Note taking guide A&P II

Chapter 12 : Somatic and Special Senses

How do all senses work?

Receptor types:

    1. Pain receptors or nociceptors - (NO-see-septors)

    2. Thermoreceptors

    3.Chemoreceptors

    4. Mechanoreceptors

                Proprioceptors -

                Baroreceptors-

                Stretch receptors -

    5. Photoreceptors

Receptor structure:

Sensation or perception occurs when:

Sensory adaptation-
       
        All senses adapt except :

General senses:

    Exteroceptive senses -

    Interoceptive senses or visceroceptive senses -

    Proprioceptive senses -

Touch and pressure sensations:
        Receptors:
                Free nerve endings -
                Meissner's corpuscles -
                Pacinian corpuscles -

Itch and tickle :
            Receptors are free nerve endings

Temperature:
        Receptors are free nerve endings
                    heat receptors -

                    cold receptors -

                    adaptation -

Pain:
        free nerve endings
        protective function
                like other senses, different neurons respond to different stimuli
                        mechanical damage
                        heat/cold
                        chemicals
                        deficiency of blood (ischemia) leading to deficiency of oxygen (hypoxia)

Adaptation:
Sensation:
            Acute pain fibers:

            Chronic pain fibers:

Referred pain:

Phantom pain:

Stretch receptors:
        Proprioceptors
                no sensation
                Muscle spindles-

               
                Golgi tendon organs -

SPECIAL SENSES
OLFACTORY SENSE: SMELL
            Linked with the sensation of :
            Receptors are                 receptors
            Location -

            Structure-
                Receptors are (cells)-
                Respond to -

            Supporting or sustentacular cells -

            Basal cells -
                    Loss and replacement of receptor cells -

Nerve pathways -
            olfactory nerves pass through :
            olfactory bulbs
            olfactory tracts
            temporal and frontal lobes

        Location

       Taste buds:
                supporting cells
                taste (gustatory) cells
                basal cells

        Basic tastes:

         Adaptation:

THE EAR:
   Receptors  are -                     receptors
   External ear - function-
                    Auricle
                    External auditory meatus
                    ceruminous glands

    Middle ear-
                tympanic membrane

                tympanic cavity

                ossicles - malleus, incus and stapes
                            function
                auditory (eustachian) tube-
                            function

                round window

                muscles -

                            tympanic reflex

        Inner ear-
                Bony labyrinth
                        perilymph
                Membranous labyrinth
                         endolymph

                Cochlea
                        scala tympani
                        scala vestibuli
                        scala media (cochlear duct)
                        organ of corti
                        hearing
       
                        nerve pathways

            Vestibule
                    static equilibrium
                    utricle and saccule
                    otoliths

            Semicircular canals
                        dynamic equilibrium
                        ampulla
                        crista ampullaris
                        cupula

                        neurological connections betweeen :

THE EYE
   Accessory structures:
            eyelids (palpebrae)
                    skin
                    muscles- orbicularis oculi
                    levator palpebrae superioris
                    connective tissue
                    conjunctiva

            eyelashes

            lacrimal apparatus

            extrinsic eye muscles

Eyeball
            Fibrous tunic
                    cornea
                    sclera
                    scleral venous sinus (canal of Schlemm)

            Vascular tunic (uvea)
                    choroid
                    ciliary body
                            aqueous humor production

                            glaucoma

                            accommodation

                    Lens
                            cataract

                    Iris
                            Pupil
                                    light
                                    accommodation

        Nervous tunic - retina
                Pigmented epithelium
               Photoreceptors
                Bipolar cells
                Ganglion cells

Photoreceptors:
        rods
                low light, fast movement, black and white

        Cones
                bright light, high resolution, color, fovea

Optic disk

Posterior cavity
            vitreous body

Refraction

        refracting elements:
                cornea
                lens
                length of eyeball

        emmetropia:

        hyperopia:

        myopia:

        astigmatism:

accommodation

                presbyopia

convergence

Visual pigments:
        rhodopsin, iodopsin
        opsin + retinal ( from vitamin A)

Physiology
        in dark, channels held open by cyclic GMP ("dark current")
        inflow of sodium causes release of neurotransmitter
       neurotransmitter is inhibitory, preventing the firing of bipolar neurons (hyperpolarization)
        light causes opsin to change shape
        opsin no longer fits into retinal, and they separate - bleaching
        enzymatic action of opsin triggers several enzymes that break down cGMP
        Na+ channels close
        Neurotransmitter release stops
        Allows bipolar neurons to transmitt impulses

Photopigment reactivation:
        in dark, retinal isomerase converts opsin back to original shape
        opsin rebinds to retinal - regeneration

Color blindness

Visual pathways
        optic nerves
        optic chiasm (near pituitary gland)
                nasals fibers cross, temporal fibers don't
        optic tracts -to thalamus
        optic radiations go to primary visual cortex in occipital lobe
        some fibers go to brain stem to aid in tracking movements

Stereoscopic vision