Somatosensory Systems Flashcards
Term: to feel, perceive, or be aware of
Sense
Function of the Sensory system
Allow organism to sense the body and environment
- Carry information from periphery to cortex for conscious awareness
- Unconscious sensation
- Mediation of sensations
3 Types of Sensation from the Skin
- Touch (pressure/vibration)
- Pain
- Temperature
2 Types of Sensation from the Musculoskeletal system
- Proprioception
- Pain
6 Types of Information from Proprioception
- Stretch of muscles
- Tension of tendons
- Position of joints
- Deep vibration
- Static positions
- Dynamic positions
Term: Sensory information about movement
Kinesthetic sense
Structure: Located at the distal ends of peripheral neurons
Receptors
Describe how nociceptors fit into the classification system of receptors
Each type of receptor (mechano/chemo/thermo) has a subset classified as nociceptors that are preferentially sensistive to stimuli that damage or threaten to damage tissue and result in a sensation of pain
Term: area of skin innervated by a single afferent neuron
Receptive field
Describe how the receptive field changes from proximal to distal locations
Smaller with greater density DISTALLY
Larger with less density PROXIMALLY
Describe the importance of receptive fields
They are important to somatosensory sensation and needed for find motor control
Term: skin innervated by axons from a single dorsal root
Dermatome
Term: axons from a dorsal root innervating specific parts of the limbs regrouped to form nerves
Peripheral nerves
3 Superficial Cutaneous Receptors
- Meissner’s Corpuscle
- Merkel’s Disc
- Free Nerve Endings
2 Deep Cutaneous Receptors
- Pacinian Corpuscle
- Ruffini Ending
Receptor: Ia
Proprioception, muscle spindles, phasic
Receptor: Ib
Proprioceptive, GTO, phasic/tonic
Receptor: II
Propriocetive, muscle spindles, tonic
Receptor: Alpha Beta - Touch and vibration
Meissner’s (s) and Pacinian (d)
Receptor: Alpha Beta - Skin stretch
Ruffini’s Endings (d)
Receptor: Alpha Beta - Pressure
Merkel’s disc and hair follicles
Receptor: Alpha Delta
Free nerve ending: conscious pain, temperature, coarse touch
Receptor: C
Free nerve ending, unconscious pain, tempterature, itch, tickle
Receptors: Primary superficial fine toch
Meissner’s corpuscles and Merkel’s discs
Structure: Sensory organ embedded in skeletal/extrafusal muscles
Muscle Spindle
3 Parts of a Muscle Spindle
- Muscle fibers
- Sensory endings
- Motor endings
Stimuli Muscle Spindles Respond to
Muscle stretch
- Quick and tonic stretch registered by Ia
- Tonic stretch registered by II
Describe how small efferent fibers adjust spindle fiber length
Small efferents/gamma motor neurons adjust spindle fiber length via specialized intrafusal spindles. There spindles are then responsive through the physiologic range of muscle length
Receptor: Type of LMN
Ia afferents and Gamma efferents
Structure: Relay information about tension in tendons from both active and passive stretch
GTO
Structure: Information transmitted via Ib afferents
GTO
Location: Cell bodies of most peripheral sensory neurons
Outside the SC in the DRG
Outside the brain in CN ganglia
Cortex: Registers receptor activations (‘maps’)
Primary (somato)sensory cortex
Cortex: Processes information from that sensory system alone
Secondary (somato)sensory cortex
Cortex: Patterns of activity and anticipation
Secondary (somato)sensory cortex
Cortex: Integrates related activity of different sensory system
Sensory association cortex
3 other names for primary somatosensory cortex
- Post central gyrus
- 312 (Broadmann’s)
- S1
Describe the organization of the somatosensory system
Somatotopic Organization from brain down through the cord
Area: Receives sensory information directly from thalamus
Primary sensory area
Area: Discriminates among different intensities and qualities of one type of input
Primary Sensory Area
Cortical Area: Discriminates shape, texture, or size of objects
Primary Somatosensory (B 312)
Cortical Area: Conscious discrimination of loudness and pitch of sound
Primary Auditory (B 41)
Cortical Area: Distinguishes intensity of light, shape, size, and location of objects
Primary visual (B 17)
Cortical Area: Discriminates among head position and head movements
Primary Vestibular
Term: Integration of tactile and proprioceptive information from manipulating an object
Sterognosis
Cortical Area: Stereognosis and memory of the tactile and spatial environment
Secondary Somatosensory (B 5&7)
Cortical Area: Analysis of motion, color, and control of visual fixation
Secondary visual (B 18&19)
Cortical Area: Classification of sounds
Secondary Auditory (B 42)
Broadmann’s Area: Sensory Association Area
39 and 40
Describe the function of the divergent pathway
It’s the medial pain system that carries slow aching diffuse pain
Divergent Pathway: Synapses in medial and intralaminar nuclei of thalamus and projects to limbic system
Spinolimbic
Divergent Pathway: Synpases in superior colliculus and periaqueductal gray
Spinomesencephalic
Divergent Pathway: Synapses in brainstem reticular formation, functions for arousal, attention, sleep/wake cycles
Spinoreticular
Pathway: Unconscious proprioception
Spinocerebellar
Pathway: Critical for adjusting movesments and posture
Spinocerebellar
