Presentation on theme: "Sensory and Motor Mechanisms"— Presentation transcript:
1 Sensory and Motor Mechanisms Samaneh Bolourchi, Jennifer Tszeng & Athena Zeng
2 Introduction: Sensory Pathways Sensory receptors transduce stimulus energy & transmit signals to CNS (central nervous system)Reception: detection via exteroreceptors or interoreceptorsTransduction: stimulus energy converted into ∆ in membrane potential of sensory receptor (receptor potential)Amplification: stimulus energy strengthens in cells in pathwaysAdaptation: decrease in responsivenessTransmission: action potentials transmitted to the CNSPerception: constructions formed in brain (ie color, smell, sounds)
3 Introduction: Types of Receptors Sensory receptors are specialized neurons or epithelial cells that exist singly or in groups with other cell types in sensory organs, such as eyes or ears.Mechanoreceptors sense physical deformation cause by forms of mechanical energy such as pressure, touch, etc.Chemoreceptors respond to chemical stimuli.Electromagnetic receptors respond to various forms of electromagnetic energy such as visible light, electricity, and magnetism.Thermoreceptors respond to heat or cold and help regulate body temperature by signaling surface and body core temperature.Pain receptors, or nociceptors, are a class of naked dendrites in the epidermis.
4 Mechanoreceptors Detect mechanical energy typically consist of ion channels linked to external cell structures (ie hairs) & internal structures (ie cytoskeleton)Bending/stretching plasma membrane changes permeability to sodium & potassium ionsType of mechanoreceptor varies greatly between organismsCrustaceans - vertebrate stretch receptorsMammals - dendrites of sensory neurons
5 Introduction: Sound & Balance Ear receives vibrations of moving air and converts into what the mind perceives as soundAlso detects body movement, position & balanceStructures vary between organismsTerrestrial vertebrates: inner ear is main organ of hearing & equilibriumFish/Amphibians: lack certain parts but also contain homologous structuresInvertebrates - statocysts
6 Sound in Humans: Structure of Human Ear Outer earPinnaTympanic membraneMiddle earMalleus, incus, stapesOval windowEustachian tubeInner earFluid-filled chambers ie semicircular canals & cochlea
7 Sensory Reception: Hair Cells Rod-shaped hairs in cortiVibration of basilar membrane bends hairs against surrounding fluid & tectorial membraneBundle direction affects receptionActivates mechanoreceptors1093; base explanation on 1094; use 1094 diagram
9 Sound & Balance: Variation in Organisms Terrestrial vertebrates: ear has = main organ of hearing & equilibriumFish/Amphibians - similar to mammalian ears; lack several structuresFrogs/toads - single middle bone (stapes)Frogs: small side pocket in saccule - basis for evolution of mammalian cochleaBirds - cochlea; single middle bone (stapes)
10 Sound & Balance: Fish/Amphibians lateral line systemhave ears outside of body; no eardrum or cochlea; air-filled swim bladder also vibrates in response to sound
12 Thermoreceptors Detect heat Located in skin and anterior hypothalamus Mammals contain a range of thermoreceptor types for particular temperature rangesReceptor proteins open a calcium channel upon binding certain productsAt least five different types of thermoreceptors belong to the transient receptor potential (TRP) family of channel proteins
13 Pain Receptors Nociceptors detect noxious conditions Essential - stimulus prompts defensive reactionAnimals also produce chemicals to enhance pain perception
14 Touch Receptors usually on skin Humans contain naked dendrites to detect noxious thermal, mechanical & chemical stimuliEpidermis, dermis, hypodermis *structure of connective tissue & location of receptors dramatically affect the type of mechanical energy that best stimulates them
15 Human Integumentary System HeatLight touchPainColdHairNerveConnective tissueHair movementStrong pressureDermisEpidermis
16 Chemoreceptors The most sensitive chemoreceptors are on sensory hairs ofthe male silkworm whichdetect sex pheromones.0.1 mm
17 GustationIn mammals, taste receptors are located in taste buds, most of which are on the surface of the tongueEach taste receptor responds to a wide array of chemicals, but is most responsive to a particular type of substance.It is the pattern of taste receptor response that determines perceived flavor.Transduction in taste receptors occurs by several mechanisms.
19 OlfactionIn mammals, olfactory receptors line the upper portion of the nasal cavity.The receptive ends of the cells contain cilia that extend into the layer of mucus coating the nasal cavity.Each olfactory receptor cell expresses only one or a few odorant receptor genes.
21 Electromagnetic Receptors Respond to various forms of electromagnetic energy such as visible light, electricity, and magnetism.Photoreceptors detect energy in form of lightExamples:Snakes—body heat of prey.Fish—electric currents—prey.Animals—earths magnetic field. (birds)
22 Types of Eyes the simplest is the eye cup of planarians In invertebrates, there are compound eyes and single-lens eyes:Compound: in crustaceans , insects, etc. (have several thousand facets called ommatidia)Single-lens: jellies, spiders, etc (single lens that focuses light)In vertebratesEvolved independently and differ from the single-lens eyes of invertebrates
24 Sensory TransductionThe human retina contains two types of photoreceptorsRods are sensitive to light but do not distinguish colorsCones distinguish colors but are not as sensitiveEach rod or cone in the vertebrate retina contains visual pigments consisting of light-absorbing molecules called retinal bonded to membrane proteins called opsinRhodopsin (retinal + opsin) is the visual pigment of rods.Absorption of light by retinal triggers a signal transduction pathway!
25 Signal Transduction cont. EXTRACELLULAR FLUIDMembrane potential (mV)– 40– 70Dark Light– Hyper- polarizationTimeNa+cGMPCYTOSOLGMPPlasma membraneINSIDE OF DISKPDEActive rhodopsinLightInactive rhodopsinTransducinDisk membrane2 Active rhodopsin in turn activates a G protein called transducin.3 Transducin activates the enzyme phos-phodiesterae(PDE).4 Activated PDE detaches cyclic guanosine monophosphate (cGMP) from Na+ channels in the plasma membrane by hydrolyzing cGMP to GMP.5 The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes.1 Light isomerizes retinal, which activates rhodopsin.
26 Signal Transduction (cont.) Three other types of neurons contribute to information processing in the retinaGanglion cells, horizontal cells, and amacrine cellsSignals from rods and cones travel from bipolar cells to ganglion cells, which then transmit info to brain by optic nerve (axon of ganglion)Horizontal cells and amacrine cells function in neural pathways that integrate visual info before sent to brain.Lateral inhibition causes a greater contrast b/n light and dark (as the horizontal cells inhibit more distant photoreceptors) and this enhances the image, and sharpens its edges.
27 Synaptic activity of rod cells in light and dark Dark ResponsesRhodopsin inactiveNa+ channels openRod depolarizedGlutamatereleasedBipolar cell eitherdepolarized orhyperpolarized,depending onglutamate receptorsLight ResponsesRhodopsin activeNa+ channels closedRod hyperpolarizedNo glutamatehyperpolarized ordepolarized, depending on glutamate receptors
28 Evolution of Visual Perception All photoreceptors contain similar pigment molecules that absorb light (despite diversity)Genetic underpinnings of all photoreceptors evolved in the earliest bilateral animals.
29 Vertebrate Skeletal Muscle Myofibrils consist of:Thin filaments: two strands of actinand two strands of a regulatory proteinThick filaments: staggered arraysof myosin moleculesStriated Muscle: regular arrangementof filaments create light/dark band patternSarcomere: basic contractile unitbetween Z- lines
32 Types of Muscle Skeletal Muscle Voluntary movements Attatched to bones Cardiac muscle is similar to skeletal musclewith striations.Smooth musclelacks striationslines walls of blood vessels and digestive system organs.
33 Skeletal Systems Support, protection, and movement Hydrostatic Skeleton – consists of fluid held under pressure in a closed body compartment. Form and movement are controlled by changing the shape of this compartment.Examples: Flatworms, Nematodes, Annelids, JellyfishExoskeleton – encasement deposited on the surface of an animal. -> chitinous or made from calcium salts, etc.Examples: Insects, Crustaceans, MollusksEndoskeleton – Interior skeleton within muscles and skin. Act as levers when the muscles contract to allow the organism to move.Examples: Mammals, Birds, Reptiles, Fish, Sponges
34 Locomotion Requires energy to overcome friction & gravity Swim: friction is major issue; gravity is minorLand: requires self-support & movement against gravityFlight: requires wings developed enough to lift & overcome gravity
35 Diseases: Color Blindness Color-Blindness: due to alterations in the genes for one or more photopsin proteins.There are different types:No color vision deficiencies.with protanopia.with deuteranopia.with tritanopia.
37 Bibliography Pictures: Information:"color blindness." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <A. Campbell, Neil, and Jane B. Reece. Biology. San Francisco: Pearson Education, Inc., 05 Jan. 2009"mechanoreceptor." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <"inner ear." Encyclopedia Britannica Encyclopedia Britannica Online. 09 Apr <Helfman G., Collette B., & Facey D.: The Diversity of Fishes, Blackwell Publishing, p 3, 1997, ISBNBejan, Adrian; Marden, James H. (2006), "Constructing Animal Locomotion from New Thermodynamics Theory", American Scientist 94 (4): 342–349