Arcs
A Reflex transducer converts a signal of one modality into another
modality:
RECEPTOR
STIMULUS
photoreceptor
mechanoreceptor
light
displacement, pressure
OUTPUT(S)
chemoreceptor
thermoreceptor
chemical
heat, cold
chemical
electrical
nociceptor
electroreceptor
magnetoreceptor
pain, intense other
electric fields
magnetic field
(coded)
Receptor and Generator Potentials
Signals
to brain
Photoreception
graded response stimulus strength
STIMULUS
receptor
potential
increasing morphological
and functional complexity
Receptors express transducer function.
Sherwood, Klandorf & Yancey, Animal Physiology:
From Genes to Organisms, Figure 5-1
receptor/transducer function
Sensory Physiology
generator
potential
ANALYSIS
TRANSDUCTION
CODED
INFORMATION
light
PHOTORECEPTOR(S)
NERVOUS
SYSTEM
EYE
retina
taste cells
lateral line & inner ear
electro- and magnetoreceptors
olfactory cells
statocyst
mechanoreceptors
Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms, Figure 6-2
1
Phylogeny of Ciliary and
Rhabdomeric Eyes
Invertebrate Photoreceptor Organs (eyes)
limpet
CILIARY PHOTORECEPTOR:
The photopigment is located in the
membrane of a modified cilium
RHABDOMERIC PHOTORECEPTOR:
The photopigment is located in the
membrane of apical microvilli
compound eye of
horseshoe crab
abalone
(8)
conch
(microvillar)
Eckert Animal Physiology, Fig. 7-40
w/ individual
lens system
Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms, Figure 6-7, 6-26
Rhabdomeric Eye of Invertebrates
compound eye of
fly
Sherwood, Klandorf & Yancey, Animal From Physiology: Genes to Organisms, Figure 6-7, 6-26
Eckert Animal Physiology, Fig. 7-36a
2
Anatomy of the Vertebrate Retina
Evolutionary Development
of Vertebrate Retina
rhabdomeric median eye
ciliary frontal/lateral eye
Ancestral Form
(Amphioxus)
Jc = photoreceptive Joseph cells
os = outer segment
n = neural retina
nc = neurocoel
v = ventricle
l = lens
Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms, Figure 6-16
Vertebrate Eye
P. Satir, Anat. Rec. 261: 224-227, 2000
Freeman, Biological Science, 2/e, Figure 46-10a
3
Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms, Figure 6-19
Photoreception and Phototransduction:
Photoreception and Phototransduction:
Vertebrates and Invertebrates
Vertebrates
photon
photoisomerization of photopigment
stuff happens
change in gion
change in Vm
change in neurotransmitter release
photon
photoisomerization of photopigment
stuff happens
decrease in gNa+
hyperpolarization of Vm
reduction in neurotransmitter release
4
Vertebrate Phototransduction
Anatomy of the Vertebrate Retina
time
Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms, Figure 6-16
Eckert Animal Physiology, Figure 7-41a, 7-42
Vertebrate Grayscale and Color Vision
light
rod cell
graded receptor potential
Rods
grayscale
dim light
high convergence
1 visual pigment
inhibitory synapse
bipolar cell
graded potential
excitatory synapse
ganglion cell
Cones
color
bright light
low convergence
4 visual pigments
(R, G, B, UV)
[cf. ? on p. 216]
graded potential w/ AP initiation
AP train
5
Mach Bands
6