Chapter 11 Flashcards
What is the somatosensory system?
The somatosensory system is the part of the sensory system concerned with the conscious perception of touch, pressure, pain, temperature, position, movement, and vibration, which arise from the muscles, joints, skin, and fascia.
Somatosensation
Bodily experienced external and internal sensations
Includes sense of pain, temperature, touch and proprioception
Begins with receptors in the skin, muscles, joints and blood vessels
Types of somatic sensation
Mechanoreception
Thermoreception
Nociception
Mechanoreception
Touch, pressure, vibration (tactile) and kinesthesia
Touch is divided into fine discriminative and diffuse
Thermoreception
Sensation of cold and heat
Nocioception
Pain related to tissue destruction
Sensory receptors
Encapsulated endings
Free nerve endings
Expanded tip endings
Encapsulated endings
Subcutaneous tissues Skin Fingertips Palms Lips External genitals Most sensitive Mediate sensations of vibration and fine discriminative touch
What is the somatosensory system divided into?
Divided into the
Dorsal column medial lemniscal system
Anterolateral system
Dorsal column medial lemniscal
Also called epicritic system
Mediates postural position sense
Fine discriminative touch
Stereognosis
graphesthesia
Stereognosis
the mental perception of depth or three-dimensionality by the senses, usually in reference to the ability to perceive the form of solid objects by touch.
graphesthesia
Graphesthesia is the ability to recognize writing on the skin purely by the sensation of touch. Its name derives from Greek graphē (“writing”) and aisthēsis (“perception”).
Neural pathways
Fasiculus gracilis
Fasiculus cuneatus
Both mediate discriminative touch from different body regions
Fasiculus gracilis
Transmits information from the lower half of the body to the dorsal caudal medulla
Fibers cross midline to merge with fasciculus cuneatus
Then to the thalamus
Then to the sensory cortex in the parietal lobe
Clinical correlates
Sensory loss
Cognitive deficits
Tactile agnosia
astereognosis
Fasiculus gracilis
Transmits information from the lower half of the body to the dorsal caudal medulla
Fibers cross midline to merge with fasciculus cuneatus
Then to the thalamus
Then to the sensory cortex in the parietal lobe
Fasciculus cuneatus
Carries sensation from the upper body and the entire spinal cord above the mid thoracic level
Fibers ascend ipsilaterally to the dorsal caudal medulla
Decussate in medulla
Thalamus
Then to sensory cortex in the parietal lobe
Anterolateral system
Is a sensory pathway from the skin to the thalamus. Also called the protopathic system.
Divided into
lateral spinothalamic
anterior spinothalamic
Lateral spinothalamic tract
Carries sensation of pain and temperature
Begins receptors of the skin
Lateral spinothalamic tract clinical correlates
Alteration in the perception of pain and temperature
Phantom limb
Types of altered response to pain
Analgesia
Hypalgesia
hyperalgesia
Thermal sensation
Athermia or thermal anesthesia
Hypothermia
hyperthermia
Anterior spinothalamic
Backup system to the lateral spinothalamic tract
Diffuse touch
Damage to this tract does not cause any obvious clinical correlates
Only when the spinal cord is completely severed
Sensory pathways for the head and face
Trigeminal nerve is the principal sensory nerve for the face and head
Three branches of the trigeminal nerve
Three branches
Maxillary
Opthalamic
Mandibular
Clinical correlates to damage to the trigeminal nerve.
Trigeminal neuralgia
Excruciating pain in the ipsilateral half of the face
Unconscious proprioception
Ventral spinocerebellar tract
Dorsal spinocerebellar tract
Cuneocerebellar
All go to the cerebellum
Clinical Correlates
Hard to determine because serves as a back up system for the dorsal column medial lemniscal system
