1. SENSATION AND THE SPECIAL SENSES
Pedro Amarante Andrade, PhD
LCSC06 BIOSCIENCES FOR SPEECH AND LANGUAGE THERAPY

2. WHAT IS MEANT BY SENSATION?
The conscious or subconscious awareness of changes in the external or internal environment

3. WHAT DO WE MEAN BY THE SPECIAL SENSES?
GENERAL SENSES:
Somatic sensation (somat = of the body) include tactile sensations (touch, pressure, vibration, itch and tickle); thermal sensations (warm and cold), pain sensations, and proprioceptive sensations (static & movement)
Visceral senses provide information about condition within internal organs
SPECIAL SENSES
Vision
Hearing
Equilibrium or balance
Smell
Taste

4. CHIAN EVENTS FOR SENSATION TO ARISE
a. Stimulation of the sensory receptors
b. Transduction of the stimulus
c. Generation of nerve impulses
d. Integration of sensory input

5. CLASSIFICATION ACCORDING TO LOCATION
EXTERORECEPTORS (near the surface)
INTERORECEPTORS (internally in the blood vessels or organs)
PROPRIOCEPTORS
define the terms exteroreceptor, interoreceptor and proprioceptor
What are the different functions of receptors?

7. CLASSIFICATION ACCORDING TO LOCATION
EXTERORECEPTORS (near the surface)
are located at or near the external surface of the body; they are sensitive to stimuli originating outside the body and provide information about the external environment.
The sensations of hearing, vision, smell, taste, touch, pressure, vibration, temperature, and pain are conveyed by exteroceptors.

8. CLASSIFICATION ACCORDING TO LOCATION
INTERORECEPTORS (internally in the blood vessels or organs)
or visceroceptors are located in blood vessels, visceral organs, muscles, and the nervous system and monitor conditions in the internal environment. They are usually not consciously perceived; occasionally, however, activation of interoceptors by strong stimuli may be felt as pain or pressure

9. CLASSIFICATION ACCORDING TO LOCATION
PROPRIOCEPTORS
are located in muscles, tendons, joints, and the inner ear. They provide information about body position, muscle length and tension, and the position and movement of your joints.

10. TYPES OR RECEPTORS

11. (sensitive to stretching that occurs as digits or limbs are moved)
Which area of the body has the highest concentration of mechanoreceptors? Why might this be?
Finger tips, hands, lips and external genitalia & bottom of your feet –
(sensitive to stretching that occurs as digits or limbs are moved)

12. TYPES OR POTENTIALS

13. ADAPTATION
Generator potentials or receptor potentials decreases in amplitude during a maintained, constant stimulus (frequency of nerve impulses in the first-order neuron to decrease) e.g. hot shower

14. INTENSITY AND DURATION

15. SOMATOTOPICALLY ORGANISATION
Somatotopy is the point-for-point correspondence of an area of the body to a specific point on the central nervous system. Typically, the area of the body corresponds to a point on the primary somatosensory cortex (postcentral gyrus).
OpenStax College

16. WHAT ASPECTS OF SENSATION ARE INTEGRATED AT THE LEVEL OF THE SPINAL CORD?
Spinal reflexes

17. VIII Vestibulocochlear
SENSORY PATHWAYS FROM THE HEAD
No./Name
Sensory
Origin/Target
Exit Foramen
Function
I Olfactory
Purely sensory
Telencephalon
Located in the olfactory foramina in the cribriform plate of the ethmoid bone.
sense of smell from the nasal cavity.[2]
II Optic
Retinal ganglion cells
Located in the optic canal.
Transmits visual signals from the retina of the eye to the brain.[3]
V Trigeminal
Both sensory and motor
Pons
Three Parts: V1 (ophthalmic nerve) is located in the superior orbital fissure V2 (maxillary nerve) is located in the foramen rotundum V3 (mandibular nerve) is located in the foramen ovale.
Receives sensation from the face and innervates the muscles of mastication.
VII Facial
Pons(cerebellopontin e angle) above olive
Located in and runs through the internal acoustic canal to the facial canal and exits at the stylomastoid foramen.
Receives the special sense of taste from the anterior 2/3 of the tongue and provides secretomotorinnervation to the salivary glands (except parotid) and the lacrimal gland.
VIII Vestibulocochlear
Mostly sensory
Lateral to CN VII (cerebellopontine angle)
Located in theinternal acoustic canal.
Mediates sensation of sound, rotation, and gravity
IX Glossopharyngeal
Medulla
Located in thejugular foramen.
Receives taste from the posterior 1/3 of the tongue. Some sensation is also relayed to the brain from the palatine tonsils

18. OLFACTORY: SENSE OF SMELL

19. OLFACTORY: SENSE OF SMELL
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

20. OLFACTORY: SENSE OF SMELL
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

21. OLFACTORY: SENSE OF SMELL
million receptors
Area ± 5 cm2
Perceive 10,000 of difference odours
High sensitivity (e.g. 1/25 billionth of milligram of methyl mercaptan* – rotten cabbage)
Adapt 50%/1st second
* Natural gas 4 cooking
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

22. OLFACTORY: SENSE OF SMELL
Chemical sense
Impulses propagate to the limbic system  evoke strong emotional responses
3 types of cells:
Olfactory receptors
Olfactory hair
Supporting
basal
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

23. OLFACTORY: SENSE OF SMELL
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

24. OLFACTORY SENSE
Odorant molecule  olfactory receptor protein + membrane protein (G protein)  activ. of adenylate cyclase (enzyme)  production of cyclic adenosine monophosphate (cAMP)  open Na+ channels  inflow of Na+  depolarization  nerve impulse
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

25. OLFACTORY SENSE
Totora, G. j., Derrickson, B Principles of anatomy and physiology.
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

26. To the limbic system and hypothalamus (sensations)
OLFACTORY: SENSE OF SMELL
Primary olfactory area of the cortex in the temporal lobe (bypassing the Thalamus)
Frontal lobe
To the limbic system and hypothalamus (sensations)
Totora, G. j., Derrickson, B Principles of anatomy and physiology. 12th edition

27. OLFACTORY: SENSE OF SMELL

28. GUSTATION: SENSE OF TASTE

29. App. 70% of taste is due to olfaction.
GUSTATION: SENSE OF TASTE
Chemical sense by only 5 primary senses can be perceived:
Sour
Sweet
Bitter
Salty
Umami (meaty or savoury)
App. 70% of taste is due to olfaction.
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

30. GUSTATION: SENSE OF TASTE
10,000 taste buds (mainly tongue but also: soft palate, pharynx and epiglottis
No. taste buds declines with age
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

31. GUSTATION: SENSE OF TASTE
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

32. GUSTATION Papillae Vallate: V-shaped 100-300 taste buds each
Foliate: leaflike. Lateral margin of the tongue. Most taste buds degenerate in early childhood
Fungiform: Mushroom-shaped. All over the tongue. 5 taste buds each
Filiform: Thredlike. Tactile receptors
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

33. GUSTATION Gustatory receptors
Three kinds of epithelial cells: supporting cells, gustatory receptors and basal cells;
Gustatory hair that projects via the taste pore
Basal cells  supporting cells 
Gustatory cells
(10 days)
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

34. GUSTATION
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

35. GUSTATION

36. GUSTATION
Totora, G. j., Derrickson, B Principles of anatomy and physiology.

37. GUSTATION
Purves et al Neuroscience, 3rd Ed. Sinauer Associates Inc.

38. GUSTATION

39. THE SENSORY PATHWAYS
Draw yourself a basic diagram showing the whole pathway, including receptor, first, second and third order neurons, the spinal cord and the thalamus.
Which pathway decussates in the spinal cord? Which pathway decussates in the brainstem?

40. Where is the nucleus of this nerve located?
SENSORY PATHWAYS FROM THE HEAD
Which cranial nerve carries the sensory information from the face to the CNS?
Where is the nucleus of this nerve located?
What cranial nerves carry somatic sensation from the buccal cavity/posterior third tongue/anterior two-thirds of the tongue?