6.1 Ion Channels to Sensations Flashcards
What are the 5 special senses
The 5 special senses are sight (visual pathway), hearing (auditory pathway), balance (vestibular pathway), smell (olfactory pathway) and taste (gustatory pathway)
Which important sensations are omitted from the 5 special senses
Sense of effort, fatigue or proprioception
What must happen for sensation to occur
Sensory neurones must ‘capture’ or transduce some form of energy in the environment and convert that into electrical potentials. These can be local receptor potentials or action potentials which propagate over distances to the CNS.
What is the difference between sensation and perception
Sensation is when you are aware that something happened but perception is when you can identify what happened and put a quality to it
What are the two ways transduction can take place
Sometimes, transduction happens at the terminal portion of a neurone, e.g with free nerve endings or where there is an accessory structure to the neuron such as a pacinian corpuscle
In other times, transduction happens via a 2nd type of cell (usually epithelial) which communicates with the neurone to allow for transduction, e.g with hair cells and merkel cells
Define sensation
Sensation - The process by which sensory systems detect and respond to stimuli from the environment or the body.
What features of an action potential give information about the stimulus
The location, when it starts/stops and any changes in intensity or changes in frequency
Why is it difficult to signal intensity of a stimuli with action potentials
Some stimuli can occur over a large range of intensities, e.g range of pressure from lightest touch to most severe. However, neurones have a very narrow range of firing frequency, a maximum of 200 action potentials/second.
What are ways to code for different stimulus intensities.
There are different receptors to respond to the different ranges of the stimuli e.g low intensity vs high intensity like rods and cones or cold and warm receptors in the skin.
The frequency coding has a logarithmic relationship between intensity and firing.
The neurons often signal relative changes in intensity rather than the absolute value of intensity
What ways can sensory receptors be classified by
location, function/behaviour and by ion channels expressed
What are TRP channels
Transient Receptor Potential (TRP) channels are a family of ion channels common in sensory neurones which are sensitive to temperature and some are also sensitive to pressure. The are either voltage gated or ligand gated. There are TRP subfamilies such as TRPA, TRPC, TRPM, TRPV. They can be polymodal, responding to multiple types of stimuli (temperature and pressure).
Describe TRPV channels
Transient receptor potential (subfamilies V 1-4), V for vanilloid that mostly respond to warm temperatures
What are ASICs
Acid sensing ion channels (subfamilies 1, 2, 3), found in mechanoreceptors (touch/pressure/pain), they bind to hydrogen ions
Describe TREKs
TREK (transient receptor K+ channels) are gated mechanically and by temperature, they bind protons and lipids
