W7 Sensory Systems and Chemical Sense Flashcards
What are the 3 common Steps in coversation of sensory processing across systems
1- Requires a physical stimulus.
2- Must transform the stimulus into nerve impulse = sensory receptors in the peripheral nervous system.
3- Evoke a response to the signal in the form of perception of sensation = Central Nervous System.
Sensory Receptors
Cells not just proteins.
Engery from the environment =[sensory transduction]=> Electrochemical signls in sensory receptors (graded and action potentials)
Sensory receptros proteins
Many sensory receptor cells prossess ion channels and G-protein coupled receptors that are common to many bodily functions
Proprioception
Detect if you are contracting or not your muscle.
5 Traditional Senses
Hearing
Vision
Small
Balance
Taste
Hearing
Mehanical stimulus, Mechanoreceptor. Located in the inner ear, cochlea
Balance
Mechanical stimulus, Mechanoreceptor. Located in the inner ear.
Vision
Light Stimulus. Photoreceptors. Located in Retina.
Touch
Mechanical Stimulus. Mechanoreceptor. Located in Skin.
Temperature
Thermal Stimulus. Thermoreceptor. Located: Skin
Pain
Mechanical thermal, checimal stimulus. Nociceptor. Located: skin, internal organs
Proprioception
Mehanical Stimulus. Mechanoreceptor. Located in Muscle tendons, jionts.
Olfaction
Chemical Stimulus, Chemoreceptor, Nassal vaity (location)
Tsate
Chemical Stimulus. Chemoreceptor. Located: tongue, pharynx, palate epiglottitis.
What happens with senses?
Stimulus => Sensory receptor is activitated => Membrane permeability is altered in the sensory cell => receptor potential develops in the sensory cell = [neurotransmitter released onto afferent neuron terminal]=> action potential is generatedin afferent neuron terminal => propagates to CNS => information intergrated by CNS.
Graded Receptors potential
Increase in size in response to increases in stimulus amplitude.
Action potentials Receptors
are always the same size but have threshold for activation
Olactory receptors (direct neuronal activation)
Large enough receptor potentials cause depolarisation in cell soma, trigger action potential to travel down to olfactory blub. Ion influx causes membrane depolaraisation and graded receptor potential develops in a cilium.
Synapse and Receptors: Taste
Ion influc causes membrane depolarisation and graded recepor potential develops. Initates synaptic vesicle fusion wiht membrane and neurotransmitter release. Neurotransmitter binds to postsynaptic receptors, generating an EPSP in dendrite of the afferent neuron. Large enough EPSP generate action potentials.
Sensory receptors can convery what 4 types of information
Modality, location, intensity, timing
Stimulus modality is coded by what?
Labelled line code. Receptor is selective for one type of stimulus energy.
Axons of the receptor/associated afferent neuron acts as a modality specific line of communication.
Labbeled line code is what ?
Faulty in syneasthesia. Research in 2018 found genes that are likely to be responsible
‘the name Kate taste like chocolate’
Stimulus location - receptors
Spatial arrangement of activated receptors within a sense organ gives information about the stimulus.
Determined by the stimulus energy and anatomy of the sneory organ/receptor
Somatic system: receptive field is region of skin innervated by the terminals of the receptor neuron.
Visual system: receptive field of photoreceptor is the region of the visual field prokected onto that receptor.
Stimulus intensity - receptors
Intensity is the total amount of stimulus energy deliered to the receptor.
Determined by stimulus amplitude adn neuronal firing rate.
The Lowest stimulus strenght that can be determined by the response amplitude of the receptor and thus the firing frequency of the afferent neuron.
Stimulus timing - receptors
Onset timing is determined by when the stimulus energy is received by the receptor and caused it to fire.
Stimulus duration - receptors
detemined by adaptation rates of receptors.
Adaptation in response to continuous stimuli, the firing rate of action potentials derease.
Tonic Receptors
Slowly adapting receptors, respond to prolonged stimulation.
Phasic receptors
Rapidly adapting receptors. Respond at the beginning an dend of a stimulus.
Chemical sense
Developed into a more complex system in other animals than in humans.
Functions of Chemical Senses
Identify food sources. Avoid noxious substances. Find a mate or mark terrotories.
Multiple processes to identify things - chemical sense
Gustarory system (taste) and Olfactory system (small) processed in parallele and then they merg after primary processing, they merge in associatio cortex (CNS)
5 Basic tastes
Salty, Sour, Sweet, Bitter, Umami (savory)
Salty
Relates to Vital electrolytes. Preference: High salt content. Relevance: Required for many physiological processes
Sour
Relates to acidity -H+ Preference: Avoid high Relevance: avoiding rotting food, injury to GI tract.
Sweet
Relates to Sugars Preference: High sugar content Relevance: Requried for energy, growth.
Bitter
Relates to diverse chemical strucutres. Preference: avoid bitter content Relevance: Avoid toxic substance, poisonous.
Umami (savory)
Relates to alino acids (glutamate). Preference: High amino acid preference. Relevance: Protein synthesis, nerotransmission
How do we perceive all of the flavors of food?
Different combination of chemical differnt, textures, smells, temperatures
Taste organs
Primarily tongue, cheeks, soft palate, pharunx, epiglottis.
Lingual papillae (part of the tongue) contain taste buds which are groups of taste cells.
2000-5000 Taste buds ~100 chemoreceptive tast cells per taste bud. Taste pore allows sensory transduction by microvilli.
Taste cell vs Tast bud
Taste cellls only respond to one type of stimulus.
Taste buds contain taste cells which respond to various stimulus.
Olfactory system
Odorants as low as a few parts per trillion can be detected. Human olfactory epithelium = 10 cm2. Dog olfactory epithelium = 170 cm2. Dogs have 100x more receptors/cm2
What type of neurons ar’e olfactory receptor cells?
Bipolar chemoreceptive neurons.
Odorants must dissolve in the mucus layer to reach olfactory recepotr cells. Transduction machinery is found within the cilia at the end of the dendrite. The primary afferent neuron is the axon (thin, unmyelinated) of the cell.
Oflactory receptor cells are regularly replaced.
Odorant receprot protiens (ORs)
Humans have ~350 odorant receptor proteins.
Olfactory receptor cells only express one odorant receptor. One odorant receptor can recognise multiple odorants. It is the unique combination of odorant receptors that recognise an odorant that allows us to distinguish a specific odor.
Traduction occurs via G[olfs]
G-protein coupled receptors. Every Odorant receprot use the same downstream pathway.
Adenylyl cyclase
cAMP
Cyclic nucleotide gated ion channels
Depolarizatio
Ca2+-gated Cl- channels
Further depolarization
Receptor potnetial strigger action potentials
Large enoughreceptro potential: threshold for action potential firing reached.
Intense stimulus = large receptor potential = inreased action potential firing rate.
