1. Chapter 13
Senses

2. Outline
Types of Sensory Receptors
Sense of Taste
Sense of Smell
Sense of Vision
Focusing
Integration of Visual Signals
Abnormalities of the Eye
Sense of Hearing
Sense of Equilibrium

3. Sensory Receptors and Sensations
Sensory receptors are specialized to detect certain types of stimuli.
Exteroceptors detect stimuli outside the body.
Taste, smell, vision.
Interoceptors detect stimuli inside the body.
Blood pressure, blood volume, pH.

4. Types of Sensory Receptors
Chemoreceptors.
Respond to chemical substances in the immediate vicinity.
Pain Receptors.
Respond to chemicals released by damaged tissue.
Mechanoreceptors.
Stimulated by mechanical forces.
Thermoreceptors.
Stimulated by changes in temperature.

5. How Sensation Occurs
Sensation occurs when nerve impulses arrive at the cerebral cortex of the brain.
Perception occurs when the cerebral cortex interprets the meaning of sensations.
All sensory receptors initiate nerve impulses; the sensation that results depends on the part of the brain receiving the nerve impulses.

6. Sensation

7. Proprioceptors
Proprioceptors are mechanoreceptors that help determine limb position in space by detecting the degree of muscle relaxation, stretch of tendons, and movement of ligaments.
Muscle spindles act to increase the degree of muscle contraction, while Golgi tendon organs act to decrease it.

8. Muscle Spindle

9. Cutaneous Receptors
The dermis contains cutaneous receptors, which include:
Mechanoreceptors.
Sensitive to touch.
Nociceptors.
Sensitive to pain.
Thermoreceptors.
Sensitive to temperature.

10. Sensory Receptors in Human Skin

11. Chemical Senses
Sense of Taste.
Receptors for taste are found in taste buds located primarily embedded in tongue epithelium.
Four primary tastes.
Sweet.
Sour.
Salty.
Bitter.

12. Taste Buds

13. Sense of Smell
Sense of smell is dependent on olfactory cells located within olfactory epithelium high in the roof of the nasal cavity.
Olfactory bulbs have direct connections with the limbic system and its centers for emotions and memory.
Sense of taste and smell work together to create a combined effect.

14. Olfactory Cell Location and Anatomy

15. Sense of Vision
The eyeball has three layers.
Sclera.
Choroid.
Retina.
The retina contains two types of photoreceptors.
Rods.
Cones.

16. Anatomy of the Human Eye

17. Focusing
When looking at an object, light rays pass through the pupil and are focused on the retina.
Focusing starts with the cornea and continues as the rays pass through the lens and the humors.

18. Focusing

19. Photoreceptors
Vision begins once light has been focused on the photoreceptors in the retina.
Rods are very sensitive to light and therefore are suited to night vision.
Cones allow detection of fine detail and color.
Color vision depends on three different kinds of cones which contain blue, green, and red pigments.

20. Photoreceptors in the Eye

21. Integration of Visual Signals in the Retina
The retina has three layers.
Layer closest to choroid contains rod cells and cone cells.
Middle layer contains bipolar cells.
Innermost layer contains ganglion cells.
Only rod and cone cells are light-sensitive, thus light must penetrate to the back of the retina before they are stimulated.

22. Structure and Function of the Retina

23. Integration of Visual Signals in the Brain
The visual pathway begins in the retina and passes through the thalamus before reaching the cerebral cortex.
The pathway and visual cortex take the visual field apart, and the cortex rebuilds it so we correctly perceive the field.

24. Optic Chiasma

25. Abnormalities of the Eye
Color blindness.
Particular type of cone is lacking.
Distance Vision
Nearsighted.
Elongated eyeball.
Farsighted.
Shortened eyeball.
Astigmatism.
Uneven cornea.

26. Eye Abnormalities and Corrective Lenses

27. Sense of Hearing
Anatomy of the Ear.
Outer ear consists of the pinna and the auditory canal.
Middle ear begins at tympanic membrane and ends at bony wall with a round window and oval window.
Ossicles found between tympanic membrane and the oval window.

28. Sense of Hearing
Anatomy of the Ear.
Inner ear consists of semicircular canals, vestibule, and cochlea.

29. Human Ear

30. Process of Hearing
When the basilar membrane (spiral organ) vibrates, stereocilia of the hair cells bend, and nerve impulses are transmitted to the brain.

31. Mechanoreceptors for Hearing

32. Sense of Equilibrium
Cupula movement within the semicircular canals detects rotation and/or angular movement of the head.
Rotational Equilibrium.
Movement of the otolithic membrane within the utricle and the saccule detects movement of the head in the vertical and horizontal planes.
Gravitational Equilibrium.

33. Review
Types of Sensory Receptors
Sense of Taste
Sense of Smell
Sense of Vision
Focusing
Integration of Visual Signals
Abnormalities of the Eye
Sense of Hearing
Sense of Equilibrium