7. sensory transduction and reflexes (how do nerves get initiated) UNFINISHED

define transduction

receptors that convert various forms of energy into electrical signals

forms:

• mechanical: touch, pressure, joint, muscle length, sounds waves

• chemical: smell and taste

• electromag: light on retina

• thermal

three types of proprioceptors

• muscle sidles

• golgi tendon organs

• joint kinesthetic receptors

monitor stretch in locomotory organs, provide info about positions of diff body parts needed to coordinate movement

• definition: measure changing length of muscle

• location: imbedded in perimysium btwn muscle fascicles

muscle spindles

• definition: monitor tension w/in tendons

• location: near muscle-joint junction

golgi tendon organs

• definition: sensory receptors in the joints that help you sense the position and movement of your body

• location: sensory nerve endings w/in joint capsule

joint kinesthetic receptors

what is generator or receptor potential?

developed by mechanical stretch deforms membranes in receptor regions of sensory neurons; deformation causes Na channels to open

generated potentials (are/not) graded

graded

increasing stretch on mechanoreceptor produces increases in generator potential amplitude

explain conversion of generator potential into action potential

generator potential reaches a sufficient threshold potential (depolarization), which triggers the opening of voltage-gated sodium channels, causing a rapid influx of sodium ions that generates a full-blown action potential; essentially, the generator potential acts as a localized depolarization that, if strong enough, initiates the self-propagating electrical signal of an action potential at the axon hillock of a neuron. 

what is frequency modulated coding?

stimulus intensity is encode into AP frequencies: higher receptor potentials produce higher frequency APs

as the intensity of a stimulus increases, the frequency or rate of action potentials, or "spike firing", increases

what is adaption and when does it occur?

when the generator potential gradually decreases resulting w the AP frequency decreasing

happens with prolonged stimulus some sensory neurons undergo