Module 3: section 1.1 - receptor physiology intro

what do afferent neurons carry

impulses from peripheral receptors and special sense organs to the central nervous system

what is another name for afferent neurons

receptors or sensory neurons

what is the typical structure of an afferent neuron

small and round cells body

one long dendrite and a short axon

what does the dendrite do

extend to the periphery and is like another axon

how does the dendrite of an afferent neuron act as another axon

once it receives a strong enough stimulus, an action potential is started and moves toward to cell body

where are afferent neurons found

in clustered called ganglia right outside the spine

where do the axons of a afferent neuron go

into the dorsal horn the spinal cord

where are the receptors on an afferent neuron

the peripheral ending of the neuron

what does an afferent neuron respond to

stimuli from internal and external environments

*need a stimulus strong enough to hit the minimum threshold to be activated tho

what is transduction

when an environmental signal (stimulus) is turned into an electrical signal

*action potential

what are the 4 properties that allow the central nervous system to distinguish different signals from the peripheral nervous system

1. modality

2. intensity

3. location

4. duration

what is modality

when each type of receptor is specialized to respond to a different kind of energy/stimulus

what kind of stimulus can a photoreceptor detect

visible wavelengths of light

what kind of stimulus do mechanoreceptors detect

mechanical energy, vibration and acceleration

(movement)

what do thermoreceptors detect

heat

what do chemoreceptors detect

specific chemicals

(ex. those for tase, smell, things in digestive tract, prescence of O2 in blood, etc.)

what is intensity

how frequent the action potentials are coming in

what does the property location mean

how the brain uses the receptive fiend, multiple sensors and gradients to determine where the site of stimulation (where activated afferent fibres are)

what is a receptive field

the area around each neuron

*if a stimulus appears within that surrounding environment of a neuron, it will fire and its location is shared with the brain

how do multiple sensors help the brain determine the location

by comparing inputs from more than one sensor

how do gradients help determine location

if that area is more intense, that is where the activated afferent fibres are

how does duration mean location

if a stimulus is present in an area for a while, the cells will also be firing for that long, meaning something is present in that location

what is receptor potential

the changing of membrane potential due to an incoming signal within a specialized receptor

what is a generator potential

the changing of membrane potential within the ending of an afferent neuron

what are receptor and generator potentials

graded potential where their amplitude and duration can change depending on the strength and duration of the stimulus

what happens with a big enough graded potential

an action potential is started in the afferent neuron

what is special about a specialized afferent nerve ending

it can cause an action potential by itself by making the fibre reach the threshold independently

what is special about a separate receptor cell

with a strong enough receptor potential it will release chemical messenger that moves into the afferent neuron to open the chemically graded channels to try and achieve a threshold

what types of receptors can change their speed of adaption

tonic and phasic receptors

what are tonic receptors

adaptive receptors (but are slow to do so or do not at all)

where are tonic receptors important

situations with a near constant signal from a stimulus

what are phasic receptors

rapidly adapting (upon initiation of a stimulus, action potential are generated, but oppositely the receptor will stop making action potentials even if a stimulus is present)