sensory system
receptors that detect stimuli in internal/external enviornment, pathways that conduct information to brains and areas of brain that do sensory infromation processing
sensory information
imformation procesed by the sensory system
sensation
sensory information that reaches the conciousness
preception
conscious understand of the mean of a sensation
transduction
Transduction involves opening or closing of ion channels in specialized receptor membrane that result in changes in ionic current(s) moving across the membrane
adequate stimulus
type of energy to which a receptor normally responds
electronic
how action potentials are propated throught sensory receptors that are directly on the primary afferents
how are receptor potentials produced (what types can they be)
are produced by ion fluxes, (essentially a graded potential, can be depolarizing or hyperpolarizing)
sensory stimuli are forms of....
graded potentials that may in turn trigger AP's in sensory neurons and transmit information to the CNS
ways in which sensory receptors are specific
They respond only to certain types of energy or Adequate energies
2 basic receptor arrageents
1. Specialized nerve endings on primary afferents (energy stim. to receptor membrane on the friamry affternt)
2. specilzied receptors cells associated with primary afferents. (energy to receptor membrane on receptor cell which releass nt to the affternt)
Describe the location of the specialized receptor membrane and how the receptor potential is produced.
if specialized receptor is on end of axon, the potential is propagated Electronically towards the neurons trigger zone; if its on a seperate cell the potential causes release of nt that bind to protein receptors on sensory afferent
Receptor potentials are types of ________ potentials
graded
Describe how a sensory stimulus may trigger an AP in a primary afferent.
These graded potentials can depolarize and trigger an AP;
Describe the relationship between stimulus intensity, receptor potential magnitude and AP firing frequency of a primary afferent.
Larger depolairations reach threshold fast--> increase AP firing freqiency (magnitude of stimulous effects magnitude of potential which effects prmary affrent firing frequency)
Describe the factors that affect receptor potential magnitude
stimulus strength, summation, and receptor adaption
slow adaption
Slow adaptation refers to a decrease in AP frequency despite lack of change in stimulus strength
Rapid adaption
Rapid adaptation relates to changes in AP frequency as a function of the rate of change in stimulus application/intensity
expalin why sensory pathways are called ascending
They go to the brain
sensory unit
single afferent neuron with all of its sensory endings or associated specialized receptors
receptive field
part of body where stimulation leads to activity in particular primary afferent (CNS receptive fields= combined receptive fields of the primary afferent that influence them "convergence)
primary afferent/first order neuron,
sensory units; Somota in DRG or crinal nerve ganglia (classified by axon diameter and conduction velocity
second order neuron
CNS cells that first order neurons synapse on; cell bodies in SC or brain (often axons cross here)
3rd/4th order
cerbral cortex
dermatome
area of skin innervated by primary afferents that project to a particular SC segment
recruitment
# of primary afferent affected by a stimulus (effects stimulus intensity)
Compare the receptive fields of a sensory unit and a central sensory neuron.
1. the receptive fields of a sensory unit come from a single part of body and leads to avtivty in particular primary afferent
2. central sensory neurons are the combination of receptive fields from many primary afferents that influence them.
Describe the course of a simple sensory pathway (location and path of first order, second order, etc. neurons).
1. in DRG or cranial nerve ganglia
2. In SC or brain stem (often cross over)
3/4. in cerebral cortex
Describe the locations and functions of the cortical association areas
Perform additional processing of sensory information, next to primary sensory areas
Describe the role of the limbic system in sensory information processing
limbic system invest processed sensory information with emotional significants
Compare specific & non-specific sensory pathways
1. speciifc: transmit through one paticular sensory motality
2: polymodal
polymodial neuron
these pathways receive input from primary afferents that detect different modalities
Describe the types of information about a stimulus that
are conveyed by sensory pathways to the brain
modailty (type of stimulus), intensity (AP firing frequency or by number of primary efferents activated), location
Describe the factors in sensory acuity
1. convergence = less acuity
2. high receptor density = more acuity
small receptive fields = more acuity
Describe how higher levels of the CNS can affect the amount of sensory information that reaches the brain.
Descending fibers can reduce the amount of sensory information that reaches the cortex by presynaptic inhibition or excitation of inhibitory interneurons.
acuity
The precision with which a stimulus can be localized and discriminated from an adjacent one (main factor is convergence = less acuity)
rapidly adapting receptors information
something is starting, ending or changing intensity
slowly adapting receptors information
provide information on stimulus duration
modailty =
type