Lecture 14- Sensory physiology Flashcards
why do we have senses? what do they accomplish?
information about the environment
information about ourselves
what are 5 conscious special senses?
vision
hearing
taste
smell
balance
what are 5 conscious somatic senses?
touch
temperature
pain
itch
proprioception (position of your body, ex. when you walk and when your joints are straight or bent)
what are 2 unconscious somatic stimuli?
muscle tension
proprioception
what are some visceral unconscious senses?
blood pressure
glucose
osmolarity
oxygen content of blood
CO2 content of blood
what are the 5 general properties of sensory systems?
- (modality)
- sensory transduction converts stimuli to graded potentials
- sensory neurons have receptive fields
- the CNS integrates sensory information
- properties of the stimulus are determined by coding and processing
- what are the two meanings of a receptor?
a protein that binds a ligand
a structure that detects sensory information (the one we’ll be using for this lecture)
- what is a modality and how is it detected?
when receptors are more sensitive to certain forms of energy or stimuli (ex. eyes stimulated by light)
they are detected by receptors
- what are the differences between simple receptors, complex receptors and special senses?
simple have free nerve endings
complex have the nerve ending surrounded by non-neuronal cells
special senses have a transducer cell at synapse
- what do simple receptors detect?
pH, O2, temperature
- what do complex receptors detect?
vibration and pressure
- what do special sense receptors detect?
smell, vision, taste
- what does the transduction process do?
changes the membrane potential of sensory neurons
- what are the 3 ways sensory neurons can experience a graded potential in transduction process?
chemical (ion gated channel)
mechanoreceptor, thermoreceptor gated channels (touch, temp, pressure, hearing, balance)
vision (channels modulated through second messenger pathways
- what is an adequate stimulus?
prefered type of stimulus for a receptor
- what is a receptor threshold?
minimum stimulus to activate a receptor
- what does it mean when theres a larger graded potential?
higher frequency and therefore a release of more neurotransmitters
- what does it mean that each sensory neuron has a receptive field?
specific region of sensory space in which an appropriate stimulus can drive an electrical response in a sensory neuron
ex. finger pad
- if the receptive field is larger what does that ential?
larger the receptive field is, the greater the area that it detects changes in but also less precise perception
- what does it mean that primary sensory neurons converge onto secondary neurons?
the more convergence (coming together) of primary sensory neurons onto secondary neurons the larger the receptive field and lower the acuity (strength of a sensory function)
- what is an example of sensory neurons having a receptive field?
she tries to determine whether she feels 1 or 2 pokes (stimuli) on her hand
when he touched with 2 she felt 1 therefore higher acuity
this occurs because the poke is activating two parts of the receptive fields therefore the receptive field is large
- areas of high acuity represent more or less convergence?
less
- where is sensory information processed
level of the spinal cord/ brainstem
cortex
- what makes sensory information travel through the spinal cord/ brainstem or the cortex?
spinal: unconscious perception
cortex: conscious perception
- with some sensory information processed in the cortex a stimulus may activate a primary sensory neuron but may not have enough intensity to surpass perceptual threshold, what is perceptual threshold?
level of stimulus necessary to be aware of particular sensation
ex. if youre scared of spiders and you watch a show with spiders on it, if theres some sort of breeze on your neck you might think its a spider
what is the olfactory pathway?
not well developed in humans but more developed in animals
olfactory senses can stimulate information and emotions stronger and helps with memory
ex. smell nates cologne and think of him
- all stimuli are converted into graded potentials then action potentials but how does the CNS determine the properties of each stimulus?
modality of the stimulus
location of the stimulus
intensity and duration of the stimulus reflected by graded potential and action potentials
- specific groups of neurons within the brain are associated with specific modalities, what does that mean?
cant just change where our receptors are because we’ve grown up with it. we can’t just put photoreceptors on our fingertips, it will just feel like texture
- what is the labeled line processing?
each modality has its own wiring system from the receptor to higher processing centre
- what is the location of the stimulus? what does it depend on?
depends on what receptive fields are activated
determined by labelled line processing
- where are stimulus from adjacent areas of the body processed?
in adjacent areas of the brain
ex. sensory info from fingers are processed in adjacent areas
- what is lateral inhibition? example
mechanism to increase contrast between activated receptive fields and non- activated ones
ex. pin touching your skin, the main point you touch will activate the primary sensory neuron (high frequency of AP), but the neurons beside the primary will also be slightly activated (lower frequency of AP). the primary neuron will then inhibit the lateral neurons and only the primary will feel the stimulus.
what is the difference between tonic receptors and phasic receptors?
tonic receptors will get a stimulus and continue to get action potentials. (will fire AP for as long as the stimulus is there)
phasic receptors will get a stimulus, get a couple action potentials then stop (even when the stimulus is still there)
ex. step in dog shit and it stinks, then after a bit you dont smell it no more even though its still there
