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Human Anatomy and Physiology


Human Anatomy and Physiology ... If hit threshold, nerve fires. A sensation or perception occurs when the brain interprets the incoming nerve impulses. – PowerPoint PPT presentation

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Title: Human Anatomy and Physiology

Human Anatomy and Physiology
  • Special Senses

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)

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

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

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

  • 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.

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.
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.

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.)
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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  • 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

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
  • Stretch receptors
  • We know how our body parts are moving
  • through our proprioceptive or kinesthetic
  • 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
Golgi tendon organs sense stretching of tendons
and cause the muscle to relax to prevent damage
to the tendon.
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