1 Sensory Physiology

2 Nervous System - Senses General Senses receptors that are widely distributed throughout the body skin, various organs and joints Special Senses specialized receptors confied to structures in the head eyes and ears

3 Senses Sensory Receptors specialized cells or multicellular structures that collect information from the environment stimulate neurons to send impulses along sensory fibers to the brain Sensation a feeling that occurs when brain becomes aware of sensory impulse Perception a person’s view of the stimulus; the way the brain interprets the information

4 Sensory Receptor Types Figure 10-1: Sensory receptors

5 Pathways From Sensation to Perception (Example of an Apple)

6 Receptor Types Chemoreceptors respond to changes in chemical concentrations Pain receptors (Nociceptors) respond to tissue damage Thermoreceptors respond to changes in temperature Mechanoreceptors respond to mechanical forces Photoreceptors respond to light

7 Sensory Adaptation ability to ignore unimportant stimuli involves a decreased response to a particular stimulus from the receptors (peripheral adaptations) or along the CNS pathways leading to the cerebral cortex (central adaptation) sensory impulses become less frequent and may cease stronger stimulus is required to trigger impulses

8 General Senses senses associated with skin, muscles, joints, and viscera three groups exteroceptive senses – senses associated with body surface; touch, pressure, temperature, pain visceroceptive senses – senses associated with changes in viscera; blood pressure stretching blood vessels, ingesting a meal proprioceptive senses – senses associated with changes in muscles and tendons

9 Touch and Pressure Senses Free nerve endings common in epithelial tissues simplest receptors sense itching Ex ( nociciptor) Meissner’s corpuscles abundant in hairless portions of skin; lips detect fine touch; distinguish between two points on the skin Pacinian corpuscles common in deeper subcutaneous tissues, tendons, and ligaments detect heavy pressure and vibrations

10 Touch and Pressure Receptors

11 Touch (pressure) Figure 10-11: Touch-pressure receptors

12 Temperature Senses Warm receptors sensitive to temperatures above 25 o C (77 o F) unresponsive to temperature above 45 o C (113 o F) Cold receptors sensitive to temperature between 10 o C (50 o F) and 20 o C (68 o F) Pain receptors (nociceptor) respond to temperatures below 10 o C respond to temperatures above 45 o C

13 Summary of Receptors of the General Senses

14 Special Senses sensory receptors are within large, complex sensory organs in the head smell in olfactory organs taste in taste buds hearing and equilibrium in ears sight in eyes

15 Sense of Smell Olfactory Receptors chemoreceptors respond to chemicals dissolved in liquids Olfactory Organs contain olfactory receptors and supporting epithelial cells cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

16 Olfactor: Sense of Smell Figure 10-14a, b: ANATOMY SUMMARY: Olfaction

17 Olfactory Receptors

18 Olfactor: Sense of Smell Figure 10-14c: ANATOMY SUMMARY: Olfaction

19 Olfactory Nerve Pathways Once olfactory receptors are stimulated, nerve impulses travel through olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

20 Figure 10-4: Sensory pathways

21 Olfactory Stimulation Olfactory Code hypothesis odor that is stimulated by a distinct set of receptor cells and its associated receptor proteins olfactory organs located high in the nasal cavity above the usual pathway of inhaled air olfactory receptors undergo sensory adaptation rapidly sense of smell drops by 50% within a second after stimulation

22 Sense of Taste Taste Buds organs of taste located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx Taste Receptors chemoreceptors taste cells – modified epithelial cells that function as receptors taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

23 Taste Receptors

24 Taste Sensations Four Primary Taste Sensations sweet – stimulated by carbohydrates sour – stimulated by acids salty – stimulated by salts bitter – stimulated by many organic compounds Spicy foods activate pain receptors

25 Taste Nerve Pathways Sensory impulses from taste receptors travel along cranial nerves to medulla oblongata to thalamus to gustatory cortex (for interpretation)

26 Figure 10-4: Sensory pathways

27 Taste: Chemoreceptors

28 Taste: Chemoreceptors Salt --- Na passive Acids– H block k channels Sweet – Gs anhydrate cyclase – protein kinase(A) – Phosphorylation of k channels so it will close Bitter – Gb – phospholipasec – release of ca from ER Depolarization –activate neurotransmitter vesicle to diffues to membrane and release neurotransmitter

29 The Ear: Hearing and Equilibrium The ear – receptor organ for hearing and equilibrium Composed of three main regions –Outer ear – functions in hearing –Middle ear – functions in hearing –Inner ear – functions in both hearing and equilibrium

30 The Outer (External) Ear Composed of: –The auricle (pinna) Helps direct sounds –External acoustic meatus Lined with skin –Contains hairs, sebaceous glands, and ceruminous glands –Tympanic membrane Forms the boundary between the external and middle ear

31 The Outer (External) Ear Figure 16.17a

32 The Middle Ear The tympanic cavity –A small, air-filled space –Located within the petrous portion of the temporal bone Medial wall is penetrated by: –Oval window –Round window Pharyngotympanic tube (auditory or eustachian tube) –Links the middle ear and pharynx

33 Structures of the Middle Ear Figure 16.17b

34 Figure The Middle Ear Ear ossicles – smallest bones in the body –Malleus – attaches to the eardrum –Incus – between the malleus and stapes –Stapes – vibrates against the oval window

35 The Inner (Internal) Ear Inner ear – also called the labyrinth Lies within the petrous portion of the temporal bone Bony labyrinth – a cavity consisting of three parts –Semicircular canals –Vestibule – Cochlea

36 The Inner (Internal) Ear Membranous labyrinth –Series of membrane-walled sacs and ducts –Fit within the bony labyrinth –Consists of three main parts Semicircular ducts Utricle and saccule Cochlear duct

37 The Inner (Internal) Ear Membranous labyrinth (continued) –Filled with a clear fluid – endolymph Confined to the membranous labyrinth –Bony labyrinth is filled with perilymph Continuous with cerebrospinal fluid

38 The Membranous Labyrinth Figure 16.20

39 The Inner (Internal) Ear Figure 16.17b

40 Cochlea Cochlear duct portion of membranous labyrinth in cochlea Vestibular membrane separates cochlear duct from scala vestibuli Basilar membrane separates cochlear duct from scala tympani

41 The Cochlea Figure 16.23a–c

42 Organ of Corti group of hearing receptor cells (hair cells) on upper surface of basilar membrane different frequencies of vibration move different parts of basilar membrane particular sound frequencies cause hairs of receptor cells to bend nerve impulse generated

43 Hearing: Mechanoreceptors Figure 10-19: Sound transmission through the ear

44 Hearing: Hair Cell Transduction Figure 10-20: The cochlea

45 Hearing: Hair Cell Transduction Figure 10-21: Signal transduction in hair cells

46

47 Summary of the Generation of Sensory Impulses from the Ear

48 Equilibrium Static Equilibrium vestibule sense position of head when body is not moving Dynamic Equilibrium semicircular canals sense rotation and movement of head and body

49 Vestibule Utricle communicates with saccule and membranous portion of semicircular canals Saccule communicates with cochlear duct Mucula hair cells of utricle and saccule

50 Macula responds to changes in head position bending of hairs results in generation of nerve impulse

51 Anatomy and Function of the Maculae Figure 16.21a

52 Semicircular Canals three canals at right angles ampulla swelling of membranous labyrinth that communicates with the vestibule crista ampullaris sensory organ of ampulla hair cells and supporting cells rapid turns of head or body stimulate hair cells

53 Crista Ampullaris

54 Vestibular System & Balance

55 Rotation & Gravity

56 Auditory Pathway from the Organ of Corti Figure 16.25

57 Sight Visual Accessory Organs eyelids lacrimal apparatus extrinsic eye muscles

58 Lacrimal Apparatus lacrimal gland lateral to eye secretes tears canaliculi collect tears lacrimal sac collects from canaliculi nasolacrimal duct collects from lacrimal sac empties tears into nasal cavity

59 Extrinsic Eye Muscles Superior rectus rotates eye up and medially Inferior rectus rotates eye down and medially Medial rectus rotates eye medially

60 Extrinsic Eye Muscles Lateral rectus rotates eye laterally Superior oblique rotates eye down and laterally Inferior oblique rotates eye up and laterally

61 Structure of the Eye hollow spherical wall has 3 layers outer fibrous tunic middle vascular tunic inner nervous tunic

62 Outer Tunic Cornea anterior portion transparent light transmission light refraction Sclera posterior portion opaque protection

63 Middle Tunic Iris anterior portion pigmented controls light intensity Ciliary body anterior portion pigmented holds lens moves lens for focusing Choroid coat provides blood supply pigments absorb extra light

64 Anterior Portion of Eye filled with aqueous humor

65 Lens transparent biconvex lies behind iris largely composed of lens fibers elastic held in place by suspensory ligaments of ciliary body

66 Ciliary Body forms internal ring around front of eye ciliary processes – radiating folds ciliary muscles – contract and relax to move lens

67 Accommodation changing of lens shape to view objects

68 Iris composed of connective tissue and smooth muscle pupil is hole in iris dim light stimulates radial muscles and pupil dilates bright light stimulates circular muscles and pupil constricts

69 Aqueous Humor fluid in anterior cavity of eye secreted by epithelium on inner surface of the ciliary body provides nutrients maintains shape of anterior portion of eye leaves cavity through canal of Schlemm

70 Inner Tunic retina contains visual receptors continuous with optic nerve ends just behind margin of the ciliary body composed of several layers macula lutea – yellowish spot in retina fovea centralis – center of macula lutea; produces sharpest vision optic disc – blind spot; contains no visual receptors vitreous humor – thick gel that holds retina flat against choroid coat

71 Posterior Cavity contains vitreous humor – thick gel that holds retina flat against choroid coat

72 Major Groups of Retinal Neurons receptor cells, bipolar cells, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve horizontal cells and amacrine cells – modify impulses

73 Layers of the Eye

74 Light Refraction Refraction bending of light occurs when light waves pass at an oblique angle into mediums of different densities

75 Types of Lenses Convex lenses cause light waves to converge Concave lenses cause light waves to diverge

76 Focusing On Retina as light enters eye, it is refracted by convex surface of cornea convex surface of lens image focused on retina is upside down and reversed from left to right

77 Visual Receptors Rods long, thin projections contain light sensitive pigment called rhodopsin hundred times more sensitive to light than cones provide vision in dim light produce colorless vision produce outlines of objects Cones short, blunt projections contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe provide vision in bright light produce sharp images produce color vision

78 Rods and Cones

79 Visual Pigments Rhodopsin light-sensitive pigment in rods decomposes in presence of light triggers a complex series of reactions that initiate nerve impulses impulses travel along optic nerve Pigments on Cones each set contains different light- sensitive pigment each set is sensitive to different wavelengths color perceived depends on which sets of cones are stimulated erythrolabe – responds to red chlorolabe – responds to green cyanolabe – responds to blue

80 Rod Cells

81 Visual Nerve Pathway

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