Overview of the Chemical Senses

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Del curso dictado por Duke University

Medical Neuroscience

1263 calificaciones

Duke University

Medical Neuroscience

1263 calificaciones

Medical Neuroscience explores the functional organization and neurophysiology of the human central nervous system, while providing a neurobiological framework for understanding human behavior. In this course, you will discover the organization of the neural systems in the brain and spinal cord that mediate sensation, motivate bodily action, and integrate sensorimotor signals with memory, emotion and related faculties of cognition. The overall goal of this course is to provide the foundation for understanding the impairments of sensation, action and cognition that accompany injury, disease or dysfunction in the central nervous system. The course will build upon knowledge acquired through prior studies of cell and molecular biology, general physiology and human anatomy, as we focus primarily on the central nervous system. This online course is designed to include all of the core concepts in neurophysiology and clinical neuroanatomy that would be presented in most first-year neuroscience courses in schools of medicine. However, there are some topics (e.g., biological psychiatry) and several learning experiences (e.g., hands-on brain dissection) that we provide in the corresponding course offered in the Duke University School of Medicine on campus that we are not attempting to reproduce in Medical Neuroscience online. Nevertheless, our aim is to faithfully present in scope and rigor a medical school caliber course experience. This course comprises six units of content organized into 12 weeks, with an additional week for a comprehensive final exam: - Unit 1 Neuroanatomy (weeks 1-2). This unit covers the surface anatomy of the human brain, its internal structure, and the overall organization of sensory and motor systems in the brainstem and spinal cord. - Unit 2 Neural signaling (weeks 3-4). This unit addresses the fundamental mechanisms of neuronal excitability, signal generation and propagation, synaptic transmission, post synaptic mechanisms of signal integration, and neural plasticity. - Unit 3 Sensory systems (weeks 5-7). Here, you will learn the overall organization and function of the sensory systems that contribute to our sense of self relative to the world around us: somatic sensory systems, proprioception, vision, audition, and balance senses. - Unit 4 Motor systems (weeks 8-9). In this unit, we will examine the organization and function of the brain and spinal mechanisms that govern bodily movement. - Unit 5 Brain Development (week 10). Next, we turn our attention to the neurobiological mechanisms for building the nervous system in embryonic development and in early postnatal life; we will also consider how the brain changes across the lifespan. - Unit 6 Cognition (weeks 11-12). The course concludes with a survey of the association systems of the cerebral hemispheres, with an emphasis on cortical networks that integrate perception, memory and emotion in organizing behavior and planning for the future; we will also consider brain systems for maintaining homeostasis and regulating brain state.

De la lección

Sensory Systems: Audition, Vestibular Sensation and the Chemical Senses

Our survey of the sensory systems continues as we now turn our attention to the auditory system, the vestibular system, and the chemical sensory systems. As you study this content, notice the similarities and the differences that pertain to the general mechanisms of sensory transduction and the broad organization of the central pathways in each of these sensory systems. In particular, note the similarity in transduction mechanisms for audition and vestibular sensation; and note the “logic” of sensory coding in the chemical sensory systems.

Overview of the Chemical Senses8:12

Olfaction, part 113:11

Olfaction, part 29:10

Olfaction, part 314:01

Olfaction, part 418:01

Gustation, part111:37

Gustation, part 214:16

Gustation, part 39:18

Trigeminal Chemoreception10:22

Conoce a los instructores

Leonard E. White, Ph.D.
Associate Professor
Department of Neurology, Department of Neurobiology, Duke University School of Medicine; Department of Psychology & Neuroscience, Trinity College of Arts & Sciences; Director of Education, Duke Institute for Brain Sciences; Duke University

Welcome to this tutorial on the chemical senses.

The chemical senses pertain to a set of special sensory systems associated with

the head region of the body. And we are going to discuss them in

several parts. In this part I'd like to give you an

overview of the chemical senses. And this discussion about chemical

sensation is going to again, illustrate for you the complexity of the brain as

the body's most complex organ. And as we get into our special sensory

systems for the chemical senses , we'll see once again evidence of genetically

determined circuits that provide the foundation for the functions of the

nervous system. And when it comes to discussion of these

chemical sensory systems, I think we'll see some, some really remarkable examples

of where there is genetic expression. In space and time that influences the

structure of circuitry that provides for, in this case, the foundation for chemical

sensation. So, I have just a brief tutorial for you.

In this particular part, you will provide an overview of the chemical senses.

And my goal for you, is that you'd be able to summarize the organization of the

neural systems for the chemical senses. So, let's get started.

And just a simple comment that will set the stage for our more detailed studies

of olfaction gestation, in just a bit. Our chemical senses are special sensory

systems primarily in the face, but also in the cavities within the head.

And these are systems that detect minute quantities of chemical molecules in the

environment. And these chemicals can serve a variety

of purposes. And that's what I want to help you

understand in this brief overview. So, consider, for example first, airborne

molecules. So, the air is full of odorants full of

molecules that have a particular shape and structure to them, particular

chemical qualities. And there are specializations of

receptors in the face and in the head that interact with these airborne

molecules. Specifically, these airborne molecules

interact with receptors that produce a sense of smell.

And this is what we call olfactions. So olfactory sensations, are a response

to the presence of these airborne molecules.

Now some of these molecules, can actually produce irritation to tissues in the

body. They are potentially damaging.

And it makes great sense that we would have a chemical sensory system that would

be dedicated to detect these potentially irritant molecules.

And that's where the third major chemical sensory system comes in.

It's called the trigeminal chemosensory system.

Now in addition to airborne molecules, of course there are molecules that are

mostly water soluble, and also lipid soluble that we ingest.

So we put these molecules into our bodies, obviously through our mouth, and

these molecules have an opportunity then to interact with the mucosa that is

present in our oral pharynx. So as we interact with these ingested

molecules these molecules can then activate a variety of receptors that give

rise to our sensation of taste. This is what we call gustation.

So ingested molecules give rise to gustatory sensations.

Now, you may be wondering about flavor. Which, as we'll talk about as we move

along here, is actually a combination, of, really all three of these chemo

sensory pathways, when we think about it. Consider for example eating your favorite

spicy food. There's a particular smell that might

first arouse our appetite when this plate of food is presented to us.

And then of course, as we begin to eat it, there is the consumption of these

molecules that we begin to ingest and then begin to interact with our gustatory

receptors. But, if it's spicy, there my also be a

mild irritant quality to it that can drive sensations through our trigeminal

chemosensory system. And somewhere in the brain, and I'll tell

you where we think it actually happens in just a little while.

These various sensory systems are combined.

And they are combined in a sense that gives us our quality that we call flavor.

Well, in addition to feeding behaviors these chemical sensory systems provide

really a number of important functions. beginning with nutrition.

So, these chemical sensory systems allow us to assess the palatability, or the

desirability of those foods and drinks that we consume.

and this is quite important as I think we all can appreciate perhaps not so much in

our, our modern societies, but certainly, as we sample the foods of the world,

wherever we may be, we are always on guard, are we not, for the palatability

of food. trying to avoid potentially harmful

substances. There are a variety of physiological

functions that are regulated by our chemo sensory systems.

these include memory, visceral motor behavior, reproductive cycles.

And very importantly infant paternal behaviors and infant maternal behaviors.

There are a variety of social interactions that are mediated via the

chemical senses. Through the chemical senses we evaluate

self and we evaluate others. As I mentioned already, safety becomes an

important domain of chemical sensation. Not just for the ingestion of potentially

harmful substances, but also our interaction with volatile chemicals in

the environment. That might be mildly irritating at low

concentrations, and potentially quite harmful at higher concentrations.

And then lastly, it's through the chemical senses that so much of our

hedonic rewards system is tuned. And what I mean by this is, those

chemical messages. That either we ingest, or that we sniff,

or that we otherwise interact with, with our chemo sensory systems.

That can drive a sense of pleasure. And one can imagine lots of examples of

this, an attractive perfume the scent of your favorite flower pleasurable foods

and drinks. And quite interestingly, also the

possibility of there being, pheromones. Now, as I'll describe as we get a little

deeper into olfaction we know that, the old world primates, including humans,

lack the specializations, in the olfactory epithelium, and in the

peripheral parts of the olfactory system. To be sensitive to pheromones in the way

that non old world primates and other non-primate mammals may be.

but nevertheless there is some tantalizing bit of evidence to suggest

that our behaviors are in fact influenced by chemical messages in a way that would

be consistent with pheromone interaction. So, that will be an interesting

discussion to bang around perhaps on the discussion forum or elsewhere.

Well, I hope you've enjoyed this brief overview of where we're going to go over

the next couple of pieces to this tutorial on the chemical senses.

And I look forward picking up with you, in just a moment, in a discussion of the

olfactory system. So, I'll see you then.

[BLANK_AUDIO]

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