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Sensory and Motor Mechanisms. Chapter 49. Sensing and Acting. Bats use sonar to detect their prey Moths  c an detect the bat’s sonar and attempt to flee Both of these organisms have complex sensory systems that facilitate their survival. Types of Sensory Receptors.

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sensing and acting
Sensing and Acting
  • Bats use sonar to detect their prey
  • Moths can detect the bat’s sonar and attempt to flee
  • Both of these organisms have complex sensory systems that facilitate their survival
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 sense physical deformation
    • Caused by stimuli such as pressure, stretch, motion, and sound
  • The mammalian sense of touch
    • Relies on mechanoreceptors that are the dendrites of sensory neurons
  • General receptors that transmit information about the total solute concentration of a solution
  • Specific receptors that respond to individual kinds of molecules
  • EX: Taste, Smell
Figure 49.5 Chemoreceptors in an insect: Female silk moth Bombyx mori releasing pheromones; SEM of male Bombyx mori antenna
electromagnetic receptors
Electromagnetic Receptors
  • Electromagnetic receptors detect various forms of electromagnetic energy
    • Such as visible light, electricity, and magnetism
  • Some snakes have very sensitive infrared receptors
    • That detect body heat of prey against a colder background
Figure 49.6 Specialized electromagnetic receptors: Rattle snake with infrared recpters, beluga whale pod
figure 49 6bx beluga whale pod
Figure 49.6bx Beluga whale pod
  • Many mammals appear to use the Earth’s magnetic field lines
    • To orient themselves as they migrate
  • 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
the mechanoreceptors hearing and equilibrium detect settling particles or moving fluid
The mechanoreceptors  hearing and equilibrium detect settling particles or moving fluid
  • Hearing and the perception of body equilibrium are related in most animals
  • Three regions of the human ear
    • The outer ear
    • The middle ear
    • The inner ear
ear structure
Ear Structure
  • The outer ear external pinna and the auditory canal
  • Collects sound and directs it to the tympanic membrane (eardrum)
middle ear
Middle Ear
  • Three small bones malleus (hammer), the incus (anvil) and stapes (stirrup) collect vibrations
  • The eustacian tube equalizes air pressure between the outer and middle ear
the cochlea



Axons ofsensoryneurons

Oval window







Basilar membrane

The Cochlea
  • Snail shaped structure organ of corti
  • 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 ultimately strike the round window
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
senses of taste and smell
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
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)
smell in humans
Smell in Humans
  • Olfactory receptor cellsAre neurons that line the upper portion of the nasal cavity
  • When odorant molecules bind to specific receptors
    • A signal transduction pathway is triggered, sending action potentials to the brain
vision in the animal kingdom
Vision in the Animal Kingdom
  • Two major types of image-forming eyes have evolved in invertebrates
    • The compound eye and the single-lens eye
  • Compound eyes are found in insects and crustaceans
    • And consist of up to several thousand light detectors called ommatidia
  • Single-lens eyes
    • Are found in some jellies, polychaetes, spiders, and many molluscs
    • Work on a camera-like principle
simplest eye
Simplest Eye
  • The eye cup of planarians provides information about light intensity and direction but does not form images
vertebrate eyes
Vertebrate Eyes
  • Camera-like they evolved independently and differ from the single-lens eyes of invertebrates
  • 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
    • The iris, which regulates the pupil
    • The retina, which contains photoreceptors
    • The lens, which focuses light on the retina
  • 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
figure 49 13 from light reception to receptor potential a rod cell s signal transduction pathway
Figure 49.13 From light reception to receptor potential: A rod cell’s signal-transduction pathway
the human skeleton
The Human Skeleton
  • Functions in support, protection, & movement
  • Animal movements result from muscles working against some type of skeleton
  • 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
muscles contraction move skeletal parts
Muscles contraction Move Skeletal Parts
  • The action of a muscle always to contract
  • Skeletal muscles are attached to the skeleton in antagonistic pairs
    • With each member of the pair working against each other
vertebrate skeletal muscle
Vertebrate Skeletal Muscle
  • Is characterized by a hierarchy of smaller and smaller units
  • 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
  • Skeletal muscle is also called striated muscle
    • Because the regular arrangement of the myofilaments creates a pattern of light and dark bands
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
  • 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
  • The filaments slide past each other longitudinally, producing more overlap between the thin and thick filaments
  • As a result of this sliding
    • The I band and the H zone shrink
  • 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
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
  • Annelids use their hydrostatic skeleton for peristalsis
    • A type of movement on land produced by rhythmic waves of muscle contractions
  • An exoskeleton is a hard encasement
    • Deposited on the surface of an animal
    • Are found in most molluscs and arthropods
  • 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