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The General & Special Senses

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Presentation on theme: "The General & Special Senses"— Presentation transcript:

1 The General & Special Senses
Chapter 18

2 Introduction Senses – our perception of what is “out there”
General senses Includes senses that are not specific Pass information through spinal nerves Special senses Found within complex sense organs to cerebral cortex Pass information through cranial nerves to cerebral cortex

3 General Senses Includes senses that are associated with skin
Temperature, pressure, touch, pain, vibration, proprioception Pass information along the spinal nerves and pathways to specific areas of the cerebral cortex

4 Special Senses Olfaction, gustation, equilibrium, hearing, & vision
Found within complex sense organs Pass information along the cranial nerves to specific areas of the cerebral cortex.

5 Receptors Sensory receptors are transducers
Change stimuli into electro-chemical impulses Specific receptors can transduce only certain types of stimuli

6 Interpretation of Sensory Information
Occurs in cerebral cortex Depends on the area of the cerebral cortex that receives the information

7 Central Processing and Adaptation
Sensory adaptation – the loss of sensitivity after continuous stimulation Tonic receptors are always active Phasic receptors only relay changes in the conditions they are monitoring Role – prevents brain from being overloaded with unimportant information

8 Receptors of the General Senses

9 Nociceptors Detect pain Referred pain Phantom pain

10 Mechanoreceptors Respond to pressure & touch Tactile receptors
Baroreceptors Proprioreceptors Thermoreceptors

11 Tactile Receptors Found in the dermis

12 Baroreceptors Monitor changes in pressure

13 Chemoreceptors Detect chemicals in solution Blood composition

14 The Special Senses

15 Olfaction (the nose) Olfactory receptors
Can detect at least 50 different primary smells Located in the epithelium of roof of nasal cavity

16 Olfactory Receptors Molecules dissolve in the mucus of the epithelium
Olfactory neurons pass through the roof of the nasal cavity and synapse in the olfactory bulb Olfactory tracts go directly to the cerebral cortex

17 Gustation (the tongue)
Taste receptors are in the taste buds 6 primary tastes Sweet, sour, salty, bitter, water, umami

18 Gustatory Receptors Located in papillae on the surface of the tongue
Contain the gustatory receptors Molecules dissolve in saliva

19 Gustatory Receptors

20 Pathway of Gustatory Sense
Cranial nerves relay sensory impulses to the cerebral cortex All pass through the medulla & thalamus

21 Equilibrium & Hearing (the ear)
External ear The auricle directs sound waves into the external auditory meatus to the tympanic membrane

22 The Middle Ear Contains the auditory ossicles
Separated from the external ear by the tympanic membrane Malleus Incus Stapes Connected to the throat by the eustachian tube

23 The Inner Ear Separated from the middle ear by the oval window

24 The Inner Ear Consists of a series of canals filled with fluid

25 The Inner Ear Consists of a series of canals filled with fluid
Vestibule Semicircular canals Cochlea contains Organ of Corti

26 The Vestibule Detects static position
Hair cells are embedded in a gelatinous material

27 Otoliths at Work Otoliths are balanced on top of gelatinous material
Slide when head tips Bend hairs Generates nerve impulse

28 The Semicircular Canals
Detect dynamic balance Arranged at right angles to each other Hair cells are embedded in gelatinous material with fluid over it Movement of head Bends the hairs Creates nerve impulses

29 Semicircular Canals at Work

30 The Cochlea Divided into 3 tunnels by membranes
Tunnels connect with the oval window and round window Organ of Corti

31 Cochlear Chambers

32 The Organ of Corti Consists of hair cells on a basement membrane
Tips of hairs touch the tectorial membrane Basement membrane vibrates Hair cells bend Sends a nerve impulse

33 Pathway of Auditory Sense

34 Summary of Hearing Sound waves enter the external auditory meatus
Tympanic membrane vibrates Auditory ossicles vibrate Oval window vibrates Fluid in cochlea moves Basement membrane moves Hairs rub against the tectorial membrane Nerve impulse is sent along the auditory nerve to the brain

35 Vision (the eye) – Accessory Structures
Eyelids protect the eye Conjunctiva lines the eyelid Lacrimal apparatus Lacrimal gland produces tears Lacrimal canals drain tears into lacrimal sacs Nasolacrimal duct drains into the nasal cavity Extrinsic muscles move the eyeball

36 Structure of the Eye – 3 Tunics
Outer tunic Includes cornea & sclera Middle tunic Includes choroid coat, ciliary body, lens, iris & pupil Inner tunic (retina) Contains photoreceptors Rods & cones Includes optic disc, macula lutea & fovea centralis

37 Photo of Posterior Eye

38 The Cavities of the Eye The lens separates the interior of the eye into 2 cavities Anterior cavity Contains aqueous humor Glaucoma Posterior cavity Contains vitreous humor

39 The Cavities of the Eye

40 The Vascular Tunic Contains many blood vessels & nerves
The iris controls the size of the pupil Suspensory ligaments attach the lens to the ciliary body Controls the shape of the lens Allows focusing on near & distant objects Cataract

41 The Retina Cones allow for sharp color vision in bright light
Contain pigments Macula lutea Fovea centralis Rods provide for vision in dim light Contain the pigment rhodopsin Most dense at periphery of retina

42 Photo of Posterior Eye

43 Pathway of Vision Sense

44 Summary of Vision Light rays enters through the pupil
Light rays cross in the lens Retina receives reversed & upside down image Rods & cones are stimulated Optic nerve carries impulse to the brain

45 Abnormal Vision Myopia Hyperopia Presbyopia Astigmatism

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