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9.14 Midterm 6
Vocab from Schneider Chapters 16-17
| Term | Definition |
|---|---|
| Correlation Center | A brain structure that receives inputs from multiple sources but has output of a specific type. Important midbrain correlation centers are the superior colliculus, the red nucleus, the midbrain locomotor area, and the central gray area. |
| Inferior Olive | A pre-cerebellar cell group which forms an olive shaped bump on the ventral surface of the hindbrain located caudal to auditory system structures. It receives diverse input important to motor control and projects to the cerebellar cortex. |
| Superior Olive | A collection of cell groups that receives projections from the ventral cochlear nuclei on both sides of the hindbrain. It forms an olive-shaped bump on the ventral surface of the hindbrain rostral to the inferior olive. |
| Dentate Nucleus | The most lateral of the deep nuclei of the cerebellum, it receives projections from the cerebellar hemispheres and is important for coordinated movement of the extremities, especially the hands. It projects to the parvocellular red nucleus and to the VL. |
| Somatotopy | Topographic organization of brain representations of somatosensory surfaces. |
| Reticulospinal Tract(s) | The largest such tract comes from the large neurons of the medial hindbrain, and is important for control of organized whole-body movement patterns. |
| Bilateral Pyramidotomy | Transection, by a surgical knife cut, of the pyramidal tract on both sides of the hindbrain. |
| Medial Brainstem Pathways | Groups of axons that course rostrocaudally through the medial parts of the hindbrain. These pathways include the tectospinal, vestibulospinal, fastigiospinal and reticulospinal tracts. |
| Lateral Brainstem Pathways | Axons that course longitudinally through the lateral parts of the hindbrain, including the rubrospinal and lateral reticulospinal tracts. |
| Sensorimotor Amalgam Hypothesis | The hypothesis that the motor cortex and primary somatosensory cortex arose in evolution from a single somatosensory area. These two regions appear to overlap nearly completely in the Virginia Opossum. |
| Parcellation | In brain evolution, the formation of distinct regions of the brain with separate inputs from a single region with overlapping inputs. |
| Prefrontal Cortex | Neocortical areas located anterior to the motor cortical areas. |
| Conduction Time | Frequently, conduction time refers to the delay between stimulus and response. In a reflex, this delay depends on rate of conduction of action potentials along axons, synaptic delays, and times for spatial and temporal summation within neurons. |
| Startle Reflex | Response to a sudden unexpected stimulus. The intensity of the response decreases with repetitions of the stimulus. The motor components of the response begin with eyeblink, followed by facial tension, neck flexion, arm flexion, and leg flexion. |
| Temporal Summation | When excitatory postsynaptic potentials are elicited by frequent incoming action potentials they overlap and the depolarizations are additive. This summation increases the likelihood that the axon hillock will fire an action potential. |
| Spatial Summation | When excitatory postsynaptic potentials are initiated simultaneously (or nearly so) at different places on a neuron, the resulting depolarizations at the axon hillock are additive, so the likelihood of firing an action potential is increased. |
| Chaining of Reflexes | When one reflex results in stimulation that triggers another reflex, which then results in another stimulus that triggers a third reflex, et cetera, it is called a reflex chain. |
| S-R Model | The model says that all behavior is the consequence of stimuli that elicit responses. This model is a more general form of the model proposed by the reflexologists of the 19th century, which include Ivan Pavlov. |
| Feedback Circuitry | Circuits that do not simply go from the stimulus to the response, but include pathways that send the output back to an earlier point in the pathway. Such loops in the flow of information are feedback loops. |
| Central Oscillator | When neurons are rhythmically activated without corresponding rhythms of input driving this activity, then we assume that they are driven by central oscillators. |
| Homeostatic Mechanism | A mechanism that causes some parameter (e.g.. body temperature) to remain within a certain limited range of values. |
| Reverberating Circuits | Pathways in the brain that are self-re-exciting so their activity is maintained for some time. It has been proposed that such circuits underlie short-term memories. |
| Reciprocal Inhibition | When motor neurons that excite a flexor muscle are activated, there are innate pathways that simultaneously inhibit extensor motor neurons that innervate opposing muscles. |
| Reticular Activating System | Neurons of the reticular formation with widespread connections to more rostral structures including the thalamus. Activity of this system thereby activates the neocortex, as indicated by low voltage fast activity in electroencephalographic recordings. |
| Monoamine Systems | Systems of widely projecting axons using monoamine neurotransmitters. The monoamines are serotonin (5-hydroxytryptamine) and the catecholamines norepinephrine and dopamine. |
| Lateral Hypothalamus | The more lateral division of the hypothalamus that contains the rostral-to-caudal running axons of the medial forebrain bundle. It contains neurons of several different groups scattered among the axons. |
| Basal Forebrain | The region of the brain located rostral to the hypothalamus, including various cell groups of the ventral striatum. |
| Nucleus Basalis of Meynert | A group of acetylcholine-containing neurons in the basal forebrain. These neurons project diffusely to most or all of the neocortex. |
| Anterior Commissure (AC) | Bundle of axons, ventral to the anterior corpus callosum that interconnects the olfactory blubs and temporal lobes. The axons cross just below the septal area in the dorsal part of the basal forebrain. |
| Raphe Nuclei | Cell groups located at the midline of the midbrain and hindbrain with axons that release serotonin. The axons distribute very widely in the CNS. |
| Serotonin | 5-hydroxy-tryptamine. The neurotransmitter of a system of axons from the raphe nuclei. The axons distribute very widely throughout the brain, and more specifically to parts of the spinal cord. |
| Betz Cells | The very large layer 5 pyramidal cells of the motor cortex (Brodmann’s area 4). The Betz cell axons project to the spinal cord. |
| Sensory Placode | A thickened region of the embryonic ectoderm of the head from which sensory organs, including primary sensory neurons, develop. |
| Norepinepherine (NE) | A catecholamine neurotransmitter, also called noradrenaline, of the sympathetic-nervous system ganglia. NE is also the neurotransmitter of a widely projecting axon system in the CNS whose cell bodies are in the locus coeruleus of the rostral hindbrain. |
| Locus Coeruleus | A small group of noradrenergic neurons located in the rostral hindbrain, in the periventricular gray area ventral to the cerebellum. These neurons project to most of the CNS (but not to the dorsal striatum), and are the main source of NE in the forebrain. |
| Dopamine (DA) | The catecholamine neurotransmitter of the brain used by the widly projecting neurons of the ventral tegmental area and the substantia nigra. They are important for the type of arousal involved in reward. Dopamine receptors are of multiple types. |
| Ventral Tegmental Area (VTA) | The region in the ventral midbrain of mammals medial to the substantia nigra and extending across the midline. The VTA neurons are the source of dopaminergic axons that project to ventral striatum, other limbic structures, and to most of the neocortex. |
| Substantia Nigra (SN) | Structure of the ventral midbrain closely connected to the dorsal striatum, as well as other structures important in movement. The input to the dorsal striatum is important for normal habit learning. |
| Catecholamine | A monoamine derived from the amino acid tyrosine, a catecholamine has an amine side chain attached to a benzene ring with two hydroxyl groups attached. The most abundant catecholamines are epinephrine (adrenaline), NE (noradrenaline) and DA. |
| Hypocretin or Orexin | A neuropeptide located in widely projecting neurons of the lateral hypothalamus. These projections are important in regulation of sleep, arousal and also appetite and lipid metabolism. Defects in this peptide can cause a form of narcolepsy. |
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