Somatic and Special Senses

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Somatic and Special Senses

• Communicating with the world around us

Mrs. S. Taylor
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The two major groups

• Somatic senses
• Touch, pressure, temperature and pain
• Found in the skin and the deeper tissues
• Structurally simple
• special senses (sensory)
• Smell, taste, hearing, vision, and equilibrium
• Found in specialized organs for that sense
• Structurally complex

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Receptors

• Types of receptors
• Chemoreceptors
• Stimulated by changes in the chemical
  concentration of substance
• Pain receptors
• Stimulated by tissue damage
• Thermoreceptors
• Stimulated by changes in temperature
• Mechanoreceptors
• Stimulated by changes in pressure and movement
• Photoreceptors
• Stimulated by light

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The sensation

• Sensation occurs when the brain interprets the
  sensory impulses.
• Different sections of the brain interpret the
  signals, dependent on what type of receptor they
  come from
• The cerebral cortex then causes the feeling to
  seem to come from the area of the stimulated
  receptor.
• This is called projection
• This allows us to know what hurts in most cases

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Did you adjust?

• There is noise all around you, things pressing
  against you... do you always feel or hear them?
• The ability for you mind to ignore unimportant
  stimuli is called sensory adaptation
• Receptors become unresponsive peripheral
  adaptation
• Inhibition along the CNS leading to the sensory
  regions of the cerebral cortex - central
  adaptation

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Somatic Sense

• Associated with the skin, muscles, joints, and
  the viscera
• Three main types
• Touch and pressure
• Temperature
• Pain

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Touch and pressure

• Comes from three different types of receptors
• They detect mechanical forces that deform or
  displace tissue
• They are
• Free nerve endings extend between the
  epithelial cells
• Meissner's corpuscles small oval masses of
  flattened connective tissue
• Abundant in the hairless regions of the body
• Respond to light touch
• Pacinian corpuscles large structures in the
  deeper subcutaneous fissures and muscles tendons
  and ligaments
• Respond toe heavy pressure and deep pressure

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Temperature Senses

• Depends on two types of free nerve endings in the
  skin
• Warm receptors
• Sensitive to temps above 25C (77F) and are
  unresponsive with temps more than 45C (113 F)
• Then the pain receptors kick in and you feel a
  burning sensation
• Cold receptors
• Sensitive to temps between 10C(50 F) and 20 C
  (68 F)
• Below 10 C produces a freezing sensation and pain

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Pain

• Free nerve endings
• Spread through the skin and internal tissues
• Exception the brain, it has none
• Protect the body
• Is stimulated by tissue damage
• How this does it is not well understood
• Don't adapt well, so pain can be persistent

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Visceral Pain

• In the vicera, you typically need a widespread
  stimulation to get a response.
• So, a small cut in a region of the intestines
  no pain
• Intestinal cramping pain
• Visceral pain feel like it is coming from some
  other part of the body
• Called referred pain
• Tends to be caused by the sharing of neural
  pathways that go to the skin as well as the
  viscera

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Pain nerve fibers

• Two main types
• Acute
• Thin and myelinated , fast impulses
• Sensation of sharp pain that seldom continues
  after the stimuli has gone. Easy to pin point
  location
• Typically only from skin
• Chronic
• Thin and unmyelinated, slow impulses
• Dull aching sensation, difficult to pinpoint,
  continuous
• From both skin and deeper tissues

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Special Senses

• Have large complex sensory organs in the head
• Smell olfactory organs
• Taste taste buds
• Hearing ears
• Equilibrium ears
• Sight eyes

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Sense of smell

• Olfactory organs
• Are located in small patches
• Covers the upper nasal cavity, nasal conchea, and
  portions of the nasal septum
• Yellowish brown masses of epithelium
• Composed of olfactory receptors
• a type of chemoreceptors
• Chemicals dissolved in liquids stimulate them
• Neurons surrounded by columnar epithelial cells
• Have cilia like ending that harbor 400 types of
  protein receptors
• Detects odorant molecules
• Smell and taste are closely related

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Sense of taste

• Taste buds - chemoreceptors
• Where are they
• Approx 10,000 are located on the tongue
• Located on papillae
• 1,000 are scattered about the roof of the mouth
  and the walls of the throat.
• Composed of
• modified epithelial cells called taste cells
  (gustatory cells)- the receptors
• 50-150 of these/ taste bud
• Taste pore hole at the top of the spherical
  shaped bud
• Taste hair protrude from taste cell into the
  the taste pore
• Nerve fibers woven about the cells

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Taste sensations

• The tastes
• 4 primary
• Sweet, Sour, Salty, Bitter
• All taste all of these, but at different levels
• Therefore there are areas of concentration of the
  flavors
• Others sometimes recognized
• Alkaline, metallic, umami (MSG)
• Some taste stimulate other nerves
• Chile peppers and ginger pain receptors
• Chile peppers (capsaicin) warm receptors
• Taste is a combination of the different nerves
  stimulated, texture, temperature, and smell

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Sense of hearing

• Three zones
• Outer ear
• Middle ear
• Inner ear

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Outer ear

• Three parts
• Auricle (pinna) outer funnel-like structure
• Collects sound waves
• External ascoustic meatus (external auditory
  canal) s-shaped tube that leads inwards for
  about 2.5 cm
• Tunnels/ directs to the eardrum
• Tympanic membrane (eardrum) semitransparent
  membrane covered by a thin layer of skin on the
  outside and a mucous membrane on the inside.
• Oval margin and cone-shaped that attaches to the
  malleus (mallet)
• Vibrates when sound waves hit it causing the
  malleus to move

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Middle Ear

• AKA Tympanic Caviry
• Air filled space in the temporal bone
• Contains 3 small bones (auditory ossicles)
• Malleus (mallet), Incus(anvil) ,Stapes (stirup)
• Attached to the cavity by small ligaments and the
  oval window (stapes)
• Covered by a mucous membrane
• The bones transmits the sound waves from the
  eardrum to the oval window
• Also help to amplify the sound waves because the
  size of the eardrum (larger) and the oval window
  (smaller)

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Middle Ear connection

• Auditory tube (Eustachian tube)
• Connects the middle ear with the nasopharynx
• Helps to regulate the air pressure in the middle
  ear.
• Must be the same as on the outside of the eardrum
• If a sudden change happens in external pressure,
  the adjustment will sound like a pop

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Inner ear

• Entire region is called the Labyrinth
• Divided into two main areas
• 3 semicircular canals used in equilbrium
• Cochlea used to hear
• Two main parts
• Osseous labyrinth tunnel through the temporal
  bone
• Secrets a fluid called perilymph
• Membranous labyrinth membrane inside of the
  bone tunnel
• Secrets endolymph

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Cochlea

• The oval window allows sound vibrations into the
  cochlea. The stapes pulls and pushes on the oval
  causing the lymphs to move
• This movement causes waves through out the
  cochlea
• Has a bony core with the bony shelf that winds
  about the core in a spiral
• The organ of Corti where the hearing receptors
  stretches from the apex to the base of the
  cochlea
• Hair like cells detect the changes in the lymph
• Two levels of sensitivity

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Equilibrium

• 2 types
• Static equilibrium
• Sense the head and maintain stability and posture
  when head and body are still
• Dynamic equilibrium
• Detects motion and aids in maintaining balance
  when head and/or body moves or rotates

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Static Equilibrium

• Organs are located in the vestibule
• A bony chamber in between the cochlea and the
  semicircular canals has two chambers
• Utricle and saccule
• Macule structures in the chambers that contain
  the sensory receptors (hairs) and gelatinous
  material, and otoliths (CaCO4)
• Hairs project into a mass of gelatinous material.
  When the gelatinous material moves and bends the
  hairs, the brain is told of the change of
  position of the head

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Dynamic Equilibrium

• Organs are in the semicircular canals
• Lie at right angles to each other, corresponding
  to a different anatomical plane
• Crista ampullaris
• Contains sensory hair cells and supporting cells
• Inside a gelatinous mass called cupula
• Responds to rapid turns of head or body
• Gelatinous material doesn't move, but hair cells
  do.

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Sense of sight

• Organs
• Eyes has the visual receptors
• Accessory organs to help out

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The Accessories

• The orbital cavity
• Pear shaped cavity in the skull
• Has fat, blood vessels, nerves, and connective
  tissues
• Eyelid
• 4 layers
• Skin, Muscle, Connective tissue, conjuntiva
• The conjunctive is a mucous membrane that lines
  the inner surface of the eyelid and the fold to
  cover the anterior surface of the eyeball, except
  the center section

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Another accessory

• Lacrimal apparatus
• Lacrimal gland - produces tears
• Located in the orbit (eye socket)
• Contains lysozyme an antibacterial agent
• Series of ducts-
• Lateral and medial ducts empty into the lacrimal
  sac which then goes to the nasolacrimal duct

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Last one

• Extrinsic Muscles
• 6 of them, moves the eyes in specific directions
• Superior rectus upward, towards midline
• Inferior rectus- downward, towards midline
• Medial rectus- towards midline
• Lateral rectus- away from midline
• Superior oblique- downwards, away from midline
• Inferior oblique upward, away from midline

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The eye

• Three layers
• Outer layer
• Sclera white of the eye
• Optic nerve attached to the back of eye
• Cornea clear window
• Middle layer
• Choroid coat -honeycombed, lots of blood vessels,
  melanocytes to absorb excess light
• Ciliary body extends from choroid coat to the
  front of the eye, forming an internal ring
• Lens transparent, focus light on retina
• Iris extends form ciliary body to the pupil,
  muscle
• Aqueous humor liquid from the ciliary body to
  the cornea
• Pupil hole in the eye that lets light in.

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Last layer

• Inner layer
• Retina contains the visual receptors
• Coats inner surface of the eye, end just behind
  the ciliary body
• Rods- see in greyscale
• Cones see color three types red, green ,
  blue
• Fovea centralis and Macula Lutea
• Macual is the central region of the retina
• Fovea depression in the middle that provides
  the clearest images
• Optic Disc
• Where the nerve fibers go in the optic nerve
• The blind spot in the eye
• Vitreous humor
• Jelly like fluid inside the eye

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