CH 10 - Sensory physiology Flashcards
What is a free nerve ending receptor?
- simple receptor
- may be myelinated or unmyelinated
What is a complex neural receptor?
- have nerve endings enclosed in connective tissue capsules
What are most special senses receptor cells?
- release neurotransmitter onto sensory neurons, initiating action potential
- have specialized receptor hair
What are the 4 sensory accessory structures and what they respond to?
- Chemoreceptors: respond to chemical ligands (smell, taste)
- oxygen, pH, glucose, etc - Mechanoreceptors: respond to mechanical energy, pressure, and sound (ex: hearing)
- cell stretch, pressure, vibration, acceleration, and sound - Thermoreceptors: respond to temperature
- Photoreceptors: for vision, respond to light
What is transduction?
- stimulus energy converted into information processed by nervous system
- ion channels or second messengers initiate membrane potential change
What is an adequate stimulus?
a form of energy to which a receptor is most responsive
What is a receptor potential?
- another name for a graded potential
- change in sensory receptor membrane potential
What is a receptor field?
- the physical area where a stimuli activates a neuron
- primary sensory neuron and secondary sensory neuron
- receptor fields frequently overlap
- neighboring fields may exhibit convergence
- the size determines sensitivity (2 point discrimination test)
- Sensitive areas have smaller receptive fields
- less sensitive areas have larger receptive fields
(figure 10.2)
What is perceptual threshold?
level of stimulus necessary to be aware of particular sensation
What is habituation?
- decreased perception through inhibitory modulation
- falls below perceptual threshold
Where do most sensory pathways project to?
The thalamus
Where do equallibrium pathways primarily project to?
the cerebellum
How does the brain distinguish between stimuli that are converted to action potentials?
- sensory modality
- the location of the stimulus
- the intensity of the stimulus
- the duration of the stimulus
How does the brain use sensory modality to distinguish between stimuli?
- depends on which sensory neurons are activated and where neurons terminate in the brain
- the type of stimulus
- Label coding —> 1:1 association of receptor with sensation
How does the brain use the location of the stimulus to distinguish between stimuli?
- which receptive fields are activated
- lateral inhibition and population coding
- sound waves hits each ear at a different rate but your brain hears them together
How does the brain use the intensity of the stimulus to distinguish between stimuli?
- the number of receptors activated and frequency coding
How does the brain use the duration of the stimulus to distinguish between stimuli?
- duration of action potentials
- receptors adapt: tonic receptors v. phasic receptors
What is population coding?
The number of sensory receptors activated encodes the intensity of the stimulus
What is lateral inhibition?
Process in which sensory neurons close to a stimulus are inhibited to intensify the perception of the stimulus
What is the difference between tonic and phasic receptors?
- Tonic: slowly adapting receptors that respond for the duration of the stimulus
- Phasic:Rapidly adapt to a constant stimulus and turn off
Where are receptors for somatic senses located?
- skin and viscera
Where do primary sensory neurons synapse?
in the CNS with secondary neurons
Where do the secondary sensory neurons synapse & what are they?
- interneurons in CNS
- synapse with tertiary sensory neurons in thalamus
Where are the tertiary sensory neurons?
project to somatosensory cortex and many project to cerebellum somatosensory cortex
