Human Anatomy and Physiology

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Human Anatomy and Physiology

• Special Senses

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All senses work the same way

• Receptors collect information
• stimulate neurons
• information is sent to the brain
• the cerebral cortex integrates the information
• forms a perception (a persons particular view of
  the stimulus)

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Receptor types

• Pain receptors or nociceptors respond to tissue
  damage due to mechanical, electrical, thermal or
  chemical energy
• Thermoreceptors
• respond to temperature change

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Receptor types

• Mechanoreceptors respond to mechanical forces,
• such as pressure or fluid movement changes
• usually deform the receptor
• Proprioceptors sense changes in muscles and
  tendons
• Baroreceptors in blood vessels detect
  changes in pressure
• Stretch receptors in lungs sense degree of
• inflation

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Receptor types

• Photoreceptors -respond to light as little as
  one photon
• Chemoreceptors sensitive to chemical
  concentration of various substances

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• Receptors are structured in two basic ways
• receptors can be nerve endings
• other kinds of cells which are associated with
  nerve endings
• When these are stimulated, they produce graded
• potentials. If hit threshold, nerve fires.

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A sensation or perception occurs when the brain
interprets the incoming nerve impulses. All
impulses coming into the brain are alike.
The sensation depends on which part of the brain
is stimulated. Synesthesia joined
perception tasting, colors, etc.
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Who has synethesia

• Women in the U.S., studies show that three times
  as many women as men have synesthesia in the
  U.K., eight times as many women have been
  reported to have it. The reason for this
  difference is not known.
• Left-handed synesthetes are more likely to be
  left-handed than the general population.
• Neurologically normal synesthetes are of normal
  (or possibly above average) intelligence, and
  standard neurological exams are normal.
• In the same family synesthesia appears to be
  inherited in some fashion it seems to be a
  dominant trait and it may be on the X-chromosome.

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Developmental Aspects of the Special Senses

• Special sense organs are formed early in
  embryonic development. Maternal infections during
  the first five or six weeks of pregnancy may
  cause visual abnormalities as well as
  sensorineural deafness in the developing child.
  An important congenital eye problem is
  strabismus. The most important congenital ear
  problem is lack of the external auditory canal.
• Vision requires the most learning. The infant has
  poor visual acuity (is farsighted) and lacks
  color vision and depth perception at birth. The
  eye continues to grow and mature until the eighth
  or ninth year of life,
• Problems of aging associated with vision include
  presbyopia, glaucoma (the most common cause of
  blindness in the U.S.), cataracts, and
  arteriosclerosis of the eye's blood vessels.
• The newborn infant can hear sounds, but initial
  responses are reflexive. By the toddler stage,
  the child is listening critically and beginning
  to imitate sounds as language development begins.
  
• Sensorineural deafness (presbycusis) is a normal
  consequence of aging.
• Taste and smell are most acute at birth and
  decrease in sensitivity after the age of 40 as
  the number of receptors decreases.

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Sensory adaptation The only receptors that dont
adapt are pain receptors Somatic
Senses Exteroceptive senses changes at
body surface Proprioceptive senses changes
in muscles and tendons and body
position Visceroceptive senses changes in
viscera(The internal organs of the
abdomen and thorax specifically, the hollow
Organs such as intestines, bladder, etc.)
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Touch and pressure senses 1. Free nerve endings
touch and pressure 2. Meissners corpuscles
light touch receptors are connective
tissue 3. Pacinian corpuscles heavy pressure
and vibrations receptors are connective
tissue Itch and Tickle Receptors are free
nerve endings
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Pain

• Also free nerve endings
• Most pain receptors can be stimulated by more
  than one stimulus
• Deficiency of blood flow (ischemia) and thus a
  deficiency of oxygen (hypoxia) can stimulate pain
  receptors.

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Pain fibers are of two types Acute pain fibers
( A or delta fibers) thin, myelinated
fibers (Conducts up to 30 meters/sec) Sharp,
localized pain Seldom continues after stimulus
stops Chronic pain fibers (C fibers) thin,
unmyelinated fibers (conduct up to 2 meters
per second) Dull, aching and widespread
pain May continue for some time after
stimulus
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• Stretch receptors
• We know how our body parts are moving
• through our proprioceptive or kinesthetic
  sense.
• These receptors adapt only slightly
• Keep brain informed of the status of body
• parts to insure coordination.
• Use specialized receptors that sense tension in
• tendons and muscles.
• No sensation occurs when these are stimulated.

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Muscle spindles sense stretching of muscle, and
cause contraction Of the muscle to maintain
position.
Golgi tendon organs sense stretching of tendons
and cause the muscle to relax to prevent damage
to the tendon.