exam 3 peripheral sensory nervous system

what nervous systems does sensation involve

peripheral and central nervous system

sensory nervous system

nervous system division that consists of sensory receptors, neurons, and parts of the brain that receive and assign meaning to those feeling

sensation

receptors transducing or sending a stimulus, an action potential, into the CNS

perception

assigning meaning to that information in the brain so the signal makes it to the brain and then we integrate that type of information

what are the 2 sensory divisions of our sense

general sensation (somatic) and special sense

general sensation, somatic

touch, pressure, temperature, and pain

how are the inputs of the general sensation (somatic) processed

consciously or subconsciously such as blood pressure

special senses

vision, olfaction, hearing, gustation

olfaction

smelling

gustation

tasting

what do special senses have

unique receptors and pathways into the CNS

sensory transduction

sending the signals from the receptor to the CNS

what can you classify sensory receptors as

functional, location, structural

functional sensory receptors

based on their adequate stimulus (modality)

an example of an adequate stimulus

voltage-gated channels that respond to a specific change in voltage

examples of functional sensory receptors

thermoreceptors, mechanoreceptors, nociceptors, photoreceptors, chemoreceptors

thermoreceptors

sensitive to the specific stimuli of hot or cold temps, can either like one

mechanreceptors

sensitive to mechanical receptors and at a cellular level this come down to a stretch stimulus

stretch stimulus

stretching of the plasma membrane as we move, can have varying thresholds

nociceptors

our pain receptors and these respond to physical tissue damage such as a tear or burn

photoreceptors

respond to different photons in light

chemoreceptors

respond to different chemicals

example of chemoreceptors

calcium receptors in thyroid and parathyroid glands

what does each type of receptor have

adequate stimulus with a very sensitive threshold

how can general sensory receptors be stimulated

other modalities if the stimulus is very strong

regardless of how a sensory neuron is stimulated how….

only one sensory modality will be perceived

examples of location sensory receptors

exteroceptors, interoceptors, and proprioceptors

exteroceptors

sense our external environment

examples of exteroreceptors

warm temperature of hot stove on hand

interoceptors

sense our internal environment we have sensory receptors for pressure and chemicals in our body

proprioceptors

gives us information about our body position in space and each body part relative to each other

where is proprioceptors located

muscles and joints

what happens without proprioceptors

twistys

twistys

a loss of proprioception and integration of proprioceptors in our brain with the motor commands that would react to that proprioception 

what is twistys caused by

stress and aging

examples of structural sensory receptors

free nerve endings, encapsulated nerve endings, rods and cones, and hair cells

where are structural sensory receptors located

all receptors are located on the dendritic ends of neurons

free nerve endings

simply dendritic ends embodied in the tissue where they respond to pain, temperature, and smell

encapsulated nerve endings

dendrites encapsulated in connective tissue, often have a specialized epithelial cell that synapses with a myelinated neuron that sends the action potential

what do the specialized epithelial cell have

unique structure such as cilia that responds to vibrations in hearing and equilbrium

in encapsulated nerve endings what responds to pressure and touch

mechanoreceptors and they physically stretch so the connective tissue can enhance that response

rods and cones

sight

hair cells

hearing and equilibrium

sensory unit

neuron and all of its receptors located on its dendrites

receptive field

area/region that can be sensed by a sensory unit and can overlap

receptor potential

to describe graded potential in a sensory neuron, means that stimulus intensities that information is encoded in an EPSP where the greater the intensity the higher our membrane potential nerves are

how does the information from the receptor potential get to the CNS

the EPSP must reach the threshold at the axon hillock to stimulate an action potential

what happens while the receptor potential is graded to encode the stimulus intensity

we get an all or nothing event of the AP sent to the CNS

if receptors send messages to the CNS using an AP how do we sense difference in stimuli intensity

once we reach threshold we can rapidly continue to send AP so if we raise number of APs sent that will raise the amount of exocytosis of neurotransmitters sent to the CNS and that will raise our perception of intensity

recruitment

stronger stimuli might call in additional afferent sensory neurons

sensory adaption

desensitization to repeated and prolonged stimuli which caries we can become desensitized to stimuli depending on type of stimulus

what are the types of sensory adaptation

tonic receptors and phasic receptors

phasic receptors

rapidly adapting receptors where if we have a continued or prolonged stimulus they will send APs but if it continues to send in the same stimuli over much time those receptors will stop initiating APs and stop perceiving that sensation

tonic receptors

slowly adapting, will respond to prolonged stimuli continuously many pain receptors slow down the number of APs they are sending over time

what is unevenly distributed throughout the body

receptors and receptor fields

who has an inverse relationship

size of receptor fields and ability to discriminate between two points throughout the body

where are receptor density

in the eyes specifically in the retina

retina

neural layer of the eye

fovea

the point of our eye where we try to bend light to ficus in our vision, where we have high number of receptor density of cones