Ascending Pathways (handout based) Flashcards
Type of exteroreceptor that transmit tactile, pressure, pain and temperature. Require direct contact of the stimulus with the body
Contact receptors
Type of exteroreceptors that respond to distant stimuli
ex.light and sound
Teloreceptors
respond to pain, temperature, touch, vibration and pressure
Exteroreceptors
Are specialized to detect sensory information from the external environment
Exteroreceptors
detect sensory information concerning the status of the body’s internal environment, such as stretch, blood pressure, pH, oxygen or carbon dioxide concentration, and osmolarity
Enteroreceptors
transmit sensory information from muscles, tendons, and joints about the position of a body part
Proprioceptors
There is a static position sense relating to a stationary position and a kinesthetic sense, relating to the movement of a body part
Proprioceptors
Rapidly adapting receptors that are sensitive to noxious or painful stimuli
Nociceptors
Located at the peripheral termination of lightly myelinated free nerve endings of Aδor unmyelinated type C fibers
Nociceptors
Type of nociceptor that is sensitive to intense mechanical stimulation (ex.Pinching)
Mechanosensitivenociceptors
Type of nociceptor that is sensitive to intense heat or cold
Temperature Sensitive nociceptors
Type of nociceptor that is sensitive to noxious stimuli that are mechanical thermal or chemical in nature
Polymodal nociceptors
Receptors that are sensitive to warmth or cold; Slowly adapting receptors
Thermoreceptors
Type of thermoreceptor that consist of free nerve endings of lightly myelinated Aδfibers
Cold receptors
Type of thermoreceptor that consist of the free nerve endings of unmyelinated C fibers that respond to increases in temperature
Warmth receptors
Type of thermoreceptor that are sensitive to excessive heat or cold
Temperature-sensitive nociceptors
Comprise both exteroceptorsand proprioceptors; Activated following physical deformation due to touch, pressure, stretch, or vibration of the skin, muscles, tendons, ligaments, and joint capsules, in which they reside
Mechanoreceptors
may be classified as nonencapsulated or encapsulated depending on whether a structural device encloses its peripheral nerve ending component
Mechanoreceptors
General Sensation Receptors: touch, pressure, pain, temperature, proprioception
- Touch- Meissner’s corpuscles, Merkel’s disc, Hair follicle endings, Golgi Mazzoni
- Pressure- Pacinian corpuscles
- Pain - Free nerve endings
*Temperature:
Cold -Krause end bulb
Hot –Ruffini’s corpuscles
*Proprioception–Tendon and Muscle spindles
Area of the skin supplied by the somatosensory fibers from a single spinal nerve ; useful in localizing the levels of lesions
Dermatomes
Parts of dermatomes
C2 –back of head C3 –neck C6 –thumb C7 –middle finger C8 –small finger T4 –nipple T10 –umbilicus L1 –inguinal L4 –L5 –big toe S1 –small toe S5 –perineum
3 Columns in the White Matter
Posterior funiculus
Lateral funiculus
Anterior funiculus
Each column in the white matter is subdivided into tracts
Ascending tract
Descending tract
Intersegmental tracts
Parts of the Gray Matter
Posterior horn
Lateral horn
Anterior horn
A system of ten layers of grey matter(I-X), identified in the early 1950’s by Bror Rexed to label portions of the spinal cord
Laminae of Rexed
Similar to Brodmann areas; defined by their cellular structure rather than by their location, but the location still remains reasonably consistent
Laminae of Rexed
Laminae of Rexed: lamina and its location
- Lamina I-VI - located in the posterior horn
- Lamina VII- located in the lateral horn
- Lamina VIII & IX- located in the anterior horn
- Lamina X- gray substance surrounding the central canal
Laminae of Rexed: lamina and cellular structure
- Lamina II –Substantia Gelatinosa
- Lamina III & IV –Nucleus Propius
- Lamina VII–Intermediolateral nucleus; Nucleus dorsalis of Clark
- Lamina VIII & IX –Motor nucleus
Ascending Sensory Pathways: its anatomical tracts and functions
- Anterolateral (ALS): Spinothalamic, Spinoreticular, Spinomesencephalic, Spinotectal, Spinohypothalamic
- Pain, temperature, crude touch, pressure, some proprioception
- Dorsalcolumn-Medial Lemniscus (DCML): fasciculus gracilis, fasciculus cuneatus
- Discriminative (Fine) touch, vibratory sense, position sense
- Somatosensory to the Cerebellum: anterior spinocerebellar, posterior spinocerebellar, rostral spinocerebellar, cuneocerebellar
- Primarily proprioceptive information (some pain and temperatrue)
Pain and Temperature Pathway (using LSTT)
Free nerve endings (from A delta or C fiber) ➡️ Dorsal root ganglion (1storder neuron) ➡️ Postero-lateral funiculus ➡️ Posterior horn ➡️ Synapse with 2ndorder neuron at the Substantia Gelatinosa (Lamina II) ➡️ Cross to the opposite side in the anterior grey and white commissure within 1 spinal segment ➡️ Lateral spinothalamic tract ➡️ VPLN of the thalamus ➡️ Axons of the 3rdorder neuron pass through the posterior limb of the internal capsule and corona radiata ➡️ Primary somatosensory area ( Brodmann’s area 3,1,2)
Light Touch and Pressure pathway (using ASTT)
Receptor ➡️ Dorsal root ganglion (1storder neuron) ➡️ Postero-lateral funiculus ➡️ Posterior horn ➡️ Synapse with 2ndorder neuron at the Substantia Gelatinosa (Lamina II) ➡️ Cross to the opposite side in the anterior grey and white commissure within 2-3 spinal segment➡️ Anterior spinothalamic tract ➡️ VPLN of the thalamus ➡️ Axons of the 3rdorder neuron pass through the posterior limb of the internal capsule and corona radiata ➡️ Primary somatosensory area ( Brodmann’s area 3,1,2)
Dorsal Column -Medial Lemniscus Pathway
Axons enter the SC and pass directly to ipsilateralposterior column ( caudal fibers below T6 enter Fasciculus gracilis and rostral fibers above T6 enter Fasciculus cuneatus to ascend) ➡️ Terminate in Nucleus gracilis and Nucleus cuneatus ➡️ Axons of secondary nuclei cross the midline as Internal arcuate fibers and form the Medial Lemniscus ➡️ Terminates in the VPLN of thalamus
Discriminative Touch and Pressure pathway
Receptors ➡️ Dorsal root ganglion (1storder neuron) ➡️ Cuneate fasciculus and Gracile fasciculus ➡️ Cuneate and Gracile nuclei (2ndorder neuron) of medulla oblongata ➡️ Medial lemniscus ➡️ VPLN of the thalamus ➡️ Axons of the 3rdorder neuron pass through the posterior limb of the internal capsule and corona radiata ➡️ Primary somatosensory area ( Brodmann’s area 3,1,2)
Conscious Proprioception Pathway
Receptors ➡️ Dorsal root ganglion ➡️ Posterior column ➡️ Cuneate and gracile fascicles ➡️ Cuneate and gracile nuclei ➡️ Medial lemniscus ➡️ VPLN of the thalamus ➡️ BA 3, 1, 2
Unconscious Proprioception Pathway (Posterior spino-cerebellar tract)
Receptor ➡️ DRG (1storder neuron) ➡️ Posterior grey column ➡️ Synapse with 2nd order neurons -Dorsal nucleus of Clarke (Lamina VII) ➡️ IpsilateralPosterolateral part of the lateral column as the Posterior Spinocerebellar tract ➡️ Medulla oblongata ➡️ Inferior cerebellar peduncle ➡️ Cerebellum
Unconscious Proprioception Pathway (Cuneocerebellar tract)
Receptors at upper limb ➡️ Dorsal root ganglion (1st order neuron) ➡️ Cuneate fasciculus ➡️ Cuneate nuclei (2ndorder neuron) of medulla oblongata ➡️ Ipsilateral Inferior cerebellar peduncle (fibers are known as posterior external arcuate fibers) ➡️ Cerebellum
Spinal Cord Hemisection;
Contralateral loss of pain & temperature; Ipsilateral loss of proprioception;Ipsilateral manifestations of upper and lower motor neuron lesions
Brown-Sequard’s syndrome
Injury to the Lemniscal Pathway can cause:
Inability to recognize limb position; Astereognosis; Loss of two point discrimination; Loss of vibration sense; (+) Romberg sign
(1) Spinal Cord lesions can cause:
Syringomyelia (progressive cavitation around the central canal; loss of pain & temperature sensations in hands & forearm)
(2) Spinal Cord lesions can cause:
Tabes Dorsalis (caused by neurosyphilis; dorsal root involvement with secondary degeneration of dorsal columns ( loss of vibration and position sense))
loss of sensitivity to pain in all / part of the body
Anesthesia
an abnormally reduced sensitivity to touch
Hypoesthesia
an abnormally heightened sensitivity of part of the body
Hyperesthesia
an abnormal or unexplained tingling, pricking or burning sensation on the skin
Paresthesia
Lesion in spinocerebellar tract can lead to:
Ataxia (loss of muscle coordination due to a loss of proprioceptive input to the cerebellum)
