Somatic and special sensesSomatic and special senses

Ch. 15Ch. 15

IntroductionIntroduction Sensory receptors - make it possible for the body

to respond to stimuli caused by changes occurring in the internal or external environment

Different types of receptors respond to different stimuli General function—responds to stimuli by converting them

to nerve impulses Sensations Sensory adaptation - receptor potential decreases

over time in response to a continuous stimulus Receptors for special senses of smell, taste,

vision, hearing, and equilibrium are grouped into localized areas or into complex organs

Sensory receptors - make it possible for the body to respond to stimuli caused by changes occurring in the internal or external environment

Different types of receptors respond to different stimuli General function—responds to stimuli by converting them

to nerve impulses Sensations Sensory adaptation - receptor potential decreases

over time in response to a continuous stimulus Receptors for special senses of smell, taste,

vision, hearing, and equilibrium are grouped into localized areas or into complex organs

Receptors and sensationsReceptors and sensations Types of receptors

Chemoreceptors activated by amount or changing concentration of certain chemicals; e.g., taste and smell

Pain receptors - Nociceptors—activated by intense stimuli that may damage tissue; the sensation produced is pain

Thermoreceptors — activated by changes in temperature Mechanoreceptors activated when “deformed” to generate

receptor potential Proprioceptors -Location limited to skeletal muscle, joint capsules,

and tendons Provide information on body movement, orientation in space, and

muscle stretch

Photoreceptor— found only in the eye; respond to light stimuli if the intensity is great enough to generate a receptor potential

Types of receptors Chemoreceptors activated by amount or changing concentration

of certain chemicals; e.g., taste and smell Pain receptors - Nociceptors—activated by intense stimuli that

may damage tissue; the sensation produced is pain Thermoreceptors — activated by changes in temperature Mechanoreceptors activated when “deformed” to generate

receptor potential Proprioceptors -Location limited to skeletal muscle, joint capsules,

and tendons Provide information on body movement, orientation in space, and

muscle stretch

Photoreceptor— found only in the eye; respond to light stimuli if the intensity is great enough to generate a receptor potential

Somatic sensesSomatic senses Touch and pressure

Free ends of dendrites Called nociceptors Receptors for pain

Meissner’s corpuscles sense touch large and superficial

Pacinian corpuscles Respond to deep

pressure/stretch Deep dermis and joint capsules

Stretch receptors Found in tendons and muscles Once stretched, the muscle

shortens

Touch and pressure Free ends of dendrites

Called nociceptors Receptors for pain

Meissner’s corpuscles sense touch large and superficial

Pacinian corpuscles Respond to deep

pressure/stretch Deep dermis and joint capsules

Stretch receptors Found in tendons and muscles Once stretched, the muscle

shortens

Temperature sensesTemperature senses

Organs of Ruffini - also called Ruffini’s corpuscles Deep in dermis Sense heat - 85 - 120 degrees

Bulbs of Krause - sense cold

Organs of Ruffini - also called Ruffini’s corpuscles Deep in dermis Sense heat - 85 - 120 degrees

Bulbs of Krause - sense cold

Sense of painSense of pain Free nerve endings Visceral pain

Referred pain

Pain nerve fibers - Chronic/acute

Regulation of pain impulse - awareness of pain - thalamus. Impulse conducted to cerebral cortex - judges intensity and location of pain. Endorphins provide natural pain

control. Serotonin inhibits release of pain

impulses in spinal cord.

Free nerve endings Visceral pain

Referred pain

Pain nerve fibers - Chronic/acute

Regulation of pain impulse - awareness of pain - thalamus. Impulse conducted to cerebral cortex - judges intensity and location of pain. Endorphins provide natural pain

control. Serotonin inhibits release of pain

impulses in spinal cord.

Special senses - receptors are in specialized organs

Special senses - receptors are in specialized organs

Smell - olfactory sense Taste - gustatory sense Hearing - auditory sense Static equilibrium - balance when

stationary Dynamic equilibrium - balance when

moving Sight - sense of vision

Smell - olfactory sense Taste - gustatory sense Hearing - auditory sense Static equilibrium - balance when

stationary Dynamic equilibrium - balance when

moving Sight - sense of vision

Sense of smellSense of smell

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Sense of smellSense of smell Olfactory receptors

Cilia in nasal cavity chemoreceptors

Olfactory organs - epithelial supporting tissue

Nerve pathways Action potential to

olfactory nerves in olfactory bulb

Thalamic and olfactory centers in brain

Olfactory receptors Cilia in nasal cavity chemoreceptors

Olfactory organs - epithelial supporting tissue

Nerve pathways Action potential to

olfactory nerves in olfactory bulb

Thalamic and olfactory centers in brain

Sense of tasteSense of taste

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Sense of tasteSense of taste Taste receptors -

chemoreceptors Taste hairs portrude from taste

pores Chemicals dissolved in saliva

Taste sensations Sweet Sour Salt Bitter

Nerve pathways Facial, glossopharyngeal, vagus

nerves to medulla oblongata to gustatory cortex in cerebrum.

Taste receptors - chemoreceptors Taste hairs portrude from taste

pores Chemicals dissolved in saliva

Taste sensations Sweet Sour Salt Bitter

Nerve pathways Facial, glossopharyngeal, vagus

nerves to medulla oblongata to gustatory cortex in cerebrum.

Sense of hearingSense of hearing

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Sense of hearingSense of hearing External ear

Auricle or pinna - visible - collects sound External auditory meatus - tube

Middle ear in temporal bone- contains ossicles

Malleus - attached to tympanic membrane

Incus - attached to malleus and stapes Stapes - attached to chochlea

Inner ear - semicircular canals - equilibrium Cochlea - hearing

Organ of corti - located in the cochlear duct. Contains supporting cells and hair cells

External ear Auricle or pinna - visible - collects sound External auditory meatus - tube

Middle ear in temporal bone- contains ossicles

Malleus - attached to tympanic membrane

Incus - attached to malleus and stapes Stapes - attached to chochlea

Inner ear - semicircular canals - equilibrium Cochlea - hearing

Organ of corti - located in the cochlear duct. Contains supporting cells and hair cells

Sense of hearingSense of hearing Nerve pathways - sound waves move

tympanic membrane Movement of membrane moves ossicles

which move oval window which create waves which bend hairs.

Hearing - stimulation of auditory area in cerebral cortex.

Nerve pathways - sound waves move tympanic membrane

Movement of membrane moves ossicles which move oval window which create waves which bend hairs.

Hearing - stimulation of auditory area in cerebral cortex.

Causes and types of hearing loss

Causes and types of hearing loss

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Sense of equilibrium - two typesSense of equilibrium - two types Static equilibrium—ability

to sense the position of the head relative to gravity or to sense acceleration or deceleration

Dynamic equilibrium—needed to maintain balance when head or body is rotated or suddenly moved; able to detect changes both in direction and rate at which movement occurs

Static equilibrium—ability to sense the position of the head relative to gravity or to sense acceleration or deceleration

Dynamic equilibrium—needed to maintain balance when head or body is rotated or suddenly moved; able to detect changes both in direction and rate at which movement occurs

Static EquilibriumStatic Equilibrium Stability of head when body is

motionless Utricle and Saccule - location

for static equilibrium sense Macula - movement provides

information about head position Otoliths located in macula,

gravity shifts them, bending hair cells.

Nerve fibers send message to brain

Body is restored to normal position.

Stability of head when body is motionless

Utricle and Saccule - location for static equilibrium sense

Macula - movement provides information about head position Otoliths located in macula,

gravity shifts them, bending hair cells.

Nerve fibers send message to brain

Body is restored to normal position.

Dynamic equilibriumDynamic equilibrium Cristae ampullaris, located in

semicircular canal Cupula - gelatinous cap in

which hairs are embedded, moves with flow of endolymph (fluid)

Semicircular canals placed at right angles - detect motion in all directions

When cupula moves, hair cells are bent, sending action potential to medulla oblongata and then other areas for interpretation.

Cristae ampullaris, located in semicircular canal

Cupula - gelatinous cap in which hairs are embedded, moves with flow of endolymph (fluid)

Semicircular canals placed at right angles - detect motion in all directions

When cupula moves, hair cells are bent, sending action potential to medulla oblongata and then other areas for interpretation.

Sense of balance and equilibrium

Sense of balance and equilibrium

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Visual accessory organsVisual accessory organs Eyelid - palpebrae

voluntary muscle and skin, lined with mucous membrane called conjunctiva.

Eyelashes and eyebrows - give some protection agains foreign objects entering eye

Lacrimal gland -secret tears. Tears are drained from surface of eyeball.

Eyelid - palpebrae voluntary muscle and

skin, lined with mucous membrane called conjunctiva.

Eyelashes and eyebrows - give some protection agains foreign objects entering eye

Lacrimal gland -secret tears. Tears are drained from surface of eyeball.

Extrinsic muscles of the eyeExtrinsic muscles of the eyeAttach to outside of eyeball and bones of the orbit

Structure of the eyeStructure of the eye Outer tunic

Cornea - transparent portion that lies over the iris.

Sclera - tough outer coat Middle tunic

Choroid coat - vascular and pigmented

Ciliary body - attaches to iris Iris - colored part of the eye

Lens - held in place by suspensory ligaments and ciliary muscles. Has elasticity - shape is adjustable.

Outer tunic Cornea - transparent portion

that lies over the iris. Sclera - tough outer coat

Middle tunic Choroid coat - vascular and

pigmented Ciliary body - attaches to iris Iris - colored part of the eye

Lens - held in place by suspensory ligaments and ciliary muscles. Has elasticity - shape is adjustable.

Inner tunic and cavities/chambers

Inner tunic and cavities/chambers Retina - innermost coat of eyeball

Contains receptors Macula lutea

Fovea centralis Optic disk Cavities - anterior and posterior

chamber Anterior cavity contains

anterior/posterior chambers Filled with aqueous humor - watery

fluid - involved in bending light Posterior cavity - right behind lens.

Filed with Vitreous humor - semisolid, maintains intraocular pressure.

Retina - innermost coat of eyeball Contains receptors

Macula lutea Fovea centralis

Optic disk Cavities - anterior and posterior

chamber Anterior cavity contains

anterior/posterior chambers Filled with aqueous humor - watery

fluid - involved in bending light Posterior cavity - right behind lens.

Filed with Vitreous humor - semisolid, maintains intraocular pressure.

Overview of the eyeOverview of the eye

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Light refraction and the process of seeing

Light refraction and the process of seeing

Refraction - Light waves bent Accomplished by cornea, lens, aqueous

humor Accomodation of the lens - increase in

curvature for near vision. Pupil constricts controlling the entering of

light

Refraction - Light waves bent Accomplished by cornea, lens, aqueous

humor Accomodation of the lens - increase in

curvature for near vision. Pupil constricts controlling the entering of

light

Visual receptors - undergo changes that generate nerve impulses

Visual receptors - undergo changes that generate nerve impulses

Rods - black and white vision Rhodopsin - photo

pigment Breaks down into opsin

and retinal Energy is required to

reform rhodopsin Cones - color vision

Three types

Rods - black and white vision Rhodopsin - photo

pigment Breaks down into opsin

and retinal Energy is required to

reform rhodopsin Cones - color vision

Three types

Visual PigmentsVisual Pigments

Rhodopsin Opsin, retinal

Isodopsin Erythrolabe -

red Chlorolabe -

green Cyanolabe -

blue

Rhodopsin Opsin, retinal

Isodopsin Erythrolabe -

red Chlorolabe -

green Cyanolabe -

blue

Visual nerve pathwaysVisual nerve pathways

Optic nerves Optic

chiasma cross over

Thalamus Visual cortex

of occipital lobe

Optic nerves Optic

chiasma cross over

Thalamus Visual cortex

of occipital lobe