Ch. 49
49.1 Sensory receptors transduce stimulus energy and transmit signals to the CNS

Functions performed by Sensory Receptors
o Sensory receptors are specialized neurons that detect environmental stimuli
o Exteroreceptors: detect external stimuli
o Interoreceptors: detect internal
o Sensory transduction – conversion of stimulus energy to membrane potential
(receptor potential)
o Signal transduction pathway in receptor cell amplifies signal

Causes receptor cell to:
1. Produce action potentials
2. Release neurotransmitter at a synapse with a sensory neuron

Types of Sensory receptors
o Mechanoreceptors – sense physical deformation caused by stimuli like pressure,
touch, sound, motion (mechanical energy)
o Chemoreceptors – general receptors that transmit info about the solute
concentration of a solution and specific receptors that respond to certain
molecules
o Electromagnetic receptors – detect electromagnetic energy like visible light,
electricity, magnetism; includes photoreceptors
o Thermoreceptors – respond to heat/cold; regulate body temperature
o Pain receptors – (nocireceptors) class of naked dendrites in the epidermis
49.2 The mechanoreceptors involved with hearing and equilibrium detect settling particles or moving
fluid

Sensing gravity and sound in invertebrates
o Invertebrates sense their orientation w/ respect to gravity through statocysts
o Arthropods sense sounds with body hairs that vibrate and with ‘ears’ consisting of
tympanic membrane and receptor cells

Hearing and equilibrium in mammals
o Tympanic membrane (eardrum) transmits sound waves to 3 small bones of the
middle ear
o The utricle, saccule, and 3 semicircular canals in inner ear function in balance and
equilibrium

Hearing and equilibrium in other vertebrates
o Detection of water movement in fishes and aquatic amphibians is brought about
by a lateral line system containing clustered hair cells
Taste and Smell
 Gustation - taste
 Olfaction – smell
 These chemical senses used to find mates, recognize territory, navigate, etc.
Taste in Humans
 Taste buds – Epithelial cells
 Transduction in taste receptors
 [figure 49.14– pg. 1506]
Smell in Humans
 Receptor cells in upper nasal cavity that send impulses to olfactory bulb in brain
 Odorant receptors bind with the substance on plasma membrane; signal triggered for
transduction pathway (G protein)
 [put in figure frm Signal trand. Chapter]
Vision
 Same mechanics applied throughout the animal kingdom as all photoreceptors contain
similar pigment molecules that absorb light
 [figure 49.18]
Vision in Invertebrates
 Ocellus is the simplest light detecting organ; does not form images
 [figure 49.16]
 Compound eyes : detects movement; provides excellent color vision; in insects,
crustaceans; 1000’s of light detectors
 Single lens eyes: camera-like; jellies, spiders, molluscs
The Vertebrate Visual System
 [eyeball structure pic]
 [flow chart for all the vocab in this section]
Sclera: white outerlayer of
connective tissue
Conjuctiva: mucuous
membrane that covers sclera
Chloroid: thin, pigmented inner
layer
[add more vocab words]
Processing visual information & sensory transduction
[figure 49.24]
Skeleton

main functions – support, protection, movement

hydrostatic skeleton – structure

Exoskeleton and endoskeleton

Three types of joints – hinge, ball and socket, pivot
Muscle

Movement of the skeleton due to muscle contraction

Parts of muscle – myofibrils, myofiliaments that consist of thin and thick filiaments

Figure 49.27 as a visual for comparing muscle contraction in different animals

Figure 49.28 as describing muscle structure

Sliding filiament model - touch very lightly on this subject

How the nervous system controls muscle contractions and other activities that involves
muscles – also skim through the basic requirements for muscle activity (for example, the
role of calcium and regulatory proteins).

Describe the functions along with the differences in all the types of skeletal muscle
fibers ( Table 49.1)

Different types of muscles – not that important but explain how different types of
muscles function differently
Role of gravity and friction

Locomotion - active travel from place to place

Energy cost and efficiency