Flashcards in Overview of Sensory System and Receptors Deck (16):
What is touch of the outside world called?
What is the Vm of rod cells in the dark?
What happens to the Vm of rod cells when they go from dark to light?
They go from -40 mV to -70mV
Why do photoreceptors use G-proteins (as opposed to light-activated ion channels)?
G-proteins allow for amplification.
All sensory input synapses at the thalamus with the exception of ______________.
At the receptive end of sensory receptor cells, there is a high density of __________. Why?
Mitochondria; necessary because transduction from one mode of energy or state of being to another (e.g., going from light to an action potential) is an energetically demanding process
Describe receptor potential.
The amount of depolarization or hyperpolarization stimulated by a specific external stimulus (such as light or chemicals in solution)
The neurotransmitter for most sensory cells is ______________.
In general, cells that depolarize in response to their stimulus do so by opening ____________. Name a specific cell that does this.
non-specific cation channels; the neurons that sense stretching in muscle fibers works this way
Why do some sensory receptor cells hyperpolarize in response to activation?
They have resting potential much higher than most other cells – closer to 0 mV – and thus opening nonspecific cation channels leads to an influx of potassium (whose membrane potential is -80 mV).
Describe how a rod cell hyperpolarizes in response to light stimuli.
In the dark, rod cells have a static level of cGMP that binds to and opens sodium channels; light stimulation induces a conformational change in rhodopsin, which activates a G protein (transducin) that itself activates a phosphodiesterase. The phosphodiesterase breaks down cGMP, causing the sodium channel to close (and the cell then hyperpolarizes).
True or false: the photoreceptor cells in the eye stimulate action potentials to myelinated conductance cells.
False! The photoreceptor cells are small (less than 1 mm) and can thus transmit information electronically.
Which thalamic nucleus codes visual input? Auditory input?
Visual: lateral geniculate nucleus
Auditory: medial geniculate nucleus
What information is carried on A-alpha, A-beta, A-delta, and C fibers?
A-alpha: muscle and tendon afferents
A-beta: mechanoreceptors of the skin
A-delta: sharp pain, cool temperature, extreme hot temperature
C fibers: warm temperature, burning pain, itch, crude touch
What is Brown-Séquard syndrome?
Hemisection of the spinal cord (BiSected) caused by trauma or MS