legs (Despite the lack of sensations from the genitals, stimulation of the genitals can produce orgasm.) cause: A cut through the spinal cord in the thoracic region or lower

Answer 12

Loss of sensation and voluntary muscle control in both arms and legs cause: Cut through the spinal cord in the cervical (neck) region (or cortical damage)

Answer 13

Loss of sensation and voluntary muscle control in the arm and leg of either the right or left side cause: Cut halfway through the spinal cord or damage to one hemisphere of the cerebral cortex

Answer 14

Impaired sensations and muscle control in the legs and pelvic region, including bowel and bladder control cause: Damage to the dorsal roots of the spinal cord from the late stage of syphilis

Answer 15

paralysis cause: A virus that damages motor neurons in the spinal cord

Answer 16

Gradual weakness and paralysis, starting with the arms and spreading to the legs cause: Unknown. Traced to genetic mutations in some cases, and to exposure to toxins in other cases

Answer 17

* A structure in the brain often associated with balance and coordination * More neurons in the cerebellum than in all other brain areas combined * Damage to the cerebellum causes trouble with rapid movements requiring aim/timing * Examples: clapping hands, speaking, writing * Allows for execution of a sequence * Responds to sensory information, especially violations of sensory info * Important for certain aspects of attention * “controls” timing – when cerebellar damage impairs movement, the reason may be that the damage impaired the perception of timed stimuli related to the movement. – damaged people = generally bad at timing tasks.

Answer 18

* Cortex sends motor instructions to the spinal cord. * Copy of same instructions sent to the cerebellum. * Sensory receptors code actual movement and report to the cerebellum. * Cerebellum has information about both versions of the movement—what you intended to do and what you actually did—and can calculate the error and tell the cortex how to correct the movement. * By comparing actual and intended movement, the error message is sent to the cortex and increases accuracy in subsequent movements. Otherwise, clumsiness! Cerebellum one of first things affected by alcohol  finger to nose test for drunk driving.

Answer 19

The cerebellum receives input from the spinal cord, from the sensory systems by way of the cranial nerve nuclei, and from the cerebral cortex. That information eventually reaches the cerebellar cortex, the surface of the cerebellum ●● The neurons are arranged in a precise geometrical pattern, with multiple repetitions of the same units. ●● The Purkinje (pur-KIN-jee) cells are flat (twodimensional) cells in sequential planes, parallel to one another. ●● The parallel fibers are axons parallel to one another and perpendicular to the planes of the Purkinje cells. ●● Action potentials in parallel fibers excite one Purkinje cell after another. Each Purkinje cell then transmits an inhibitory message to cells in the nuclei of the cerebellum (clusters of cell bodies in the interior of the cerebellum) and the vestibular nuclei in the brainstem, which in turn send information to themidbrain and the thalamus. ●● Depending on which and how many parallel fibers are active, they might stimulate only the first few Purkinje cells or a long series of them. Because the parallel fibers’ messages reach Purkinje cells one after another, the greater the number of excited Purkinje cells, the greater their collective duration of response

Answer 20

• The basal ganglia is a large group of large subcortical structures in the forebrain • Responsible for initiating an action not guided by a stimulus • Comprises the following structures – surrounds thalamus • Caudate nucleus • Putamen • Globus pallidus (caudate and putamen = striatum) • Function: modulate cortical motor system activities (inhibits thalamus)- used in wide range of functions (also e.g. emotion I think) The direct pathway from the striatum inhibits the globus pallidus, which inhibits part of the thalamus. By inhibiting an inhibitor, the net effect is excitation Probably the direct pathway enhances the selected movement, whereas the indirect pathway inhibits inappropriate competing movements. * Cerebral cortex --> caudate nucleus and putamen ---> globus pallidus * Globus pallidus --> thalamus --> motor areas and the prefrontal cortex * Basal ganglia select a movement to make by ceasing to inhibit it * Tourette Syndrome * Involuntary tics and complex movements * Abnormality of basal ganglia * The basal ganglia are particularly important for spontaneous, self-initiated behaviors. (compared to stimulus-initiated actions) * In general, self-initiated behaviors have a slower onset than those in response to a stimulus

Answer 21

* The learning of new skills requires multiple brain areas involved in the control of movement * Basal ganglia are critical for learning motor skills, organizing sequences of movement, “automatic” behaviors, and new habits * Example: driving a car * The pattern of activity of the neurons in the motor cortex becomes more consistent (and the neurons fire more when the movement becomes faster) as a new skill is learned

Answer 22

* The conscious decision to move, and the movement itself, occur at two different times * A readiness potential: activity in the motor cortex that occurs before we make the conscious decision and before voluntary movement * Decision to move (conscious) Begins on average 200 ms before the movement * But readiness potential occurs 500 ms before movement. * Implies we become conscious of the decision to move, AFTER the decision to move has occurred. An experiment by Soon et al. demonstrated brain activity occurs 7-10 seconds before “voluntary decision” = you see the importance of the distinction between stimulus-triggered movements and self-initiated movements (stimulus = fast, voluntary = slow)

Answer 23

Movement Symptoms: • muscle tremors (shaking movements – often exhibited as trembling in extremities) • rigidity (stiffness of arms or legs, contributes to decrease in “range” of motion) • slow movements (also very shuffled gait) • difficulty initiating physical and mental activity • decrease in ability to initiate spontaneous movement in absence of stimuli Symptoms also include depression, memory and reasoning (and lnugauge and attention) deficits, loss of olfaction, and other cognitive deficits (+ lack of motivation and pleasure)

Answer 24

• Brain disorders, such as Parkinson’s disease and Huntington’s disease not only affect movement, but also impair mood, memory, and cognition

Answer 25

* Caused by gradual and progressive death of neurons, especially in the substantia nigra * Substantia nigra usually sends dopamine-releasing axons to the caudate nucleus and putamen * With the loss of this input, the striatum decreases its inhibition of the globus pallidus, which therefore increases its inhibitory input to the thalamus * * Loss of dopamine leads to less stimulation of the motor cortex and slower onset of movements Loss could be due to… • Genetics (particularly early onset parkinson’s seems to have genetic link – michael j fox in 30’s) – genetic factors really only a small factor in later onset. (28 potential genes identified – none of them have large effects on their own, but may accumulate) • Drugs (i.e. MPTP) and Toxins (e.g. much exposure to insecticides, herbicides, and fungicides) • Trauma (e.g. TBI) • Lifestyle factors (e.g. cigarette smoking and coffee drinking – with DECREASED chance) • Damaged mictochondria seem to be the most common thing in these factors to developing PD. • Conclusion = most cases are likely a result of a combination of factors.

Answer 26

As the disease results from a dopamine deficiency, a logical goal is to restore the missing dopamine • The drug L-dopa is the primary treatment for Parkinson’s and is a precursor to dopamine that easily crosses the blood-brain barrier - L-dopa reaches the brain, where neurons convert it to dopamine. • But often ineffective for people in later stage – doesn’t prohibit further loss of neurons – and may have other side effects. • Other “disappointments”: It increases dopamine release in all axons, including those that had deteriorated and those that were still functioning normally. It produces spurts of high release alternating with lower release. Even if it adequately replaces lost dopamine, it does not replace other transmitters that are also depleted • Other Treatments • Drugs that directly stimulate dopamine receptors • Drugs the block the metabolic breakdown of dopamine • Both of these may decrease symptoms but don’t halt the disease. • Implanting electrodes to stimulate areas deep in the brain (Deep brain stimulation) • Experimental: Stem cells (still much in the research phase) – stemm cells to produce large quantities of l-dopa • Brain transplants: transplanted tissue released neurotrophins that stimulated axon and dendrite growth in the recipient’s own brain. Work with mice has shown promising results for a neurotrophin to repair Parkinson-like damage – surgery needed, as neurotrophins doesn’t cross blood brain barrier.

Answer 27

* A neurological disorder characterized by various motors symptoms (has movement, cognitive and emotion components/symptoms) – considered hereditary? * Affects 1 in 7,000 in Canada * Usually onset occurs between age 30-50 (earlier than parkinson’s) * Associated with gradual and extensive brain damage especially in the basal ganglia but also in the cerebral cortex Symptoms Motor symptoms usually begin with arm jerks and facial twitches. Then tremors spread to other parts of the body and develop into writhing. Gradually, the tremors interfere more and more with walking, speech, and other voluntary movements. People lose the ability to develop motor skills * Physical symptoms: (also arm jerks and facial twitches) weight loss, involuntary movements (chorea), diminished coordination, difficulty walking, talking and swallowing * Cognitive symptoms: difficulty with focus, planning, recall of information and making decisions; impaired insight * Emotional symptoms: depression, apathy, irritability, anxiety, obsessive behaviour * Presymptomatic tests can identify with high accuracy who will develop the disease * Huntington’s controlled by an autosomal dominant gene on chromosome #4 (the gene is longer than it should be) – child of huntington parent and healthy parent has 50% risk of huntington * The higher the number of consecutive repeats of the combination C-A-G, the more certain and earlier the person is to develop the disease * But there is still variation (especially in age of onset for those with fewer CAG repetitions = Evidently other factors besides genes also influence the age of onset, such as stressful experiences, drug or alcohol abuse, and perhaps diet and exercise) As a rule, heritability is greater for early-onset disorders than for those with later onset.

Movement Flashcards

(51 cards)