Transcript Hearing

Activated rhodopsin triggers a signal transduction cascade
Reminder on Ion Distribution and
Transport in Cells
Cells (eukaryotes) divided into a number
of membrane-bound compartments.
Concentrations in different compartments
can be orders of magnitude different.
Proteins (ion channels, transporters)
mediate these concentration gradients.
Membrane proteins central to huge range
of processes – cell signaling, nerve
impulses, nutrient transport, etc.
Ion Channels and Transient
Permeability
Channels open in
response to a variety of
different stimuli.
Key mechanisms are
voltage gating, ligand
binding-induced gating
and mechanical tension
in the membrane.
Mwc models of ligand-gated channels
Light-induced hyperpolarization of
the rod cell membrane
Hydrolysis of cGMP
causes cation channels to
close
Rod cell membrane
hyperpolarizes
cGMP
Electrical consequences of illumination
http://www.d.umn.edu/~jfitzake/Lectures/DMED/Vision/Retina/Recept
orPotential.html
Each dot in the figure below represents delivery of a very dim pulse of
light containing only a few quanta. Voltage responses appear to come
in 3 sizes: none, small, and large, representing the detection of 0, 1 or 2
quanta in each flash. The granularity of response to dim light stimuli is
evident.
http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-theretina/photoreceptors/
Synapse diffusion
http://www.colorado.edu/intphys/Class/IPHY3430-200/008sensory.htm
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication
Other examples of synaptic communication