Other Important Senses

Skin Senses, Taste, Smell, Balance

Touch

• Sense of touch is a mix of four distinct skin senses – pressure– warmth– cold– pain

Skin Senses: Touch• Physical stimuli = mechanical, thermal, and

chemical energy impinging on the skin – Pathway: Sensory receptors -> the spinal column ->

brainstem -> cross to opposite side of brain -> thalamus -> somatosensory (parietal lobe)

Skin Senses

• Only pressure has identifiable receptors • All other skin sensations are variations of

pressures, warmth, cold and pain– Temperature: free nerve endings in the skin – Pain receptors: also free nerve endings

• Ex. Warm water + cold water = BURNING HOT!

PAIN

• Pain tells the body that something has gone wrong.

• Usually pain results from damage to theskin and other tissues. • Anhidrosis: rare disease in which the person

feels no pain.

GATE-CONTROL Theory• Melzak and Wall (1965, 1983) – proposed that our spinal cord contains neurological “gates”

that either block pain or allow it to be sensed.

• One way to treat chronic pain is to stimulate it through massage, by electrical stimulation (ESTIM) or acupuncture– Massage causes competitive stimulation to pain thus reduces

its effect.– ESTIM can distract muscles that are cramping and increases

bloodflow

PAIN CONTROL• Pain can be controlled by a number of therapies

including– drugs, surgery, acupuncture, exercise, hypnosis and

even thought distraction

• Burn victims can be distracted by allowing them to engage in illusory virtual reality– Brain scans show evidence of change in pain

perception

Figure 4.53 Pathways for pain signals

The Chemical Senses: Taste

• Taste (gustation)– Physical stimulus: soluble chemical substances – Receptor cells found in taste buds

• Pathway: taste buds -> neural impulse -> thalamus -> cortex – Four primary tastes: sweet, sour, bitter, and salty– Taste: learned and social processes

Figure 4.49 The tongue and taste

The Chemical Senses: Smell

• Smell (Olfaction)– Physical stimuli: substances carried in the air • dissolved in fluid, the mucus in the nose

– Olfactory receptors = olfactory cilia

• Pathway: Olfactory cilia -> neural impulse -> olfactory nerve -> olfactory bulb (brain)– Does not go through thalamus

Figure 4.51 The olfactory system

Other Senses: Kinesthetic and Vestibular

• Kinesthesis - knowing the position of the various parts of the body– Receptors in joints/muscles (detects bending, tautness,

extensions) • Vestibular - equilibrium/balance– Semicircular canals & vestibular sacs (fluid shifts when

head tilts) – Problems can occur with age, disease, or damage • Benign Paroxysmal Positional Vertigo (BPPV)

– Calcium carbonate crystals in inner ear – sends false messages to brain