1. Lesson Overview
31.4 The Senses

2. Touch and Related Senses
How does the body sense touch, temperature, and pain?

3. Touch and Related Senses
your skin can be considered your largest sense organ, and responds to touch.

4. Touch
Human skin contains mechanoreceptors that respond to varying levels of touch.
Not all parts of the body are equally sensitive,
ex: the skin on your fingers has a much higher density of touch receptors than your back

5. Temperature Thermoreceptors.
are found throughout the skin and in the hypothalamus,

6. Pain Pain receptors The brain does not have pain receptors.
in the skin, respond to physical injuries like cutting or tearing.
respond to chemicals released during infection or inflammation.
The brain does not have pain receptors.

7. Smell and Taste
How are the senses of smell and taste similar?

8. Smell and Taste
chemoreceptors in the nose and mouth are responsible for taste and smell

9. Smell and Taste The sense organs that detect taste are the taste buds.
salty, bitter, sweet, and sour foods, umami, (savory),

10. Hearing and Balance
How do the ears and brain process sounds and maintain balance?

11. Hearing and Balance
The human ear has 2 types of mechanoreceptors—hearing and detecting positional changes b/c of movement.

12. Hearing
Sound is a result of vibrations moving through the air around us.
Vibrations enter the ear through the auditory canal and cause the tympanum (eardrum) to vibrate.

13. Hearing
the hammer, anvil, and stirrup, transmit these vibrations to a membrane called the oval window.
which create pressure waves in the fluid-filled cochlea of the inner ear.

14. Hearing
The cochlea is lined with tiny hair cells that are pushed back and forth by these waves.
this produces nerve impulses that travel to the brain via cochlear nerve. Where its processed as sound.

15. Balance
each ear the semicircular canals, and two tiny sacs (both fluid filled) behind them monitor the position of your body/head in relation to gravity.

16. Balance
As the head changes position, the fluid in the canals also changes position, causing the hair on the cells to bend, this sends impulses to the brain that enable it to determine body motion and position

17. Vision
How do the eyes and brain produce vision?

18. Structures of the Eye
Light enters the eye through the cornea which, a tough transparent layer of cells.
focuses the light, then passes it through the aqueous humor.

19. Structures of the Eye At the back of the chamber is the iris,
In the middle of the iris is a opening, pupil.

20. Structures of the Eye
Tiny muscles in the iris adjust the size of the pupil to regulate the amount of light that enters the eye.
In dim light, = larger = more light enters.
In bright light, = smaller = less light enters

21. Structures of the Eye behind the iris is the lens.
Small muscles change its shape, helping to adjust the eyes’ focus
Behind the lens is a large chamber filled with fluid called vitreous humor.

22. How You See The lens focuses light onto the retina,
Photoreceptors convert light into nerve impulses that are carried to the brain via optic nerve.

23. How You See two types of photoreceptors:
Rods are extremely sensitive to light, but not colors,
Cones are less sensitive than rods, but respond to different colors, are concentrated in the fovea.