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Lecture

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Department
Neuroscience
Course
NROC64H3
Professor
Matthias Niemeier
Semester
Winter

Description
Nroc64 sensory motor system Introduction to sensory and motor system We have good understanding of the sensory side and some motor (like the coastlines of a continent) but have missing and limited understanding of the middle parts. (Integra- tion) Ramon y Cajal- brought the concept of the neuron Simple minds – Studying simple brains allows more easier learning about system since our brain is more complex. Studying sensorimotor systems – memory – learning - e.g. you don't get burned on the same thing twice to learn not to touch it again The chemical senses – the oldest senses - gustation – olfactory – smell helps on most identify things e.g. danger (survival) – chemoreceptors Taste – salt, sour, sweet, bitter, umami – molecules activate special receptors – bitter – should be avoided – poison – survival – we learn to enjoy but primitive is sur- vival – taste in combination (not only sweet) – but also use other senses e.g. taste and smell The organ of taste – Tongue, pallet, pharynx – all have taste receptors – Tongue Is the organ of taste specifically papillae – the tip of the tongue is sweetness – papillae are used to increase the surface area of the taste on tongue – tastebuds on the top or side of papillae – hundreds of taste buds per papillae – microvilli allow to sense taste using receptor potential Taste receptor cells – Tuning – typically tastes cells are not only for one taste (sweet or salty) but have differ- ent levels of tuning to all tastes. Taste – mechanism for taste transduction sensory transduction – 3 mechanisms for 5 types of taste 1. through ion channels 2. block ion channels 3. bind to G protein coupled receptors Saltiness – mostly sense NaCl – special sodium channels (insensitive to voltage) cause depolarization – then open voltage gated sodium channels – and calcium vesicles fusion – cation and anion– anion have inhibitory effects to the point that you don't perceive sodium saccharine at salty but as sweet. Sourness – low pH Bitterness – poison detection – to G protein coupled receptors – Perceive different poisoning – T1R, T2R – different receptors but we don't really care what type of poison just that it is poison Sweetness – pair of receptors T1R2, T1R3 same 2nd messenger systems as bitterness Umami – pair of receptors T1R1, T1R3 - detect amino acid Taste Central Pathways -Three cranial nerves (VII, IX, X) – Information about taste travels on three cranial nerves - goes to gustaory nucleus – then to the thalamus, ventromedial nucleus, primary gustaory cortex Lesions – Ageusia – the loss of taste Labeled line hypothesis – selective Population coding – information is actually not encoded in only one cell but an entire set of neurons Pheromones – smell – ID information, food, survival, aggression, territory etc. – basal cells – future or olfactory cells – mucous layer – molecules of smell called odorants enter mucous layer to activate sen- sory receptors – cilia in mucus are the dendrites of the cell – axons are thin but also slow because they enter through the skull - very susceptible to damage Within the cilia – olfactory transduction Humans 300-400 smell receptor genes Adaptation – smell after effect – decreases response, less sensitive to odors after smelling for a while Rats have a very large snout to have a large nasal olfactory receptive area Glomeruli – there are inhibition between Glomerulus to enhance some things for over another Smell and memory have a projection between them – you remember the smell you rec- ognize Thalamus – not controlling smell – when you sleep, the thalamus shut down but since smell is not controlled by thalamus, it does not shut down when sleeping What is flavor? Not same as taste – retronasal olfaction – based on olfaction but it isn't smell, the brain make sense of it in a different way – involves touched (to the mouth), smell and taste Ventriloquism – audio-visual illusion – the system that is more reliable will dominate so vision dominates which is why the puppet moving his mouth we see and perceive it as it talking. Multisensory – flavor of food seems to come from mouth actually from the nose by retronasal olfac- tion taste – only sweet or sour flavor – if it tastes like apples or bananas Food appears to come from mouth because you sense that there is something in your mouth Multiplication - more salt or sugar is added so your brain believes more food is in your mouth so stronger flavor Flavor is ONLY when you sense that there is food in your mouth Lecture 2 - vision – Contrast than relative Optics – Light is waves – wavelength, frequency (brightness) and amplitude (color) – Polarity of light – Birds use, humans cannot – Three concepts: 1. reflection 2. absorption 3. refraction (transparent surfaces) - depends on which of the two mediums denser Anatomy of the eye – Pupil, sclera, Iris, cornea, optic nerve – cornea is important for the focus of light – only the cornea cannot change shape (like the lens) which is also important for focus – Optic disk = blind spot – macula – acute (good) vision – fovea – best vision here – helpfullness of iris – you can tell if the person is looking at you or what they are look- ing at (difference between Iris and Sclera) – contraction of the ciliary fibers stretches the lens flat – pressure of vitreous humor gives the eye round shape Eye disorders – Strabism: one eye becomes weak and affects oculomotor so you have double vision so you pick one eye causing oculardominance and eventually that becomes blind (the week eye) (cross eyes) – Cataracts - clouding of the lens – needs to replace the lens (artificial lens) – Glaucoma – the vitreus pressure if there is too much then you get glacoma and this is usually in the blind spot so usually don't even notice – Detached retina - the retina detaches from the back of the eye- this can be lasered back to the eye – Retinitis pigmentosa - hereditary autoimmune disease where the body attacks the area right around the retina so you lose your sight starting with night vision. Spatial vision -Light that comes from a single source comes and collects at the cornea and then re- fracts the light – The cornea cannot change shape but the lens can – When the cilliary fibres relax, the lens stretches and thinner for far images – When the ciliary fibers contract, the lens relaxes (back to regular form) and thicker for images closer. Vision correction – Emmetropia – normal – Hyperopia – myopia – astigmatism – Cornia not being completely properly structured - not spherical The pupillary light reflex – the smaller the pupil, the more focused the vision is – the pupil controls the level of light going into the eye – consensual – both pupils should construct/relax at the same time – If the pupils are not consensual, it is a find that something is not right in the brainstem The visual field Visual acuity: the minimum distance between two dots that you can still see both dots. Anatomy of the retina Vertical pathway – photoreceptors– bipolar cells – ganglion cells Horizontal pathway Light enters from the ganglion cell layer and ends at the photoreceptor layer photoreceptors are special types of neurons Graph – 0= the fovea – the blue curve equals count of cones – red is count of rods – so in the fovea there are only cones and no rods – in the peripheral retina, the further you go, the less light there is so you see less (al- most blind) – there are more rods in the retina than cones 1 photoreceptor is attached to 2 bipolar cells is attached to it 1 ganglion cell – with the more photoreceptors/ bipolar/ ganglion cells, the more you can see (sensitive) but the less acuity so sensitivity and acuity are opposite. Pit shape of fovea – more visual acuity (find out why it is pit shaped) Phototransduction of rods – Rods are in the dark – don't send out action potentials, they send out graded potentials – since it is graded potential, it is more detailed and more sensitive to how much light is there and not just the presence or absence of light. – In dark, the sodium channels are open and let sodium flow in the depolarize the cell – Photodiesterase (PE) – know what happens in rods and cones when in the light and dark situations – Cones have different colors for different wavelengths so all three cones (for red, green, and blue) are all needed to perceive all the colors - Depending on how much each is activated or inhibited – Blue cones = 430 – green cones = 530 – red cones = 560 – rods (only see grey, black, and white) in the dark Li
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