Vestibular System Responsible for balance maintenance of the head in an upright position and adjustment of eye movement to compensate for head movements 2 components vestibular sacs and semicircular canals second and third components of inner ear plus cochlea make up inner ear Vestibular sacs 2 kinds utricle little pouch and saccule little sack After cochlea before semicircular canals Responds to the force of gravity and head s orientation Utricle floor and Saccule wall contain receptive tissue and cilia Cilia embedded in gelatinous mass containing otoconia small crystals of calcium carbonate Weight of crystals cause gelatinous mass to move as orientation of head changes Semicircular canals Approximate the three planes of the head sagittal transverse horizontal Respond to angular acceleration changes in the rotation of the head Receptors respond to the movements of head in particular plane Membranous canal floating within a bony one Membranous canal contains endolymph fluid Contains an enlargement which is next to the vestibular sacs called ampulla Ampulla contains hair cells sensory receptors whose cilia are in cupula gelatinous mass Rotation of the head causes endolymph to go in opposite direction and pushes against cupula causing receptor potentials in hair cells Pathway to brain Vestibular nerve has a nodule called vestibular ganglion which transmits info from vestibular system to brain Parts of brain info goes to cerebellum spinal cord medulla pons temporal cortex Lower brain stem projections are accompanied by nausea and vomiting associated with motion sickness Somatosenses Provide info about what s happening on surface of body and inside it Cutaneous senses touch senses stimuli that involves the skin Cutaneous senses respond to pressure vibration temperature changes tissue damage pain Kinesthesia perception of the body s own movements Especially important feedback coming from receptors that respond to changes in the stretching of the skin during movements of the joints or the muscles themselves but also responds to the receptors within joints between adjacent bones Proprioception perception of the body s position and posture Organic senses arise from receptors in and around the internal organs Glabrous skin skin that does not contain hair skin of the palms and bottom of feet Contains a dense complex mixture of receptors including Merkel s disks touch sensitive end organs found at the base of the epidermis adjacent to sweat ducts an encapsulated receptor Ruffini corpuscle a vibration sensitive organ located in hairy skin an encapsulated receptor Meissner s corpuscles touch sensitive end organs located in the papillae small elevations of the dermis that project up into the epidermis an encapsulated receptor Pacinian corpuscles specialized encapsulated somatosensory nerve ending that detects mechanical stimuli especially vibrations an encapsulated receptor Skin has free nerve endings temperature pain Touch Sensitivity to pressure and vibration is caused by the movement of the skin which moves the dendrites of mechanoreceptors Some touches are sensed by small diameter unmyelinated axons limbic system touches Some touches are sensed by large myelinated axons some tickles limbic system touches what scientists mainly think of as regular touches Olausson found that we expect hairy skin to feel good from other people touching us and we expect to feel good for our glabrous skin no hair touching others Temperature Six mammalian thermoreceptors of the TRP family sense temperature from toxic noxious cold 8C to toxic noxious hot 52C these are free nerve endings Cold sensors located just beneath epidermis and conveyed to CNS by thinly myelinated A fibers Warm sensors located more deeply in skin and conveyed by unmyelinated C fibers Pain Accomplished by free nerve endings in the skin Pain receptors nociceptors detectors of noxious stimuli High threshold mechanoreceptors respond to intense pressure striking stretching pinching Fibers containing TRPV1 receptors respond to hot acids capsaicin family vanilloid family Fibers containing TRPA1 receptors sensitive to pungent irritants vehicle exhaust tear gas chemicals which can cause inflammation Perception of pain 3 effects 1 perception of physical painful stimulus pathway from spinal cord to ventral posterolateral thalamus to primary and secondary somatosensory cortex does not activate when seeing someone else have pain 2 immediate emotional feelings accompanying pain pathways reaching the anterior cingulate cortex ACC activates when seeing someone else have pain 3 long term emotional implications pain as a threat to future pathways reaching the prefrontal cortex activates when seeing someone else have pain Phantom limb sensations that appear to originate in a limb that has been amputated Pathway to brain Precise touch kinesthesia to the fifth cranial nerve dorsal root ganglion dorsal columns of spinal cord nuclei of dorsal columns in lower medulla medial lemniscus of midbrain ventral posterior nuclei of thalamus relay nuclei for somatosensory cortex in thalamus primary somatosensory cortex secondary somatosensory cortex Pain temperature to the fifth cranial nerve dorsal root ganglion spinothalamic tract medial lemniscus ventral posterior nuclei of the thalamus relay nuclei for somatosensory cortex primary somatosensory cortex secondary somatosensory cortex damage to the somatosensory association cortex can cause tactile agnosia Gustation We taste by molecules of a substances dissolving in saliva Six qualities of taste bitterness sourness sweetness saltiness umami fat Umami taste sensation produced by detecting MSG monosodium glutamate which identifies the presence of amino acids proteins in foods Means good taste in Japanese Fat is detected by two G protein couples receptors and the enzyme lingual lipase in taste buds 10 000 taste buds on tongue palate pharynx larynx Papillae are protuberances on tongue Taste buds consist of twenty to fifty receptor cells Receptors have life span of 10 days Cilia on taste buds and protrude to opening of taste bud into saliva that coats the tongue Perception of taste Salty best stimulus is NaCl sodium chloride A substance must ionize to taste salty Receptor for sodium is sodium channel Sodium latches to receptor and depolarizes taste cell Sourness Hydrogen in acidic solutions must be present as well as anions Sweet two different receptors responsible for detection of sweet tastes Bitterness detected by