Sensory and Motor Mechanics

Sensory and Motor Mechanics - Chapter 49: Chapter Sensory...

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Unformatted text preview: Chapter 49: Chapter Sensory and Motor Mechanics Portia, Mandi, Amir, & Elie S e ns o ry R e c e p tio n The brain gives the perception of a stimuli when it becomes aware of a sensation Sensations are action potentials that reach the brain via sensory neurons. Ex. Light, heat, sound, smell The brain then interprets them and gives the person the perception Sensations first start with sensory receptors Sensory Receptors A sensory receptors recognizes a stimulus Types of sensory receptors ­exteroreceptors Neurological receptors receive information from the environment external ­interorecpetors Neurological receptors receive information about the organism's internal body C o nve rs io n fro m Ene rg y Sensory transduction is the conversion of an action potential into a chemical released by neurotransmitters chemical or physical stimulus is converted by sensory receptors into an electrical signal Ex. the visual system Rod and cone cells in the retina of the eye convert the energy of light into electrical impulses that travel to the brain C o nve rs io n fro m Ene rg y 1st response is the change in membrane permeability 2nd a change in membrane potential 3rd a change in receptor potential Amplification is when a weak stimulus is strengthened so it is carried to the nervous system Ex Sound waves are enhanced by outer ear and inner ear structures Transmission is the conduction of impulses to the CNS or central nervous system. Some receptors act as the sensory neuron and conducts action potentials to the central nervous system Other receptors transmit neurotransmitters across the synapse with a sensory neuron The strength of the stimulus influences the amount of neurotransmitter released by the receptor Func tio ns o f re c e p to r c e lls F unc Integration is the processing of information Sensory adaption decrease in responsiveness during continued stimulation. Ex when placing your hand on a table you immediately feel the table’s surface but after a while you do not feel the table’s surface Func tio ns o f re c e p to r c e lls Func Categories of sensory receptors: mechanoreceptors, pain receptors, thermo receptors, chemoreceptor, electromagnetic receptors Mechanoreceptors are stimulated by physical deformation caused by touch, stretch, motion, and sound Some receptor detect hair movement ex. mice and cat whiskers Muscle spindle contains fibers attached to sensory neurons running parallel to the muscle Hair cell are found in the ear and they detect movement in the environment C a te g o rizing S e ns o ry R e c e p to rs Categorizing Sensory Receptors Categorizing Pain Receptors are dendrites in the epidermis of the skin called nociceptors. Some respond to heat pressure or chemicals released from damaged tissues. The stimulus becomes translated into a defense reaction in order to avoid danger to the body Chemicals such as histamine and acids trigger pain. Prostaglandins increase pain by sensitizing the receptors or lowering the threshold Categorizing Sensory Receptors Categorizing Thermo receptors responds to either heat or cold and help to regulate body temperature Many researchers believe that in mammalian skin encapsulated dendrites are actually modified pressure receptors and non encapsulated dendrites of some sensory neurons are the thermo receptors in the skin Categorizing Sensory Receptors Categorizing Chemoreceptor transmits info about the total solute Chemoreceptor transmits info about the total solute concentration in a solution. Gustatory receptors are taste receptors and olfactory receptors are smell receptors both are types of chemoreceptor used to respond to different chemicals Some classifications of human taste include something being sweet, sour, salty, and bitter Categorizing Sensory Receptors Categorizing Electromagnetic Receptors detect various forms of electromagnetic energy ex light, electricity, and magnetism Photoreceptors detect radiation known as visible light, which is viewed by our eyes. Ex snakes and the platypus uses it to locate objects • It is the simplest Provides information about light intensity and direction without forming a image. Photoreceptor cells in a cup formed by a layer of cells containing a screening pigment that blocks light. Light enters through a opening on one side a cup. The brain compares the nerve impulses coming from the two cups. Results in the animal moving away from the light source ex. planarians Eye Cup Eye • Works like a camera. The eye’s pupil allows light to enter and is focused onto the retina, the light is absorbed by the converting receptor cells. The iris changes the pupil’s diameter, and muscles move the lens forward and back in order to focus images on the retina Ex. of invertebrates with single lens eyes are octopus, jellyfish, spiders Single Lens Eyes Single Parts of the Vertebrate Eye Parts cornea transparent front of the sclera, lets light in Pupil hole in the center of the iris Iris is anterior choroid, colored part of the eye Retina contains millions of photoreceptors that capture light rays and convert it to electrical impulses Photoreceptors and Vision Photoreceptors Compound eyes found in insects and crustaceans It consists of ommatidia (several thousands of light detectors that point in several directions) When compared to simple eyes the compound eye contains a large view angle, and can detect fast movement and the polarization of light Insects respond far better to moving objects than stationary ones. Sclera "the white of the eye” the eye's protective outer coat Choroid thin pigmented layer that nourish the back of the eye. conjunctive is the mucous membrane covering the outer surface of the sclera, moistens eye Parts of the Vertebrate Eye Parts The light-absorbing pigment rhodopsin triggers a signal-transduction pathway triggers Rods’ & cones’ outer segment contains discs Visual pigments are embedded in discs Retinal (light­absorbing pigment) is bonded to opsin (membrane protein) Rods(w/specific opsin) + retinal= visual pigment: rhodopsin ‘bleaching of rhodopsin’­ retinal component changes shapes & separates from opsin In dark: enzymes convert retinal back & recombines w/opsin (rods unresponsive in bright light) In light: altered opsin sends relay molecule (transducin): 1. G protein­transduction 2. transduction activates enzymes that alters cGMP (cyclic guanosine monophosphate) In dark: cGMP is bound to Na ion channels & keeps In dark: cGMP is bound to Na ion channels & keeps them open Rod­cell membrane depolarized­> releases glutamate @ synapses w/bipolar cells Glutamate excites or inhibits bipolar cells When light alters retinal, enzymes converts cGMP to GMP Conversion cGMP to GMP disengages from NA+ channels­> closes Decreases permeability to Na+ & hyperpolarizes membrane potiental Hyperpolarization slows rod’s release glutamate­ >excitation/inhibition of bipolar cells Color­vison depends on photopsins (red, Color­vison depends on photopsins (red, green, & blue cones) Absorption spectra overlaps & brain perceives hue based on cones most strongly stimulated Colorblindness: deficiency/absence of 1+ types photopsin The retinal assists the cerebral cortex in process visual information in Axons of rods & cones synapse w/bipolar cells ­ > synapse w/ganglion cells Horizontal & amacrine cells in retina integrate visual info before sent to brain Ganglion axon cells send info to brain via action potientals via optic nerve Vertical pathway: info ­> receptor cells to Vertical pathway: info ­> receptor cells to bipolar ­> ganglion cells Lateral pathway: 1. horizontal cells carry signals from rods/cones to other photoreceptor cells 2. amacrine cells spread info from bipolar cell to several ganglion cells Lateral inhibition: sharpens edges & enhances visual contrast via horizontal cells Horizontal cells inhibit distant receptors & non­illuminated bipolar cells Optic chiasm: where optic nerves (axons Optic chiasm: where optic nerves (axons of ganglion cells) meet @ base of cerebral cortex Nerve tracts of optic chiasm make left visual field transmit to right side of brain & vice versa Ganglion cells’ axons go to lateral geniculate nuclei (thalamus) Lateral geniculate nuclei go back to primart visual cortex (cerebrum) Visual field info projected onto visual cortex according to position in retina Hearing & Equilibrium Hearing The mammalian hearing organ is within the inner ear Outer ear made of pinna & auditory canal/ ear canal Tympanic membrane (eardrum) separates outer & middle ear Middle ear: malleus (hammer), incus (anvil), stapes(stirrup), oval window, & Eustachian tube Inner ear: channels lined by membrane w/fluid; cochlea, organ of Corti, & round window Pinna & auditory canal: collect sound Pinna & auditory canal: collect sound waves Tympanic membrane: vibrations conducted via (malleus, incus, & stapes) to inner ear (cochlea) Cochlea’s 2 chambers: upper vestibular canal & lower tympanic canal Canals contain fluid: perilymph; duct filled w/endolymph Ear converts sound waves to nerve impulses Ear converts sound waves to nerve impulses Cochlea transfers vibrating fluid into action potentials Pressure waves in vestibular canal push on cochelar duct & basilar membrane Movement of hairs opens ion channels, K+ enters Hair cells depolarize & release neurotransmitter Action potiental in a sensory neuron is triggered Volume determined by height/amplitude of Volume determined by height/amplitude of sound wave; no. action potentials Pitch determined by frequency of sound wave; basilar membrane in cochlea The inner ear also contains the organs of equilibrium of Behind oval window: utricle & saccule Utricle opens to 3 semicircular canals: apparatus for equilibrium Hair cells in utricle & saccule respond to head changes in movement & gravity ‘ear stones’/otoliths are heavier than endolymph & gravity causes constant action potentials Body angles affect different hair cells & sensory neurons to be activated Inner ears of fish stimulated by movement of otoliths (from H20) Lateral line system: detects low­frequency waves via mechanoreceptors only in H20 H20 bends cupula, which contains neuromasts (clusters of sensory hairs) Amphibians have lateral line system as tadpoles, but not as adult Soundwaves travel to inner ear via tympanic membrane & middle ear bone A lateral line system & inner ear detect pressure waves in most fishes and aquatic amphibians amphibians Many invertebrates have gravity sensors and are sound-sensitive sensors Invertebrates have statocysts (contain mechanoreceptors­sense of equilibrium) Statolith: chamber within statocyst surrounded by hairs, contains grains of sand/dense granules Statolith’s settle & stimulate hair cells in statocysts Insects have body hairs that vibrate in response to sound waves Insect “ears” are tympanic membranes stretched over internal air chambers Nerve impulses are sent to brain after receptor cells are stimulated Chemoreception- Taste and Smell Smell Animals use chemical senses for several purposes: In order to find mates (ex: silk moths responding to pheromones) To recognize marked territory (ex: dogs spraying territory) To help navigate during migration (ex: salmon using streams of origin) Check out this Brain Explorer Site on the senses of taste and smell: ses.php?page=senses3 Both taste and smell depend on chemoreceptors. Land animals can taste for chemicals or smell those in the air. Insects have taste receptors on hairs called Sensillae. These hairs are located on both the feet and mouthparts. With these hairs, insects can distinguish a large variety of tastes. Airborne chemicals are distinguished with olfactory sensillae on their antennae Perceptions of Taste and Smell are Interrelated Interrelated Taste and Smell Perceptions in Humans Humans In both taste and smell in humans, the molecule must first dissolve in a liquid before reaching the receptor cell. The molecule then binds to a specific protein This protein is located in the receptor cell membrane. This then depolarizes the membrane and releases neurotransmitters. Receptor cells for taste are organized into taste buds. With each taste of food, the brain integrates the differential input from the taste buds Four basic taste receptions are recognized: Sweet Sour Salty Bitter Human Taste and Smell Continued Human Human Smells Human The olfactory sense detects airborne chemicals. Smell receptors are neurons lining the nasal cavity. The receptors send impulses to the olfactory bulb of the brain. Odorous substances bind to plasma membrane of olfactory cilia. This triggers signal transduction with a G­protein and the enzyme adenylyl cyclase and second messenger cyclic AMP. The second messenger generates action potentials that go to the brain. Movement and Locomotion Movement Movement is key to survival in many animals. Sessile animals like sponges have no movement, but they use cilia to trap food particles. Many animals spend a large portion of energy searching from food or escaping danger. Locomotion is defined as active travel from one location to another. Check out this fun and creative Bill Nye the Science guy video on animal locomotion: Locomotion Requires Energy Locomotion Animals can crawl, walk, run, swim, fly, or hop. All forms require the use of energy. The energy is used in opposition to gravity as well as friction. Energy wise, swimming is considered the most efficient means of transport. Flying animals use more energy than swimming or walking animals. A Cost of Transport Graph Swimming and Land Locomotion In Detail Detail Overcoming gravity is less of a problem for swimming animals. However, water is more dense than air and thus has more friction. Land locomotion problems are opposite those of swimming. Air gives little resistance while gravity plays a large factor. Crawling involves overcoming a large amount of friction. Snakes are known to crawl by undulating the entire body from side to side. Flying and the Cellular and Skeletal Underpinning of Locomotion Underpinning The key to flight is the shape of the wings and the overcoming of gravity. The two systems of cell motility are microtubules and microfilaments. Microtubules are responsible for the beating of cilia Microfilaments are the contractile elements of muscle cells. All locomotion involves muscles working against some type of skeleton. Skeletons Support and Protect the Animal Body and are Important for Movement Body The skeleton functions to support, protect, and move. Skeletons aid in movement by giving muscles something firm to work against. Many animals would be frameless without a skeleton. The skeletons of animals protect vital organs such as the skull protecting the brain in humans. There are three main types of skeletons: Hydrostatic Skeletons Exoskeletons Endoskeletons Hydrostatic Skeletons consist of fluid held under pressure in a closed body compartment. Type of skeleton in cnidarians, flatworms, and annelids. These animals control movement and form with muscles that change the shape of the fluid filled compartments. The hydrostatic skeleton allows some organisms to move through peristalsis. Peristalsis involves locomotion through rhythmic waves of muscle contractions. This type of skeleton cannot support any organism on land! Hydrostatic Skeletons Hydrostatic Exoskeletons Exoskeletons The exoskeleton is a hard encasement deposited on the surface of an animal. The shell can grow through adding to the outer surface. The jointed exoskeleton in arthropods is a nonliving coat secreted from the epidermis. 30 to 50 percent of the skeleton is chitin which is a polysaccharide similar to cellulose. Fibrils of chitin are embedded in a matrix made of protein making a strong a flexible material. The exoskeleton or arthropods is periodically shed. Endoskeletons Endoskeletons Endoskeletons consist of supporting elements such as bones within soft tissues. The ossicles are composed of magnesium carbonate and calcium carbonate crystals. Separate plates are usually bound together by protein fibers. The mammalian skeleton consists of more than 200 bones­ some fused and some connected at joints. Anatomists divide the frame into the skull, backbone, rib cage, and appendicular skeleton. Joints provide flexibility for body movement. Physical Support on Land Depends on Body Adaptations on The size of an animals legs, the posture of the animal, and the position of the legs relative to the main body are all important factors of structural support. Skeletal muscles are attached to the bones and responsible for movement. The skeletal muscles consist of a bundle of long fibers running the length of the muscle. Each fiber is itself a bundle of smaller myofibrils which are arranged longitudinally. Myofibrils are composed of myofilaments. Muscles Move Skeletal Parts by Contracting Parts Muscles are attached to Muscles are attached to skeleton in antagonistic pairs Each muscle working in opposite directions Skeletal muscle is attached to the bones is responsible for the movement It is characterized by a hierarchy of small parallel units Fig 49­31 Each muscle is made up of a bundle of fibers Each fiber is a single cell with many nuclei Each fiber is a bundle of smaller myofibrils arranged longitudinally Myofibrils are made up of two kinds of myofilaments (thin and thick filaments) Skeletal muscle is called striated muscle Function and General Structure of Vertebrae Skeletal Muscle Vertebrae Thin Filaments consist of two strands of and one strand of regulatory protein. Thick Filaments are staggered arrays of myosin molecules. The arrangement of the myofilaments creates a repeating pattern of light and dark bands. Each repeating unit is a sarcomere. Z lines are the borders of the sarcomere and are lined up in adjacent feature in supporting body weight. The A band is the broad region of the muscle. Muscles and tendons are relatively straight and bear most of the load. Interactions Between Myosin and Actin Generate Force During Muscle Contractions Contractions When a muscle contracts, the distance from one Z line to the next becomes shorter The changes of a contracting muscle can be explained by the sliding­ filament model Fig 49­32 According to the model, neither the thick or thin filaments shorten in length Rather the filaments slide past each other longitudinally The sliding is based on the interactions of the actin and myosin molecules Those molecules make up the thin and thick filaments Fig 49-33 Calcium Ions and Regulatory Proteins Control Muscle Contraction Proteins The muscle contracts when stimulated by a motor neuron When at rest, tropomyosin blocks the binding sites on the actin molecules The troponin complex controls the position of tropomyosin on the thin filament. Fig 49­34 Calcium ions cause the active sites to become available The ions bind to troponin This alters the interaction between troponin and tropomyosin When calcium ions are present, sliding can occur When the amount of calcium falls, the active sites are covered again The amount of calcium is regulated by the saroplasmic reticulum It is a storehouse for calcium Fig 49­35 Fig 49-36 Diverse Body Movements Require Variation in Muscle Activity Variation A single action potential will produce an increase in muscle tension This lasts about 100msec or less If a second action occurs, then the tension will sum It will also produce a greater response If rate of tension is fast enough, the twitches blur This causes a sustained and smooth contraction, called tetanus In a vertebrate muscle, each muscle cell is innervated by one motor neuron But each motor neuron may make connections with many muscle cells Motor unit: consists of a single motor neutron and all the muscle fibers it controls When the motor neuron fires, the fibers in the motor unit contract as a group Tension can be increased by activating more and more motor neurons This is called recruitment Fast muscle fiber: used for short, rapid, powerful contractions Slow muscle fibers: found in muscles that are used for posture, and long contractions Slow fibers have less sarcoplasmic reticulum and slower calcium pumps This causes a twitch which lasts five time longer than a fast muscle twitch Slow muscle fibers also have many mitochondria, a rich blood supply, and myoglobin Myoglobin binds more oxygen more tightly than hemoglobin, is it can extract oxygen from the blood effectively Cardiac muscle is only found in one place The junctions between cardiac muscle cells contain intercalated discs These regions are where gap junctions provide direct electrical coupling among cells Cardiac cells can generate action on their own. The plasma membrane has pacemaker properties This causes rhythmic depolarizations Smooth muscles are made up of spirals of the filaments It also contain less myosin Smooth muscles do not have well­developed sarcoplasmic reticulum Contractions are slow, but there is a great amount of control http://highered.mcgraw­ Bibliography Bibliography Biologie.uni. 30 Jan. 2009 <http://www.biologie.uni­­online/ library/falk/vision/eyeRetinaToNerve.jpg >. Colorblind Homepage. 30 Jan. 2009 <>. Colour Therapy Healing. 30 Jan. 2009 <>. DIY Calculator. 29 Jan. 2009 < cvision­left­to­right.gif >. Fresh Brainz. 30 Jan. 2009 <>. St. Luke's Eye. 26 Jan. 2009 < sclera.asp>. The Hearing Professionals. 29 Jan. 2009 <http://www.hearingprofessionals.­Human­Ear.gif >. Think Quest. 29 Jan. 2009 < soundwave2.GIF >. School Science. 29 Jan. 2009 < Corus/11­14/images/cochlea1.jpg>. Richard Seaman. 26 Jan. 2009 <http://www.richard­ Underwater/Belize/SportFish/BigSilverFishWithYellowTail.jpg >. ...
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This note was uploaded on 11/12/2010 for the course BSCI BSCI 110B taught by Professor Johnson during the Spring '09 term at Vanderbilt.

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