10.1 Introduction

Sensory Receptors - detect environmental changes and trigger nerve impules

- somatic senses (touch, pressure, temp, pain)
- special senses (smell, taste, vision, equilibrium)

10.2 Receptors and Sensations

1. Chemoreceptors = _______________________________
2. Pain receptors = _______________________________
3. Thermoreceptors = _______________________________
4. Mechanoreceptors = _______________________________
5. Photoreceptors = _______________________________

Sensation = feeling that occurs when a brain interprets a sensory impulse
Projection = process where the cerebral cortex causes a feeling to stem from a source (eyes, ears)

Sensory adaptation = sensory receptors stop sending signals when they are repeatedly stimulated

10.3 Somatic Senses

1. Sensory Nerve Fibers - epithelial tissue, pain and pressure
2. Meissner's corpuscles - hairless areas of skin (lips, fingertips)
3. Pacinian corpuscles - deep pressure (tendons, joints)

Temperature Senses (warm and cold receptors)

Sense of Pain - pain receptors do not adapt, prompts a person to take action to avoid stimulus

Visceral Pain - occurs in visceral tissues such as heart, lungs, intestine
Referred pain - feels as though it is coming from a different part (heart pain may be felt as pain in arm or shoulder)

Acute Pain - originates from skin, usually stops when stimulus stops (needle prick)
Chronic Pain - dull aching sensation

Regulation of Pain impulses

Inhibitors of Pain (natural brain chemicals can be mimiced by drugs such as morphine)

Enkephalins
Serotonin
Endorphins

10.4 Special Senses

Smell (olfactory organs); Taste (taste buds); Hearing & Equilibrium (ears); Sight (eyes)

10.5 Sense of Smell

Olfactory organs contain olfactory receptors
Odor Molecule --> olfactory receptor cell --> olfactory bulb --> olfactory tract --> limbic system

10.6 Sense of Taste

Taste buds = Papillae

Sweet / Sour / Salty / Bitter

Taste Receptors --> cranial nerves --> medulla oblongata --> Thalamus --> Parietal Lobe of Cerebrum

10.7 Sense of Hearing

External Ear

Auricle (pinna) - outer ear
External Auditory Meatus

Middle Ear (tympanic cavity)

Eardrum
Auditory Ossicles - malleus, incus, stapes - transmit vibrations and amplify the signal

Auditory Tube (eustachian tube) - connects the middle ear to the throat - helps maintain air pressure

Inner Ear

Labyrinth - communicating chambers and tubes
Osseous Labyrinth and Membranous Labyrinth
Perilymph and Endolymph (fluids within the labyrinth)

Semicircular Canals - sense of equilibrium
Cochlea - sense or hearing

Organ of Corti - contains hearing receptors, hair cells detect vibrations

Pathway: Nerve cells --> interpreted by the temporal lobe of the cerebrum

Steps in Hearing

1. Sound waves enter external auditory meatus
2. Eardrum vibrates
3. Auditory ossicles (malleus, incus, stapes) amplify vibrations
4. Stapes hits oval window and transmits vibrations to cochlea
5. Organs of corti contain receptor cells (hair cells) that deform from vibrations
6. Impulses sent to the vestibulocochlear nerve
7. Auditory cortex of the temporal lobe interprets sensory impulses
8. (Round window dissipates vibrations within the cochlea)

10.8 Sense of Equilibrium

Static Equilibrium - sense the position of the head, maintain stability and posture
Dynamic Equilibrium (semicircular canals) - balance the head during sudden movement

Cerebellum - interprets impulses from the semicircular canals and maintains overall balance and stability