SOMATIC & SPECIAL SENSES

• Somatic Senses


  Receptors associated with the skin, muscles, joints, and viscera
• Special Senses


  Senses of smell, taste, hearing, static equilibrium, dynamic equilibrium, and sight
• Reception and Sensation


  1. Changes within or outside the body are picked up by sensory receptors

  2. Nerve impulses travel to the brain for interpretation

  3. Person experiences a certain feeling or sensation
• Types of sensory receptors

  • Mechanoreceptors
  • Thermoreceptors
  • Nociceptors
  • Photoreceptors
  • Chemoreceptors
• Somatic Senses


  Touch, pressure, vibration, temperature, and pain
• Tactile


  Receptors in the skin or subcutaneous layer
• Pressure


  Sustained sensation felt over a larger area and occurs in deeper tissues than touch
• Vibration


  Results from rapidly repetitive sensory signals from tactile receptors
• Itch


  Stimulation of free nerve endings by certain chemicals often because of local inflammatory response
• Tickle


  Probably mediated by free nerve endings, cannot tickle oneself probably because of action in the cerebellum when you are moving your own fingers
• Thermoreceptors


  Free nerve endings, rapidly adapting but continue to generate nerve impulses more slowly
• Cold Receptors


  Located in the epidermis, activated by temperatures between 10-40 C (50-105 F)
• Warm Receptors


  Located in the dermis, activated by temperatures between 32-48 C (90-118 F)
• Nociceptors


  Sensory receptors for pain, in practically every tissue of the body except the brain, respond to several types of stimuli
• Nociceptive Pain


  Special nerve endings called nociceptors send pain signals to the central nervous system
• Neuropathic Pain


  Caused by dysfunction in the nervous system or damage to the nerve itself
• Proprioception


  Allows us to know where we are in space, where our limbs are relative to one another, and how we are moving without visual feedback
• Muscle Spindles and Golgi Tendon Organs

  Sensory receptors in muscle
• Vision


  5 of the 12 pairs of cranial nerves are dedicated, at least in part, to either receiving visual stimuli or coordinating the eyes
• Orbit


  The eye is protected from mechanical injury by being enclosed in a socket, or orbit, which is made up of portions of several of the bones of the skull to form a four-sided pyramid
• Pupil


  An opening located in the center of the eye and is surrounded by the colored iris
• Sclera


  The white of the eye and it is covered by a membrane, known as the conjunctiva, that continues underneath the eyelids
• Eyelids


  The upper eyelid and eyelashes and the lower eyelid and eyelashes, which prevent material from entering the eyes and (in the case of the eyelids) reduce visual stimulation when we sleep
• Eyebrows


  Located superficial to the supraorbital ridge
• Extrinsic Muscles of the Eye

  • Lateral rectus
  • Medial rectus
  • Superior rectus
  • Inferior rectus
  • Inferior oblique
  • Superior oblique
• Conjunctiva


  Composed of epithelial tissue and is an important indicator of a number of clinical conditions
• Cornea


  The transparent structure in the center of the eye that is important for bending light rays that strike the eye, allowing us to focus light
• Aqueous Humor


  Produced by the ciliary body and fills the anterior and posterior chambers of the eye
• Iris


  What gives us a particular eye color, people with blue or gray eyes are more sensitive to ultraviolet light than those with brown eyes
• Pupil


  The space enclosed by the iris, constricted by the sphincter pupillae in bright light and dilated by the dilator pupillae in dim light
• Lens


  Made of a crystalline protein, becomes more round for focusing on closer images, less elastic as a person ages
• Vitreous Humor


  A clear, jellylike fluid that fills the vitreous chamber and maintains the shape of the eyeball
• Fibrous Tunic


  The outermost layer of the eye, composed of dense connective tissue
• Vascular Tunic


  The middle layer of the eye, consisting of the choroid, ciliary body, and iris, nourishes the eye and prevents light scattering
• Nervous Tunic


  The innermost layer of the eye, consisting of the retina which converts light to action potentials
• Taste


  Gustation, a special sense that helps us evaluate what we eat or drink
• Taste Receptors


  Located on the tongue, soft palate, pharynx, and epiglottis, convert chemical energy into electrical signals that travel to the brain
• Taste Buds


  Adults typically have 10,000 taste buds, primarily situated on the surface of the tongue and within the soft tissues of the mouth, house specialized taste receptor cells
• Types of Papillae


  • Fungiform
  • Circumvallate
  • Foliate
• Gustatory Transduction


  1. Activation of G Proteins

  2. Ion Channel Opening

  3. Neurotransmitter Release

  4. Nerve Impulse Generation