1 / 137

Chapter 49

Chapter 49. Sensory and Motor Mechanisms. 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. Both organisms have complex sensory systems that facilitate survival

erica-sullivan
Download Presentation

Chapter 49

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 49 Sensory and Motor Mechanisms

  2. 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

  3. Both organisms have complex sensory systems that facilitate survival • These systems include diverse mechanisms that sense stimuli and generate appropriate movement

  4. 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 • The brain interprets sensations, giving the perception of stimuli

  5. Sensations and perceptions begin with sensory reception, detection of stimuli by sensory receptors • Exteroreceptors detect outside stimuli • Interoreceptors detect internal stimuli

  6. Functions Performed by Sensory Receptors • All stimuli represent forms of energy • Sensation involves converting energy into change in the membrane potential of sensory receptors • Functions of sensory receptors: sensory transduction, amplification, transmission, and integration

  7. The stretch receptor in a crayfish is an example of a sensory receptor

  8. LE 49-2a Weak muscle stretch Strong muscle stretch Muscle Dendrites Receptor potential –50 –50 –70 –70 Stretch receptor Membrane potential (mV) Action potentials 0 0 Axon –70 –70 0 2 0 2 1 3 4 5 6 7 1 3 4 5 6 7 Time (sec) Time (sec) in the axon of the stretch receptor. A stronger stretch produces a larger receptor potential and higher frequency of action potentials. muscles and dendrites stretch, producing a receptor potential in the stretch receptor. The receptor potential triggers action potentials Crayfish stretch receptors have dendrites embedded in abdominal muscles. When the abdomen bends,

  9. Another sensory receptor is the hair cell, which detects motion in the vertebrate ear and lateral line systems of fishes and amphibians

  10. LE 49-2b No fluid movement Fluid moving in one direction Fluid moving in other direction “Hairs” of hair cell More neuro- trans- mitter Neuro- trans- mitter at synapse Less neuro- trans- mitter Axon –50 –50 –50 Receptor potential –70 –70 –70 Membrane potential (mV) Membrane potential (mV) Membrane potential (mV) Action potentials 0 0 0 –70 –70 –70 0 2 0 2 1 3 4 5 6 7 0 2 1 3 4 5 6 7 1 3 4 5 6 7 Time (sec) Time (sec) Time (sec) at a synapse with a sensory neuron, which conducts action potentials to the CNS. Bending in one direction depolarizes the hair cell, causing it to release more Vertebrate hair cells have specialized cilia or microvilli (“hairs”) that bend when surrounding fluid moves. Each hair cell releases an excitatory neurotransmitter neurotransmitter and increasing frequency 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.

  11. Sensory Transduction • Sensory transduction is the conversion of stimulus energy into a change in the membrane potential of a sensory receptor • This change in membrane potential is called a receptor potential

  12. Many sensory receptors are very sensitive, able to detect the smallest physical unit of stimulus

  13. Amplification • Amplification is the strengthening of stimulus energy by cells in sensory pathways

  14. Transmission • After energy has been transduced into a receptor potential, some sensory cells generate action potentials, which are transmitted to the CNS • Sensory cells without axons release neurotransmitters at synapses with sensory neurons

  15. Integration • Integration of sensory information begins when information is received • Integration occurs at all levels of the nervous system • Some receptor potentials are integrated through summation • Another integration is sensory adaptation, decreased responsiveness during stimulation

  16. Types of Sensory Receptors • Based on energy transduced, sensory receptors fall into five categories: • Mechanoreceptors • Chemoreceptors • Electromagnetic receptors • Thermoreceptors • Pain receptors

  17. Mechanoreceptors • Mechanoreceptors sense physical deformation caused by stimuli such as pressure, stretch, motion, and sound • The sense of touch in mammals relies on mechanoreceptors that are dendrites of sensory neurons

  18. LE 49-3 Cold Hair Pain Heat Light touch Epidermis Dermis Hypodermis Strong pressure Hair movement Connective tissue Nerve

  19. Chemoreceptors • General chemoreceptors transmit information about the total solute concentration of a solution • Specific chemoreceptors respond to individual kinds of molecules • The antennae of the male silkworm moth have very sensitive specific chemoreceptors

  20. LE 49-4 0.1 mm

  21. Electromagnetic Receptors • Electromagnetic receptors detect electromagnetic energy, such as light, electricity, and magnetism • Some snakes have very sensitive infrared receptors that detect body heat of prey against a colder background

  22. LE 49-5 Eye Infrared receptor 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. Some migrating animals, such as these beluga whales, apparently sense Earth’s magnetic field and use the information, along with other cues, for orientation.

  23. Many mammals appear to use Earth’s magnetic field lines to orient themselves as they migrate

  24. Thermoreceptors • Thermoreceptors, which respond to heat or cold, help regulate body temperature by signaling both surface and body core temperature

  25. Pain Receptors • In humans, pain receptors, or nociceptors, are a class of naked dendrites in the epidermis • They respond to excess heat, pressure, or chemicals released from damaged or inflamed tissues

  26. Concept 49.2: The mechanoreceptors involved with hearing and equilibrium detect settling particles or moving fluid • Hearing and perception of body equilibrium are related in most animals

  27. Sensing Gravity and Sound in Invertebrates • Most invertebrates have sensory organs called statocysts • Statocysts contain mechanoreceptors and function in the sense of equilibrium

  28. LE 49-6 Ciliated receptor cells Cilia Statolith Sensory nerve fibers

  29. Many arthropods sense sounds with body hairs that vibrate or with localized “ears” consisting of a tympanic membrane and receptor cells

  30. LE 49-7 Tympanic membrane 1 mm

  31. Hearing and Equilibrium in Mammals • In most terrestrial vertebrates, sensory organs for hearing and equilibrium are closely associated in the ear

  32. LE 49-8 Middle ear Outer ear Inner ear Semicircular canals Stapes Skull bones Middle ear Incus Auditory nerve, to brain Malleus Tympanic membrane Pinna Auditory canal Eustachian tube Cochlea Oval window Round window Tympanic membrane Eustachian tube Tectorial membrane Hair cells Bone Cochlea duct Auditory nerve Vestibular canal Tympanic canal Basilar membrane Axons of sensory neurons To auditory nerve Organ of Corti

  33. 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 • These vibrations create pressure waves in the fluid in the cochlea that travel through the vestibular canal and strike the round window

  34. LE 49-9 Cochlea Stapes Axons of sensory neurons Vestibular canal Perilymph Oval window Apex Base Basilar membrane Tympanic canal Round window

  35. Pressure waves in the canal cause the basilar membrane to vibrate, bending its hair cells • This bending of hair cells depolarizes their membranes, sending action potentials that travel via the auditory nerve to the brain

  36. The cochlea can distinguish pitch because the basilar membrane is not uniform along its length • Each region vibrates most vigorously at a particular frequency and leads to excitation of a specific auditory area of the cerebral cortex

  37. LE 49-10 Cochlea (uncoiled) Basilar membrane Apex (wide and flexible) 500 Hz (low pitch) 1 kHz 2 kHz 4 kHz 8 kHz 16 kHz (high pitch) Frequency producing maximum vibration Base (narrow and stiff)

  38. Equilibrium • Several organs of the inner ear detect body position and balance: the utricle, saccule, and semicircular canals

  39. LE 49-11 Semicircular canals Ampulla Flow of endolymph Flow of endolymph Vestibular nerve Cupula Hairs Hair cell Vestibule Nerve fibers Utricle Body movement Saccule

  40. Hearing and Equilibrium in Other Vertebrates • Like other vertebrates, fishes and amphibians have inner ears near the brain • Most fishes and aquatic amphibians also have a lateral line system along both sides of their body • The lateral line system contains mechanoreceptors with hair cells that respond to water movement

  41. LE 49-12 Lateral line Lateral line canal Scale Opening of lateral line canal Neuromast Epidermis Lateral nerve Segmental muscles of body wall Cupula Sensory hairs Supporting cell Hair cell Nerve fiber

  42. Concept 49.3: The senses of taste and smell are closely related in most animals • Gustation (taste) and olfaction (smell) are dependent on chemoreceptors that detect specific chemicals in the environment • Taste receptors of insects are in sensory hairs called sensilla, located on feet and in mouthparts

  43. LE 49-13a To brain Chemoreceptors Sensillum Microelectrode To voltage recorder Pore at tip Pipette containing test substance

  44. LE 49-13b Chemoreceptors 50 Number of action potentials in first second of response 30 10 0 Honey 0.5 M NaCl Meat 0.5 M Sucrose Stimulus

  45. Taste in Humans • In humans, receptor cells for taste are modified epithelial cells organized into taste buds • Five taste perceptions: sweet, sour, salty, bitter, and umami (elicited by glutamate) • Transduction in taste receptors occurs by several mechanisms

  46. LE 49-14 Sugar molecule Taste pore Sensory receptor cells Taste bud Sensory neuron Tongue G protein Sugar Adenylyl cyclase Sugar receptor ATP cAMP Protein kinase A SENSORY RECEPTOR CELL K+ Synaptic vesicle Ca2+ Neurotransmitter Sensory neuron

  47. Smell in Humans • Olfactory receptor cells are neurons that line the upper portion of the nasal cavity • Binding of odorant molecules to receptors triggers a signal transduction pathway, sending action potentials to the brain

  48. LE 49-15 Brain potentials Action Olfactory bulb Nasal cavity Bone Odorant Epithelial cell Odorant receptors Chemoreceptor Plasma membrane Cilia Odorant Mucus

  49. 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

More Related