lesson overview 31.4 the senses
DESCRIPTION
Touch, pressure, & vibration Sensory receptors are categorized by the type of stimuli to which they respond. Sensory Receptors Type Responds to Locations Chemoreceptor Chemicals Mouth & nose Photoreceptor Light Eyes Mechanoreceptor Touch, pressure, & vibration Skin & ears Thermoreceptor Temperature Skin Pain receptor Tissue injuryTRANSCRIPT
Lesson Overview The Senses
Lesson Overview31.4 The Senses
Lesson Overview The Senses
• Sensory receptors are categorized by the type of stimuli to which they respond. Sensory Receptors
Type Responds to LocationsChemoreceptor Chemicals Mouth & nosePhotoreceptor Light Eyes
Mechanoreceptor Touch, pressure, & vibration
Skin & ears
Thermoreceptor Temperature SkinPain receptor Tissue injury Skin
Lesson Overview The Senses
Touch • Human skin contains at least seven types of
mechanoreceptors that respond to different levels of pressure and creates the sensation of touch.
• Not all parts of the body are equally sensitive to touch. For example, the skin on your fingers has a much higher density of touch receptors than the skin on your back.
Lesson Overview The Senses
Temperature • Thermoreceptors respond to heat and cold
and are found throughout the skin • The hypothalamus is part of the brain that
senses blood temperature
Lesson Overview The Senses
Pain • Pain receptors in the skin respond to physical
injuries like cutting or tearing. • Many tissues also have pain receptors that respond
to chemicals released during infection or inflammation.
• The brain does not have pain receptors. o For this reason, patients are often kept
conscious during brain surgery, enabling them to tell surgeons what sensations are produced when parts of the brain are stimulated.
Lesson Overview The Senses
Smell and Taste• Your senses of taste and smell
involve the ability to detect chemicals.
• Chemoreceptors = chemical-sensing cells o Taste buds = the sense organs in the mouth
that detect taste o Olfactory receptors = the sense organs in
the nose that detect smell
Lesson Overview The Senses
Hearing and Balance• The human ear has two sensory functions—
hearing and detecting movement• Mechanoreceptors found in parts of the ear
transmit impulses to the brain. o The brain translates the impulses into
sound and information about balance.
o Hearing = cochlea (see the notes below)
o Balance = semicircular canals
Lesson Overview The Senses
Hearing 1. Sound is a result of vibrations moving
through the air around us. 2. Vibrations enter the ear cause the eardrum
to vibrate.
Lesson Overview The Senses
Hearing 3. Three tiny bones, called the hammer, anvil,
and stirrup, transmit these vibrations to a membrane that creates pressure waves in the fluid-filled cochlea of the inner ear.
Lesson Overview The Senses
Hearing 4. The cochlea is lined with tiny hair cells that are
pushed back and forth by these pressure waves. 5. The motion of these sensitive hair cells produces
nerve impulses that travel to the brain which processes these nerve impulses as sound.
Lesson Overview The Senses
Balance • Semicircular canals = Three tiny canals
within the inner ear that monitor the position of your body, especially your head, in relation to gravity.
Lesson Overview The Senses
1.The semicircular canals are filled with fluid and lined with hair cells.
2.As the head changes position, the fluid in the canals also changes position, causing the hair on the hair cells to bend.
Lesson Overview The Senses
Balance 3.This bending sends impulses to the brain that
enable it to determine body motion and position.
Lesson Overview The Senses
Vision• How do the eyes and brain produce vision?• Vision occurs when photoreceptors in the
eyes transmit impulses to the brain, which translates these impulses into images.
Lesson Overview The Senses
Order that light passes through the eye:
1. Cornea = a tough transparent layer of cells.
Lesson Overview The Senses
2. Iris = colored part of the eye • Pupil = small opening in
the middle of the iris
Lesson Overview The Senses
3.Lens = focuses the eyes to see near or distant objects clearly• Small muscles attached to
the lens change its shape helping to adjust the eyes’ focus
Lesson Overview The Senses
4.Retina = inner layer of the eye where the lens focuses• Photoreceptors arranged
in a layer in the retina convert light energy into nerve impulses that are carried to the brain
Lesson Overview The Senses
oThere are two types of photoreceptors: rods and cones.
oRods = only sense in black and white oCones = respond to different colors,
producing color vision
Lesson Overview The Senses
Label the eye: