OMM/OPP Flashcards
Touch
perception that derives from neural activity in a complex network that includes the somatic sensory system including portions of many of the cortical regions in the cerebrum
Perception
The conscious mental registration or awareness of a sensory stimulus
Receptive field
An area within which a stimulus can excite a cell causing it to fire an action potential or alter the firing of the neuron associated with it.
2 point discrimination-
The ability to discern that two nearby objects are touching the skin at two distinct points. The smallest most dense sensory units are located in the areas with the greatest somatosensory cortical representation (lips and finger pads)
Stereognosis
The ability to recognize the 3-D shape of an object solely based on touch
Threshold
the least amount of energy of force needed to cause a measurable response. The threshold of different receptors varies, therefore vary the pressure used for the most complete picture.
Adaption
when a continuous sensory stimulus is applied the receptors initially respond at a high impulse rate but then drop off until they may no longer respond
Mechanoreceptors
Sensitive to physical distortion: bending, stretching, vibration and pressure
Nociceptors
Signal that the body is being damaged or is at risk of being damaged
4 categories: mechanical (strong pressure from sharp objects), thermal (extreme temperatures), chemically sensitive (pH), polymodal
Free, unbranching lightly myelineated or unmyelinated nerve endings
Thermoreceptors
Receptors that are sensitive to extreme hot or cold
Proprioceptors
Measure length and tendon and limb position so the body knows where it is in space, how fast it is going and what direction it is going
Encapsulated ending mechanoreceptors
4 examples
Pacinian corpuscle
Meissner’s corpuscle
Merkel disks
Ruffini endings
Pacinian corpuscle
receptors with rapidly adapting endings/ quickly change discharge patterns to static stimulus , better for dynamic
Detect deep pressure and rapid vibration
Large receptive Field
Meissner’s corpuscle
rapidly adapting endings, better for dynamic, 1/10 size of Pacinian corpuscles, light touch, help create adaptation, small receptive fields, fingertips, lips, soles of feet, tongue and face, more superficial
Merkel disks
better at detecting static stimulus, sustained pressure and texture, surface structure, moisture, tactile discrimination, small receptive fields, greater number on finger pads
Ruffini endings
better at detecting static stimulus, spindle-shaped and are sensitive to sustained pressure and skin stretch-located deeper in the dermis
Hair root plexus
known for detecting light touch
Krause’s end bulbs
found in border regions of dry skin and mucous membranes and participate in crude touch
Explain how somatic sensation is transmitted to the brain.
1st order neuron (primary afferent)- Periphery- sensory receptors (i.e. mechanoreceptors)- responds to a stimulus, transduces it and transmits the encoded information to the CNS.
Dorsal root ganglion- up the dorsal column nuclei
2nd order neuron (secondary afferents)- located in spinal cord or brainstem/ medulla
3rd order- resides within the thalamus
4th order- the somatosensory cortex (located in the postcentral gyrus of the cerebral cortex)- this is now where perception occurs- the conscious awareness of the stimulus
Dorsal or Posterior Columnar-Medial Lemniscal Pathway:
transmits information about touch and vibration, tactile pressure, stereognosis, recognition of texture, 2 point discrimination from the skin and proprioceptive signals and kinesthesia (sense of body motion) from the limbs. It is a high speed pathway carrying touch and proprioceptive sensory information to the primary somatic sensory cortex
Spinothalamic pathway
carries information about pain, itch, temperature, crude or non-discriminative touch
Sensory Homunculus:
distorted human figure used to represent the relative area of cerebral cortex devoted to sensation of corresponding skin areas at the postcentral gyrus.
Motor Homunculus
distorted human figure used to represent the relative area of cerebral cortex devoted to movement of corresponding motor areas at the precentral gyrus.
palpation
The act of feeling with the hand, The application of the fingers with varying pressure to the surface of the body during physical diagnosis, for the purpose of determining the condition of the parts beneath.
