Other Senses

http://www.youtube.com/watch?v=W0w5oGVwJ_Q

1. Gustation (taste)

A. Taste cells are chemical sensitive receptors located in taste bud clusters

• Taste buds and papillae are located on the tongue, in the throat, and on the soft palate

• For a stimulus to be tasted, it must be dissolved

1. Gustation (taste)

B. Receptors are sensitive to 4… or 6 basic taste qualities

1. Sweetness

2. Saltiness

3. Sourness

4. Bitterness

5. Umami – glutamates (currently up for debate as of 2009)

6. Curry/Eastern spices (currently up for debate)

1. Gustation (taste)

C. Other influences on taste– Smell, touch, temperature

• Ex: flavor can be changed by food’s texture or aroma

1. Gustation (taste)D. Types of tasters• Non tasters – people unable to taste chemical

propylthiouracil (PROP), a bitter compound

• Medium tasters – people with average number of taste buds; they taste bitter PROP at avg. level

• Supertasters – people with extremely sensitive taste buds, high number of taste buds, highly sensitive to PROP (women more likely than men)

2. Olfaction (smell)

A. Receptors for smell located on olfactory epithelium

• Thin membrane found in upper nasal cavity

***THE ONLY SENSORY INFORMATION NOT ROUTED THRU THE THALAMUS BEFORE IT PROJECTS TO THE CORTEX***

2. Olfaction (smell)

1. Olfactory cells carry info to olfactory bulb• Olfactory bulb activates the prefrontal cortex

2. Olfactory receptor neurons have a life cycle of about 30 days and are continually created

3. Olfactory cells in the olfactory epithelium are stimulated by gases dissolved in the fluid covering the membrane

4. For a stimulus to be smelled it must be dissolved

2. Olfaction (smell)

B. Odors or scents stimulate the olfactory epithelium

1. Odors can evoke highly emotional memories

• On avg., women detect odors more readily than men (brain responses are stronger)

2. Olfaction (smell)

C. Pheromones: same species odors, used as a form of chemical communication

D. Anosmia: loss or lack of smell. Specific anosmia is the inability to smell a single chemical

The case of asparagus and methanethiol…

3. Somesthesis – (the mechanical senses)

A. Somesthesis refers to the mechanical senses (kinesthesis, vestibular sensation, skin senses)

3. Somesthesis

B. Kinesthesis

1. Communication information about movement and location of body parts

2. Receptors found in joints and ligaments

3. SomesthesisC. Vestibular Sense

1. also called equilibratory sense

2. receptors are in the semicircular canals and vestibular sacs found in the inner ear

3. This is concerned with the sense of balance and knowledge of body position

3. Somesthesis

D. Skin Cells

1. basic sensations include cold, warmth, pressure, pain

current research does not support the belief that specialized receptor cells for each of the four skin sensations exist

3. Somesthesis

E. Touch Plasticity

• When area of skin is used a lot, it becomes more sensitive and receptors “take over” more brain space

• Ex: blind people use first two fingers for brail, the region of the cortex devoted to these two fingers spreads and takes over less-used cortex from other touch areas

3. Somesthesis

F. Pain

1. Pain – experience evoked by a harmful stimulus; directs our attention toward a danger and holds attention

Somesthesis

Basics of Pain

a. Pain is not triggered by one stimulusb. At certain intensities, other stimuli cause

painc. Pain circuit: sensory receptors respond

to potentially damaging stimuli by sending impulse to the spinal cord and thus the brain to interpret signal as pain

3. SomesthesisD. Thicker and faster axons convey sharp

pain, thinner to dull pain. These axon enter the spinal cord, where neurotransmitters are released depending on severity of pain

• Mild pain releases glutamate• Severe pain releases both glutamate and

Substance P – a neuromodulator• Pain receptors can also react to chem

– Capsaicin – found in hot peppers – stimulates pain receptors

– Also leads to insensitivity to pain

3. Somesthesis

3. Pain relief – endorphins block release of Substance P in the spinal cord and brainstem

4. Gate control theory of pain: the brain can only focus on one pain stimulus at a time

Gate Control Theory of Pain

• Pain messages from body travel along a set of spinal cord nerve fibers

• All other sensory messages travel along another set (bottom up processing)

• Fibers carrying pain messages have pain gates, which open during painful experiences

• Non pain fibers can sometimes close pain gates if there is a COMPETING STIMULUS to large nerve fibers– Explains how rubbing or icing can seem to relieve pain

Gate Control Theory of Pain

Top down processing example:

Your brain plays an important role in perception of pain

• Athletes don’t notice pain until after the game is over

• Shock

Gate Control Theory of Pain

Phantom limb pain: a person feels pain in an area of an amputated limb

a. Suggests the brain can misinterpret spontaneous CNS activity

Mirror Box Therapy

http://www.youtube.com/watch?v=gc3CmS8_vUI