Reflex and Sensory Integrity

Somatosensation

input from the skin and musculoskeletal system; interprets and discriminate the incoming sensory information

dermatome

band or region of skin supplies by a single sensory nerves or dorsal root

superficial sensation

externoreceptors

deep sensation

proprioreceptors

combined cortical sensation

both superficial and deep

what is the anterolateral spinothalamic system known for

self protection reactions

what is the dorsal column-medial lemniscal system known for

discriminative sensations

externoreceptors

are responsible for superficial sensations and receive stimuli from the external environment via the skin and subcutaneous tissue

what does the externoreceptors perceive

pain, temperature, light touch, pressure

proprioreceptors

Receptors in the deeper somatic structures (muscles, ligaments, tendons, joints, fascia)

what do proprioreceptors perceive

position sense, movement awareness, vibration

What needs to be intact for combined cortical sensation

receptor and cortex must be intacted

what is included in combined cortical sensation

stereognosis, two-point discrimination, barognosis, graphesthesia, tactile localization, recognition of texture

free nerve endings

throughout the body, perceive pain, temperature, touch, pressure, tickle and itch

merkel's discs

epidermis in hairless smooth skin (fingertips) that perceive localization of touch and 2 point discrimination

ruffini endings

Deeper layers of the dermis the perceive touch and pressure. Also in joint capsule and assist with joint position sense

meissner's corpuscles

in dermis with discriminative touch (texture) and movement of objects over skin

pacinian corpuscles

subcutaneous and deep tissues (i.e tendons and soft tissues around joints). Sense deep touch and vibration

Golgi Type Endings (Joint Receptors)

within ligaments and detect rate of joint movement

free nerve ending (joint receptors)

within joint capsule and ligaments that respond to pain and crude joint motion

Where are Ruffini endings (joint receptors) located?

Within joint capsule and ligaments

What do Ruffini endings (joint receptors) perceive?

Direction and velocity of joint movement ~ minute joint position changes

Paciniform Endings (Joint Receptors)

within joint capsule and monitor rapid joint movements ~ detects rapid changes in joint angle

Anterior (ventral) spinothalamic tract

crude localization touch and pressure

lateral spinothalamic tract

pain and temperature

spinoreticular tract

diffuse pain

Quality of cutaneous sensation

depends on the nerve fiber that is stimulated

intensity of cutaneous sensation

sensation is related to the frequency of stimulation

temporal summation

impulse frequency determines intensity of stimulus

spatial summation

more sensory units are recruited as the intensity of stimulus increases

threshold of stimulation

the stimulus needed in order to depolarize the nerve ending must pass through the skin with enough energy

peripheral generator potential

nerve impulse that is generated during stimulation is graded one, not an all or nothing principle

what are the superficial sensations for sensory exam

light touch, pain, thermal sense, pressure

what are the deep sensation for sensory exam

proprioceptive, kinesthesia, vibration, deep pressure