Sensory Physio Flashcards
Peripheral nerves are classified by two schemes.
- Their contribution to a compound ACTION POTENTIAL (A, B, and C waves)
recorded from an entire mixed peripheral nerve. - Based on FIBER diameter, myelin thickness, and conduction velocity
(classes I, II, III, and IV).
Which sensory (afferent) fiber type has the largest fiber diameter and the fastest conduction velocity?
A(alpha)
Which sensory (afferent) fiber type has the smallest fiber diameter and the slowest conduction velocity?
C
An appropriate stimulus applied to a somatosensory receptor produces a ? that, when large enough, leads to action potentials that can be carried over a considerable distance into the central nervous system
generator potential
Information from all sensory systems except the olfactory are relayed through the ? on its
way to the cerebral cortex.
thalamus
Sensory receptors encode the ? of the stimulus in the ?
of the receptor potential
- intensity
- amplitude
The number of active receptors ? with increased intensity of the stimulus
increases
When a stimulus persists unchanged for several minutes without a change in position or amplitude, the neural response diminishes and sensation is lost.
Receptor adaptation
Receptors that respond to prolonged and constant stimulation
slowly adapting receptors
Receptors that respond only at the beginning or end of a stimulus are only active when the stimulus intensity increases or decreases.
rapidly adapting receptors
? are responsible for the sense of touch
Mechanoreceptors
Individual mechanoreceptor fibers convey information from a limited area of skin
Receptive fields
Allows for spatial resolution of detailed textures
2-point discrimination
2-point discrimination:
- Tactile acuity is highest in?
fingertips and lips (smallest receptive fields)
2-point discrimination:
- Tactile acuity is lowest on?
the calf, back and thigh (largest receptive
field)
Primary afferent neurotransmission is controlled by ? and ?
pre- and
postsynaptic inhibitory mechanisms.
probably the more powerful form of
inhibitory control in all primary afferent fibers.
Presynaptic inhibition
This inhibition is actually a diminished excitatory signal:
- GABAergic associated influx of Cl- into the axon
- Results in hyperpolarization
- Less Ca2+ enters cytosol
- Leads to less NT release
Cortical processing steps
- Initial processing of the signal
- Integration of the initial processing into
larger schemes - Emotional response to the processing
Each area of sensory cortex
shares with its subcortical
components a map of at least
part of the sensory periphery.
Response mapping
Which layer of the cortex is enlarged in primary sensory cortex?
III and IV
Which layer of the cortex is the main site of termination of axons from the
thalamus?
III and IV
Cortex:
- Main output neurons are the?
pyramidal cells
- Neurons stacked above and below each other are fundamentally ?
- Neuronal columns side by side are significantly ? from one
another.
- similar
- different
Sensory information arrives at it’s column in layer ? (via thalamus)
IV
Sensory cortex includes ?, ?, and ?
primary, secondary and association areas
- Located in post-central gyrus
- Brodmann Area 3, 1, 2
- First stop for most cutaneous senses
- Somatotopic representation
Primary somatosensory cortex (S1)
involved in the integration of the information for position sense as well as size, shape discrimination.
Primary somatosensory cortex (S1)
- Located in wall of the sylvian fissure
- Receives input from S1
- Somatotopic representation (less detailed)
- Cognitive touch
Secondary somatosensory cortex (S2)
Comparisons between objects, different tactile sensations and determining whether something becomes a memory.
Secondary somatosensory cortex (S2)
• High level interpretation of
sensory inputs
• Receives input from multiple
sensory areas
• Analyzes spatial coordinates
of self in environment
- Names objects
- Many more functions
Parieto-temporal-occipital association cortex (PTO)