Other Senses: Outline

• Balance (Vestibular System)• Taste• Smell• Touch

Balance

• Three sources of balance:– Vision– Stretch receptors in muscles– Vestibular system

• Worst case scenario:– getting up in the middle of the night (no vision), from your

futon (poor info from stretch receptors), in a yacht (poor vestibular info).

• Balance• Coordinates head

& body movements• Keep eyes fixed

when head moves

Semicircular Canals• Rotations (3-D)

Dizziness is triggered- By rotation (kids) - By hot water in ear:

stimulates movement of fluid in vestibular chambers

- vertigo

Vestibular System: Functions

Vestibular Sacs: Function– linear accelerations– static head positions

From inner ear, output goes to Medulla & from there to:

- Spinal Cord,

- Oculomotor Nerve,

- Cortex,

- Cerebellum

• Flavor is inferred from: – Taste (5)– Smell (500-10,000 odors), and – Tactile information, & pain receptors (chili peppers)

• Supertasters– Genetic differences in receptors– Increased sensitivity to bitterness, sweet

Taste

Taste Receptors

Papillae • Bitter • Sweet • Sour: • Saltiness: Na+ channel

• Umami– elicited by the amino

acid glutamate found in proteins (meat, fish, beans, ketchup)

– MSG (monosodium glutamate)

Taste Pathway

• Orbitofrontal cortex (S2)

• Amygdala• Post central

gyrus and Insula (S1)

• Thalamus• Medulla• Cranial

nerves

Amygdala & OFC are important for valence, reinforcement

Olfactory System• The primary mode of communication for most animals• Critical for survival

– eating• toxic substances often smell/taste bad; good things smell good

– reproduction• mating partners• aggression in rivals

– location of predators and prey

Olfactory Anatomy

Olfactory tract projects to– amygdala,– hippocampus– hypothalamus– Insula

Pheromones

• Airborne molecules that affect behavior• Especially involved in reproduction• VNO- Vomeronasal Organ

– Physically distinct– evolved separately– Projects to Limbic areas

VNO

SomatosensesThe stimuli

The cutaneous senses respond to several different types of stimuli: pressure, vibration, heating, cooling, and events that cause tissue damage (and hence pain).

Some receptors report changes in muscle length to the brain; providing our sense of kinethesia.

Additional receptors provide information about the internal organs such as the linings of muscles and the gastrointestinal system.

SomatosensesAnatomy of the Skin and its Receptive Organs

Cuntaneous sense: One of the somatosenses; includes sensitivity to

stimuli that involve the skin.

Kinesthesia: Perception of the body’s own movements.

Organic sense: A sense modality that arises from receptors located

within the inner organs of the body.