NERVOUS SYSTEM III
SENSES
INTRODUCTION
• General Senses: are those with receptors widely
distributed throughout the body
• EX. Skin, various organs and joints
• Special senses: more specialized receptors and arise
from receptors located primarily in the head.
• EX. Eyes and ears
RECEPTORS, SENSATION AND
PERCEPTION
Receptors:
1. Chemoreceptors- respond to changes in
concentration of chemicals
• Olfactory (smell) receptors
• Detect changes in cerebrospinal fluid pH
2. Pain receptors (nociceptors)- respond to tissue
damage.
RECEPTORS, SENSATION AND
PERCEPTION
Receptors:
3. Thermoreceptors- sense temperature change
4. Mechanoreceptors- respond to touch, pressure,
vibration, and stretch
5. Photoreceptors- detect changes in light intensity,
color, and movement
RECEPTORS, SENSATION AND
PERCEPTION
• The brain interprets input from sensory receptors as
perception.
• Sensation- Conscious awareness of incoming sensory
information
• Sensory adaptation- ability to ignore unimportant
stimuli
• EX. Not constantly noticing/sensing your socks around
your ankles
GENERAL SENSES
• Touch is the only one of the five senses that is
considered a general sense
• Detected by mechanoreceptors and
thermoreceptors and pain receptors
SPECIAL SENSES
Vision:
Eyeball has outer, middle, and inner tunic (layers)
• The outermost tunic of the eyeball is the sclera
• The transparent anterior portion of the sclera is the
cornea
• Choroid Coat- Middle tunic
• Retina- the inner tunic of the eye
SPECIAL SENSES
Vision:
• Detected by photoreceptors
• The blink reflex is designed to. D. keep the eyes moist.
• The contractile structure that surrounds the pupil is the
iris.
• Lacrimal glands: constantly produce a fluid called
tears.
SPECIAL SENSES
Hearing:
• inner ear-contains the sense organs for hearing and
balance
• The external ear terminates at the tympanic
membrane.
• The auditory tube equalizes air pressure between the
middle ear and outside air.
• The malleus, incus, and stapes transmit vibrations
from the eardrum to the oval window.
SPECIAL SENSES
Hearing:
• Order of structures in the ear that vibrate when a sound
wave enters the ear.
•
•
•
•
•
Eardrum
Ossicles
Oval window
Perilymph
Endolymph
• Inner ear bones from lateral to medial:
Malleus
Incus
Stapes
SPECIAL SENSES
Taste:
• The sense of taste is called gustation.
• Primary taste sensations:
• Sweet
• Salty
• Sour
• Bitter
• umami
• Sensory structures that detect taste are taste buds.
SPECIAL SENSES
Smell:
• Smell is the special sense relayed directly to the
cerebral cortex without going to the thalamus
• Detected by chemoreceptors called olfactory
receptors
SPECIAL SENSES
Smell:
• In order for a molecule to be detected by the olfactory
neurons, it must be dissolved in fluid covering the olfactory
epithelium.
• Inhaling deeply and slowly through the nose help to
identify an odor because more air containing the odor is
brought into contact with the olfactory epithelium
• A person's nose run when he cries because tears drain
into the nasal cavity via the nasolacrimal duct.
SPECIAL SENSES
Equilibrium:
• Static equilibrium- maintenance of balance when
the head and body are not moving
• Dynamic equilibrium- maintenance of balance
when the head and body are suddenly moved or
rotated
SPECIAL SENSES
Equilibrium:
• Maintained by inner ear structures
• The position of the head with respect to gravity is
determined by the movements of otoliths in
response to gravity.