Post on 01-Jan-2016
Sensory and Motor MechanismsChapter 49
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
Based on the energy they transduce, sensory receptors fall into five categories Mechanoreceptors Chemoreceptors Electromagnetic receptors Thermoreceptors Pain receptors
Mechanoreceptors
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
Figure 49.4 Mechanoreception by a hair cell
Chemoreceptors 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
Figure 49.x1 Chemoreceptors: Snake tongue
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
Many mammals appear to use the Earth’s magnetic field linesTo orient themselves as they migrate
Thermoreceptors Thermoreceptors, which respond to
heat or cold Help regulate body temperature by
signaling both surface and body core temperature
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
Hearing and the perception of body equilibrium are related in most animals
Three regions of the human earThe outer earThe middle earThe inner ear
Ear Structure The outer ear
external pinna and the auditory canal
Collects sound and directs it to the tympanic membrane (eardrum)
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
Snail shaped structure organ of corti
Cochlea
Stapes
Oval window
Apex
Axons ofsensoryneurons
Roundwindow Basilar
membrane
Tympaniccanal
Base
Vestibularcanal Perilymph
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
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
Figure 49.18 How the cochlea distinguishes pitch
Figure 49.19 Organs of balance in the inner ear
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
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)
Figure 49.2 Sensory transduction by a taste receptor
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
Olfaction in Humans
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 The eye cup of planarians provides
information about light intensity and direction but does not form images
Figure 49.8 Compound eyes
(a)
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
Structure of the Human Eye
Focusing of the Mammalian Eye
Photoreceptors 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
The effect of light on synapses between rod cells and bipolar cells
Figure 49.15 The vertebrate retina
Neural pathways for vision
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 bonesSome fused together and others
connected at joints by ligaments that allow freedom of movement
The Human Skeleton
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 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
Skeletal Muscle
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
The sliding-filament model of muscle contraction
One hypothesis for how myosin-actin interactions generate the force for muscle contraction
Hypothetical mechanism for the control of muscle contraction
Review of skeletal muscle contraction
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
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
Exoskeletons
An exoskeleton is a hard encasement Deposited on the surface of an animal Are found in most molluscs and
arthropods
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