Lecture 11: Sensory Physiology Flashcards
What 2 things can be used to classify a peripheral nerve?
Contribution to an action potential. (Letter)
Fiber diameter, myelin thickness. (Number)
Aalpha nerve
Classification:
Fiber diameter:
Conduction velocity:
Classification: Ia, Ib
Fiber diameter: large
Conduction velocity: fast
C nerve
Classification:
Fiber diameter:
Conduction velocity:
Classification: IV
Fiber diameter: small
Conduction velocity: slow
What is a generator potential?
A stimulus, when large enough, can trigger an AP to be carried over a distance into the CNS.
Receptor adaptation
When a stimulus persists for awhile, the neural response diminishes and sensation is lost.
Slowly adapting receptors
Receptors that respond to prolonged and constant stimulation
Rapidly adapting receptors
Receptors that respond only at beginning or end of stimulus when the intensity of stimulus increases or decreases.
Meissner’s corpuscle
Adaptation rate:
Sensation produced:
Receptive field size:
Receptor Adaptation rate: RA
Sensation produced: tap, flutter
Receptive field size: small
Hair follicle receptors
Adaptation rate:
Sensation produced:
Receptive field size:
Receptor Adaptation rate: RA or SA
Sensation produced: motion, direction
Receptive field size: N/A
Pacinian corpuscle
Adaptation rate:
Sensation produced:
Receptive field size:
Receptor Adaptation rate: RA
Sensation produced: vibration
Receptive field size: large
Merkel disk
Receptor Adaptation rate:
Sensation produced:
Receptive field size:
Receptor Adaptation rate: SA
Sensation produced: touch, pressure
Receptive field size: small
Ruffini corpuscle
Receptor Adaptation rate:
Sensation produced:
Receptive field size:
Receptor Adaptation rate: SA
Sensation produced: skin stretch
Receptive field size: large
Where is tactile acuity highest?
Small receptor fields (fingertips, lips, etc).
Where is tactile acuity lowest?
Large receptor fields (calf, thigh, back, etc)
Pre-synaptic inhibition
Diminishes excitatory signal.
- GABA –> influx of Cl-.
- Hyperpolarization
- Less Ca++
- Less NT release
What is the use for pre-synaptic inhibition? How?
It helps the brain localize the signal.
The activated neuron can send collateral branches to inhibit nearby neurons, which would enlarge the sensory area.
3 roles of cortical processing
Initial processing of signal.
Integration of the initial processing into larger schemes.
Emotional response to the processing.
What is interesting about the somatotopic maps?
They can be changed (i.e. magnified (OMM) or diminished (amputation, severed nerve)).
What layers of the cortex are enlarged in the primary sensory cortex?
III and IV
What layers of the cortex are the main site of termination of axons from the thalamus?
III and IV