12. Sensory Physiology Flashcards
What are the two schemes that peripheral nerves are classified by?
electrical properites such as APs (ABC waves) physical properties such as fiber diameter/myelin (class 1/2/3/4)
A-alpha is a sensory afferent fiber type with a ____ diameter, ______ conduction velocity, and supply what?
Large diameter
Fast conduction velocity
Muscle spindle/golgi tendon
C sensory fibers are type IV/4 fibers with a ______ diameter, ______ conduction velocity and supplies what?
Small diameter
Slow conduction velocity
Skin/thermal receptors and nociceptors
A stimulus applied to a somatosensory receptor produces what? that when large enough leads to action potentials that can be carried into the CNS?
generator potential
info from all sensory systems are relayed through the thalamus on the way to the cerebral cortex. What is convergence and divergence?
Convergence is when two stimuli neurosn converge onto one receptor
Divergence is when one stimuli neuron relays info
The number of active receptors increases with increased intensity of the stimulus. The seonsory receptor tells how intense the stimulus is and?
transforms a signal of intesnsity into a digital pulse
What is it called when a stimulus persists for minutes leading to the neural response diminishing and losing sensation?
receptor adaptation
Receptors that respond to prolonged and constant stimulation are?
slowly adapting receptors
Receptors that respond only at beginning and end of a stimulus (only active when stimulus intensity inc/dec) are?
rapidly adapting receptors
Meissner Corpuscle
Receptor Type:
Sensation produced:
Receptive field size:
Receptor Type: Rapidly adapting
Sensation produced: tap/flutter
Receptive field size: small
Hair Follicle Receptors
Receptor Type:
Sensation produced:
Receptive field size:
Receptor Type: BOTH
Sensation produced: motion/direction
Receptive field size: N/A
Pacinian Receptor
Receptor Type:
Sensation produced:
Receptive field size:
Receptor Type: RA
Sensation produced: Vibration
Receptive field size: Large
Merkel Disk
Receptor Type:
Sensation produced:
Receptive field size:
Receptor Type: SA
Sensation produced: touch/pressure
Receptive field size: Small
Ruffini Corpuscle
Receptor Type:
Sensation produced:
Receptor Type: SA
Sensation produced: Skin stretch
What are individual mechanoreceptor fibers that convey information from a limited area of skin?
receptive fields
2-point discrimination is the ability to tell the difference between nearby stimuli. Where is tactile acuity the highest and lowest?
highest in fingertips and lips (smallest fields)
Lowest on calf, back, and thigh (largest receptive fields)
Where there is a lot of convergence of primary sensory neurons in one receptive fields the two stimuli will be received as one, but when there are fewer primary neurons converging in small receptive fields, what can be expected?
they will not converge and there will be point differentiation
Primary afferent neurotransmission is controlled by pre and postsynaptic inhibitory mechs, PRESYNAPTIC INHIBITION being more powerful. The inhibition is actually what?
a diminished excitatory signal
Presynaptic inhibition results in reduced NT release from the presynaptic terminal which improves?
the brains ability to localize the signal
When there are three primary neurons responding to a stimulus, the neuron closest to the stimuli will do what?
inhibits other 2, enhancing perception of stimulus
Somatotopic maps are not fixed. What does this mean?
We can train our senses to feel better. Ei: OMM hands over time will mature sensation and be able to feel things
Can also decrease senation d/t amputation/nerve probs
The cortex has 6 layers. the MAIN output neurons are the pyrimidal cells. Which layers are enlarge in primary somatocortex and are main site of input from thalamus?
Layers III and IV
Neurons that are stacked above and below eachother are fundamentally similar while neuronal columns that are side by side are?
significantly different from one another
The columns extend through all 6 layers, and each column deals with ONE sensory modality in one body part. What is the main input layer?
IV
Primary somatosensory cortex SI is in the post-central gyrus and aligns with brodmann areas 3a,3b 1 and 2. What is the main involvment of the SI?
integration of information for position sense as well as size shape discrimination