Podcast
Questions and Answers
What is the primary function of the gustatory pathway?
What is the primary function of the gustatory pathway?
Which cranial nerve is NOT involved in the gustatory pathway?
Which cranial nerve is NOT involved in the gustatory pathway?
How does a blockage of the nose affect the perception of taste?
How does a blockage of the nose affect the perception of taste?
What influences the sense of taste aside from taste receptors?
What influences the sense of taste aside from taste receptors?
Signup and view all the answers
What role do the limbic system and hypothalamus play in taste sensation?
What role do the limbic system and hypothalamus play in taste sensation?
Signup and view all the answers
What initiates the activation of olfactory receptors?
What initiates the activation of olfactory receptors?
Signup and view all the answers
What is the mechanism through which odorants are removed from the receptor proteins?
What is the mechanism through which odorants are removed from the receptor proteins?
Signup and view all the answers
Which statement best describes the relationship between olfactory and gustatory senses?
Which statement best describes the relationship between olfactory and gustatory senses?
Signup and view all the answers
What role do chemoreceptors play in the sensory system?
What role do chemoreceptors play in the sensory system?
Signup and view all the answers
Which region of the brain processes information from the olfactory system?
Which region of the brain processes information from the olfactory system?
Signup and view all the answers
What characteristic differentiates gustatory receptor cells from olfactory receptor cells?
What characteristic differentiates gustatory receptor cells from olfactory receptor cells?
Signup and view all the answers
What is required for odorants to activate olfactory receptors?
What is required for odorants to activate olfactory receptors?
Signup and view all the answers
Which of the following taste modalities is most sensitive to low concentrations of stimuli?
Which of the following taste modalities is most sensitive to low concentrations of stimuli?
Signup and view all the answers
Which proteins are involved in the olfactory transduction process?
Which proteins are involved in the olfactory transduction process?
Signup and view all the answers
What is the role of microvilli in gustatory receptor cells?
What is the role of microvilli in gustatory receptor cells?
Signup and view all the answers
How do olfactory sensory neurons respond to odorants?
How do olfactory sensory neurons respond to odorants?
Signup and view all the answers
Which function does the limbic system serve concerning olfactory stimuli?
Which function does the limbic system serve concerning olfactory stimuli?
Signup and view all the answers
Which taste modality is associated with the detection of sodium?
Which taste modality is associated with the detection of sodium?
Signup and view all the answers
What process allows the removal of odorants from olfactory receptors?
What process allows the removal of odorants from olfactory receptors?
Signup and view all the answers
Which neurotransmitter is commonly involved in transmitting taste signals to the brain?
Which neurotransmitter is commonly involved in transmitting taste signals to the brain?
Signup and view all the answers
What is the mechanism by which sour taste is activated?
What is the mechanism by which sour taste is activated?
Signup and view all the answers
Which of these concepts describes the olfactory processing in the brain?
Which of these concepts describes the olfactory processing in the brain?
Signup and view all the answers
Study Notes
Special Senses: Chemoreception
- Chemoreception is the ability to detect chemicals.
- Two types of chemoreceptors are gustatory (taste) and olfactory (smell).
- Gustatory chemoreceptors detect dissolved chemicals at relatively high concentrations.
- Olfactory chemoreceptors detect airborne or dissolved chemicals at relatively low concentrations.
- Chemoreceptors have general characteristics: chemical signals bind to membrane-bound receptor proteins regulating cell membrane permeability. Information is transmitted to the cerebral frontal cortex for processing.
- Distinguishing features include different cell types and locations, different transduction mechanisms, and different neural pathways. Coverage of the frontal cortex is also a distinguishing factor.
Olfaction
- Odorants must be volatile (easily vaporized) and soluble in mucus layers to enter the nose.
- Olfactory epithelium is the organ of smell in the roof of the nasal cavity, which contains olfactory sensory neurons.
- Olfactory sensory neurons are bipolar neurons with thin apical dendrites containing several olfactory cilia.
- These neurons regenerate approximately every two months.
- Olfactory cilia are on the apical dendrites and are where odorant molecules bind.
Olfactory Transduction
- Odorants activate G protein-coupled receptors on olfactory cilia.
- A second messenger (cAMP) opens cation channels, facilitating Na+ and Ca2+ influx into the cell.
- This depolarization results in a graded receptor potential.
- The graded receptor potential triggers action potentials via voltage-gated Na+ channels.
Olfactory Receptor Cells
- Olfactory receptor cells can detect a wide variety of odorants (over 10,000).
- Each receptor cell expresses only one specific type of receptor protein, but a receptor cell can have a broad sensitivity.
- Receptor proteins bind a specific component of an odorant, and a variety of receptors can detect components of the same odorant.
- Odorants stimulate a population of receptor cells forming a combinatorial code for each odorant stimulus.
Olfactory Receptors & Odorant
- Odorant 1 will activate multiple receptors.
- Odorant 2 will also activate multiple receptors.
- The response to each odorant differs, so the responses can be distinguished.
Olfactory Pathway
- The olfactory bulb contains glomeruli where mitral cells receive input from many olfactory cells with similar characteristics.
- Olfactory tracts extend to the primary olfactory cortex in the temporal lobe and the pathway continues to the frontal lobe, allowing interpretation/identification of smells.
- Olfactory pathways also project to the limbic system causing emotional responses to odors.
Olfactory Receptors
- Olfactory receptors have a low threshold and high sensitivity (requiring low odorant concentration).
- Olfactory adaptation occurs quickly with intrinsic and extrinsic mechanisms removing odorants.
- Odorants are removed by similar detoxification enzymes found in the liver.
Gustation
- Taste buds are sensory receptor organs for taste, mainly located within papillae of the tongue.
- Within taste buds are gustatory receptor cells, epithelial sensory receptors, which aren’t neurons.
- Microvilli project into taste pores (location of receptor proteins).
- Gustatory receptor cells synapse with afferent neurons which carry signals to the brain (cortex).
- Basal cells, stem cells, rapidly turnover/replace gustatory receptor cells approximately every 10 days.
- Tastants dissolve in saliva, entering taste pores, to interact with taste receptors.
Five Primary Tastes
- Sweet, salty, sour, bitter, and umami are the five localized tastes associated with different taste receptor cells.
Gustatory Transduction
- Taste receptor proteins are in microvilli on apical surfaces of taste receptor cells.
- Various protein types & intracellular signals are used (e.g., salty – Na+ channel; sour – H+ channel; sweet, bitter, umami – G protein-coupled receptors).
- Receptor activation ↑ intracellular [Ca2+] leading to neurotransmitter release and an action potential in the afferent sensory neuron.
Salty & Sour
- Ion channels allow Na+ (salty) or H+ (sour) into the cell.
- Positive ion movement causes depolarization to receptor potential.
- Voltage-gated Ca2+ channels open and ↑ intracellular [Ca2+] causing neurotransmitter release.
Sweet, Bitter, Umami
- G protein-coupled receptor transduction systems activate phospholipase C (PLC) to increase IP3 levels.
- The increase in intracellular [Ca2+] triggers neurotransmitter release.
Thresholds & Adaptation
- Thresholds of activation vary by gustatory cell (bitter receptors most sensitive, salty/sweet less sensitive).
- Adaptation occurs within 1-5 minutes using intrinsic and extrinsic mechanisms.
Gustatory Pathway
- Three cranial nerves (facial, glossopharyngeal, vagus) carry signals to the medulla.
- Signals continue to the limbic system-hypothalamus for emotional responses and to the thalamus-gustatory cortex for conscious taste perception.
- Taste is strongly influenced by smell, thermoreceptors, mechanoreceptors, and nociceptors. Blockages of the nose can reduce taste perception.
Check Your Knowledge (Questions)
- Olfactory and gustatory receptors detect chemicals dissolved in fluids (e.g., saliva—taste; air—smell).
- Olfactory receptor cells are of epithelial origin.
- One olfactory receptor type binds to one component of an odorant, but one odorant may stimulate several receptor types.
- G protein-coupled receptor systems are involved in detecting sour tastants.
- Increased intracellular calcium levels from activation of gustatory receptor proteins trigger neurotransmitter release.
- Taste perception is affected by factors beyond stimulation of gustatory receptor cells.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the fascinating world of chemoreception in this quiz. Learn about the two main types of chemoreceptors: gustatory and olfactory, and how they function to detect chemicals. Dive into the mechanisms of smell and taste, and understand the role of the cerebral cortex in processing these sensations.
