Ch 12 Flashcards
When dynamic γ-motor neurons are activated at the same time as α-motor neurons to muscle,
A. prompt inhibition of discharge in spindle Ia afferents takes place.
B. clonus is likely to occur.
C. the muscle will not contract.
D. the number of impulses in spindle Ia afferents is smaller than when α discharge alone is increased.
E. the number of impulses in spindle Ia afferents is greater than when α discharge alone is increased.
E. the number of impulses in spindle Ia afferents is greater than when α discharge alone is increased.
The inverse stretch reflex
A. occurs when Ia spindle afferents are inhibited.
B. is a monosynaptic reflex initiated by activation of the Golgi tendon organ.
C. is a disynaptic reflex with a single interneuron inserted between the afferent and efferent limbs.
D. is a polysynaptic reflex with many interneurons inserted between the afferent and efferent limbs.
E. uses type II afferent fibers from the Golgi tendon organ.
C. is a disynaptic reflex with a single interneuron inserted between the afferent and efferent limbs.
Withdrawal re exes are NOT A. initiated by nociceptive stimuli. B. prepotent. C. prolonged if the stimulus is strong. D. an example of a flexor reflex. E. accompanied by the same response on both sides of the body.
E. accompanied by the same response on both sides of the
body.
While exercising, a 42-year-old woman developed sudden onset of tingling in her right leg and an inability to control movement in that limb. A neurologic exam showed a hyperactive knee jerk reflex and a positive Babinski sign. Which of the following is NOT characteristic of a reflex?
A. Reflexes can be modifed by impulses from various parts of the CNS
B. Reflexes may involve simultaneous contraction of some muscles and relaxation of others
C. Reflexes are chronically suppressed after spinal cord transection
D. Reflexes involve transmission across at least one synapse
E. Reflexes often occur without conscious perception
C. Reflexes are chronically suppressed after spinal cord transection
Increased neural activity before a skilled voluntary movement is first seen in the A. spinal motor neurons. B. precentral motor cortex. C. midbrain. D. cerebellum. E. cortical association areas.
E. cortical association areas.
A 58-year-old woman was brought to the emergency department of her local hospital because of a sudden change of consciousness. All four limbs were extended, suggestive of decerebrate rigidity. A brain CT showed a rostral pontine hemorrhage. Which of the following describes components of the central pathway responsible for control of posture?
A. The tectospinal pathway terminates on neurons in the dorsolateral area of the spinal ventral horn that innervate limb muscles.
B. The medullary reticulospinal pathway terminates on neurons in the ventromedial area of the spinal ventral horn that innervate axial and proximal muscles.
C. The pontine reticulospinal pathway terminates on neurons in the dorsomedial area of the spinal ventral horn that innervate limb muscles.
D. The medial vestibular pathway terminates on neurons in the dorsomedial area of the spinal ventral horn that innervate axial and proximal muscles.
E. The lateral vestibular pathway terminates on neurons in the dorsolateral area of the spinal ventral horn that innervate axial and proximal muscles.
B. The medullary reticulospinal pathway terminates on neurons in the ventromedial area of the spinal ventral horn that innervate axial and proximal muscles.
A 38-year-old woman with a metastatic brain tumor was brought to the emergency department of her local hospital because of irregular breathing and progressive loss of consciousness. She also showed signs of decerebrate posturing. Which of the following is NOT true about decerebrate rigidity?
A. It involves hyperactivity in extensor muscles of all four limbs.
B. The excitatory input from the reticulospinal pathway activates γ-motor neurons, which indirectly activate α-motor neurons.
C. It is actually a type of spasticity due to inhibition of the stretch reflex.
D. It resembles what ensues after uncal herniation.
E. Lower extremities are extended with toes pointed inward.
C. It is actually a type of spasticity due to inhibition of the stretch reflex.
Which of the following describes a connection between components of the basal ganglia?
A. The subthalamic nucleus releases glutamate to excite the globus pallidus, internal segment.
B. The substantia nigra pars reticulata releases dopamine to inhibit the striatum.
C. The substantia nigra pars compacta releases dopamine to excite the globus pallidus, external segment.
D. The striatum releases acetylcholine to excite the substantia nigra pars reticulata.
E. The globus pallidus, external segment releases glutamate to excite the striatum.
A. The subthalamic nucleus releases glutamate to excite the globus pallidus, internal segment.
A 60-year-old man with Parkinson disease, which was diagnosed 15 years ago, has been taking carbidopa and levodopa (Sinemet); until recently, he has been able to continue to work and help with routine jobs around the house. Now his tremor and rigidity interfere with these activities. His clinician has suggested that he undergo deep brain stimulation therapy. The therapeutic effect of L-dopa in patients with Parkinson disease eventually wears off because
A. antibodies to dopamine receptors develop.
B. inhibitory pathways grow into the basal ganglia from the frontal lobe.
C. there is an increase in circulating α-synuclein.
D. the normal action of nerve growth factor (NGF) is disrupted.
E. the dopaminergic neurons in the substantia nigra continue to degenerate.
E. the dopaminergic neurons in the substantia nigra continue to degenerate.
An 8-year-old girl was brought to her pediatrician because her parents noted frequent episodes of gait unsteadiness and speech difficulties. Her mother was concerned because of a family history of Friedreich ataxia. Which of the following is a correct description of connections involving cerebellar neurons?
A. Basket cells release glutamate to activate Purkinje cells.
B. Climbing fiber inputs exert a strong excitatory effect on Purkinje cells, and mossy fiber inputs exert a strong
inhibitory e ect on Purkinje cells.
C. Granule cells release glutamate to excite basket cells and stellate cells.
D. The axons of Purkinje cells are the sole output of the cerebellar cortex, and they release glutamate to excite the deep cerebellar nuclei.
E. Golgi cells are inhibited by mossy fiber collaterals.
C. Granule cells release glutamate to excite basket cells and stellate cells.
A er falling down a flight of stairs, a young woman is found to have partial loss of voluntary movement on the right side of her body and loss of pain and temperature sensation on the left side below the midthoracic region. It is probable that she has a lesion
A. transecting the left half of the spinal cord in the lumbar region.
B. transecting the left half of the spinal cord in the upper thoracic region.
C. transecting sensory and motor pathways on the right side of the pons.
D. transecting the right half of the spinal cord in the upper thoracic region.
E. transecting the dorsal half of the spinal cord in the upper thoracic region.
D. transecting the right half of the spinal cord in the upper thoracic region.
At the age of 30, a male postal worker reported weakness in his right leg. Within a year the weakness had spread to his entire right side. A neurologic examination revealed flaccid paralysis, muscular atrophy, fasciculations, hypotonia, and hyporeflexia of muscles in the right arm and leg. Sensory and cognitive function tests were normal. Which of the following diagnosis is likely?
A. A large tumor in the le primary motor cortex
B. A cerebral infarct in the region of the corona radiate
C. A vestibulocerebellar tumor
D. Damage to the basal ganglia
E. Amyotrophic lateral sclerosis
E. Amyotrophic lateral sclerosis
