transduction, encoding and transmission of information by single neuron
TRANSCRIPT
Transduction, Encoding and Transmission of Information by Single Neuron
Sensation vs. Perception
Sensation“The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.”
Perception “The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.”
The brain receives input
from the sensory organs.
The brain makes sense out of the
input from sensory organs.
Sensation Process
Sensation Process
• Sensory receptors transduce stimulus energy & transmit signals to CNS
• Electromagnetic receptors– Responds to electromagnetic energy e.g. visible light, electricity– Detected by photoreceptors in light form
Sensation Process
Transduction of Information by Single Neuron
• Most of the process occurs at the retina
• Photoreceptors– First layer activated by light – Composed of rods and cones
Rods Cones
Sensitivity Night time vision Day time vision
Vision type Low – light black and white vison
Colour vison
Acuity form Low acuity High acuity
Area affected Peripheral area Central area
Quantity 125 million 6 million
Transduction of Information by Single Neuron
• Rods and Cones – Also known as photo pigments– Contain opsin and 11 – cis – retinal (retinal)– Rods carry rhodopsin and cones carry iodopsin
• Retinal – Absorbs light – Embedded in opsin– Changes shape and activates opsin – Signal transduction cascade induced
Transduction of Information by Single Neuron
EXTRACELLULARFLUID
Membranepotential (mV)
0
– 40
– 70
Dark Light
– Hyper- polarization
Time
Na+
Na+
cGMP
CYTOSOL
GMP
Plasmamembrane
INSIDE OF DISK
PDEActive rhodopsin
Light
Inactive rhodopsinTransducin
Disk membrane
2 Active rhodopsin in turn activates a G protein called transducin
3 Transducinactivates theenzyme phosphodiesterase (PDE)
4 Activated PDE detaches cyclic guanosine monophosphate (cGMP) from Na+ channels in
the plasma membrane by hydrolyzing cGMP to GMP
5 The Na+ channels close when cGMP detaches. The membrane’s permeability to Na+ decreases, and the rod hyperpolarizes
1 Light isomerizes retinal, which activates rhodopsin
Signal Transduction Cascade
Transduction of Information by Single Neuron
• Information processing contributed by– Ganglion cells– Horizontal cells– Amacrine cells
• Signals are transmitted from ganglion cells to optic nerve
• Horizontal and Amacrine cells– Function in neural pathways– Integrates visual information before sent to brain
Transduction of Information of Single Neurons
1
234
5
Flow of Light
Encoding of Information by Single Neuron
Fundamental Encoding Attributes
Transmission of Information by Single Neuron
Transmission of Information by Single Neuron
Take Home Points
• Classes of neurons involved:– Photoreceptors– Bipolar cells– Horizontal cells– Amacrine cells– Ganglion cells
• Photoreceptor cells made up of:– Opsin– Retinal
Take Home Points
• Light absent, neurons inhibited by rods and cones
• Light stimulation of rods and cones causes hyperpolarization and induces activation process
• Ganglion cells send action potentials to optic nerve – Caused by activated neuron stimulation
• Horizontal cells cause lateral inhibition– Increases quality of light and dark contrast images
• Blindness caused by problems within different parts of visual system
References
• http://www.slideshare.net/
• http://slideplayer.com/
• http://www.appsychology.com/Book/Biological/vision.htm
• https://faculty.washington.edu/chudler/eyetr.html • http://openwetware.org/wiki/BIO254:Coding• https://www.youtube.com/watch?v=E3gbDz9RlSY • http://sites.sinauer.com/neuroscience5e/animations11.02
.html