1. Sensory Pathways and the Somatic Nervous System

2. Sensations from body reaches the opposite side of the brain
Sensory pathways
Physiology
Sensory pathways allow us to detect, analyse and organise response to our environment
Each ascending pathway (dorsal column/medial leminiscal and spinothalamic tract (carry information from sensory receptors to the brain)
Sensations from body reaches the opposite side of the brain

3. Analyse and response
Convey / mediate
Detect

4. Special senses: vision, olfaction and hearing and balance
Sensory pathways
Physiology
Types of sensation
Somatic
Special senses: vision, olfaction and hearing and balance
Somatic sensation: works through mechanoreceptors, thermoreceptors, pain receptors and others

5. Sensory pathways Physiology Mechanoreceptors: tactile and position
Thermal receptors: heat and cold
Nociceptors: pain

6. Some types of ensory receptorsA B C D
A: Free nerve endings (pain, temperature)
B: Pacinian corpuscle (pressure)
C: Meissner’s corpuscle (touch)
D: Muscle spindle (stretch)

7. Illustration of different receptors and sensation modalities in one image

8. Sensory pathways
3 order neuron
Both spinothalamic and dorsal column/medial leminiscal systems are 3 order neurons
3 order neurons: means use 3 neurons or synapses until they trasduct the stimulus and finaly reach the somatosensory cortex
Dorsal root ganglion
Spinal cord neuron
Thalamic nucleus

9. Dorsal column/Medial leminiscal

10. Spinothalamic tract
Pain, temp,. Crude touch itch and sexual sensation

11. Spinothalamic
pathway
Dorsal
coloumn
pathway

12. Postcentral gyrus, somatotopic representation/mapping

14. Dorsal column: fine touch, joint position and pressure
pathway
Left
spinal cord injury
Loss of sense of:
Fine touch
proprioception
vibration in left leg
Dorsal column: fine touch, joint position and pressure
Proprioception (pron.: /ˌproʊpri.ɵˈsɛpʃən/ PRO-pree-o-SEP-shən), from Latin proprius, meaning "one's own", "individual" and perception, is the sense of the relative position of neighboring parts of the body and strength of effort being employed in movement.
Position , pressure
Basis of proprioceptive sense
The initiation of proprioception is the activation of a proprioreceptor in the periphery.[13] The proprioceptive sense is believed to be composed of information from sensory neurons located in the inner ear (motion and orientation) and in the stretch receptors located in the muscles and the joint-supporting ligaments (stance). There are specific nerve receptors for this form of perception termed "proprioreceptors," just as there are specific receptors for pressure, light, temperature, sound, and other sensory experiences.
Conscious and unconscious proprioception
In humans, a distinction is made between conscious proprioception and unconscious proprioception:
Conscious proprioception is communicated by the posterior column-medial lemniscus pathway to the cerebrum.[20]
Unconscious proprioception is communicated primarily via the dorsal spinocerebellar tract[21] and ventral spinocerebellar tract,[22] to the cerebellum.
An unconscious reaction is seen in the human proprioceptive reflex, or righting reflex – in the event that the body tilts in any direction, the person will cock their head back to level the eyes against the horizon.

15. Spinothalamic: crude touch, pain, tepmrature
spinothalamic pathway
Left
spinal cord injury
Loss of sense of:
Crude touch
Pain
Warmth/cold in right leg
Crude touch (or non-discriminative touch) is a sensory modality which allows the subject to sense that something has touched them, without being able to localise where they were touched (contrasting fine touch)
d) Tickle and itch.
e) Sexual sensation .

16. Dermatomes
Spinal nerves have motor fibres and sensory fibres. The motor fibres innervate certain muscles, while the sensory fibres innervate certain areas of skin. A skin area innervated by the sensory fibres of a single nerve root is known as a dermatome. A group of muscles primarily innervated by the motor fibres of a single nerve root is known as a myotome.
Dermatome is a Greek word which literally means "skin cutting". A dermatome is an area of the skin supplied by nerve fibers originating from a single dorsal nerve root.  The dermatomes are named according to the spinal nerve which supplies them. The dermatomes form into bands around the trunk but in the limbs their organisation is more complex as a result of the dermatomes being "pulled out" as the limb buds form and develop into the limbs during embryological development.

18. Dermatomes are areas of skin supplied by same/individual nerve roots from the spinal cord

19. Components of the sensory examination
Crude touch
Pain and temperature
Vibration and position
Fine touch
2 point discrimination
Stereognosis

20. Pin prick

21. Light touch

22. Temperature sensation

23. Joint position

24. Joint position

25. Two-Point Discrimination

26. Stereognosis