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General (Somatic) and Special Senses. I. Receptors and Sensations. Sensory Receptors Detect change, trigger nerve impulses . Five general types Chemoreceptors Pain receptors Thermoreceptors Mechanoreceptors Photoreceptors. I. Receptors and Sensations. Sensations

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i receptors and sensations
I. Receptors and Sensations
  • Sensory Receptors
    • Detect change, trigger nerve impulses.
    • Five general types
      • Chemoreceptors
      • Pain receptors
      • Thermoreceptors
      • Mechanoreceptors
      • Photoreceptors
i receptors and sensations1
I. Receptors and Sensations
  • Sensations
    • Feelings that occur when the brain interprets sensory impulses.
    • Projection
      • Cerebral cortex sends the sensation back to its point of origin
      • Person can pinpoint the area of stimulation.
    • Sensory Adaptation
      • Impulses are sent at decreasing rates
      • Finally receptors fail to send impulses.
ii sense of sight
II. Sense of Sight
  • Visual Accessory Organs
    • Eyelid
      • Protects the eye
      • The thinnest skin of the body.
      • Lined with conjunctiva (folds back to cover eyeball).
    • Lacrimal Apparatus
      • Produces tears that lubricate and cleanse the eye.
      • Inferior and superior canaliculi drain tears into the nasal cavity (by nasalacrimal duct).
      • Tears also contain an antibacterial enzyme.
    • Extrinsic muscles of the eye attach to the sclera and move the eye.
ii sense of sight1
II. Sense of Sight
  • Structure of the Eye (three distinct layers, or tunics)
    • The Outer Tunic (fibrous tunic)
      • Cornea
        • Transparent due to few cells and no blood vessels.
        • Helps focus light rays.
      • Sclera (white of eye)
        • Continuous with cornea.
        • Protects eye and is attachment for muscles.
        • The optic nerve and blood vessels pierce the sclera at the posterior of the eye.
ii sense of sight2
II. Sense of Sight
  • The Middle Tunic (vascular tunic)
    • Choroid coat
      • Loosely joined to the sclera.
      • Highly vascular to nourish other tissues of the eye.
      • Darkly pigmented to keep the inside of the eye dark.
    • Ciliary body
      • Forms a ring around the front of the eye.
      • Composed of folds called ciliary processes and ciliary muscles.
ii sense of sight3
II. Sense of Sight
  • Suspensory ligaments hold the lens in position and change its shape (focus).
  • Lens
    • Composed of epithelial cells called lens fibers.
    • The ability of the lens to adjust shape to facilitate focusing is called accommodation.
  • Iris
    • Colored portion of eye.
    • Adjusts the amount of light entering the pupil.
    • Has a circular set and a radial set of smooth muscle fibers.
ii sense of sight4
II. Sense of Sight
  • Anterior cavity (two chambers)
    • Anterior chamber (between the cornea and iris)
    • Posterior chamber (between the iris and suspensory ligaments)
      • Filled with aqueous humor (from ciliary body).
      • Aqueous humor circulates from one chamber to the other through the pupil.
      • Too much aqueous humor causes glaucoma.
ii sense of sight5
II. Sense of Sight
  • The Inner Tunic (Retina)
    • Covers the back side of the eye
    • Surrounds the posterior cavity
    • Filled with vitreous humor.
    • Composed of pigmented epithelium, visual receptor cells, and a layer of neurons
ii sense of sight6
II. Sense of Sight
  • Macula lutea
    • Center of retina
    • Depression in middle is fovea centralis (the point of sharpest vision)
  • Optic disk
    • Medial to the fovea centralis
    • Your blind spot
    • Where nerve fibers leave the eye.
ii sense of sight7
II. Sense of Sight
  • Light Refraction
    • Light waves must bend to be focused.
    • The cornea and lens bend light waves to focus them on the retina.
      • Myopia: nearsighted
      • Hyperopia: farsighted
ii sense of sight8
II. Sense of Sight
  • Visual Receptors
    • Rods (elongated)
      • Function in dim light
      • Produce colorless vision.
    • Cones (blunt-shaped)
      • Provide sharp images in bright light
      • Enable us to see in color.
      • Highest concentration on the fovea centralis
ii sense of sight9
II. Sense of Sight
  • Visual Pigments
    • Rhodopsin (in rods and cones)
      • Breaks down into a protein (opsin) and retinal (from vitamin A) in the presence of light.
      • Decomposition activates a nerve impulse.
      • Night blindness is caused by vitamin A deficiency.
ii sense of sight10
II. Sense of Sight
  • Isodopsins (in cones)
    • Three types of cones.
    • Each sensitive to different wavelengths of light (red, green, blue)
    • All three sets stimulated, the color is white
    • None are stimulated, the color is black.
ii sense of sight11
II. Sense of Sight
  • Visual Nerve Pathways
    • The axons of ganglion cells leave the eyes to form the optic nerves.
    • Fibers from the medial(nasal) half of the retina cross over in the optic chiasma.
    • Impulses are transmitted to the thalamus and then to the visual cortex of the occipital lobe.
iii sense of hearing
III. Sense of Hearing
  • The ear provides the senses of hearing and equilibrium.
  • Human Range: 20-2000 Hz
  • External Ear
    • Auricle (pinna): collects sound waves
    • External auditory meatus (canal).
iii sense of hearing1
III. Sense of Hearing
  • Middle Ear
    • Begins with the tympanic membrane (eardrum)
    • Air-filled space (tympanic cavity) housing the 3 auditory ossicles.
    • Ossicles are the malleus, incus, and stapes.
    • Tympanic membrane vibrates the malleus, which vibrates the incus, then the stapes.
iii sense of hearing2
III. Sense of Hearing
  • The stapes vibrates the fluid inside the oval window of the inner ear.
  • Auditory ossicles both transmit and amplify sound waves.
  • Auditory Tube (eustachiantube)
    • Connects the middle ear to the throat.
    • Helps maintain equal air pressure on both sides of the eardrum.
iii sense of hearing3
III. Sense of Hearing
  • Inner Ear
    • An osseous labyrinth (canal) in the bone of the temporal bone.
    • A Membranous labyrinth is inside the osseous labyrinth.
    • Between the two labyrinths is perilymph (fluid).
    • Endolymph is inside the membranous labyrinth.
iii sense of hearing4
III. Sense of Hearing
  • The cochlea houses the organ of hearing
  • The semicircular canals function in equilibrium.
  • The oval window leads to the upper compartment, called the scala vestibuli.
  • The lower compartment is the scala tympani.
  • The cochlear duct lies between these two compartments
  • Duct is separated from the scala vestibuli by the vestibular membrane, and from the scala tympani by the basilar membrane.
iii sense of hearing5
III. Sense of Hearing
  • The Organ of Corti
    • Houses receptors called hair cells
    • Lies on the basilar membrane.
  • Hairs of cells extend into the endolymph of the cochlear duct.
  • Above the hair cells lies the tectorial membrane.
  • Sound waves make hairs rub against tectorial membrane stimulating receptor cells.
iii sense of hearing6
III. Sense of Hearing
  • Auditory Nerve Pathways
    • Epithelial receptor cells depolarize, allowing calcium to flood in.
    • Calcium forces vesicles to release neurotransmitters from cell base (no axons or dendrites).
    • Neurotransmitters stimulate sensory nerve fibers.
    • Nerve fibers carry impulses to the auditory cortices of the temporal lobes.
iv sense of equilibrium
IV. Sense of Equilibrium
  • Consists of two parts: static and dynamic equilibrium.
  • Static Equilibrium
    • Determines the orientation of the head and body
    • Organs are the utricle and saccule (expansions of the membranous labyrinth).
    • A macula, consisting of hair cells and supporting cells, lies inside the utricle and saccule.
iv sense of equilibrium1
IV. Sense of Equilibrium
  • The hair cells contact gelatinous material holding otoliths (calcium carbonate stones).
  • Gravity causes the otoliths and gelatinous material to shift, bending hair cells and generating a nervous impulse.
  • Brain interprets as the position of the head.
iv sense of equilibrium2
IV. Sense of Equilibrium
  • Dynamic Equilibrium
    • Maintains balance when the head and body suddenly move and rotate.
    • Three semicircular canals detect rotational motion of the head
    • Ampulla are located in each semicircular canal
    • The organs of dynamic equilibrium are called cristae ampullaris and are located in the ampulla
iv sense of equilibrium3
IV. Sense of Equilibrium
  • Hair cells extend into a dome-shaped gelatinous cupula.
  • Rapid turning of the head or body generates impulses as the cupula bends hair cells
v sense of smell
V. Sense of Smell
  • Olfactory Receptors
    • Olfactory receptors are chemoreceptors.
    • The senses of smell and taste operate together.
  • Olfactory Organs
    • Yellowish-brown masses in the upper nasal cavity.
    • Contain the olfactory receptors plus epithelial supporting cells.
v sense of smell1
V. Sense of Smell
  • Chemicals are first dissolved in the watery fluid of the nasal cavity.
  • Olfactory receptors are stimulated by chemicals.
  • Neurons carry the signal to the olfactory lobes.
v sense of smell2
V. Sense of Smell
  • Olfactory Stimulation
    • Each odor stimulates a set of specific protein receptors in cell membranes.
    • The brain interprets different receptor combinations as an olfactory code.
    • Olfactory receptors adapt quickly.
    • Anosmia is partial or complete loss of smell.
vi sense of taste
VI. Sense of Taste
  • Taste buds
    • Located within papillae of the tongue
    • Organs of taste
    • Scattered throughout the mouth and pharynx.
vi sense of taste1
VI. Sense of Taste
  • Taste Receptors
    • Taste cells are modified epithelial cells that function as receptors.
    • Taste cells contain the taste hairs that are the portions sensitive to taste.
    • Chemicals must be dissolved in water (saliva) in order to be tasted.
    • Taste involves specific membrane protein receptors that bind with specific chemicals in food.
    • Taste receptors rapidly undergo adaptation.
vi sense of taste2
VI. Sense of Taste
  • There are four types of taste cells.
    • Sweet receptors are plentiful near the tip of the tongue.
    • Sour receptors occur along the lateral edges of the tongue.
    • Salt receptors are abundant in the tip and upper portion of the tongue.
    • Bitter receptors are at the back of the tongue.
vii general somatic senses
VII. General (Somatic) Senses
  • Receptors associated with the skin, muscles, joints, and viscera
  • Types
    • Touch
    • Pressure
    • Temperature
    • Pain
viii touch and pressure senses
VIII. Touch and Pressure Senses
  • Sensory Nerve Fibers
    • In the epithelial tissues
    • Detect changes in pressure and touch
  • Meissner's Corpuscles
    • Flattened connective tissue sheaths.
    • Abundant in hairless areas
    • Sensitive to light touch
  • Pacinian Corpuscles
    • Large structures of connective tissue and cells
    • Detect deep pressure
viii touch and pressure senses1
VIII. Touch and Pressure Senses
  • Proprioceptors
    • Monitor body joint positions
    • In tendons and muscle
  • Baroreceptors- respond to blood pressure changes
ix temperature senses
IX. Temperature Senses
  • Heat Receptors and Cold Receptors (free nerve endings)
  • Both adapt quickly.
  • Temperatures near 45o C stimulate pain receptors
  • Temperatures below 10o C also stimulate pain receptors
x sense of pain
X. Sense of Pain
  • Pain receptors
    • Free nerve endings that are stimulated when tissues are damaged
    • Adapt little, if at all.
    • None in nervous tissue of brain.
    • Visceral pain receptors are the only receptors in the viscera that produce sensations.
  • Referred Pain
    • Feels like it comes from elsewhere.
    • Due to common nerve pathways.
x sense of pain1
X. Sense of Pain
  • Pain Nerve Fibers
    • Conduct pain impulses away from their source.
    • Acute pain fibers
      • Thin, myelinated fibers.
      • Carry impulses rapidly and cease when the stimulus stops.
    • Chronic pain fibers
      • Thin, unmyelinated fibers.
      • Conduct impulses slowly and continue sending impulses after the stimulus stops.
x sense of pain2
X. Sense of Pain
  • Regulation of Pain Impulses
    • Aware of pain when impulses reach the thalamus.
    • Cerebral cortex mediates a response.
    • Brain can release presynaptic biochemicals which inhibit the pain impulses in the spinal cord.
      • Endorphins- In the pituitary and hypothalamus and provide natural pain control.
      • Serotonin- Stimulates other neurons to release enkalphins.
      • Enkalphins- Suppress acute and chronic pain (same receptors as morphine).