Special Senses (Olfaction&Gustation) PDF

Special Senses (Olfaction&Gustation) Olfaction: Bi-polar neurons with tips in mucus Mucus dissolves ordants & allows them to be perceived Simple columnar epithelium supports/nourishes,& detoxifies Olfactory stem cells divide to make new ones Receptors life a m...

Special Senses (Olfaction&Gustation) Olfaction: Bi-polar neurons with tips in mucus Mucus dissolves ordants & allows them to be perceived Simple columnar epithelium supports/nourishes,& detoxifies Olfactory stem cells divide to make new ones Receptors life a month Facial nerve controls olfactory gland & supporting cell Olfaction Pathway: Starts at olfactory hairs&propagates upwards 1.Odorant binds to receptor 2.Receptor activates G-protein 3.G-protein activates adenylate cyclase 4. ATP to cAMP 5.cAMP opens channel&allows Na&Ca to depolarize Frontal lobe identifies smell Hypothalamus&Amygdala create emotional response to smell Gustation: Sour, sweet, bitter, salty, umami Receptors on tastebuds Tastebuds are very protected Basal epithelial cells are stem cells that replace every 10 days Gustatory cells respond to tastant&release neurotransmitter  Circumvallate papillae:most,forms V,100-300 taste buds Fungiform papillae:elevations,5 taste buds Folate papillae:lateral, found in children Filiform papillae:no taste buds,make texture Salty&Acidic:Channel, Na depolarizes Sweet,Bitter,&Umami:Receptor binding, stimulates G-proteins When tastebuds are stimulated, nerve impulses run along nerves to medulla oblongata, take info to thalamus, then to taste area of cortex in insula of Ryle Special Senses (Vison) Over ½ of all sensory receptors are in eye Lacrimal Apperatus makes&drains tears Pass medially&leads to lacrimal sac Contains salt, mucus, and lysozyme(antibacterial) cleans&lubes eye Nerves Oculomotor: superior,medial,&inferior rectus. Inferior oblique Trochelar: superior oblique Abducens: lateral rectus Eye(Autonomic) Scleral venous sinus drains aqueous humor Ciliary muscle focuses lens&changes shape  Parasympathetic= bright light Sympathetic= dark light Rods&Cones (photoreceptors) Not evenly distributed 6 million cones 10 million rods Rods are at edge of eye 1 bipolar cell=1 cone Focused=hitting central fovea Optic disc=blind spot Lens is made of crystalines Special Senses (vision physiology) Vision Central fovea has ganglia and bipolar cells that scatter light and make clear image Ciliary muscle flattens lens with tension, and rounds lens when relaxed (to bend light) Image Formation Light refracts (bends) when it goes from one medium to another Cornea refracts 75% of light Lens refracts 25% of light Accommodation reflex= lens changing shape Images are upside down&inverted, but brain corrects Sympathetic Activation: 20ft or further, lens flattens, suspensory ligaments tighten, ciliary body relaxes  Parasympathetic Activation: 20ft or less, rounded lens, suspensory ligaments relax, ciliary body tightens Inhibitory synaptic event Neurotransmitter(glutamic acid) is released from photoreceptors, inhibits bipolar cell via hyperpolarization, and stops action potential from propagating ACTION POTENTIONAL STARTS WHEN NEUROTRAMSMITTER GLUTAMIC ACID STOPS When neurotransmitter stops, bipolar cells depolarize, action potential starts, and nerve impulse propagates info to brain for interpretation Photopigments Opsin: protein, amino acid sequence - rod=rhodopsin - cone=lodopsin Retinol: derivative of vitamin A Below Light Threshold (CANT COMMUNICATE) cGMP is the key to keep channel open When channel is open,transducin and phosphodiesterase do nothing ➡️ ➡️ ➡️ ➡️ cisretinal&opsin open Na channel lots of Na+ ➡️ inside membrane depolarization (-30mv) glutamic acid releases bipolar cell hyperpolarized Above Light Threshold (CAN COMMUNICATE) transretinol=cisretinol that changed shape via isomerization, and turns on transducer&phosphodiesterase Phosphodiestrase= takes cGMP and converts to CMP Channel closes as cGMPs fall off  ➡️ ➡️ ➡️ ➡️ transretinol&opsin closes Na channel little Na+ ➡️ inside Membrane polarized (-70mv) No glutamic acid released Bipolar cell depolarized Visual Pathway Medial: switch via optic nerve chiasm Lateral: normal side pathway Path= rods&cones,bipolar cells,ganglionic cells,axons of ganglia, axons of optic nerve Special Senses (hearing) External ear Elastic cartilage&adipose tissue Traps&directs sound waves to middle ear Pinna is attached via ligaments External acoustic meatus in inside temporal bone -contains vibrancy hairs&sarmanus hairs Tympanic membrane=end of external, beginning of middle -made of elastic fibers, collagen Middle ear Air filled cavity in temporal bone Connects external ear to windows Contains auditory ossicles (bones) -malleus=attaches internal surface to tympanum -incus=middle bone -stapes=base attaches to oval window Eustachian tube consists of cartilage, and connects the middle ear to nasopharynx. Opens  during swallow/yawn to let air in & equalize pressure Contains 2 major muscles -tensory tympani=limits movement, increases tension, prevents damage, cranial nerve 5 -stapedius muscle=attaches to stapes, contracts away, facial nerve Acoustic Attenuation Reflex= muscles reduce vibrations on ossicles to prevent inner ear damage Inner ear Bony&membranous portions Bony labyrinth contains 3 cavities in temporal bone -semicircular canals=semicircular ducts&ampulle -vestibule=utricle saccule -cochlea=cochlear duct Semicircular ducts have hair cells for equilibrium -ampulla=angular&rotational head movement -vestibule=head position -cochlea=hearing Tectorial membrane does not move Spiral Organ Inner hair cells: hearing,sensory Outer hair cells: sound tone, motor Ear hair is called Stereocilia Basilar membrane movement leads to hair movement, then to sensory neurons leading to cochlear nerve Sound Volume:loudness -depends on how much the membrane vibrates -loud=lots of movement&pressure -quiet=little movement&pressure Pitch:frequency  wavelengths travel to different places in basilar membrane -high frequency=displacement near base -medium frequency=displacement near middle -low frequency=displacement at end Route of sound 1.Sound waves vibrate tympanic membrane 2.Auditory ossicles vibrate and increase pressure 3.Pressure waves made by stapes pushing on oval window move fluid in scala vestibule 4. A. Sound below healing range never excite hair cells 4. B. Sound above hearing range goes through cochlear duct, vibrates basilar membrane, and excites inner hair cells The auditory pathway starts in cochlea, where sound vibrations are detected and sent through vestibular cochlear nerve to brainstem. After that, the signals pass through superior olivary nucleus in medulla, inferior colliculus in midbrain, and thalamus in brain before reaching the auditory cortex in the temporal lobe for processing. - Acoustic attenuation reflex via tensor tympani and stapedius muscle protect the ear from loud sounds