Download Sensory Organs and Processes, Part II

Taste
Sensory systems 2
Sugar molecule
G protein
Sweet
receptor
Tongue
Today s topics:
•  Sensory receptors
–  Chemoreceptors
Taste pore
•  Taste and Smell
Taste
bud
–  Photoreceptors
•  Vision
Sugar
molecule
SENSORY
RECEPTOR
CELL
Sensory
receptor
cells
IP3
(second
messenger)
•  Nervous systems
Sensory
neuron
–  Afferent and efferent neurons
–  Sympathetic and parasympathetic
–  Organization of the brain (briefly)
•  Plant Senses
ER
Sodium
channel
Ca2+
(second
messenger)
Na+
5 December 2016
Taste
Humans have many bitter receptors.
Each responds to just a few
compounds.
Smell
Brain
Action potentials
Olfactory
bulb
Odorants
Nasal cavity
Bone
Epithelial
cell
Odorant
receptors
e.g.
TAS2R38 detects
PTC
Chemoreceptor
Plasma
membrane
Cilia
Odorants
Mucus
Each odor has a different receptor
Fig. 50-17
Retina
Retina
Choroid
Photoreceptors
Neurons
Vision
Cone Rod
Rod
Light
To
brain
INSIDE
OF DISK
Optic nerve
cis isomer
Light
Light
Enzymes
Cell body
CYTOSOL
Ganglion
cell
Amacrine
cell
Optic
nerve
axons
Synaptic
terminal
Horizontal
cell
Bipolar
cell
Rhodopsin
Retinal
Opsin
trans isomer
Retinal acts as a switch
Pigmented
epithelium
1
Fig. 50-19
Activation by light closes sodium channels and
hyperpolarizes the cell
EXTRACELLULAR
FLUID
Light
Dark Responses
Light Responses
Rhodopsin inactive
Rhodopsin active
Na+ channels open
Na+ channels closed
Rod depolarized
Rod hyperpolarized
Glutamate
released
No glutamate
released
Bipolar cell either
depolarized or
hyperpolarized
Bipolar cell either
hyperpolarized or
depolarized
Active rhodopsin
CYTOSOL
cGMP
Inactive
rhodopsin
GMP
Sodium
channel
Na+
Membrane
potential (mV)
Dark
0
–40
Light
Hyperpolarization
–70
Na+
Time
Compound eyes
Other Senses?
Trout have magnets in
their noses.
Others have a centralized
nervous system (brain)
Some animals
just have neural
nets
Snakes sense infrared
Bees see UV light
Human
Bees
response of individual particles
2
Autonomous nervous system
A very simple
neural circuit
Norepinephine
Ach
Organization of the brain
Can plants smell?
Butenolide receptors
detect smoke
Dodder uses odor to locate host plants
Plants also use volatiles to warn of herbivores
Can plants taste?
Can plants hear?
•  Nutrient sensing by plant roots
•  No
L
H
L
3
Can plants touch?
•  Tendrils coil after they
touch a stem
•  Venus Fly Trap has trigger
hairs.
Can plants see?
•  Phototropism
•  Shade avoidance
4