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Type of exteroreceptors that respond to distant stimuli
(ex.light and sound)

Teloreceptors

1

Type of exteroreceptor that transmit tactile, pressure, pain and temperature. Require direct contact of the stimulus with the body

Contact receptors

2

respond to pain, temperature, touch, vibration and pressure

Exteroreceptors

3

Are specialized to detect sensory information from the external environment

Exteroreceptors

4

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

5

transmit sensory information from muscles, tendons, and joints about the position of a body part

Proprioceptors

6

There is a static position sense relating to a stationary position and a kinesthetic sense, relating to the movement of a body part

Proprioceptors

7

Rapidly adapting receptors that are sensitive to noxious or painful stimuli

Nociceptors

8

Located at the peripheral termination of lightly myelinated free nerve endings of Aδor unmyelinated type C fibers

Nociceptors

9

Type of nociceptor that is sensitive to intense mechanical stimulation (ex.Pinching)

Mechanosensitivenociceptors

10

Type of nociceptor that is sensitive to intense heat or cold

Temperature Sensitive nociceptors

11

Type of nociceptor that is sensitive to noxious stimuli that are mechanical thermal or chemical in nature

Polymodal nociceptors

12

Receptors that are sensitive to warmth or cold; Slowly adapting receptors

Thermoreceptors

13

Type of thermoreceptor that consist of free nerve endings of lightly myelinated Aδfibers

Cold receptors

14

Type of thermoreceptor that consist of the free nerve endings of unmyelinated C fibers that respond to increases in temperature

Warmth receptors

15

Type of thermoreceptor that are sensitive to excessive heat or cold

Temperature-sensitive nociceptors

16

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

17

may be classified as nonencapsulated or encapsulated depending on whether a structural device encloses its peripheral nerve ending component

Mechanoreceptors

18

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

19

Area of the skin supplied by the somatosensory fibers from a single spinal nerve ; useful in localizing the levels of lesions

Dermatomes

20

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

21

3 Columns in the White Matter

Posterior funiculus
Lateral funiculus
Anterior funiculus

22

Each column in the white matter is subdivided into tracts

Ascending tract
Descending tract
Intersegmental tracts

23

Parts of the Gray Matter

Posterior horn
Lateral horn
Anterior horn

24

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

25

Similar to Brodmann areas; defined by their cellular structure rather than by their location, but the location still remains reasonably consistent

Laminae of Rexed

26

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

27

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

28

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)

29

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)

30

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)

31

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

32

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)

33

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

34

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

35

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

37

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

38

Injury to the Lemniscal Pathway can cause:

Inability to recognize limb position; Astereognosis; Loss of two point discrimination; Loss of vibration sense; (+) Romberg sign

39

(1) Spinal Cord lesions can cause:

Syringomyelia (progressive cavitation around the central canal; loss of pain & temperature sensations in hands & forearm)

40

(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))

41

loss of sensitivity to pain in all / part of the body

Anesthesia

42

an abnormally reduced sensitivity to touch

Hypoesthesia

43

an abnormally heightened sensitivity of part of the body

Hyperesthesia

44

an abnormal or unexplained tingling, pricking or burning sensation on the skin

Paresthesia

47

Lesion in spinocerebellar tract can lead to:

Ataxia (loss of muscle coordination due to a loss of proprioceptive input to the cerebellum)