Intro to Sensory Systems pp Flashcards
Mechanoreceptor examples
Encapsulated nerve endings in the skin Hair cells in the cochlea & vestibule Thermoreceptors Photoreceptors Chemoreceptors Nociceptors
Receptor specificity
Normal is only affected by one stimulus
Receptor potential
membrane potential produced by transducer - local graded potential
Action potential
Created when depolarization reaches threshold, rate can increase as receptor potential rises
How do we know what stimulus is
Labeled line principle
Sensory modalities
Synesthesia
Labeled line response
Chain connects neurons from sensory receptors to the brain AREA that responds to stimulus
Sensory modalities
Vision Hearing Taste Smell Feel Proprioception
How we know where stimulus is coming from
Receptive field of a neuron is the region of tissue, evoke change in firing rate
Stimulus duration
Continuous signal
On/Off signal
Stimulus strength
Increase frequency of nerve impulses
Increase number of fibers activated
Non adapting receptor
Nocireceptors
Slowly adapting receptors
AKA Tonic receptors
Merkels, useful for giving continuous info about stimulus strength & duration
Rapidly adapting receptors
AKA Phasic receptors or rate receptors
Pacinian
Meissner’s
Useful for beginning and end stimulus. Disadvantage cannot give continuous signal
Tactile Sensations
Touch Crude & Light
Discriminitive
Pressure/Deep touch
Vibration
Free nerve endings
Crude Touch
Low threshold mechanoreceptors
Encapsulated ending of myelinated fibers II and Abeta or merkel
Merkel’s Disks
Base of epidermis Iggo dome, group together, innervated by one Abeta Merkel cell afferent SAI 25% in hand Highest spatial resolution
SAA II
Ruffini afferent
Stretch of skin
20%
Meissner’s corpuscles
RA1 40% nonsensory hand High at finger tips Closer to skin surface than Merkel's disks Vibration 30-50 Hz Detects slippage
Pacinian Corpuscles
Rapidly adapting faster than Meissner’s
250-350 Hz
Found in subcutaneous tissue
Hair End Organ
Peritrichial nerve ending.
Stimulated by slight movement of hair
Adapts rapidy slower Adelta
Detects movement
Active tactile exploration
Need relative movement btw skin. Accurate discrimination periphery receptors must be influenced by motor signals
Other sensations
Cold Warmth Pain Itch Free nerve ending C fibers
Two point discrimination
Test depends on receptive fields and where
Proprioception
sense of self
Info from joint angles, muscle length & muscle tension, input w/ vestibular input
Importance of proprioception
Maintain balance
Control limb movement
evaluate shape
Dorsal Column
aka Posterior column
Fine tactile discrimination, vibratory sense
Proprioceptive
Precise localization
Lesion in dorsal column causes
Deficits in tactile, vibratory and proprioception
Anterolateral System
Nociception transmitted, crosses midline at spinal cord
Somatosensory SI
Brodmann areas 3b/a, 1, 2
SII
Show attention modulated responses
Nerve Pressure Palsy
Affected limb falls asleep
Spinal root injuries
Impairment of cutaneous sensation
not all lost because of over lap
Peripheral neuropathies
Stocking glove patter
Brown Sequard
Hemisection of spinal cord
Aa
100m/s
1 muscle spindle primary Ia & GTO Ib
Ab
50 m/s
muscle spindle 2
axons of cutaneous mechanoreceptors
Ay
gamma motor neuron muscle spindle fibers
Ad
fast pain some temp
B
sympathetic preganglionic axon
C
Slow pain some temp
and sympathetic post ganglionic axons
