CAP 54 2/2: Sentido del olfato l Fisiología de Guyton

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In this section, the video introduces the sense of smell (olfaction) as a complex and subjective phenomenon, contrasting it with taste. It delves into the anatomy of the olfactory membrane and highlights its relatively limited development in humans compared to other animals.

Olfactory Sense Complexity

• The sense of smell is subjective, evident in how individuals perceive scents differently, such as perfumes.

• Humans have a less developed sense of smell compared to mammals like dogs, capable of detecting scents over vast distances.

Anatomy of Olfactory Membrane

• The olfactory membrane spans an area of 2.4 cm² located at the top of the nasal cavities.

• Comprised of two main cell types: olfactory cells responsible for detecting odors and supporting cells aiding in structure.

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This segment explores the functions and composition of olfactory cells within the olfactory membrane, emphasizing their specialized nature as neuronal cells responsible for odor detection.

Olfactory Cell Functions

• Olfactory cells are specialized neurons tasked with detecting odors; up to 100 million may be present in the olfactory membrane.

• These cells possess cilia that detect and trap odors, with each cell containing 4 to 25 cilia measuring around 3 micrometers wide and 200 micrometers long.

Supporting Structures

• Alongside olfactory cells, glands called Bowman's glands secrete mucus to create a mucous layer aiding in odor trapping by cilia.

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In this section, the discussion revolves around the structure of odorants and how they interact with the olfactory system.

Odorant Structure and Interaction

• Odorants need to have both a hydrophilic and lipophilic part.

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This part delves into the rapid adaptation of olfactory sensations and the growth in potential action numbers during stimulation.

Rapid Adaptation of Olfactory Sensations

• The number of action potentials increases from 20 to 30 per second during olfactory cilia stimulation.

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Here, the concept of rapid adaptation in olfactory sensations is further explored through an illustrative scenario.

Illustration of Rapid Adaptation

• Olfactory receptors adapt by around 50% within the first second of stimulation.

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This segment discusses how olfactory sensations extinguish over time through centrifugal neurons' inhibition.

Extinguishing Olfactory Sensations

• Centrifugal neurons inhibit synaptic connections in olfactory cells, leading to rapid adaptation.

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The focus here is on inhibitory neurons in the olfactory system that contribute to sensory adaptation.

Role of Inhibitory Neurons

• Inhibitory neurons in the vomeronasal organ inhibit synaptic transmission, aiding in quick adaptation.

Transmitting Olfactory Information in the Brain

The discussion delves into how olfactory information is transmitted in the brain, focusing on the specialized neurons involved and the key brain structures responsible for processing this sensory input.

Transmission of Olfactory Information

• Olfactory cells are specialized neurons that transmit signals once stimulated by odorants.

• The olfactory portions of the brain were among the first structures to develop in primitive animals, with the olfactory bulb playing a crucial role.

• Nerve fibers from olfactory cells synapse at glomeruli where connections are made with mitral and tufted cells.

• Mitral and tufted cells project their axons to different points in the central nervous system, dividing olfactory pathways into medial and lateral areas.

• The medial olfactory system, located in septal nuclei, is associated with basic emotional responses triggered by odors.

Processing Olfactory Information in Different Brain Areas

This section explores how olfactory information is processed differently in distinct brain regions, influencing behaviors and emotional responses.

Medial vs. Lateral Olfactory Pathways

• The lateral olfactory area includes cortical structures like piriform cortex and amygdala nuclei, involved in learning to enjoy or dislike certain smells.

• This region's connection with the hippocampus aids memory formation related to odors and emotional experiences tied to them.

Ancient vs. Modern Olfactory Systems

Discusses ancient and modern olfactory systems' roles in memory formation, emotional responses, and sensory perception.

Ancient vs. Modern Olfactory Pathways

• Ancient pathway (paleocortex): Located anteromedially in the temporal lobe; involved in unconscious odor processing.

• Modern pathway (neocortex): Found anteroposteriorly in orbitofrontal cortex; responsible for conscious analysis of odors based on past experiences.

Conscious Perception of Odors

Explores how conscious awareness influences odor perception through active analysis and memory recall mechanisms.

Conscious Analysis of Odors

• The modern pathway allows for conscious evaluation of odors based on characteristics consciously recognized by individuals.

Regulation of Odor Perception

Examines how neural circuits regulate odor perception through habituation processes and selective enhancement of specific smells.

Neural Regulation of Odor Perception