Presentation on theme: "Sensory and Motor Mechanisms Samaneh Bolourchi, Jennifer Tszeng & Athena Zeng."— Presentation transcript:
Sensory and Motor Mechanisms Samaneh Bolourchi, Jennifer Tszeng & Athena Zeng
Introduction: Sensory Pathways Sensory receptors transduce stimulus energy & transmit signals to CNS (central nervous system) Reception: detection via exteroreceptors or interoreceptors Transduction: stimulus energy converted into ∆ in membrane potential of sensory receptor (receptor potential) Amplification: stimulus energy strengthens in cells in pathways Adaptation: decrease in responsiveness Transmission: action potentials transmitted to the CNS Perception: constructions formed in brain (ie color, smell, sounds)
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.
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 ions Type of mechanoreceptor varies greatly between organisms Crustaceans - vertebrate stretch receptors Mammals - dendrites of sensory neurons
Introduction: Sound & Balance Ear receives vibrations of moving air and converts into what the mind perceives as sound Also detects body movement, position & balance Structures vary between organisms Terrestrial vertebrates: inner ear is main organ of hearing & equilibrium Fish/Amphibians: lack certain parts but also contain homologous structures Invertebrates - statocysts
Sound in Humans: Structure of Human Ear Outer ear Pinna Tympanic membrane Middle ear Malleus, incus, stapes Oval window Eustachian tube Inner ear Fluid-filled chambers ie semicircular canals & cochlea
Sensory Reception: Hair Cells Rod-shaped hairs in corti Vibration of basilar membrane bends hairs against surrounding fluid & tectorial membrane Bundle direction affects reception Activates mechanoreceptors
Balance in Humans: Utricle & Saccule
Sound & Balance: Variation in Organisms Terrestrial vertebrates: ear has = main organ of hearing & equilibrium Fish/Amphibians - similar to mammalian ears; lack several structures Frogs/toads - single middle bone (stapes) Frogs: small side pocket in saccule - basis for evolution of mammalian cochlea Birds - cochlea; single middle bone (stapes)
Sound & Balance: Fish/Amphibians lateral line system have ears outside of body; no eardrum or cochlea; air-filled swim bladder also vibrates in response to sound
Sound & Balance in Invertebrates
Thermoreceptors Detect heat Located in skin and anterior hypothalamus Mammals contain a range of thermoreceptor types for particular temperature ranges Receptor proteins open a calcium channel upon binding certain products At least five different types of thermoreceptors belong to the transient receptor potential (TRP) family of channel proteins
Pain Receptors Nociceptors detect noxious conditions Essential - stimulus prompts defensive reaction Animals also produce chemicals to enhance pain perception
Touch Receptors usually on skin Humans contain naked dendrites to detect noxious thermal, mechanical & chemical stimuli Epidermis, dermis, hypodermis * structure of connective tissue & location of receptors dramatically affect the type of mechanical energy that best stimulates them
Heat Light touch Pain Cold Hair Nerve Connective tissue Hair movement Strong pressure Dermis Epidermis Human Integumentary System
Chemoreceptors The most sensitive chemoreceptors are on sensory hairs of the male silkworm which detect sex pheromones. 0.1 mm
Gustation In mammals, taste receptors are located in taste buds, most of which are on the surface of the tongue Each 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.
Olfaction In 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.
Electromagnetic Receptors Respond to various forms of electromagnetic energy such as visible light, electricity, and magnetism. Photoreceptors detect energy in form of light Examples: Snakes—body heat of prey. Fish—electric currents—prey. Animals—earths magnetic field. (birds)
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 vertebrates Evolved independently and differ from the single-lens eyes of invertebrates
Sensory Transduction The human retina contains two types of photoreceptors Rods are sensitive to light but do not distinguish colors Cones distinguish colors but are not as sensitive Each rod or cone in the vertebrate retina contains visual pigments consisting of light-absorbing molecules called retinal bonded to membrane proteins called opsin Rhodopsin (retinal + opsin) is the visual pigment of rods. Absorption of light by retinal triggers a signal transduction pathway!
Signal Transduction cont. EXTRACELLULAR FLUID Membrane potential (mV) 0 – 40 – 70 Dark Light – Hyper- polarization Time Na + cGMP CYTOSOL GMP Plasma membrane INSIDE OF DISK PDE Active rhodopsin Light Inactive rhodopsin Transducin Disk membrane 2Active rhodopsin in turn activates a G protein called transducin. 3Transducin activates the enzyme phos- phodiestera e(PDE). 4Activated PDE detaches cyclic guanosine monophosphat e (cGMP) from Na + channels in the plasma membrane by hydrolyzing cGMP to GMP. 5The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes. 1Light isomerizes retinal, which activates rhodopsin.
Signal Transduction (cont.) Three other types of neurons contribute to information processing in the retina Ganglion cells, horizontal cells, and amacrine cells Signals 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.
Synaptic activity of rod cells in light and dark Dark Responses Rhodopsin inactive Na + channels open Rod depolarized Glutamate released Bipolar cell either depolarized or hyperpolarized, depending on glutamate receptors Light Responses Rhodopsin active Na + channels closed Rod hyperpolarized No glutamate released Bipolar cell either hyperpolarized or depolarized, depending on glutamate receptors
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.
Vertebrate Skeletal Muscle Myofibrils consist of: Thin filaments: two strands of actin and two strands of a regulatory protein Thick filaments: staggered arrays of myosin molecules Striated Muscle: regular arrangement of filaments create light/dark band pattern Sarcomere: basic contractile unit between Z- lines
Types of Muscle Cardiac muscle is similar to skeletal muscle with striations. Smooth muscle lacks striations lines walls of blood vessels and digestive system organs. Skeletal Muscle Voluntary movements Attatched to bones
Skeletal Systems Support, protection, and movement 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. 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, Jellyfish Exoskeleton – encasement deposited on the surface of an animalchitinous or made from calcium salts, etc. Exoskeleton – encasement deposited on the surface of an animal. -> chitinous or made from calcium salts, etc. Examples: Insects, Crustaceans, Mollusks Endoskeleton – Interior skeleton within muscles and skin. Act as levers when the muscles contract to allow the organism to move. Endoskeleton – 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
Locomotion Requires energy to overcome friction & gravity Swim: friction is major issue; gravity is minor Land: requires self- support & movement against gravity Flight: requires wings developed enough to lift & overcome gravity
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.
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