Sensory and Motor Mechanisms

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 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)

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 ions • Type of mechanoreceptor varies greatly between organisms • Crustaceans - vertebrate stretch receptors • Mammals - dendrites of sensory neurons

5. 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

6. 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

7. 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

8. Balance in Humans: Utricle & Saccule

9. 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)

10. 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

11. Sound & Balance in Invertebrates

12. 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

13. Pain Receptors • Nociceptors detect noxious conditions • Essential - stimulus prompts defensive reaction • Animals also produce chemicals to enhance pain perception

14. 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

15. Cold Light touch Pain Hair Heat Epidermis Dermis Hair movement Nerve Strong pressure Connective tissue Human Integumentary System

16. 0.1 mm Chemoreceptors • The most sensitive chemoreceptors are on sensory hairs of the male silkworm which detect sex pheromones.

17. 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.

19. 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.

21. 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)

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 vertebrates • Evolved independently and differ from the single-lens eyes of invertebrates

23. Eye Structure

24. 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!

25. Light EXTRACELLULARFLUID INSIDE OF DISK Active rhodopsin PDE Membranepotential (mV) Plasmamembrane CYTOSOL 0 Dark Light cGMP Transducin Inactive rhodopsin Disk membrane – 40 GMP – Hyper- polarization Na+ – 70 1Light isomerizes retinal, which activates rhodopsin. 3Transducinactivates theenzyme phos-phodiesterae(PDE). 2Active rhodopsin in turn activates a G protein called transducin. 4 Activated PDE detaches cyclic guanosine monophosphate (cGMP) from Na+ channels in the plasma membrane by hydrolyzing cGMP to GMP. Time 5The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes. Na+ Signal Transduction cont.

26. 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.

27. Dark Responses Light Responses Rhodopsin active Rhodopsin inactive Na+ channels closed Na+ channels open Rod hyperpolarized Rod depolarized Glutamate released No glutamate released Bipolar cell either depolarized or hyperpolarized, depending on glutamate receptors Bipolar cell either hyperpolarized or depolarized, depending on glutamate receptors Synaptic activity of rod cells in light and dark

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 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

32. Types of Muscle • Skeletal Muscle • Voluntary movements • Attatched to bones • Cardiac muscle is similar to skeletal muscle • with striations. • Smooth muscle • lacks striations • lines 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, Jellyfish • 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. • Examples: Mammals, Birds, Reptiles, Fish, Sponges

34. 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

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.

36. Diseases (Cont.) • \ALS, amyotrophic lateral sclerosis, or Lou Gehrig’s • Myasthenia gravis

37. Bibliography Pictures: • http://www.geocities.com/HotSprings/Falls/5568/images/bones.jpg • http://porpax.bio.miami.edu/~cmallery/150/neuro/49x6.jpg • http://farm4.static.flickr.com/3029/2998700309_b6cfce6edf_o.jpg • http://media-2.web.britannica.com/eb-media/86/4086-004-EA855487.gif • http://farm4.static.flickr.com/3164/2619281157_8e80f2dfd1.jpg • http://www.backyardnature.net/pix/birdear.jpg • http://www.nhm.ac.uk/about-us/news/2006/jan/images/ancient-fish-spiracle-370_7483_1.gif • http://caspar.bgsu.edu/%7Ecourses/Neuroethology/Labs/Images/Statocyst.jpg • http://tolweb.org/tree/ToLimages/PhippocampusEye111.250a.jpg Information: • "color blindness." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online. 09 Apr. 2009 <http://www.britannica.com/EBchecked/topic/126712/colour-blindness>. • A. Campbell, Neil, and Jane B. Reece. Biology. San Francisco: Pearson Education, Inc., 05 Jan. 2009 • "mechanoreceptor." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online. 09 Apr. 2009 <http://www.britannica.com/EBchecked/topic/371976/mechanoreception>. • "inner ear." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online. 09 Apr. 2009 <http://www.britannica.com/EBchecked/topic/288499/inner-ear>. • Helfman G., Collette B., & Facey D.: The Diversity of Fishes, Blackwell Publishing, p 3, 1997, ISBN 0-86542-256-7 • Bejan, Adrian; Marden, James H. (2006), "Constructing Animal Locomotion from New Thermodynamics Theory", American Scientist 94 (4): 342–349