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