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Bell Work 4/25/11

Bell Work 4/25/11 . Identify the special senses A: Smell, Taste, Hearing, Vision, Balance. Somatic and Special Senses. Chapter 12. Types of Senses.

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Bell Work 4/25/11

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  1. Bell Work 4/25/11 Identify the special senses A: Smell, Taste, Hearing, Vision, Balance

  2. Somatic and Special Senses Chapter 12

  3. Types of Senses • Somatic Senses include: Tactile (touch, pressure, and vibration), thermal (hot and cold), pain and proprioceptive sensations (joint and muscle position sense, and movements of limbs and head). • Visceral Senses provide information about conditions within the body fluids and internal organs.

  4. What is a Sensation? • The conscious or subconscious awareness of internal or external conditions of the body.

  5. Sensation Conditions • For a sensation to occur 4 conditions must be met: • A stimulus or change in the environment that is capable of activating certain sensory neurons. (may be in the form of light, heat, pressure, mechanical energy or chemical energy) • A sensory receptor must convert the stimulus to an electrical signal-producing 1 or more nerve impulses.

  6. Sensation Conditions 3. Nerve impulses must be conducted along a neural pathway from the sensory receptor to the brain. 4. A region of the brain must receive and integrate the nerve impulses into a sensation.

  7. Sensation Characteristics • Perceptions are conscious sensations that are integrated in the cerebral cortex. (sight, pain, and hearing) • Sensory impulses from each part of the body arrive in a specific region of the cerebral cortex interpreting the sensation as it comes from the stimulated receptors. • A given sensory neuron carries info for one type of sensation only.

  8. Sensation Characteristics • Adaptation is a characteristic of most sensory receptors that decrease sensation strength during a prolonged stimulus. • Caused in part by a decrease in responsiveness to sensory receptors. • As a result of adaptation, perception of sensation may fade or disappear. • Receptors vary in how fast they adapt; pressure, touch, and smell adapt rapidly.

  9. Types of Sensory Receptors • Free nerve endings include receptors for pain, thermal, tickle, itch and some touch sensations. • Encapsulated nerve endings include receptors for other somatic and visceral sensations such as touch, pressure and vibrations.

  10. Homework Complete checkpoints 1-5

  11. Bell Work 4/26/11 Which receptors are especially abundant in the fingertips, palms and soles? A: Corpuscles of touch (Meissner corpuscles) are abundant in the fingertips, palms and soles.

  12. Somatic Senses Objectives: • Describe the location and fxn of the receptors for tactile, thermal, and pain sensations. • Identify the receptors for proprioception and describe their functions

  13. Somatic Senses • Arise from stimulation of sensory receptors in the skin, mucous membranes, muscles, tendons, and joints. • Distributed unevenly • Largest amount of sensory receptors includes: tip of the tongue, lips and fingertips.

  14. Tactile Sensations • Touch, pressure, vibration, itch, and tickle • Tactile receptors in the skin include corpsucles of touch, hair root plexuses, type I and II cutaneous mechanoreceptors, laminated corpuscles and free nerve endings.

  15. Touch • Result of stimulation of tactile receptors in the skin. • Corpuscles of touch (Meissner corpuscles) are located in the dermal papillae of hairless skin. • Each corpuscle is an egg shaped mass of dendrites enclosed by a capsule of connective tissue-abundant in hands, eyelids, tip of the tongue, lips, nipples, soles, clitoris, and tip of the penis.

  16. Touch • Hair root plexuses consist of free nerve endings wrapped around hair follicles in hairy skin. • Detect movement on the skin surface that disturb hairs. • 2 types of slowly adapting touch receptors: • Type I cutaneous mechanoreceptors aka merkel disks

  17. Touch • Type I cutaneous mechanoreceptors are saucer shaped, flattened nerve nedings that contact Merkel cells of the stratum basale (plentiful in fingertips, hands, lips and external genetalia) • Type II cutaneous mechanoreceptors or ruffini corpuscles are elongated, encapsulated receptors located deep in the dermis, ligaments, and tendons. Present in the hands, and abundant in the soles, they are the most sensitive to stretching that occurs as digits or limbs are moved.

  18. Pressure and Vibration • Pressure is a sustained sensation that is felt over a larger area than touch. • Receptors that contribute to sensations of pressure include corpuscles of touch, type I mechanoreceptors, and lamellatedcorpscles. • Lamellatedor pacinian corpuscles are large oval structures composed of a multi layered connective tissue capsule that encloses a nerve ending.

  19. Pressure and Vibration • Adapt rapidly • Widely distributed thru the body • Vibration results from rapidly repetitive sensory signals from tactile receptors • Corpuscles of touch detect low frequency vibrations • Lamellated corpuscles detect higher frequencies

  20. Itch and Tickle • Itch results from stimulation of free nerve endings by certain chemicals: bradykinin, often as a result of an inflammatory response. • Tickle thought to be free nerve endings and lamellated corpuscles. • Arises when someone else touches you rather than when you touch yourself.

  21. Thermal Sensations • Thermal receptors are free nerve endings • 2 distinct sensations are cold and warmth • Cold are located in the epidermis, warm are located in the dermis • Cold receptors are activated 50*-105*F • Warm receptors are activated 90*-118*F • Both adapt rapidly at the onset of the stimulus

  22. Bell Work 4/27/11 Which visceral organ has the broadest area for referred pain? A: Kidneys

  23. Pain Sensations • Nociceptorsare the sensory receptors for pain; found in almost every tissue of the body except the brain and respond to several types of stimuli. • Sensation of pain is caused by excessive stimulation of sensory receptors, excessive stretching of structure, prolonged muscular contractions, inadequate blood flow, or presence of certain chemicals.

  24. Pain Sensations • Pain may persist even after the pain-producing stimulus is removed b/c the pain causing chem remain longer and b/c nociceptors do not exhibit little adaptation. • If adaptation to painful stimuli could occur, irreparable tissue damage could result.

  25. Pain Sensations • Cerebral cortex is responsible for pain recognition type, and intensity • Somatic pain is projected from the cerebral cortex back to the location of the pain. • Visceral pain is felt in the skin overlaying the stimulated organ known as referral pain.

  26. Types of Pain Sensations • Fast: occurs rapidly- w/in .1 sec after a stimulus is applied. (needle prick or knife cut) • Aka acute, sharp, or pricking pain. • Precise and localized to the stimulated area • Not felt in deeper tissues of body • Slow: begins a second or more after a stimulus occurs, gradually increasing over time. • Excruciating pain • Referred to as chronic, burning, aching, or throbbing pain • Can occur in skin and deeper tissues and organs (toothache)

  27. Proprioceptive Sensations • Inform you consciously and subconsciously of the degree to which your muscles are contracted, amount of tension present in your tendons, position of your joints, and the orientation of your head. • Proprioceptors adapt slowly –beneficial so the brain can be aware of what is occurring at different parts of your body at all times.

  28. Proprioceptive Sensations • Kinesthesia allows you to walk, type or dress w/o using your eyes. • Proprioceptors allow you to estimate the weight of an object, and the effort necessary to perform the task (bag of books vs bag of feathers) • Proprioceptors are located in skeletal muscles, tendons around synovial joints and the inner ear.

  29. Olfaction: Sense of Smell • The nose contains 10mill-100mill receptors for smell-aka olfaction • b/c some nerve impulses for smell and taste return to the limbic system, certain odors and tastes can bring back a flood of memories.

  30. Bell Work 4/28/11 What is the function of basal stem cells A: Basal stem cells undergo cell division to produce new olfactory receptors.

  31. Structure of the Olfactory Epithelium • Olfactory receptors are the first order neurons of the olfactory pathway. • Olfactory hairs are cilia that project from a knob shaped tip on the olfactory receptor-respond to inhaled chemicals which in turn stimulates he olfactory hairs initiating olfactory receptors by odorants.

  32. Structure of the Olfactory Epithelium • Supporting cells provide physical support, nourishment, and electrical insulation for the olfactory receptors, and help to detoxify chemicals that come in contact w/ olfactory epithelium. • Basal stem cells produce new olfactory receptors; live for a month before they are replaced.(these are neurons) • Olfactory Glands produce mucus that moistens the surface of olfactory epithelium & acts as a solvent for inhaled odorants.

  33. Stimulation of Olfactory Receptors • Our ability to recognize ~10,000 diff odors probably depends on brain activity that arise from activation of many different combinations of olfactory receptors. • Olfactory receptors adapt by 50% in the first second after stimulation, and very slowly thereafter. • Olfactory receptors react to odorants by producing an electrical molecule that triggers the nerve impulse.

  34. Olfactory Pathway • Olfactory nerves form the right and left cranial nerve consisting of ~40 bundles of axons. • Olfactory bulbs contain axons terminals of olfactory nerves that form synapses w/dendrites of neurons in the olfactory pathway. Sense of Smell

  35. Olfactory Pathway • The axons of the neurons from the olfactory bulb form the olfactory tract. • Primary olfactory area is where the conscious awareness of smell begins .

  36. Gustation: Sense of Taste • 5 primary tastes: sweet, sour, bitter, salty, and umami (meaty/savory) • All other flavors are a combination of tastes in conjunction w/touch and smell. • Odors from food an pass upward from the mouth into the nasal cavity, stimulating olfactory receptors. • Aromas from food can stimulate the olfactory system 1,000’s of times stronger than the gustatory system. • Lack of taste during illness is due to blockage of olfaction.

  37. Structure of Taste Buds • The receptors for taste sensations are located in the taste buds • w/age, taste bud # declines dramatically • Found in elevations on tongue called papillae

  38. Structure of Taste Buds • Vallate papillae form an inverted v shape row at the back of the tongue • Fungi papillae mushroom shaped elevations over the entire surface of the tongue • Filliform papillae contain touch receptors, but no taste buds • Each taste bud is an oval body w/epithelial cells-supporting, gustatory receptors, basal cells

  39. Structure of Taste Buds • Supporting cells surround 50 gustatory receptor cells • Single long gustatory hair projects from gustatory receptor cell to the external surface thru the taste pore-opening in the taste bud • Basal cells produce supporting cells that develop into gustatory receptor cells that have a life span of ~10 days

  40. Stimulation of Gustatory Receptors • Tastantsare chemicals that stimulate gustatory receptor cells. • Once the chemical is dissolved in the saliva, taste pores make contact with plasma membrane of the gustatory hair=electrical signal that stimulates neurotransmitter release. • Indiv gustatory receptor cells may respond more than one of five primary tastes

  41. Stimulation of Gustatory Receptors • Complete adaptation (loss of sensitivity) to a specific taste can occur w/in 1-5min • Different tastes arise from activation of different groups of taste neurons; some responding stronger to certain tastants that others.

  42. Gustatory Pathway • From taste buds, impulses propigate along cranial nerve VII, IX and X to the medulla oblongata • Taste signals that project from the hypothalamus to the primary gustatory area give rise to the conscious perception of taste.

  43. Bell Work 5/3/11 In order from the tongue to the brain, what structures form the gustatory pathway. A: gustatory receptor cells-> cranial nerves VII, IX, and X -> medulla oblongata -> thalamus ->primary gustatory area in the parietal lobe of the cerebral cortex.

  44. Vision • Objectives: • Describe the accessory structures of the eye, layers of the eyeball, the lens, interior of the eyeball, image formation and binocular vision. • Describe the receptors for vision and the visual pathway to the brain.

  45. Vision • More than ½ the sensory receptors in the human body are located in the eyes, and a large part of the cerebral cortex is devoted to processing visual information.

  46. Accessory Structures of the Eye • Eyebrow, eyelashes, eyelids, muscles that move the eyeballs and lacrimal (tear-producing) apparatus. • The eyebrows and eyelashes protect the eyeballs from foreign object such as perspiration (sweat), and direct rays of the sun. • Upper and lower eyelids shade the eyes during sleep, protect from excessive light and spread lubricating secretions over the eyeball by blinking.

  47. Accessory Structures of the Eye • Six eye muscles work together to move the eyeball each direction. • Neurons in the brain stem and cerebellum coordinate and synchronize the movements of the eyes.

  48. Accessory Structures of the Eye • Lacrimal apparatus is a group of glands, ducts, canals and sacs that produce and drain lacrimal fluid of tears.

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