Sensory System Flashcards
What is the most common neurotransmitter utilized by sensory receptors?
Glutamate
Must sensory neurons use action potentials to propagate?
Sometimes.. only if the neuron is > 0.1mm in length. Shorter neurons simply use passive electronic transmission.
How are hyperpolarizing receptors (rod photoreceptor for example) hyperpolarized when activated? (what channel is responsible for the hyperpolarization?)
Due to closing of cation channels
Describe the transduction of a rod photoreceptor that leads to hyperpolarization.
Light enters the photoreceptor and activates rhodopsin. When a molecule of l-cis-retinal bound to rhodopsin absorbs light retinal changes in conformation to l-trans-retinal. Rhodopsin undergoes a conformational change to metarhodopsin, which stimulates the G-protein transducin. Transducin activates a cGMP phosphodiesterase enzyme which breaks down cGMP to guanosine. The cation channel then closes leading to hyperpolarization.
Describe how stretch depolarizes mechanoreceptors.
Mechanosensitive cation channels open in response to stretch –> depolarization of cell.
How is the depolarized resting potential of a rod photoreceptor maintained?
Maintained by the opening of cGMP-gated cation channels in the presence of high cGMP concentrations under resting conditions.
How does a short receptor encode stimulus intensity?
Short receptors encode stimulus intensity by altering the amount of time their channels stay open (or closed)
How does a long receptor encode stimulus intensity?
As an increase in action potential firing
What type of information does an A-alpha axon carry?
Muscle spindle afferents & tendon organ afferents
What type of information does an A-beta axon carry?
Mechanoreception of skin and secondary muscle spindle afferents
What type of information does an A-delta axon carry?
Sharp pain and cold temperature
What type of information does a C axon carry?
Burning pain, warm temperature, itch, and crude touch
What is the relationship between axon size and conduction velocity?
The bigger the diameter, the higher the velocity
What is the relationship between axon myelination and conduction velocity?
The more the myelination, the higher the velocity
Which axon type is unmyelinated?
C fibers
Which axon type is poorly myelinated?
A-delta fibers
What fiber type are somatosensory mechanoreceptors of the Lemniscal system?
A-beta fibers
(Of Merkel’s disc, Meissner’s corpuscle, Pacinian corpuscle, & Ruffini’s ending) Which receptor has a small receptive field size and slow adaptation?
Merkel’s disk
What does the word “corpuscle” indicate?
Fast adaptation - responds to vibration
(Of Merkel’s disc, Meissner’s corpuscle, Pacinian corpuscle, & Ruffini’s ending) Which receptor has a small receptive field size and fast adaptation?
Meissner’s corpuscle
(Of Merkel’s disc, Meissner’s corpuscle, Pacinian corpuscle, & Ruffini’s ending) Which receptor has a large receptive field size and slow adaptation?
Ruffini’s ending
(Of Merkel’s disc, Meissner’s corpuscle, Pacinian corpuscle, & Ruffini’s ending) Which receptor has a large receptive field size and fast adaptation?
Pacinian corpuscle
The cell bodies of Lemniscal system receptor neurons are located where?
Dorsal root ganglia
What fiber type are proprioreceptors of skeletal muscle?
A-alpha
