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9.14 Quiz 7
Vocab from Olfactory/Gustatory Chapter
| Term | Definition |
|---|---|
| Olfactory Bulb | The most rostral structure of the vertebrate endbrain, where axons from the olfactory receptor cells of the olfactory epithelium terminate. These axons form cranial nerve I. |
| Olfactory Tract | Axons of secondary sensory neurons from the olfactory bulb are often called the lateral olfactory tract. This tract forms a visible white rostro-caudal band caudal to the olfactory bulb. |
| Olfactory Cortex | The cortex of the endbrain that the mitral cells of the olfactory bulb project to. The largest part of the olfactory cortex is called the piriform cortex. |
| Nucleus of the Solitary Tract | The visceral sensory column in the hindbrain which receives inputs from the visceral organs and from primary sensory neurons of the gustatory system. The rostral part of the nucleus of the solitary tract is often called the gustatory nucleus. |
| Macrosmatic | Adjective describing a vertebrate animal, usually a mammal, with a relatively large olfactory system, including large olfactory bulbs. |
| Microsmatic | Adjective describing a vertebrate animal, usually a mammal, with a relatively small olfactory system, including small olfactory bulbs. Microsmatic animals are less sensitive to odors that are the macrosmatic animals. |
| Chemoreception | Sensory responses to specific chemical substances. Chemoreception is a property of the gustatory and olfactory systems. There are other chemoreptors in the body as well. |
| Carotid Body | A group of chemoreceptive cells located close in the carotid artery sensitive to carbon dioxide levels. The information reaches the nucleus of the solitary tract in the hindbrain through the glossopharyngeal nerve (cranial nerve IX). |
| Area Postrema | A region of the caudal hindbrain just rostral to the obex, where specialized ependymal cells are located. These cells lack a blood-brain barrier so they can detect toxins in the bloodstream. Such detection triggers the vomiting reflex. |
| Solitary Chemosensory Cells | Cells with similarities to taste buds. They are scattered mainly in the surface layers of the respiratory and digestive tracts of mammals. Inputs from these cells reach the CNS largely through the 5th cranial nerve and through dorsal roots. |
| Common Chemical Sense | Free nerve endings in the skin which react to chemical stimulants. More primitive than taste and olfactory senses, the common chemical sense can cause sneezing, arrest of breathing, tear secretion, and sensations of pain or irritation. |
| Umami | Pleasant and savory: one of the most recently discovered of the basic tastes. The other basic tastes are sweet, salty, sour, and bitter. |
| 7th Cranial Nerve | In addition to carrying axons from the facial motor nucleus to facial muscles, and axons innervating salivatory glands, the 7th nerve innervates taste buds of the anterior tongue, in front of the vallate (circumvallate) papillae. |
| 5th Cranial Nerve | Trigeminal nerve innervation of the tongue is necessary for somatosensory inputs that convey touch and pressure information. |
| 9th Cranial Nerve | The glossopharyngeal nerve innervates the taste receptors of the tongue behind, and including, the circumvallate papillae. |
| Circumvallate Papillae | A row of raised areas at the back of the tongue that includes taste buds innervated by the 9th cranial nerve and ducts of lingual salivary glands. Inputs from touch stimulation behind these papillae triggers swallowing. |
| 12th Cranial Nerve | Tongue muscles are innervated by axons of the hypoglossal nerve. |
| Parabrachial Nucleus | Cell group of the rostral hindbrain with input from the nucleus of the solitary tract. Projections from this nucleus go to the forebrain via the ventral posteromedial thalamus, the hypothalamus and the amygdala. conjunctivum. |
| Pontine Taste Area | The taste-receptive portion of the parabrachial nucleus. |
| Ventral Posterior Nucleus (of the Thalamus) | The thalamic nucleus that receives somatosensory projections from spinal cord and from the trigeminal nuclei and also, in its most medial portion, from gustatory nuclei: the rostral nucleus of the solitary tract and the parabrachial nucleus. |
| Brachium Conjunctivum | Axons of the superior cerebellar peduncle, which carry information from the deep nuclei of the cerebellum to the red nucleus in the midbrain and the ventrolateral nucleus of the thalamus in the‘tweenbrain. |
| Salivatory Nuclei | Preganglionic motor neurons of the parasympathetic nervous system found in small groups in the hindbrain. The axons from these nuclei use acetylcholine as a neurotransmitter, innervating small ganglia whose axons stimulate salivation and mucus production. |
| Nucleus Ambiguus | A branchial motor nucleus of the hindbrain that innervates muscles of swallowing and vocalization. Axons from this nucleus pass through cranial nerves IX and X to the pharynx and larynx. |
| Gustatory Nucleus | The rostral portion of the nucleus of the solitary tract in the hindbrain. It receives gustatory inputs from the tongue and throat via cranial nerves VII, IX and X. |
| Midbrain Extrapyramidal Area | Neurons located medial to the main structure of the midbrain locomotor area, less involved in locomotor control and more involved in other movements including turning of head and body. |
| Transcortical Pathways | Axonal pathways in the brain that originate in one cortical area and terminate in another. |
| Rhinencephalon | The “nose brain.” The term became largely replaced by the term “limbic system” or limbic endbrain structures. |
| Piriform Cortex | The pear-shaped cortex: a name for the olfactory cortical areas. The pear shape is seen in smooth-brained mammals, like small rodents, especially if one includes nearby non-neocortical areas. |
| Accessory Olfactory Bulb | A caudo-dorsal portion of the olfactory bulb that receives inputs from the vomeronasal organ in the roof of the mouth in many species, rather than from the olfactory epithelium. This organ responds to pheromones. |
| Olfactory Tubercle | A structure located at the surface of the basal forebrain rostral to the optic chiasm. Axons from the olfactory bulb terminate in its most superficial layer. It is part of the ventral striatum. |
| Rhinal Fissure | A sulcus, or in some species just a shallow groove, that separates the olfactory cortex on the ventromedial side from the neocortex and transitional areas on the dorsolateral side |
| Entorhinal Cortex | Part of the piriform lobe, the margins of the entorhinal cortex receive direct olfactory input. It is also reciprocally connected to the hippocampal formation, and is also closely connected to neocortical association areas via paralimbic cortical areas. |
| Segregation of Modalities | Overlap of axons of different modalities has been observed early in development, followed by a segregation later on. This segregation resulted in a parcellation of brain tissue into separated regions. |
| Cribiform Plate | The bone that separates the nasal cavity from the olfactory bulbs in mammals. Axons of olfactory receptor cells pass through tiny openings in the cribiform plate and reach the olfactory bulbs just inside the brain case. |
| Glomerulus | The olfactory glomeruli are found near the surface of the olfactory bulbs: they are onion-shaped clusters of end-arborizations of axons from the olfactory epithelium that form terminations on dendritic arborizations of mitral cells of the olfactory bulb. |
| Periglomerular Cell | Small interneurons of the olfactory bulbs with processes that enter glomeruli and participate in synaptic complexes there. The periglomerular cells interconnect adjacent glomeruli. |
| Mitral Cell | The major secondary sensory neuron of the olfactory bulbs. The mitral cell axons form the lateral olfactory tract. |
| Granule Cell | A small interneuron of the CNS. The granule cells of the olfactory bulbs, which do not fire action potentials, interconnect nearby mitral cells, resulting in lateral inhibition. |
| Centrifugal Axons | In the olfactory bulbs, centrifugal axons coming from olfactory cortex connect with interneurons of the bulbs—the granule cells and the periglomerular cells. By this means the brain can modulate the amount of lateral inhibition. |
| Terminal Field | The region over which the synapsing terminals of a group of axons are distributed. However, the term is sometimes used for a single axon. |
| Basal Ganglia (Basal Nuclei) | Subcortical structures of the endbrain: The term “basal ganglia” refers to the corpus striatum, pallidal structures, and the amygdala. The septal nuclei may also be included. |
| Cortical Nucleus (of the Amygdala) | A component of the amygdala derived from the embryonic pallium which reaches the brain surface. Its surface layer receives direct projections from the accessory olfactory bulb. In some species this connection is critical for normal mating behavior. |
| Jacobson’s Organ (Vomeronasal Organ) | A sensory structure located at the base of the nasal cavity. It responds to pheromones in the liquids of the mouth. The receptors are primary sensory neurons with axons that connect with the accessory olfactory bulb. |
| Olfactory Filaments | A name for the tiny, unmyelinated axons of the primary sensory neurons of the olfactory epithelium that connect to the olfactory bulb. |
| Anterior Perforated Space | An area at the base of the brain which is penetrated by branches of the anterior and middle cerebral arteries. These vessels supply the basal forebrain, corpus striatum, internal capsule and the olfactory tubercle. |
| Interpenduncular Fossa (Posterior Perforated Substance) | The recessed surface of the midbrain at its base between the cerebral peduncles. It extends from the anterior border of the pons to the mammillary bodies. It is penetrated by many branches of the posterior cerebral artery. |
| Periamygdalar Cortex | The portions of the piriform cortex in the temporal region that overlie the amygdala but are not part of the amygdala. |
| Tufted Cells | Secondary sensory neurons in the olfactory bulb which synapse in olfactory glomeruli on primary sensory neurons and periglomerular cells. Tufted cells are like mitral cells but smaller with more limited dendritic spread. |
| Polymorphic Cell | In the CNS, a cortical layer where the cells are of multiple shapes, and sometimes multiple sizes. |
| Axon Bifurcation | A point along an axon where it branches. |
| Mediodorsal Nucleus (of the Thalamus) | The thalamic nucleus which projects to prefrontal neocortex. The medial division of MD receives inputs from olfactory cortex, as well as other inputs. |
| Lateral Inhibition | When each neuron in an array of neurons inhibits its neighbors, this lateral inhibition results in a sharpening of contrast between more active and less active regions. |
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