Sensory and Motor Mechanisms

Chapter 49 : Chapter 49 Sensory and Motor Mechanisms

Slide2 : Overview: Sensing and Acting Bats use sonar to detect their prey Moths, a common prey for bats Can detect the bat’s sonar and attempt to flee Figure 49.1

Slide3 : Both of these organisms Have complex sensory systems that facilitate their survival The structures that make up these systems Have been transformed by evolution into diverse mechanisms that sense various stimuli and generate the appropriate physical movement

Slide4 : Concept 49.1: Sensory receptors transduce stimulus energy and transmit signals to the central nervous system Sensations are action potentials That reach the brain via sensory neurons Once the brain is aware of sensations It interprets them, giving the perception of stimuli

Slide5 : Sensations and perceptions Begin with sensory reception, the detection of stimuli by sensory receptors Exteroreceptors Detect stimuli coming from the outside of the body Interoreceptors Detect internal stimuli

Functions Performed by Sensory Receptors : Functions Performed by Sensory Receptors All stimuli represent forms of energy Sensation involves converting this energy Into a change in the membrane potential of sensory receptors

Slide7 : Sensory receptors perform four functions in this process Sensory transduction, amplification, transmission, and integration

Slide8 : Two types of sensory receptors exhibit these functions A stretch receptor in a crayfish

Slide9 : A hair cell found in vertebrates of action potentials in the sensory neuron. Bending in the other direction has the opposite effects. Thus, hair cells respond to the direction of motion as well as to its strength and speed.s

Sensory Transduction : Sensory Transduction Sensory transduction is the conversion of stimulus energy Into a change in the membrane potential of a sensory receptor This change in the membrane potential Is known as a receptor potential

Slide11 : Many sensory receptors are extremely sensitive With the ability to detect the smallest physical unit of stimulus possible

Amplification : Amplification Amplification is the strengthening of stimulus energy By cells in sensory pathways

Transmission : Transmission After energy in a stimulus has been transduced into a receptor potential Some sensory cells generate action potentials, which are transmitted to the CNS

Slide14 : Sensory cells without axons Release neurotransmitters at synapses with sensory neurons

Integration : Integration The integration of sensory information Begins as soon as the information is received Occurs at all levels of the nervous system

Slide16 : Some receptor potentials Are integrated through summation Another type of integration is sensory adaptation A decrease in responsiveness during continued stimulation

Types of Sensory Receptors : Types of Sensory Receptors Based on the energy they transduce, sensory receptors fall into five categories Mechanoreceptors Chemoreceptors Electromagnetic receptors Thermoreceptors Pain receptors

Mechanoreceptors : Mechanoreceptors Mechanoreceptors sense physical deformation Caused by stimuli such as pressure, stretch, motion, and sound

Slide19 : The mammalian sense of touch Relies on mechanoreceptors that are the dendrites of sensory neurons Figure 49.3

Chemoreceptors : Chemoreceptors Chemoreceptors include General receptors that transmit information about the total solute concentration of a solution Specific receptors that respond to individual kinds of molecules

Slide21 : Two of the most sensitive and specific chemoreceptors known Are present in the antennae of the male silkworm moth Figure 49.4

Electromagnetic Receptors : Electromagnetic Receptors Electromagnetic receptors detect various forms of electromagnetic energy Such as visible light, electricity, and magnetism

Slide23 : Some snakes have very sensitive infrared receptors That detect body heat of prey against a colder background Figure 49.5a (a) This rattlesnake and other pit vipers have a pair of infrared receptors, one between each eye and nostril. The organs are sensitive enough to detect the infrared radiation emitted by a warm mouse a meter away. The snake moves its head from side to side until the radiation is detected equally by the two receptors, indicating that the mouse is straight ahead.

Slide24 : Many mammals appear to use the Earth’s magnetic field lines To orient themselves as they migrate Figure 49.5b (b) Some migrating animals, such as these beluga whales, apparently sense Earth’s magnetic field and use the information, along with other cues, for orientation.

Thermoreceptors : Thermoreceptors Thermoreceptors, which respond to heat or cold Help regulate body temperature by signaling both surface and body core temperature

Pain Receptors : Pain Receptors In humans, pain receptors, also called nociceptors Are a class of naked dendrites in the epidermis Respond to excess heat, pressure, or specific classes of chemicals released from damaged or inflamed tissues

Slide27 : Concept 49.2: The mechanoreceptors involved with hearing and equilibrium detect settling particles or moving fluid Hearing and the perception of body equilibrium Are related in most animals

Sensing Gravity and Sound in Invertebrates : Sensing Gravity and Sound in Invertebrates Most invertebrates have sensory organs called statocysts That contain mechanoreceptors and function in their sense of equilibrium Figure 49.6

Slide29 : Many arthropods sense sounds with body hairs that vibrate Or with localized “ears” consisting of a tympanic membrane and receptor cells Figure 49.7

Hearing and Equilibrium in Mammals : Hearing and Equilibrium in Mammals In most terrestrial vertebrates The sensory organs for hearing and equilibrium are closely associated in the ear

Slide31 : Exploring the structure of the human ear Figure 49.8

Hearing : Hearing Vibrating objects create percussion waves in the air That cause the tympanic membrane to vibrate The three bones of the middle ear Transmit the vibrations to the oval window on the cochlea

Slide33 : These vibrations create pressure waves in the fluid in the cochlea That travel through the vestibular canal and ultimately strike the round window Figure 49.9

Slide34 : The pressure waves in the vestibular canal Cause the basilar membrane to vibrate up and down causing its hair cells to bend The bending of the hair cells depolarizes their membranes Sending action potentials that travel via the auditory nerve to the brain

Slide35 : The cochlea can distinguish pitch Because the basilar membrane is not uniform along its length Figure 49.10

Slide36 : Each region of the basilar membrane vibrates most vigorously At a particular frequency and leads to excitation of a specific auditory area of the cerebral cortex

Equilibrium : Equilibrium Several of the organs of the inner ear Detect body position and balance

Slide38 : The utricle, saccule, and semicircular canals in the inner ear Function in balance and equilibrium Figure 49.11

Hearing and Equilibrium in Other Vertebrates : Hearing and Equilibrium in Other Vertebrates Like other vertebrates, fishes and amphibians Also have inner ears located near the brain

Slide40 : Most fishes and aquatic amphibians Also have a lateral line system along both sides of their body

Slide41 : The lateral line system contains mechanoreceptors With hair cells that respond to water movement Figure 49.12

Slide42 : Concept 49.3: The senses of taste and smell are closely related in most animals The perceptions of gustation (taste) and olfaction (smell) Are both dependent on chemoreceptors that detect specific chemicals in the environment

Slide43 : The taste receptors of insects are located within sensory hairs called sensilla Which are located on the feet and in mouthparts

Slide44 : Figure 49.13 EXPERIMENT Insects taste using gustatory sensilla (hairs) on their feet and mouthparts. Each sensillum contains four chemoreceptors with dendrites that extend to a pore at the tip of the sensillum. To study the sensitivity of each chemoreceptor, researchers immobilized a blowfly (Phormia regina) by attaching it to a rod with wax. They then inserted the tip of a microelectrode into one sensillum to record action potentials in the chemoreceptors, while they used a pipette to touch the pore with various test substances. Number of action potentials in first second of response CONCLUSION Any natural food probably stimulates multiple chemoreceptors. By integrating sensations, the insect’s brain can apparently distinguish a very large number of tastes. To brain Chemo- receptors Pore at tip Pipette containing test substance To voltage recorder Sensillum Microelectrode 50 30 10 0 0.5 M NaCl Meat 0.5 M Sucrose Honey Stimulus Chemoreceptors RESULTS Each chemoreceptor is especially sensitive to a particular class of substance, but this specificity is relative; each cell can respond to some extent to a broad range of different chemical stimuli.

Taste in Humans : Taste in Humans The receptor cells for taste in humans Are modified epithelial cells organized into taste buds Five taste perceptions involve several signal transduction mechanisms Sweet, sour, salty, bitter, and umami (elicited by glutamate)

Slide46 : Transduction in taste receptors Occurs by several mechanisms Figure 49.14

Smell in Humans : Smell in Humans Olfactory receptor cells Are neurons that line the upper portion of the nasal cavity

Slide48 : When odorant molecules bind to specific receptors A signal transduction pathway is triggered, sending action potentials to the brain

Slide49 : Concept 49.4: Similar mechanisms underlie vision throughout the animal kingdom Many types of light detectors Have evolved in the animal kingdom and may be homologous

Vision in Invertebrates : Vision in Invertebrates Most invertebrates Have some sort of light-detecting organ

Slide51 : One of the simplest is the eye cup of planarians Which provides information about light intensity and direction but does not form images Figure 49.16

Slide52 : Two major types of image-forming eyes have evolved in invertebrates The compound eye and the single-lens eye

Slide53 : Compound eyes are found in insects and crustaceans And consist of up to several thousand light detectors called ommatidia Figure 49.17a–b

Slide54 : Single-lens eyes Are found in some jellies, polychaetes, spiders, and many molluscs Work on a camera-like principle

The Vertebrate Visual System : The Vertebrate Visual System The eyes of vertebrates are camera-like But they evolved independently and differ from the single-lens eyes of invertebrates

Structure of the Eye : Structure of the Eye The main parts of the vertebrate eye are The sclera, which includes the cornea The choroid, a pigmented layer The conjunctiva, that covers the outer surface of the sclera

Slide57 : The iris, which regulates the pupil The retina, which contains photoreceptors The lens, which focuses light on the retina

Slide58 : The structure of the vertebrate eye Figure 49.18

Slide59 : Humans and other mammals Focus light by changing the shape of the lens Figure 49.19a–b

Slide60 : 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

Sensory Transduction in the Eye : Sensory Transduction in the Eye Each rod or cone in the vertebrate retina Contains visual pigments that consist of a light-absorbing molecule called retinal bonded to a protein called opsin

Slide62 : Rods contain the pigment rhodopsin Which changes shape when it absorbs light

Processing Visual Information : Processing Visual Information The processing of visual information Begins in the retina itself

Slide64 : Absorption of light by retinal Triggers a signal transduction pathway Figure 49.21

Slide65 : In the dark, both rods and cones Release the neurotransmitter glutamate into the synapses with neurons called bipolar cells, which are either hyperpolarized or depolarized

Slide66 : In the light, rods and cones hyperpolarize Shutting off their release of glutamate The bipolar cells Are then either depolarized or hyperpolarized Figure 49.22

Slide67 : Three other types of neurons contribute to information processing in the retina Ganglion cells, horizontal cells, and amacrine cells Figure 49.23

Slide68 : Signals from rods and cones Travel from bipolar cells to ganglion cells The axons of ganglion cells are part of the optic nerve That transmit information to the brain Figure 49.24

Slide69 : Most ganglion cell axons lead to the lateral geniculate nuclei of the thalamus Which relays information to the primary visual cortex Several integrating centers in the cerebral cortex Are active in creating visual perceptions

Slide70 : Concept 49.5: Animal skeletons function in support, protection, and movement The various types of animal movements All result from muscles working against some type of skeleton

Types of Skeletons : Types of Skeletons The three main functions of a skeleton are Support, protection, and movement The three main types of skeletons are Hydrostatic skeletons, exoskeletons, and endoskeletons

Hydrostatic Skeletons : Hydrostatic Skeletons A hydrostatic skeleton Consists of fluid held under pressure in a closed body compartment This is the main type of skeleton In most cnidarians, flatworms, nematodes, and annelids

Slide73 : Annelids use their hydrostatic skeleton for peristalsis A type of movement on land produced by rhythmic waves of muscle contractions Figure 49.25a–c

Exoskeletons : Exoskeletons An exoskeleton is a hard encasement Deposited on the surface of an animal Exoskeletons Are found in most molluscs and arthropods

Endoskeletons : Endoskeletons An endoskeleton consists of hard supporting elements Such as bones, buried within the soft tissue of an animal Endoskeletons Are found in sponges, echinoderms, and chordates

Slide76 : The mammalian skeleton is built from more than 200 bones Some fused together and others connected at joints by ligaments that allow freedom of movement

Slide77 : The human skeleton Figure 49.26

Physical Support on Land : Physical Support on Land In addition to the skeleton Muscles and tendons help support large land vertebrates

Slide79 : Concept 49.6: Muscles move skeletal parts by contracting The action of a muscle Is always to contract

Slide80 : Skeletal muscles are attached to the skeleton in antagonistic pairs With each member of the pair working against each other Figure 49.27

Vertebrate Skeletal Muscle : Vertebrate Skeletal Muscle Vertebrate skeletal muscle Is characterized by a hierarchy of smaller and smaller units Figure 49.28

Slide82 : A skeletal muscle consists of a bundle of long fibers Running parallel to the length of the muscle A muscle fiber Is itself a bundle of smaller myofibrils arranged longitudinally

Slide83 : The myofibrils are composed to two kinds of myofilaments Thin filaments, consisting of two strands of actin and one strand of regulatory protein Thick filaments, staggered arrays of myosin molecules

Slide84 : Skeletal muscle is also called striated muscle Because the regular arrangement of the myofilaments creates a pattern of light and dark bands

Slide85 : Each repeating unit is a sarcomere Bordered by Z lines The areas that contain the myofilments Are the I band, A band, and H zone

The Sliding-Filament Model of Muscle Contraction : The Sliding-Filament Model of Muscle Contraction According to the sliding-filament model of muscle contraction The filaments slide past each other longitudinally, producing more overlap between the thin and thick filaments

Slide87 : As a result of this sliding The I band and the H zone shrink Figure 49.29a–c

Slide88 : The sliding of filaments is based on The interaction between the actin and myosin molecules of the thick and thin filaments The “head” of a myosin molecule binds to an actin filament Forming a cross-bridge and pulling the thin filament toward the center of the sarcomere

Slide89 : Myosin-actin interactions underlying muscle fiber contraction Figure 49.30

The Role of Calcium and Regulatory Proteins : The Role of Calcium and Regulatory Proteins A skeletal muscle fiber contracts Only when stimulated by a motor neuron

Slide91 : When a muscle is at rest The myosin-binding sites on the thin filament are blocked by the regulatory protein tropomyosin Figure 49.31a

Slide92 : For a muscle fiber to contract The myosin-binding sites must be uncovered This occurs when calcium ions (Ca2+) Bind to another set of regulatory proteins, the troponin complex Figure 49.31b

Slide93 : The stimulus leading to the contraction of a skeletal muscle fiber Is an action potential in a motor neuron that makes a synapse with the muscle fiber Figure 49.32

Slide94 : The synaptic terminal of the motor neuron Releases the neurotransmitter acetylcholine, depolarizing the muscle and causing it to produce an action potential

Slide95 : Action potentials travel to the interior of the muscle fiber Along infoldings of the plasma membrane called transverse (T) tubules The action potential along the T tubules Causes the sarcoplasmic reticulum to release Ca2+ The Ca2+ binds to the troponin-tropomyosin complex on the thin filaments Exposing the myosin-binding sites and allowing the cross-bridge cycle to proceed

Slide96 : Review of contraction in a skeletal muscle fiber Figure 49.33

Neural Control of Muscle Tension : Neural Control of Muscle Tension Contraction of a whole muscle is graded Which means that we can voluntarily alter the extent and strength of its contraction

Slide98 : There are two basic mechanisms by which the nervous system produces graded contractions of whole muscles By varying the number of fibers that contract By varying the rate at which muscle fibers are stimulated

Slide99 : In a vertebrate skeletal muscle Each branched muscle fiber is innervated by only one motor neuron Each motor neuron May synapse with multiple muscle fibers Figure 49.34

Slide100 : A motor unit Consists of a single motor neuron and all the muscle fibers it controls Recruitment of multiple motor neurons Results in stronger contractions

Slide101 : A twitch Results from a single action potential in a motor neuron More rapidly delivered action potentials Produce a graded contraction by summation Figure 49.35

Slide102 : Tetanus is a state of smooth and sustained contraction Produced when motor neurons deliver a volley of action potentials

Types of Muscle Fibers : Types of Muscle Fibers Skeletal muscle fibers are classified as slow oxidative, fast oxidative, and fast glycolytic Based on their contraction speed and major pathway for producing ATP

Slide104 : Types of skeletal muscles

Other Types of Muscle : Other Types of Muscle Cardiac muscle, found only in the heart Consists of striated cells that are electrically connected by intercalated discs Can generate action potentials without neural input

Slide106 : In smooth muscle, found mainly in the walls of hollow organs The contractions are relatively slow and may be initiated by the muscles themselves In addition, contractions may be caused by Stimulation from neurons in the autonomic nervous system

Slide107 : Concept 49.7: Locomotion requires energy to overcome friction and gravity Movement is a hallmark of all animals And usually necessary for finding food or evading predators Locomotion Is active travel from place to place

Swimming : Swimming Overcoming friction Is a major problem for swimmers Overcoming gravity is less of a problem for swimmers Than for animals that move on land or fly

Locomotion on Land : Locomotion on Land Walking, running, hopping, or crawling on land Requires an animal to support itself and move against gravity

Slide110 : Diverse adaptations for traveling on land Have evolved in various vertebrates Figure 49.36

Flying : Flying Flight requires that wings develop enough lift To overcome the downward force of gravity

Slide112 : CONCLUSION For animals of a given body mass, swimming is the most energy-efficient and running the least energy-efficient mode of locomotion. In any mode, a small animal expends more energy per kilogram of body mass than a large animal. CONCLUSION The energy cost of locomotion Depends on the mode of locomotion and the environment Figure 49.37 Comparing Costs of Locomotion

Slide113 : Animals that are specialized for swimming Expend less energy per meter traveled than equivalently sized animals specialized for flying or running