Olfaction is one the major sense. In the following presentation, a brief description of the olfactory system is given. In this following topics are discussed: olfactory membrane, olfactory bulb, odor pathway, anosmia, directional smelling and plasticity. By the end of it, you will be able to describe the olfactory pathway of the nervous system.
olfactory system and functioning, pathway of olfaction, neural tract involved in olfaction , endocrine pathway of olfaction, cells and neurons involved in olfaction
The tongue is the sense organ specialized in detecting the taste of something (e.g. food). Therefore the slides simplifies the anatomy and physiology of GUSTATION.
Olfaction is one the major sense. In the following presentation, a brief description of the olfactory system is given. In this following topics are discussed: olfactory membrane, olfactory bulb, odor pathway, anosmia, directional smelling and plasticity. By the end of it, you will be able to describe the olfactory pathway of the nervous system.
olfactory system and functioning, pathway of olfaction, neural tract involved in olfaction , endocrine pathway of olfaction, cells and neurons involved in olfaction
The tongue is the sense organ specialized in detecting the taste of something (e.g. food). Therefore the slides simplifies the anatomy and physiology of GUSTATION.
Olfaction, or the sense of smell, is an ancient sensory system that together with taste enables an organism to detect chemicals in the external environment. Olfaction is one of the five major human senses (vision, hearing, olfaction, taste, and touch) that occurs when odorants bind to specific sites in olfactory receptors.Olfaction is present in most species such as insects, worms, fish, amphibians, birds, and mammals. It is essential for survival by permitting the location of food, mates, and predators, although in humans, olfaction is often viewed as an esthetic sense capable of triggering emotion and memory.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
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TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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2. Mastication (Chewing) The incisors provide a strong cutting action and the molars cause grinding action. Function: 1- increase total surface area exposed to the digestive secretions. 2- Prevents excoriation of the gastrointestinal tract. 3- Break the indigestible cellulose in most fruits and raw vegetables around their nutrient portions.
3. Chewing mechanism (chewing reflex): The presence of food in the mouth reflex inhibition of the muscles of mastication the lower jaw drop stretch reflex of the jaw muscles contraction and the jaw raise again to cause closure of the teeth, compresses the bolus again , which inhibits the jaw muscles once again, allowing the jaw to drop and rebound ; this is repeated.
4. Sense of Smell (Olfaction) Function of smell: Initiate conditional reflexes concerned with food intake. Animals heavily on olfaction for survival searching for food , defense, and reproduction Together with taste add flavor for food.
5. Sense of Smell Olfactory receptors: Olfactory cells which are bipolar nerve cells found in the olfactory epithelium their ends contains olfactory cilia that project into the nasal mucosa. These cilia react to odors in the air and stimulate the olfactory cells.
6. Stimulation of the Olfactory Cells (Receptors): The odorant substance, on coming in contact with the olfactory membrane it diffuses into the mucus that covers the cilia. Then: It binds with receptor in the cilium. And then activation of the receptor protein by the odorant with activation of the G-protein . This, in turn, activates adenylylcyclase inside the olfactory cell membrane with formation of cAMP. The cAMP opens sodium ion channels and allows large numbers of sodium ions to enter the olfactory cell. Thus exciting the olfactory neuron and transmitting action potentials to the CNS.
7. Most odorants cause depolarization of the olfactory cell membrane, decreasing the negative potential in the cell from the normal level of –55 millivolts to –30 millivolts or less. Physical factors of the odorant sustances that affect the degree of stimulation: Only volatile substances that can be sniffed into the nostrils can be smelled. Water soluble substances to pass through the mucus to reach the olfactory cilia. Lipid soluble to pass through cilia membrane.
8. Transmission of Smell Signals intothe Central Nervous System - Axons from the olfactory cells pass through perforations in the cribriform plate and terminate in the olfactory bulb that send its axons through the olfactory tract (cranial nerve I ) to transmit olfactory signals to olfactory cortex in the limbic system which is a part of the brain intimately associated with emotions, food intake, and sexual behavior. Olfactory Pathways into the Central Nervous System: Olfactory tract divides into two pathways the medial olfactory area (very old olfactory system), and the lateral olfactory area input to less old olfactory system, a newer system:
10. 1) A very old olfactory system: subserves the basic olfactory reflexes, such as licking the lips, salivation, and other feeding responses caused by the smell of food. 2) less old system that provides partially learned control of food intake and aversion to toxic and unhealthy foods. 3) A newer system that is used for conscious perception and analysis of olfaction.
11. Olfactory sensitivity: - Smell has low threshold, a minute quantity of odor in air can elicit a smell sensation. - A substance as methylmercaptan can be smelled in very small concentration. Because of this very low threshold, this substance is mixed with natural gas to give the gas an odor can be detected when gas leak occurs. - Sensitivity is greater in hungry subjects; in women more than men; smoking decrease smell sensitivity, also smell sensitivity decrease with age and when the mucosa is congested, as in a common cold.
12. Olfactory Adaptation: The olfactory receptors adapt about 50% in the first second after stimulation. Thereafter, they adapt very slowly. smell sensations adapt almost to disappearance within a minute. Most of the adaptation occurs within the CNS. Olfactory discrimination: At least 100 primary sensations of smell are found, in contrast to only three primary sensations of color discriminated by the eyes and only five primary sensations of taste detected by the tongue. Some people have odor blindness for certain substances due to lack of the receptor protein in olfactory cells for that substance.
13.
14. Taste Bud and Its Function: Detects chemicals that are dissolved in the saliva. The taste buds are found on three types of papillae of the tongue: surround the circumvallate papillae, on the fungiform papillae and on the foliate papillae. The receptor cells are arranged in the taste buds like the segments of an orange arround a taste pore. From the tip of each taste cell microvilliprotrude outward into the taste pore. Each taste bud responds to one of the five primary taste stimuli (sour, salty, sweet, bitterer and umami taste).
15. Mechanism of Stimulation of Taste Buds: The inner membrane of the taste cell in the taste buds has a negative potential. Application of a substance to the taste microvilli causes loss of this negative potential, and the taste cell becomes depolarized and stimulate taste nerve fibers.
16. The neuronal pathways for transmission of taste signals to the CNS: Taste impulses from the anterior two thirds of the tongue pass in the facial nerve. From the posterior regions of the tongue and throat are transmitted through the glossopharyngeal nerve. From the base of the tongue by the vagus nerve. All taste fibers ascend and synapse in the brain stem in the nuclei of the tractussolitarius. These nuclei send second-order neurons to the ventral posterior medial nucleus of the thalamus. From the thalamus, third-order neurons are transmitted to the postcentralgyrus in the parietal cerebral cortex, taste pathways, is closely parallel the somatosensory pathways from the tongue.