The Eight Senses: Touch, Pain, Balance and Kinesthesis
|
Types |
Physical stimulus |
Equipment |
Sub-Structures |
Roles of the Brain |
Theories |
| Touch | Cutaneous receptors for stimuli:
pressure, vibration, heat, cold, etc. |
Hair follicle ending (in the skin): for hair displacement
Ruffini endings (under epidermis): for pressure
Krause corpuscle (lips, tongue, genitals): for pressure
Pacinian corpuscle (deep skin layers): for vibration (150-300 Hz)
Meissner corpuscle (deep hairless skin layers): for vibration (20-40 Hz)
Merkel discs (hairless skin top layer): for pressure
Thermoreceptors (under epidermis): for temperature (30-43o)
Cold receptors (under epidermis): for temperature (20-35 o) |
Receptors -> action potential -> afferent nerve tracts -> spinal column -> thalamus -> parietal lobes (cerebral cortex) | Primary somatosensory cortex, motor cortex:
frontal lobe (elaboration of thought, mastication, motor elaboration, swallowing, tongue); occipital lobe (bilateral vision, contralateral vision), cerebellum; parietal lobe (sensory elaboration, salivation); temporal lobe (perceptual judgment, visual and auditory recollection, hearing); motor (arm, leg, hand, lips, articulation); sensory (arm, leg, hand, lips, tongue, mouth); The sensory homunculus |
Phantom limb phenomenon:
the brain has specific space for the limb, stimulation in neighboring areas -> cause physical sensation |
| Pain | Nociception:
an unpleasant response caused by tissue damage and emotional responses as warning messages to avoid self-injury |
Nociceptor: free nerve endings for sending pain messages (action potentials -> afferent nerve tracts -> spinal cord) | Pain + touch messages -> primary somatosensory cortex | Gate control theory:
pain messages have to get through a neuronal gateway -> proceed/block |
|
| Substance P: elevate pain signals | Pain -> brain -> emotional response (with memory in the limbic system) -> avoid future stimuli | ||||
| Endorphins: decrease substance P’s effects | Hypnosis, placebo effect -> pain relief | ||||
| Balance | Vestibular sense:
head position, head/body moving speed |
Semicircular canals: in different directions, with fluid, hair cells | Posture, movements, self-protection | Motion sickness:
conflicts of information between the balance system (e.g., no motion) and the visual system (e.g., motion) |
|
| Otolith organs: otoliths (calcium carbonate particles) -> hair cells -> cranial nerve 8 -> the brain | |||||
| Kinesthesis | Limb and joint motions, weights;
procedural memory |
Proprioceptors/mechanoreceptors:
Muscle spindle in skeletal muscles for muscle stretching; Golgi tendon organs for tension in tendons; Joint receptors around joints for joint motions |
Muscle, tendons, joint information -> brain regions |
