| A | B |
|---|
| The largest collection of noradrenergic neurons | the pons in the locus ceruleus |
| The locus ceruleus | maintains vigilance and responsiveness to novel stimuli |
| The largest group of dopaminergic neurons | the midbrain, includes substantia nigra and the adjacent ventral tegmental area |
| dopaminergic neurons in the midbrain | provide input to the cerebral cortex and the basal ganglia important in initiation of behavioral responses |
| Dopaminergic neurons in the hypothalamus | participate in autonomic and endocrine regulation |
| Serotonergic neurons | found mainly in the raphe nuclei |
| neurons of the raphe in the lower pons and medulla | participate in regulating tone in motor systems and pain perception |
| rostral raphe nuclei | helps regulate wake-sleep cycles, affective behavior, food intake, thermoregulation, and sexual behavior |
| largest groups of cholinergic neurons in the brain | found in the midbrain and the basal forebrain |
| pedunculopontine and laterodorsal tegmental nuclei of the midbrain | provide cholinergic innervation to the brain stem and the thalamus critical for inducing a state of cortical arousal, awake and dreaming |
| cholinergic neurons in the basal forebrain | nucleus basalis of Meynert |
| nucleus basalis of Meynert | enhance cortical responses to incoming sensory stimuli |
| Histaminergic neurons are found in | tuberomammillary nucleus in the posterior lateral hypothalamus |
| Histaminergic neurons | important in regulating the level of behavioral arousal |
| project to all major parts of the nervous system, like the locus ceruleus | Histaminergic neurons |
| Pain Is Modulated by | Descending Monoaminergic Projections |
| Monoaminergic projections to the dorsal horn of the spinal cord descend from | the serotoninergic raphe magnus nucleus and from the noradrenergic cell groups in the pons |
| Activation of either monoaminergic pathways can | inhibit the transmission of nociceptive information |
| ascending arousal system divides into two major branches | at the junction of the midbrain and diencephalon |
| ascending arousal system: thalamic and cortical | Lesions that disrupt either of these two branches impair consciousness |
| rostral pons through the thalamus and hypothalamus | ascending arousal system |
| Damage to the lower midbrain or upper pons causes | decerebrate posturing, in which both the upper and lower extremities are extended |
| Damage to the upper midbrain may cause | decorticate posturing: the upper extremities flex, the lower extremities are extended, and the toes extend downward |
| A unilateral large, unreactive pupil | an ominous sign that the brain stem is about to be compressed from above |
| loss only of abduction of the ipsilateral eye | focal injury of the pons involving the abducens nerve |
| Injury to the upper brain stem | posturing of the limbs, either spontaneously or in response to pain |
| A large lesion of the lateral pontine tegmentum (CN VI, PPRF) | loss of conjugate movements of both eyes toward that side |
| injury of the medial longitudinal fasciculus | would prevent adduction of the ipsilateral eye during contralateral gaze |
| pupils are slightly smaller than normal but respond vigorously to light | metabolic encephalopathy, drug ingestion, or diffuse pressure on the diencephalon |
| Pressure on the pretectal area (eg, from a pineal tumor) | prevents visual stimulation from causing pupillary constriction |
| Damage to the midbrain tegmentum itself | complete loss of pupillary response to light, although the pupils may dilate if a painful stimulus |
| Injury to the pons | may result in pinpoint pupils |
| the doll's head maneuver | the eyes rotate counter to the direction of head movement |
| Pt. w/ metabolic encephalopathy, in whom the brain stem is intact | the doll's head maneuver |
| Placing cold water in the external ear canal (caloric stimulation) | causes the eyes to turn to the ipsilateral side |
| causes the eyes to look downward | cold water in both ears |
| Placing warm water in the external ear | causes the eyes to look upward |
| normally | caloric stimulation produces nystagmus |
| extensive injury to the pons on one side will cause | loss of movement of either eye to that side (gaze paralysis) |
| internuclear ophthalmoplegia | An injury to the medial longitudinal fasciculus (MLF) |
| combination of gaze paralysis in one direction and internuclear ophthalmoplegia in the other direction | indicates an extensive paramedian pontine lesion |
| the one-and-a-half syndrome | one eye does not adduct and the other does not abduct or adduct |
| A lesion involving the midbrain oculomotor nuclei | allows abduction of the eyes but not adduction or vertical eye movement |
